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RE2JAVA(1)							    RE2JAVA(1)

NAME
       re2java - generate fast lexical analyzers for Java

SYNOPSIS
       re2java [ OPTIONS ] [ WARNINGS ]	INPUT

       Input can be either a file or - for stdin.

INTRODUCTION
       re2java works as	a preprocessor.	It reads the input file	(which is usu-
       ally  a	program	 in Java, but can be anything) and looks for blocks of
       code enclosed in	special-form start/end markers.	The  text  outside  of
       these  blocks  is copied	verbatim into the output file. The contents of
       the blocks are processed	by re2java. It translates them to code in Java
       and outputs the generated code in place of the block.

       Here is an example of a small program that checks  if  a	 given	string
       contains	a decimal number:

	  // re2java $INPUT -o $OUTPUT

	  class	Main {
	      static boolean lex(String	yyinput) {
		  int yycursor = 0;

		  /*!re2c
		      re2c:YYCTYPE = "char";
		      re2c:YYPEEK = "yyinput.charAt(yycursor)";
		      re2c:yyfill:enable = 0;

		      [1-9][0-9]* { return true; }
		      *		  { return false; }
		  */
	      }

	      public static void main(String []args) {
		  assert lex("1234\0");
	      }
	  };

       In  the output re2java replaced the block in the	middle with the	gener-
       ated code:

	  // Generated by re2java
	  // re2java $INPUT -o $OUTPUT

	  class	Main {
	      static boolean lex(String	yyinput) {
		  int yycursor = 0;

	  {
	      char yych	= 0;
	      int yystate = 0;
	      yyl: while (true)	{
		  switch (yystate) {
		      case 0:
			  yych = yyinput.charAt(yycursor);
			  yycursor += 1;
			  switch (yych)	{
			      case 0x31:
			      case 0x32:
			      case 0x33:
			      case 0x34:
			      case 0x35:
			      case 0x36:
			      case 0x37:
			      case 0x38:
			      case 0x39:
				  yystate = 2;
				  continue yyl;
			      default:
				  yystate = 1;
				  continue yyl;
			  }
		      case 1:
			  { return false; }
		      case 2:
			  yych = yyinput.charAt(yycursor);
			  switch (yych)	{
			      case 0x30:
			      case 0x31:
			      case 0x32:
			      case 0x33:
			      case 0x34:
			      case 0x35:
			      case 0x36:
			      case 0x37:
			      case 0x38:
			      case 0x39:
				  yycursor += 1;
				  yystate = 2;
				  continue yyl;
			      default:
				  yystate = 3;
				  continue yyl;
			  }
		      case 3:
			  { return true; }
		      default:
			  throw	new IllegalStateException("internal lexer error");
		  }
	      }
	  }

	      }

	      public static void main(String []args) {
		  assert lex("1234\0");
	      }
	  };

BASICS
       A re2java program consists of a sequence	of blocks intermixed with code
       in the target language. A block	may  contain  definitions,  configura-
       tions, rules, actions and directives in any order:

       name = regular-expression ;
	      A	definition binds name to regular-expression. Names may contain
	      alphanumeric  characters and underscore. The regular expressions
	      section gives an overview	of re2java syntax for regular  expres-
	      sions.  Once  defined, the name can be used in other regular ex-
	      pressions	and in rules.  Recursion in named definitions  is  not
	      allowed,	and  each  name	should be defined before it is used. A
	      block inherits named definitions from the	global scope. Redefin-
	      ing a name that exists in	the current scope is an	error.

       configuration = value ;
	      A	configuration allows one to change re2java behavior  and  cus-
	      tomize  the  generated  code.  For a full	list of	configurations
	      supported	by re2java see the configurations  section.  Depending
	      on  a  particular	 configuration,	 the value can be a keyword, a
	      nonnegative integer number or a one-line string which should  be
	      enclosed	in  double  or single quotes unless it consists	of al-
	      phanumeric characters. A block inherits configurations from  the
	      global  scope  and may redefine them or add new ones. Configura-
	      tions defined inside of a	block affect the whole block, even  if
	      they appear at the end of	it.

       regular-expression code
	      A	 rule binds regular-expression to its semantic action (a block
	      of code in curly braces, or a block of code that starts with  :=
	      and ends on a newline followed by	any non-whitespace character).
	      If  the  regular-expression matches, the associated code is exe-
	      cuted.  If multiple rules	match, the longest match takes	prece-
	      dence. If	multiple rules match the same string, the earliest one
	      takes  precedence. There are two special rules: the default rule
	      *	and the	end of input rule $.  Default rule  should  always  be
	      defined,	it  has	the lowest priority regardless of its place in
	      the block, and it	matches	any code unit (not necessarily a valid
	      character, see the encoding support section). The	end  of	 input
	      rule  should be defined if the corresponding method for handling
	      the end of input is used.	 With start conditions rules have more
	      complex syntax.

       !action code
	      An action	binds a	user-defined block of  code  to	 a  particular
	      place  in	the generated finite state machine (in the same	way as
	      semantic actions bind code to the	final states). See the actions
	      section for a full list of predefined actions.

       !directive ;
	      A	directive is one of the	special	 predefined  statements.  Each
	      directive	 has  a	unique purpose.	See the	directives section for
	      details.

   Blocks
       Block start and end markers are either /*!re2c and */,  or  %{  and  %}
       (both  styles are supported). Starting from version 2.2 blocks may have
       optional	names that allow them to be referenced in other	blocks.	 There
       are different kinds of blocks:

       /*!re2c[:<name>]	... */ or %{[:<name>] ... %}
	      A	global block contains definitions, configurations,  rules  and
	      directives.   re2java  compiles  regular	expressions associated
	      with each	rule into a deterministic finite automaton, encodes it
	      in the form of conditional jumps in the target language and  re-
	      places  the  block with the generated code. Names	and configura-
	      tions defined in a global	block are added	to  the	 global	 scope
	      and  become  visible  to	subsequent blocks. At the start	of the
	      program  the  global  scope  is  initialized  with  command-line
	      options.

       /*!local:re2c[:<name>] ... */ or	%{local[:<name>] ... %}
	      A	local block is like a global block, but	the names and configu-
	      rations  in  it  have  local  scope  (they  do  not affect other
	      blocks).

       /*!rules:re2c[:<name>] ... */ or	%{rules[:<name>] ... %}
	      A	rules block is like a local block, but it  does	 not  generate
	      any  code	 by  itself,  nor  does	 it add	any definitions	to the
	      global scope -- it is meant to be	reused in other	 blocks.  This
	      is  a  way  of sharing code (more	details	in the reusable	blocks
	      section).	Prior to re2java version 2.2 rules blocks required  -r
	      --reusable option.

       /*!use:re2c[:<name>] ...	*/ or %{use[:<name>] ... %}
	      A	use block that references a previously defined rules block. If
	      the  name	 is  specified,	 re2java looks for a rules blocks with
	      this name. Otherwise the most recent rules block is used (either
	      a	named or an unnamed one). A use	 block	can  add  definitions,
	      configurations and rules of its own, which are added to those of
	      the  referenced  rules  block.  Prior to re2java version 2.2 use
	      blocks required -r --reusable option.

       /*!max:re2c[:<name1>[:<name2>...]] ... */ or
       %{max[:<name1>[:<name2>...]] ...	%}
	      A	block that generates YYMAXFILL definition. An optional list of
	      block names specifies which blocks should	be included when  com-
	      puting YYMAXFILL value (if the list is empty, all	blocks are in-
	      cluded).	 By  default  the generated code is a macro-definition
	      for C (#define YYMAXFILL <n>), or	a global variable for Go  (var
	      YYMAXFILL	int = <n>). It can be customized with an optional con-
	      figuration format	that specifies a template string where @@{max}
	      (or  @@  for short) is replaced with the numeric value of	YYMAX-
	      FILL.

       /*!maxnmatch:re2c[:<name1>[:<name2>...]]	... */ or %{maxn-
       match[:<name1>[:<name2>...]] ...	%}
	      A	block that generates YYMAXNMATCH definition  (it  requires  -P
	      --posix-captures option).	An optional list of block names	speci-
	      fies  which blocks should	be included when computing YYMAXNMATCH
	      value (if	the list is empty, all blocks are included).   By  de-
	      fault  the  generated  code is a macro-definition	for C (#define
	      YYMAXNMATCH <n>),	or a global variable for Go  (var  YYMAXNMATCH
	      int  = <n>). It can be customized	with an	optional configuration
	      format that specifies a template string where @@{max} (or	@@ for
	      short) is	replaced with the numeric value	of YYMAXNMATCH.

       /*!stags:re2c[:<name1>[:<name2>...]] ...	*/,
       /*!mtags:re2c[:<name1>[:<name2>...]] ...	*/ or
       %{stags[:<name1>[:<name2>...]] ... %}, %{mtags[:<name1>[:<name2>...]]
       ... %{
	      Blocks that specify a template piece of code  that  is  expanded
	      for  each	s-tag/m-tag variable generated by re2java. An optional
	      list of block names specifies which blocks  should  be  included
	      when  computing  the set of tag variables	(if the	list is	empty,
	      all blocks are included).	 There	are  two  optional  configura-
	      tions:  format  and separator.  Configuration format specifies a
	      template string where @@{tag} (or	@@ for short) is replaced with
	      the name of each tag variable.  Configuration  separator	speci-
	      fies  a  piece  of code used to join the generated format	pieces
	      for different tag	variables.

       /*!svars:re2c[:<name1>[:<name2>...]] ...	*/,
       /*!mvars:re2c[:<name1>[:<name2>...]] ...	*/ or
       %{svars[:<name1>[:<name2>...]] ... %}, %{mvars[:<name1>[:<name2>...]]
       ... %{
	      Blocks that specify a template piece of code  that  is  expanded
	      for  each	s-tag/m-tag that is either explicitly mentioned	by the
	      rules (with --tags option) or implicitly	generated  by  re2java
	      (with  --captvars	or --posix-captvars options). An optional list
	      of block names specifies which blocks should  be	included  when
	      computing	 the set of tags (if the list is empty,	all blocks are
	      included).  There	are two	optional  configurations:  format  and
	      separator.   Configuration  format  specifies  a template	string
	      where @@{tag} (or	@@ for short) is replaced  with	 the  name  of
	      each  tag.   Configuration  separator  specifies a piece of code
	      used to join the generated format	pieces for different tags.

       /*!getstate:re2c[:<name1>[:<name2>...]] ... */ or %{get-
       state[:<name1>[:<name2>...]] ...	%}
	      A	block that generates conditional dispatch on the  lexer	 state
	      (it requires --storable-state option). An	optional list of block
	      names  specifies	which  blocks  should be included in the state
	      dispatch.	The default transition goes to the start label of  the
	      first  block  on	the list. If the list is empty,	all blocks are
	      included,	and the	default	transition goes	to the first block  in
	      the  file	that has a start label.	 This block type is incompati-
	      ble with the --loop-switch option, as  it	 requires  cross-block
	      transitions that are unsupported without goto or function	calls.

       /*!conditions:re2c[:<name1>[:<name2>...]] ... */, /*!types:re2c... */
       or %{conditions[:<name1>[:<name2>...]] ... %}, %{types... %}
	      A	block that generates condition enumeration (it requires	--con-
	      ditions option). An optional list	of block names specifies which
	      blocks  should  be included when computing the set of conditions
	      (if the list is empty, all blocks	are included).	By default the
	      generated	code is	an enumeration	YYCONDTYPE.  It	 can  be  cus-
	      tomized with optional configurations format and separator.  Con-
	      figuration format	specifies a template string where @@{cond} (or
	      @@  for  short) is replaced with the name	of each	condition, and
	      @@{num} is replaced with a  numeric  index  of  that  condition.
	      Configuration  separator	specifies a piece of code used to join
	      the generated format pieces for different	conditions.

       /*!include:re2c <file> */ or %{include <file> %}
	      This block allows	one to include <file>, which must  be  a  dou-
	      ble-quoted  file	path.  The  contents of	the file are literally
	      substituted in place of the block, in the	same way  as  #include
	      works  in	C/C++. This block can be used together with the	--dep-
	      file option to generate build system  dependencies  on  the  in-
	      cluded files.

       /*!header:re2c:on*/ or %{header:on %}
	      This  block  marks the start of header file. Everything after it
	      and up to	the following header:off block is processed by re2java
	      and written to the header	file specified with  -t	 --type-header
	      option.

       /*!header:re2c:off*/ or %{header:off %}
	      This block marks the end of header file started with header:on*/
	      block.

       /*!ignore:re2c ... */ or	%{ignore ... %}
	      A	 block	which contents are ignored and removed from the	output
	      file.

   Configurations
       Here is a full list of configurations supported by re2java:

       re2c:api, re2c:input
	      Same as the --api	option.

       re2c:api:sigil
	      Specify the marker ("sigil") that	is used	 for  argument	place-
	      holders  in the API primitives. The default is @@. A placeholder
	      starts with sigil	followed by the	argument name in curly braces.
	      For example, if sigil is set to $, then placeholders  will  have
	      the  form	 ${name}. Single-argument APIs may use shorthand nota-
	      tion without the name in braces. This option can	be  overridden
	      by  options for individual API primitives, e.g.  re2c:YYFILL@len
	      for YYFILL.

       re2c:api:style
	      Specify API style. Possible values are  functions	 (the  default
	      for  C)  and  free-form (the default for Go and Rust).  In func-
	      tions style API primitives are generated with an	argument  list
	      in  parentheses  following  the name of the primitive. The argu-
	      ments are	provided only for autogenerated	 parameters  (such  as
	      the number of characters passed to YYFILL), but not for the gen-
	      eral lexer context, so the primitives behave more	like macros in
	      C/C++ or closures	in Go and Rust.	 In free-form style API	primi-
	      tives  do	 not  have  a  fixed  form:  they should be defined as
	      strings containing free-form pieces of  code  with  interpolated
	      variables	 of  the  form @@{var} or @@ (they correspond to argu-
	      ments in function-like style).  This configuration may be	 over-
	      ridden  for  individual API primitives, see for example re2c:YY-
	      FILL:naked configuration for YYFILL.

       re2c:bit-vectors, re2c:flags:bit-vectors, re2c:flags:b
	      Same as the --bit-vectors	 option,  but  can  be	configured  on
	      per-block	basis.

       re2c:captures, re2c:leftmost-captures
	      Same as the --leftmost-captures option, but can be configured on
	      per-block	basis.

       re2c:captvars, re2c:leftmost-captvars
	      Same as the --leftmost-captvars option, but can be configured on
	      per-block	basis.

       re2c:case-insensitive, re2c:flags:case-insensitive
	      Same  as the --case-insensitive option, but can be configured on
	      per-block	basis.

       re2c:case-inverted, re2c:flags:case-inverted
	      Same as the --case-inverted option, but  can  be	configured  on
	      per-block	basis.

       re2c:case-ranges, re2c:flags:case-ranges
	      Same  as	the  --case-ranges  option,  but  can be configured on
	      per-block	basis.

       re2c:computed-gotos, re2c:flags:computed-gotos, re2c:flags:g
	      Same as the --computed-gotos option, but can  be	configured  on
	      per-block	basis.

       re2c:computed-gotos:threshold, re2c:cgoto:threshold
	      If  computed goto	is used, this configuration specifies the com-
	      plexity threshold	that triggers the generation  of  jump	tables
	      instead  of  nested if statements	and bitmaps. The default value
	      is 9.

       re2c:cond:abort
	      If set to	a positive integer value, the default case in the gen-
	      erated condition dispatch	aborts program execution.

       re2c:cond:goto
	      Specifies	a piece	of code	used for  the  autogenerated  shortcut
	      rules :=>	in conditions. The default is goto @@;.	 The @@	place-
	      holder  is  substituted  with condition name (see	configurations
	      re2c:api:sigil and re2c:cond:goto@cond).

       re2c:cond:goto@cond
	      Specifies	 the  sigil  used   for	  argument   substitution   in
	      re2c:cond:goto  definition.  The default value is	@@.  Overrides
	      the more generic re2c:api:sigil configuration.

       re2c:cond:divider
	      Defines the divider for condition	blocks.	 The default value  is
	      /*  ***********************************  */.   Placeholders  are
	      substituted  with	 condition  name   (see	  re2c:api;sigil   and
	      re2c:cond:divider@cond).

       re2c:cond:divider@cond
	      Specifies	  the	sigil	used   for  argument  substitution  in
	      re2c:cond:divider	definition. The	default	is @@.	Overrides  the
	      more generic re2c:api:sigil configuration.

       re2c:cond:prefix, re2c:condprefix
	      Specifies	 the prefix used for condition labels.	The default is
	      yyc_.

       re2c:cond:enumprefix, re2c:condenumprefix
	      Specifies	the prefix used	for condition  identifiers.   The  de-
	      fault is yyc.

       re2c:debug-output, re2c:flags:debug-output, re2c:flags:d
	      Same  as	the  --debug-output  option,  but can be configured on
	      per-block	basis.

       re2c:empty-class, re2c:flags:empty-class
	      Same as the --empty-class	 option,  but  can  be	configured  on
	      per-block	basis.

       re2c:encoding:ebcdic, re2c:flags:ecb, re2c:flags:e
	      Same  as the --ebcdic option, but	can be configured on per-block
	      basis.

       re2c:encoding:ucs2, re2c:flags:wide-chars, re2c:flags:w
	      Same as the --ucs2 option, but can be  configured	 on  per-block
	      basis.

       re2c:encoding:utf8, re2c:flags:utf-8, re2c:flags:8
	      Same  as	the  --utf8 option, but	can be configured on per-block
	      basis.

       re2c:encoding:utf16, re2c:flags:utf-16, re2c:flags:x
	      Same as the --utf16 option, but can be configured	 on  per-block
	      basis.

       re2c:encoding:utf32, re2c:flags:unicode,	re2c:flags:u
	      Same  as	the --utf32 option, but	can be configured on per-block
	      basis.

       re2c:encoding-policy, re2c:flags:encoding-policy
	      Same as the --encoding-policy option, but	can be	configured  on
	      per-block	basis.

       re2c:eof
	      Specifies	the sentinel symbol used with the end-of-input rule $.
	      The  default  value  is  -1 ($ rule is not used).	Other possible
	      values include all valid code units. Only	 decimal  numbers  are
	      recognized.

       re2c:fn:sep
	      Specifies	 separator  used  in  YYFN elements (defaults to semi-
	      colon).

       re2c:header, re2c:flags:type-header, re2c:flags:t
	      Specifies	the name of the	generated header file relative to  the
	      directory	of the output file. Same as the	--header option	except
	      that the file path is relative.

       re2c:indent:string
	      Specifies	the string used	for indentation. The default is	a sin-
	      gle  tab character "\t". Indent string should contain whitespace
	      characters only.	To disable indentation entirely, set this con-
	      figuration to an empty string.

       re2c:indent:top
	      Specifies	the minimum amount of indentation to use. The  default
	      value  is	 zero. The value should	be a non-negative integer num-
	      ber.

       re2c:invert-captures
	      Same as the --invert-captures option, but	can be	configured  on
	      per-block	basis.

       re2c:label:prefix, re2c:labelprefix
	      Specifies	 the  prefix used for DFA state	labels.	The default is
	      yy.

       re2c:label:start, re2c:startlabel
	      Controls the generation of a  block  start  label.  The  default
	      value  is	 zero,	which  means that the start label is generated
	      only if it is used. An integer value greater  than  zero	forces
	      the generation of	start label even if it is unused by the	lexer.
	      A	 string	 value also forces start label generation and sets the
	      label name to the	specified string. This	configuration  applies
	      only  to	the current block (it is reset to default for the next
	      block).

       re2c:label:yyFillLabel
	      Specifies	the prefix of YYFILL labels used with re2c:eof and  in
	      storable state mode.

       re2c:label:yyloop
	      Specifies	 the  name of the label	marking	the start of the lexer
	      loop with	--loop-switch option. The default is yyloop.

       re2c:label:yyNext
	      Specifies	the name of the	optional label that follows YYGETSTATE
	      switch in	storable state mode (enabled  with  re2c:state:nextla-
	      bel). The	default	is yyNext.

       re2c:lookahead, re2c:flags:lookahead
	      Deprecated (see the deprecated --no-lookahead option).

       re2c:monadic
	      If  set  to non-zero, the	generated lexer	will use monadic nota-
	      tion (this configuration is specific to Haskell).

       re2c:nested-ifs,	re2c:flags:nested-ifs, re2c:flags:s
	      Same as the  --nested-ifs	 option,  but  can  be	configured  on
	      per-block	basis.

       re2c:posix-captures, re2c:flags:posix-captures, re2c:flags:P
	      Same  as	the  --posix-captures option, but can be configured on
	      per-block	basis.

       re2c:posix-captvars
	      Same as the --posix-captvars option, but can  be	configured  on
	      per-block	basis.

       re2c:tags, re2c:flags:tags, re2c:flags:T
	      Same  as	the  --tags option, but	can be configured on per-block
	      basis.

       re2c:tags:expression
	      Specifies	the expression used for	 tag  variables.   By  default
	      re2java  generates expressions of	the form yyt<N>. This might be
	      inconvenient, for	example	if tag variables are defined as	fields
	      in a struct. All occurrences of @@{tag} or @@ are	replaced  with
	      the actual tag name. For example,	re2c:tags:expression = "s.@@";
	      results  in  expressions	of  the	form s.yyt<N> in the generated
	      code.  See also re2c:api:sigil configuration.

       re2c:tags:negative
	      Specifies	the constant expression	that is	used for negative  tag
	      value (typically this would be -1	if tags	are integer offsets in
	      the input	string,	or null	pointer	if they	are pointers).

       re2c:tags:prefix
	      Specifies	the prefix for tag variable names. The default is yyt.

       re2c:sentinel
	      Specifies	 the  sentinel symbol used for the end-of-input	checks
	      (when bounds checks are disabled with  re2c:yyfill:enable	 =  0;
	      and  re2c:eof  is	 not  set). This configuration does not	affect
	      code generation: its purpose is to verify	that the  sentinel  is
	      not  allowed  in the middle of a rule, and ensure	that the lexer
	      won't read past the end of buffer. The default value is -1`  (in
	      that  case  re2java  assumes that	the sentinel is	zero, which is
	      the most common case). Only decimal numbers are recognized.

       re2c:state:abort
	      If set to	a positive integer value, the default case in the gen-
	      erated state dispatch aborts program execution, and an  explicit
	      -1 case contains transition to the start of the block.

       re2c:state:nextlabel
	      Controls if the YYGETSTATE switch	is followed by an yyNext label
	      (the default value is zero, which	corresponds to no label).  Al-
	      ternatively  one can use re2c:label:start	to generate a specific
	      start label, or an  explicit  getstate  block  to	 generate  the
	      YYGETSTATE switch	separately from	the lexer block.

       re2c:unsafe, re2c:flags:unsafe
	      Same  as	the  --no-unsafe  option,  but	can  be	 configured on
	      per-block	basis.	If set to zero,	it suppresses  the  generation
	      of unsafe	wrappers around	YYPEEK.	The default is non-zero	(wrap-
	      pers are generated).  This configuration is specific to Rust.

       re2c:YYBACKUP, re2c:define:YYBACKUP
	      Defines generic API primitive YYBACKUP.

       re2c:YYBACKUPCTX, re2c:define:YYBACKUPCTX
	      Defines generic API primitive YYBACKUPCTX.

       re2c:YYCONDTYPE,	re2c:define:YYCONDTYPE
	      Defines API primitive YYCONDTYPE.

       re2c:YYCTYPE, re2c:define:YYCTYPE
	      Defines API primitive YYCTYPE.

       re2c:YYCTXMARKER, re2c:define:YYCTXMARKER
	      Defines API primitive YYCTXMARKER.

       re2c:YYCURSOR, re2c:define:YYCURSOR
	      Defines API primitive YYCURSOR.

       re2c:YYDEBUG, re2c:define:YYDEBUG
	      Defines API primitive YYDEBUG.

       re2c:YYFILL, re2c:define:YYFILL
	      Defines API primitive YYFILL.

       re2c:YYFILL@len,	re2c:define:YYFILL@len
	      Specifies	the sigil used for argument substitution in YYFILL de-
	      finition.	  Defaults   to	  @@.	 Overrides  the	 more  generic
	      re2c:api:sigil configuration.

       re2c:YYFILL:naked, re2c:define:YYFILL:naked
	      Overrides	the more generic re2c:api:style	configuration for  YY-
	      FILL.  Zero value	corresponds to free-form API style.

       re2c:YYFN
	      Defines API primitive YYFN.

       re2c:YYINPUT
	      Defines API primitive YYINPUT.

       re2c:YYGETCOND, re2c:define:YYGETCONDITION
	      Defines API primitive YYGETCOND.

       re2c:YYGETCOND:naked, re2c:define:YYGETCONDITION:naked
	      Overrides	 the  more  generic  re2c:api:style  configuration for
	      YYGETCOND. Zero value corresponds	to free-form API style.

       re2c:YYGETSTATE,	re2c:define:YYGETSTATE
	      Defines API primitive YYGETSTATE.

       re2c:YYGETSTATE:naked, re2c:define:YYGETSTATE:naked
	      Overrides	the  more  generic  re2c:api:style  configuration  for
	      YYGETSTATE. Zero value corresponds to free-form API style.

       re2c:YYGETACCEPT, re2c:define:YYGETACCEPT
	      Defines API primitive YYGETACCEPT.

       re2c:YYLESSTHAN,	re2c:define:YYLESSTHAN
	      Defines generic API primitive YYLESSTHAN.

       re2c:YYLIMIT, re2c:define:YYLIMIT
	      Defines API primitive YYLIMIT.

       re2c:YYMARKER, re2c:define:YYMARKER
	      Defines API primitive YYMARKER.

       re2c:YYMTAGN, re2c:define:YYMTAGN
	      Defines generic API primitive YYMTAGN.

       re2c:YYMTAGP, re2c:define:YYMTAGP
	      Defines generic API primitive YYMTAGP.

       re2c:YYPEEK, re2c:define:YYPEEK
	      Defines generic API primitive YYPEEK.

       re2c:YYRESTORE, re2c:define:YYRESTORE
	      Defines generic API primitive YYRESTORE.

       re2c:YYRESTORECTX, re2c:define:YYRESTORECTX
	      Defines generic API primitive YYRESTORECTX.

       re2c:YYRESTORETAG, re2c:define:YYRESTORETAG
	      Defines generic API primitive YYRESTORETAG.

       re2c:YYSETCOND, re2c:define:YYSETCONDITION
	      Defines API primitive YYSETCOND.

       re2c:YYSETCOND@cond, re2c:define:YYSETCONDITION@cond
	      Specifies	 the sigil used	for argument substitution in YYSETCOND
	      definition. The default value is @@.  Overrides the more generic
	      re2c:api:sigil configuration.

       re2c:YYSETCOND:naked, re2c:define:YYSETCONDITION:naked
	      Overrides	the more generic re2c:api:style	configuration for  YY-
	      SETCOND. Zero value corresponds to free-form API style.

       re2c:YYSETSTATE,	re2c:define:YYSETSTATE
	      Defines API primitive YYSETSTATE.

       re2c:YYSETSTATE@state, re2c:define:YYSETSTATE@state
	      Specifies	the sigil used for argument substitution in YYSETSTATE
	      definition. The default value is @@.  Overrides the more generic
	      re2c:api:sigil configuration.

       re2c:YYSETSTATE:naked, re2c:define:YYSETSTATE:naked
	      Overrides	 the more generic re2c:api:style configuration for YY-
	      SETSTATE.	Zero value corresponds to free-form API	style.

       re2c:YYSETACCEPT, re2c:define:YYSETACCEPT
	      Defines API primitive YYSETACCEPT.

       re2c:YYSKIP, re2c:define:YYSKIP
	      Defines generic API primitive YYSKIP.

       re2c:YYSHIFT, re2c:define:YYSHIFT
	      Defines generic API primitive YYSHIFT.

       re2c:YYCOPYMTAG,	re2c:define:YYCOPYMTAG
	      Defines generic API primitive YYCOPYMTAG.

       re2c:YYCOPYSTAG,	re2c:define:YYCOPYSTAG
	      Defines generic API primitive YYCOPYSTAG.

       re2c:YYSHIFTMTAG, re2c:define:YYSHIFTMTAG
	      Defines generic API primitive YYSHIFTMTAG.

       re2c:YYSHIFTSTAG, re2c:define:YYSHIFTSTAG
	      Defines generic API primitive YYSHIFTSTAG.

       re2c:YYSTAGN, re2c:define:YYSTAGN
	      Defines generic API primitive YYSTAGN.

       re2c:YYSTAGP, re2c:define:YYSTAGP
	      Defines generic API primitive YYSTAGP.

       re2c:yyaccept, re2c:variable:yyaccept
	      Defines API primitive yyaccept.

       re2c:yybm, re2c:variable:yybm
	      Defines API primitive yybm.

       re2c:yybm:hex, re2c:variable:yybm:hex
	      If set to	nonzero, bitmaps for the --bit-vectors option are gen-
	      erated in	hexadecimal format. The	default	is zero	 (bitmaps  are
	      in decimal format).

       re2c:yych, re2c:variable:yych
	      Defines API primitive yych.

       re2c:yych:emit, re2c:variable:yych:emit
	      If  set  to zero,	yych definition	is not generated.  The default
	      is non-zero.

       re2c:yych:conversion, re2c:variable:yych:conversion
	      If set to	non-zero, re2java automatically	generates a conversion
	      to YYCTYPE every time yych is read. The default is to  zero  (no
	      conversion).

       re2c:yych:literals, re2c:variable:yych:literals
	      Specifies	 the  form  of	literals that yych is matched against.
	      Possible values are: char	(character literals in single  quotes,
	      non-printable  ones  use	escape sequences that start with back-
	      slash), hex (hexadecimal integers) and char_or_hex (a mixture of
	      both, character literals for printable characters	and  hexadeci-
	      mal integers for others).

       re2c:yyctable, re2c:variable:yyctable
	      Defines API primitive yyctable.

       re2c:yynmatch, re2c:variable:yynmatch
	      Defines API primitive yynmatch.

       re2c:yypmatch, re2c:variable:yypmatch
	      Defines API primitive yypmatch.

       re2c:yytarget, re2c:variable:yytarget
	      Defines API primitive yytarget.

       re2c:yystable, re2c:variable:yystable
	      Deprecated.

       re2c:yystate, re2c:variable:yystate
	      Defines API primitive yystate.

       re2c:yyfill, re2c:variable:yyfill
	      Defines API primitive yyfill.

       re2c:yyfill:check
	      If  set  to  zero, suppresses the	generation of pre-YYFILL check
	      for the number of	input characters (the YYLESSTHAN definition in
	      generic API and the YYLIMIT-based	comparison in C	pointer	 API).
	      The default is non-zero (generate	the check).

       re2c:yyfill:enable
	      If  set  to  zero, suppresses the	generation of YYFILL (together
	      with the check). This should be used when	the whole  input  fits
	      into  one	 piece	of memory (there is no need for	buffering) and
	      the end-of-input checks do not rely on the YYFILL	 checks	 (e.g.
	      if  a sentinel character is used).  Use warnings (-W option) and
	      re2c:sentinel configuration to verify that the  generated	 lexer
	      cannot read past the end of input.  The default is non-zero (YY-
	      FILL is enabled).

       re2c:yyfill:parameter
	      If set to	zero, suppresses the generation	of parameter passed to
	      YYFILL.	The parameter is the minimum number of characters that
	      must be supplied.	 Defaults to non-zero (the parameter is	gener-
	      ated).  This  configuration  can	be  overridden	with  re2c:YY-
	      FILL:naked or re2c:api:style.

   Regular expressions
       re2java uses the	following syntax for regular expressions:

       "foo"  Case-sensitive string literal.

       'foo'  Case-insensitive string literal.

       [a-xyz],	[^a-xyz]
	      Character	class (possibly	negated).

       .      Any character except newline.

       R \ S  Difference of character classes R	and S.

       R*     Zero or more occurrences of R.

       R+     One or more occurrences of R.

       R?     Optional R.

       R{n}   Repetition of R exactly n	times.

       R{n,}  Repetition of R at least n times.

       R{n,m} Repetition of R from n to	m times.

       (R)    Just R; parentheses are used to override precedence. If submatch
	      extraction  is  enabled,	(R)  is	a capturing or a non-capturing
	      group depending on --invert-captures option.

       (!R)   If submatch extraction is	enabled, (!R) is a non-capturing or  a
	      capturing	group depending	on --invert-captures option.

       R S    Concatenation: R followed	by S.

       R | S  Alternative: R or	S.

       R / S  Lookahead: R followed by S, but S	is not consumed.

       name   Regular  expression defined as name (or literal string "name" in
	      Flex compatibility mode).

       {name} Regular expression defined as name in Flex compatibility mode.

       @stag  An s-tag:	saves the last input position at which	@stag  matches
	      in a variable named stag.

       #mtag  An  m-tag: saves all input positions at which #mtag matches in a
	      variable named mtag.

       Character classes and string literals may contain the following	escape
       sequences: \a, \b, \f, \n, \r, \t, \v, \\, octal	escapes	\ooo and hexa-
       decimal escapes \xhh, \uhhhh and	\Uhhhhhhhh.

   Actions
       Here is a list of predefined actions supported by re2java:

       !entry code
	      Entry  action  binds  a  user-defined block of code to the start
	      state of the current finite state	machine. If  start  conditions
	      are used,	the entry action can be	set individually for each con-
	      dition.  This action may be used to perform initialization, e.g.
	      to save start location of	a lexeme.

       !pre_rule code
	      Pre-rule action prepends a user-defined block of code to	seman-
	      tic  actions of all rules	in the current block (or condition, if
	      start conditions are used). This action may be  used  to	factor
	      out the common part of all semantic actions (e.g.	saving the end
	      location of a lexeme).

       !post_rule code
	      Post-rule	 action	appends	a user-defined block of	code to	seman-
	      tic actions of all rules in the current block (or	condition,  if
	      start conditions are used). This action may be used to emit trap
	      statements that guard against unintended control flow.

   Directives
       Here is a full list of directives supported by re2java:

       !use:name ;
	      An in-block use directive	that merges a previously defined rules
	      block with the specified name into the current block. Named def-
	      initions,	 configurations	 and rules of the referenced block are
	      added to the current ones. Conflicts between  overlapping	 rules
	      and configurations are resolved in the usual way:	the first rule
	      takes  priority, and the latest configuration overrides the pre-
	      ceding ones. One exception is the	special	rules *, $ and <!> for
	      which a block-local definition always takes priority. A use  di-
	      rective  can  be placed anywhere inside of a block, and multiple
	      use directives are allowed.

       !include	file ;
	      This directive is	the same as include  block:  it	 inserts  file
	      contents verbatim	in place of the	directive.

   Program interface
       The  generated  code interfaces with the	outer program with the help of
       primitives, collectively	referred to  as	 the  API.   Which  primitives
       should be defined for a particular program depends on multiple factors,
       including  the complexity of regular expressions, input representation,
       buffering and the use of	various	features. All the necessary primitives
       should be defined by the	user in	the form of macros,  functions,	 vari-
       ables  or any other suitable form that makes the	generated code syntac-
       tically and semantically	correct. re2java does not (and	cannot)	 check
       the  definitions, so if anything	is missing or defined incorrectly, the
       generated program may have compile-time or run-time errors.  This  man-
       ual provides examples of	API definitions	in the most common cases.

       re2java	has  three  API	flavors	that define the	core set of primitives
       used by a program:

       Simple API
	      This is the default API for the Java backend. It consists	of the
	      following	primitives: YYINPUT (which should be defined as	a  se-
	      quence  of  code	units,	e.g. a string) and YYCURSOR, YYMARKER,
	      YYCTXMARKER, YYLIMIT (which should be defined as indices in  YY-
	      INPUT).

       Record API
	      Record API is useful in cases when lexer state must be stored in
	      a	 class.	  It is	enabled	with --api record option or re2c:api =
	      record configuration. This API consists of a  variable  yyrecord
	      (the  name  can be overridden with re2c:yyrecord)	that should be
	      defined as a class with fields yyinput, yycursor,	yymarker, yyc-
	      txmarker,	yylimit	(only the fields used by  the  generated  code
	      need to be defined, and their names can be configured).

       Generic API
	      This  is the most	flexible API. It is enabled with --api generic
	      option or	re2c:api = generic configuration.  It contains	primi-
	      tives  for generic operations: YYPEEK, YYSKIP, YYBACKUP, YYBACK-
	      UPCTX, YYSTAGP,  YYSTAGN,	 YYMTAGP,  YYMTAGN,  YYRESTORE,	 YYRE-
	      STORECTX,	 YYRESTORETAG,	YYSHIFT, YYSHIFTSTAG, YYSHIFTMTAG, YY-
	      LESSTHAN.

       Here is a full list of API primitives that may be used by the generated
       code in order to	interface with the outer program.

       YYCTYPE
	      The type of the  input  characters  (code	 units).   For	ASCII,
	      EBCDIC and UTF-8 encodings it should be 1-byte unsigned integer.
	      For  UTF-16  or  UCS-2 it	should be 2-byte unsigned integer. For
	      UTF-32 it	should be 4-byte unsigned integer.

       YYCURSOR
	      An l-value that stores the current input position	(a pointer  or
	      an  integer  offset in YYINPUT). Initially YYCURSOR should point
	      to the first input character, and	later it is  advanced  by  the
	      generated	 code.	When  a	rule matches, YYCURSOR position	is the
	      one after	the last matched character.

       YYLIMIT
	      An r-value that stores the end of	input position (a  pointer  or
	      an integer offset	in YYINPUT). Initially YYLIMIT should point to
	      the position after the last available input character. It	is not
	      changed  by  the	generated code.	The lexer compares YYCURSOR to
	      YYLIMIT in order to determine if there are enough	input  charac-
	      ters left.

       YYMARKER
	      An  l-value  that	stores the position of the latest matched rule
	      (a pointer or an integer offset in YYINPUT). It is used  to  re-
	      store  the  YYCURSOR  position if	the longer match fails and the
	      lexer needs to rollback.	Initialization is not needed.

       YYCTXMARKER
	      An l-value that stores the position of the trailing  context  (a
	      pointer  or  an integer offset in	YYINPUT). No initialization is
	      needed. YYCTXMARKER is needed only if the	lookahead  operator  /
	      is used.

       YYFILL A	 generic  API  primitive with one variable len.	 YYFILL	should
	      provide at least len more	input characters or fail.  If re2c:eof
	      is used, then len	is always 1 and	 YYFILL	should	always	return
	      to  the  calling	function; zero return value indicates success.
	      If re2c:eof is not used, then YYFILL return value	is ignored and
	      it should	not return on failure. The maximum value of len	is YY-
	      MAXFILL.

       YYFN   A	primitive that defines function	prototype in --recursive-func-
	      tions code model.	Its value should be an array of	 one  or  more
	      strings, where each string contains two or three components sep-
	      arated  by  the  string  specified  in re2c:fn:sep configuration
	      (typically a semicolon). The first array element	defines	 func-
	      tion  name  and return type (empty for a void function).	Subse-
	      quent elements define function arguments:	first, the  expression
	      for  the	argument  used in function body	(usually just a	name);
	      second, argument type; third, an optional	formal	parameter  (it
	      defaults	to the first component - usually both the argument and
	      the parameter are	the same identifier).

       YYINPUT
	      An r-value that stores  the  current  input  character  sequence
	      (string, buffer, etc.).

       YYMAXFILL
	      An  integral constant equal to the maximum value of the argument
	      to YYFILL.  It can be generated with a max block.

       YYLESSTHAN
	      A	generic	API primitive with one variable	len.  It should	be de-
	      fined as an r-value of boolean type that equals true if and only
	      if there are less	than len input characters left.

       YYPEEK A	generic	API primitive with no variables.  It should be defined
	      as an r-value of type YYCTYPE that is equal to the character  at
	      the current input	position.

       YYSKIP A	 generic  API  primitive that should advance the current input
	      position by one code unit.

       YYBACKUP
	      A	generic	API primitive that should save the current input posi-
	      tion (to be restored with	YYRESTORE later).

       YYRESTORE
	      A	generic	API primitive that should restore  the	current	 input
	      position to the value saved by YYBACKUP.

       YYBACKUPCTX
	      A	generic	API primitive that should save the current input posi-
	      tion  as	the  position  of the trailing context (to be restored
	      with YYRESTORECTX	later).

       YYRESTORECTX
	      A	generic	API primitive that should restore the trailing context
	      position saved with YYBACKUPCTX.

       YYRESTORETAG
	      A	generic	API primitive with one variable	tag  that  should  re-
	      store the	trailing context position to the value of tag.

       YYSTAGP
	      A	 generic API primitive with one	variable tag, where tag	can be
	      a	pointer	or an offset in	YYINPUT	(see submatch extraction  sec-
	      tion  for	 details). YYSTAGP should set tag to the current input
	      position.

       YYSTAGN
	      A	generic	API primitive with one variable	tag, where tag can  be
	      a	 pointer or an offset in YYINPUT (see submatch extraction sec-
	      tion for details). YYSTAGN should	to set tag  to	a  value  that
	      represents non-existent input position.

       YYMTAGP
	      A	 generic  API primitive	with one variable tag.	YYMTAGP	should
	      append the current position to the submatch history of tag  (see
	      the submatch extraction section for details.)

       YYMTAGN
	      A	 generic  API primitive	with one variable tag.	YYMTAGN	should
	      append a value that represents non-existent input	position posi-
	      tion to the submatch history of tag (see the submatch extraction
	      section for details.)

       YYSHIFT
	      A	generic	API primitive with  one	 variable  shift  that	should
	      shift  the current input position	by shift characters (the shift
	      value may	be negative).

       YYCOPYSTAG
	      A	generic	API primitive with two variables,  lhs	and  rhs  that
	      should   copy   right-hand-side	s-tag	variable  rhs  to  the
	      left-hand-side s-tag variable lhs. For most languages this prim-
	      itive has	a default definition that assigns lhs to rhs.

       YYCOPYMTAG
	      A	generic	API primitive with two variables,  lhs	and  rhs  that
	      should   copy   right-hand-side	m-tag	variable  rhs  to  the
	      left-hand-side m-tag variable lhs. For most languages this prim-
	      itive has	a default definition that assigns lhs to rhs.

       YYSHIFTSTAG
	      A	generic	 API primitive with two	variables, tag and shift  that
	      should  shift  tag  by  shift code units (the shift value	may be
	      negative).

       YYSHIFTMTAG
	      A	generic	API primitive with two variables, tag and  shift  that
	      should  shift  the  latest  value	in the history of tag by shift
	      code units (the shift value may be negative).

       YYMAXNMATCH
	      An integral constant equal to the	maximal	number of  POSIX  cap-
	      turing groups in a rule. It is generated with a maxnmatch	block.

       YYCONDTYPE
	      The type of the condition	enum.  It can be generated either with
	      conditions block or --header option.

       YYGETACCEPT
	      A	 primitive  with one variable var that stores numeric selector
	      of the accepted rule. For	most languages this  primitive	has  a
	      default definition that reads from var.

       YYSETACCEPT
	      A	 primitive with	two variables: var (an l-value that stores nu-
	      meric selector of	the accepted rule), and	val (the value of  se-
	      lector). For most	languages this primitive has a default defini-
	      tion that	assigns	var to val.

       YYGETCOND
	      An  r-value of type YYCONDTYPE that is equal to the current con-
	      dition identifier.

       YYSETCOND
	      A	primitive with one variable cond that should set  the  current
	      condition	identifier to cond.

       YYGETSTATE
	      An  r-value  of  integer type that is equal to the current lexer
	      state. It	should be initialized to -1.

       YYSETSTATE
	      A	primitive with one variable state that should set the  current
	      lexer state to state.

       YYDEBUG
	      This primitive is	generated only with -d,	--debug-output option.
	      Its purpose is to	add logging to the generated code (typical YY-
	      DEBUG  definition	 is a print statement).	YYDEBUG	statements are
	      generated	in every state and have	two variables: state (either a
	      DFA state	index or -1) and symbol	(the current input symbol).

       yyaccept
	      An l-value of unsigned integral type that	stores the  number  of
	      the  latest matched rule.	User definition	is necessary only with
	      --storable-state option.

       yybm   A	table containing compressed bitmaps for	up  to	8  transitions
	      (used  with  the	--bitmaps option). The table contains 256 ele-
	      ments and	is indexed by 1-byte code units.  Each	8-bit  element
	      combines	boolean	 values	 for  up to 8 transitions. k-Th	bit of
	      n-th element is true iff n-th code unit is in the	range of  k-th
	      transition.  The	idea  of  this	bitmap	is  to replace many if
	      branches or switch cases with one	check of a single bit  in  the
	      table.

       yych   An l-value of type YYCTYPE that stores the current input charac-
	      ter.  User definition is necessary only with -f --storable-state
	      option.

       yyctable
	      Jump table generated for the initial condition dispatch (enabled
	      with  the	 combination  of --conditions and --computed-gotos op-
	      tions).

       yyfill An l-value that stores the result	of YYFILL call	(this  may  be
	      necessary	 for  pure  functional	languages,  where  YYFILL is a
	      monadic function with complex return value).

       yynmatch
	      An l-value of unsigned integral type that	stores the  number  of
	      POSIX  capturing	groups in the matched rule.  Used only with -P
	      --posix-captures option.

       yypmatch
	      An array of l-values that	are used to hold the tag values	corre-
	      sponding to the capturing	parentheses in the matching rule.  Ar-
	      ray  length must be at least yynmatch * 2	(usually YYMAXNMATCH *
	      2	is a good choice).  Used only with -P --posix-captures option.

       yystable
	      Deprecated.

       yystate
	      An l-value used with the --loop-switch option to store the  cur-
	      rent DFA state.

       yytarget
	      Jump  table that contains	jump targets (label addresses) for all
	      transitions from a state.	This table is  local  to  each	state.
	      Generation  of  yytarget tables is enabled with --computed-gotos
	      option.

   Options
       Some of the  options  have  corresponding  configurations,  others  are
       global  and cannot be changed after re2c	starts reading the input file.
       Debug options generally require building	re2c in	 debug	configuration.
       Internal	 options are useful for	experimenting with the algorithms used
       in re2c.

       -? --help -h
	      Show help	message.

       --api <simple | record |	generic>
	      Specify the API used by the generated  code  to  interface  with
	      used-defined  code.  Option simple shold be used in simple cases
	      when there's no need for	buffer	refilling  and	storing	 lexer
	      state. Option record should be used when lexer state needs to be
	      stored in	a record (struct, class, etc.).	 Option	generic	should
	      be  used in complex cases	when the other two APIs	are not	flexi-
	      ble enough.

       --bit-vectors -b
	      Optimize conditional jumps using bit masks.  This	option implies
	      --nested-ifs.

       --captures, --leftmost-captures
	      Enable  submatch	extraction  with  leftmost  greedy   capturing
	      groups. The result is collected into an array yybmatch of	capac-
	      ity 2 * YYMAXNMATCH, and yynmatch	is set to the number of	groups
	      for the matching rule.

       --captvars, --leftmost-captvars
	      Enable   submatch	 extraction  with  leftmost  greedy  capturing
	      groups. The result is collected into variables yytl<k>,  yytr<k>
	      for k-th capturing group.

       --case-insensitive
	      Treat  single-quoted  and	double-quoted strings as case-insensi-
	      tive.

       --case-inverted
	      Invert the meaning of single-quoted and  double-quoted  strings:
	      treat  single-quoted strings as case-sensitive and double-quoted
	      strings as case-insensitive.

       --case-ranges
	      Collapse consecutive cases in a switch statements	into  a	 range
	      of the form low ... high.	This syntax is a C/C++ language	exten-
	      sion that	is supported by	compilers like GCC, Clang and Tcc. The
	      main advantage over using	single cases is	smaller	generated code
	      and faster generation time, although for some compilers like Tcc
	      it  also	results	 in  smaller binary size.  This	option is sup-
	      ported only for C.

       --computed-gotos	-g
	      Optimize conditional jumps using	non-standard  "computed	 goto"
	      extension	 (which	 must  be  supported by	the compiler). re2java
	      generates	jump tables only in complex cases with a lot of	condi-
	      tional branches. Complexity threshold  can  be  configured  with
	      cgoto:threshold  configuration.  This  option implies --bit-vec-
	      tors. It is supported only for C.

       --conditions --start-conditions -c
	      Enable support of	Flex-like "conditions":	multiple  interrelated
	      lexers  within  one  block.  This	 is an alternative to manually
	      specifying different re2java blocks connected with goto or func-
	      tion calls.

       --depfile FILE
	      Write dependency information to FILE in the form of  a  Makefile
	      rule  <output-file>  : <input-file> [include-file	...]. This al-
	      lows one to track	build dependencies in the presence of  include
	      blocks/directives,  so  that updating include files triggers re-
	      generation of the	output	file.	This  option  depends  on  the
	      --output option.

       --ebcdic	--ecb -e
	      Generate	a  lexer  that reads input in EBCDIC encoding. re2java
	      assumes that the character range is 0 -- 0xFF and	character size
	      is 1 byte.

       --empty-class <match-empty | match-none | error>
	      Define the way re2java  treats  empty  character	classes.  With
	      match-empty (the default)	empty class matches empty input	(which
	      is  illogical,  but backwards-compatible). With match-none empty
	      class always fails to match.  With error empty  class  raises  a
	      compilation error.

       --encoding-policy <fail | substitute | ignore>
	      Define  the  way	re2java	 treats	Unicode	surrogates.  With fail
	      re2java aborts with an error when	a  surrogate  is  encountered.
	      With  substitute	re2java	 silently replaces surrogates with the
	      error code point	0xFFFD.	 With  ignore  (the  default)  re2java
	      treats  surrogates  as  normal code points. The Unicode standard
	      says that	standalone surrogates are invalid, but real-world  li-
	      braries and programs behave in different ways.

       --flex-syntax -F
	      Partial  support for Flex	syntax:	in this	mode named definitions
	      don't need the equal sign	and  the  terminating  semicolon,  and
	      when used	they must be surrounded	with curly braces. Names with-
	      out curly	braces are treated as double-quoted strings.

       --goto-label
	      Use  "goto/label"	code model: encode DFA in form of labeled code
	      blocks connected with goto transitions across  blocks.  This  is
	      only supported for languages that	have a goto statement.

       --header	--type-header -t HEADER
	      Generate	a  HEADER file.	The contents of	the file can be	speci-
	      fied using special blocks	header:on and  header:off.  If	condi-
	      tions  are used, the generated header will have a	condition enum
	      automatically appended to	it (unless there is an explicit	condi-
	      tions block).

       -I PATH
	      Add PATH to the list of locations	which are used when  searching
	      for include files. This option is	useful in combination with in-
	      clude  block  or directive. re2java looks	for FILE in the	direc-
	      tory of the parent file and in the include  locations  specified
	      with -I option.

       --input <default	| custom>
	      Deprecated alias for --api. Option default corresponds to	simple
	      (it  is  indeed the default for most backends, but not for all).
	      Option custom corresponds	to generic.

       --input-encoding	<ascii | utf8>
	      Specify the way re2java parses regular expressions.  With	 ascii
	      (the  default)  re2java  handles input as	ASCII-encoded: any se-
	      quence of	code units is a	sequence of standalone 1-byte  charac-
	      ters.   With utf8	re2java	handles	input as UTF8-encoded and rec-
	      ognizes multibyte	characters.

       --invert-captures
	      Invert the meaning of capturing and non-capturing	groups.	By de-
	      fault (...) is capturing and (! ...) is non-capturing. With this
	      option (!	...) is	capturing and (...) is non-capturing.

       --lang <none | c	| d | go | haskell | java | js | ocaml | python	| rust
       | v | zig>
	      Specify the target language. Supported languages are C,  D,  Go,
	      Haskell,	Java,  JS, OCaml, Python, Rust,	V, Zig (more languages
	      can be added via user-defined syntax files, see the --syntax op-
	      tion). Option none disables default suntax configs, so that  the
	      target language is undefined.

       --location-format <gnu |	msvc>
	      Specify  location	 format	 in  messages.	With gnu locations are
	      printed as 'filename:line:column:	...'.  With msvc locations are
	      printed as 'filename(line,column)	...'.  The default is gnu.

       --loop-switch
	      Use "loop/switch"	code model: encode DFA in form of a loop  over
	      a	 switch	 statement,  where individual states are switch	cases.
	      State is stored  in  a  variable	yystate.  Transitions  between
	      states update yystate to the case	label of the destination state
	      and continue execution to	the head of the	loop.

       --nested-ifs -s
	      Use  nested if statements	instead	of switch statements in	condi-
	      tional jumps. This usually results in more efficient  code  with
	      non-optimizing compilers.

       --no-debug-info -i
	      Do  not output line directives. This may be useful when the gen-
	      erated code is stored in a version control system	(to avoid huge
	      autogenerated diffs on small changes).

       --no-generation-date
	      Suppress date output in the generated file.

       --no-version
	      Suppress version output in the generated file.

       --no-unsafe
	      Do not generate unsafe wrapper over YYPEEK (this option is  spe-
	      cific  to	 Rust).	 For  performance  reasons YYPEEK should avoid
	      bounds-checking, as  the	lexer  already	performs  end-of-input
	      checks  in a more	efficient way.	The user may choose to provide
	      a	safe YYPEEK definition,	or a definition	that is	unsafe only in
	      release builds, in which case the	--no-unsafe  option  helps  to
	      avoid warnings about redundant unsafe blocks.

       --output	-o OUTPUT
	      Specify the OUTPUT file.

       --posix-captures, -P
	      Enable  submatch	extraction  with POSIX-style capturing groups.
	      The result is collected into an array yybmatch of	capacity  2  *
	      YYMAXNMATCH, and yynmatch	is set to the number of	groups for the
	      matching rule.

       --posix-captvars
	      Enable  submatch	extraction  with POSIX-style capturing groups.
	      The result is collected into variables yytl<k>, yytr<k> for k-th
	      capturing	group.

       --recursive-functions
	      Use code model based on co-recursive functions, where  each  DFA
	      state is a separate function that	may call other state-functions
	      or itself.

       --reusable -r
	      Deprecated since version 2.2 (reusable blocks are	allowed	by de-
	      fault now).

       --skeleton -S
	      Ignore user-defined interface code and generate a	self-contained
	      "skeleton"  program.  Additionally,  generate  input  files with
	      strings derived from the regular grammar	and  compressed	 match
	      results  that  are used to verify	"skeleton" behavior on all in-
	      puts. This option	is useful for finding  bugs  in	 optimizations
	      and code generation. This	option is supported only for C.

       --storable-state	-f
	      Generate	a lexer	which can store	its inner state.  This is use-
	      ful in push-model	lexers which are stopped by an	outer  program
	      when there is not	enough input, and then resumed when more input
	      becomes available. In this mode users should additionally	define
	      YYGETSTATE  and YYSETSTATE primitives, and variables yych, yyac-
	      cept and state should be part of the stored lexer	state.

       --syntax	FILE
	      Load configurations from the specified FILE and  apply  them  on
	      top of the default syntax	file. Note that	FILE can define	only a
	      few  configurations  (if	it's  used to amend the	default	syntax
	      file), or	it can define a	whole new  language  backend  (in  the
	      latter case it is	recommended to use --lang none option).

       --tags -T
	      Enable submatch extraction with tags.

       --ucs2 --wide-chars -w
	      Generate	a lexer	that reads UCS2-encoded	input. re2java assumes
	      that the character range is 0 -- 0xFFFF and character size is  2
	      bytes.  This option implies --nested-ifs.

       --utf8 --utf-8 -8
	      Generate a lexer that reads input	in UTF-8 encoding. re2java as-
	      sumes  that  the	character range	is 0 --	0x10FFFF and character
	      size is 1	byte.

       --utf16 --utf-16	-x
	      Generate a lexer that reads UTF16-encoded	input. re2java assumes
	      that the character range is 0 -- 0x10FFFF	and character size  is
	      2	bytes.	This option implies --nested-ifs.

       --utf32 --unicode -u
	      Generate a lexer that reads UTF32-encoded	input. re2java assumes
	      that  the	character range	is 0 --	0x10FFFF and character size is
	      4	bytes.	This option implies --nested-ifs.

       --verbose
	      Output a short message in	case of	success.

       --vernum	-V
	      Show version information in MMmmpp format	(major,	minor, patch).

       --version -v
	      Show version information.

       --single-pass -1
	      Deprecated. Does nothing (single pass is the default now).

       --debug-output -d
	      Emit YYDEBUG invocations in the generated	code. This  is	useful
	      to trace lexer execution.

       --dump-adfa
	      Debug option: output DFA after tunneling (in .dot	format).

       --dump-cfg
	      Debug  option:  output  control  flow graph of tag variables (in
	      .dot format).

       --dump-closure-stats
	      Debug option: output statistics on the number of states in  clo-
	      sure.

       --dump-dfa-det
	      Debug  option:  output DFA immediately after determinization (in
	      .dot format).

       --dump-dfa-min
	      Debug option: output DFA after minimization (in .dot format).

       --dump-dfa-tagopt
	      Debug option: output DFA after tag optimizations (in  .dot  for-
	      mat).

       --dump-dfa-tree
	      Debug  option:  output DFA under construction with states	repre-
	      sented as	tag history trees (in .dot format).

       --dump-dfa-raw
	      Debug  option:  output  DFA  under  construction	with  expanded
	      state-sets (in .dot format).

       --dump-interf
	      Debug  option:  output  interference  table produced by liveness
	      analysis of tag variables.

       --dump-nfa
	      Debug option: output NFA (in .dot	format).

       --emit-dot -D
	      Instead of normal	output generate	lexer graph  in	 .dot  format.
	      The  output  can	be  converted  to  an  image  with the help of
	      Graphviz (e.g. something like dot	-Tpng -odfa.png	dfa.dot).

       --dfa-minimization <moore | table>
	      Internal option: DFA minimization	algorithm used by re2java. The
	      moore option is the Moore	algorithm (it is the default). The ta-
	      ble option is the	"table	filling"  algorithm.  Both  algorithms
	      should produce the same DFA up to	states relabeling; table fill-
	      ing  is simpler and much slower and serves as a reference	imple-
	      mentation.

       --eager-skip
	      Internal option: make the	generated lexer	advance	the input  po-
	      sition  eagerly  --  immediately after reading the input symbol.
	      This changes the default behavior	when the input position	is ad-
	      vanced lazily -- after transition	to the next state.

       --no-lookahead
	      Internal option, deprecated.  It used to	enable	TDFA(0)	 algo-
	      rithm. Unlike TDFA(1), TDFA(0) algorithm does not	use one-symbol
	      lookahead.  It applies register operations to the	incoming tran-
	      sitions rather than the outgoing ones.  Benchmarks  showed  that
	      TDFA(0) algorithm	is less	efficient than TDFA(1).

       --no-optimize-tags
	      Internal	option:	suppress optimization of tag variables (useful
	      for debugging).

       --posix-closure <gor1 | gtop>
	      Internal option: specify shortest-path algorithm	used  for  the
	      construction of epsilon-closure with POSIX disambiguation	seman-
	      tics:  gor1  (the	default) stands	for Goldberg-Radzik algorithm,
	      and gtop stands for "global topological order" algorithm.

       --posix-prectable <complex | naive>
	      Internal option: specify the algorithm  used  to	compute	 POSIX
	      precedence  table. The complex algorithm computes	precedence ta-
	      ble in one traversal of tag history tree and has quadratic  com-
	      plexity  in  the	number	of TNFA	states;	it is the default. The
	      naive algorithm has worst-case cubic complexity in the number of
	      TNFA states, but it is much simpler  than	 complex  and  may  be
	      slightly faster in non-pathological cases.

       --stadfa
	      Internal	option,	 deprecated.   It  used	to enable staDFA algo-
	      rithm, which differs from	TDFA in	that register  operations  are
	      placed  in  states rather	than on	transitions. Benchmarks	showed
	      that staDFA algorithm is less efficient than TDFA.

       --fixed-tags <none | toplevel | all>
	      Internal option:	specify	 whether  the  fixed-tag  optimization
	      should  be  applied  to  all tags	(all), none of them (none), or
	      only those in toplevel concatenation (toplevel). The default  is
	      all.   "Fixed"  tags  are	 those that are	located	within a fixed
	      distance to some other tag (called "base"). In such  cases  only
	      the base tag needs to be tracked,	and the	value of the fixed tag
	      can  be computed as the value of the base	tag plus a static off-
	      set. For tags that are under alternative	or  repetition	it  is
	      also necessary to	check if the base tag has a no-match value (in
	      that case	fixed tag should also be set to	no-match, disregarding
	      the  offset).  For  tags in top-level concatenation the check is
	      not needed, because they always match.

   Warnings
       Warnings	can be invividually enabled, disabled and turned into  an  er-
       ror.

       -W     Turn on all warnings.

       -Werror
	      Turn  warnings  into errors. Note	that this option alone doesn't
	      turn on any warnings; it only affects those warnings  that  have
	      been turned on so	far or will be turned on later.

       -W<warning>
	      Turn on warning.

       -Wno-<warning>
	      Turn off warning.

       -Werror-<warning>
	      Turn  on warning and treat it as an error	(this implies -W<warn-
	      ing>).

       -Wno-error-<warning>
	      Don't treat this particular warning as an	 error.	 This  doesn't
	      turn off the warning itself.

       -Wcondition-order
	      Warn  if	the generated program makes implicit assumptions about
	      condition	numbering. One should use either  --header  option  or
	      conditions  block	 to  generate  a mapping of condition names to
	      numbers and then use the autogenerated condition names.

       -Wempty-character-class
	      Warn if a	regular	expression contains an empty character	class.
	      Trying  to  match	 an  empty  character class makes no sense: it
	      should always fail.  However, for	backwards  compatibility  rea-
	      sons  re2java permits empty character classes and	treats them as
	      empty strings. Use the --empty-class option to  change  the  de-
	      fault behavior.

       -Wmatch-empty-string
	      Warn  if	a  rule	is nullable (matches an	empty string).	If the
	      lexer runs in a loop and the empty match is  unintentional,  the
	      lexer may	unexpectedly hang in an	infinite loop.

       -Wswapped-range
	      Warn  if	the  lower  bound of a range is	greater	than its upper
	      bound. The default  behavior  is	to  silently  swap  the	 range
	      bounds.

       -Wundefined-control-flow
	      Warn  if	some input strings cause undefined control flow	in the
	      lexer (the faulty	patterns are reported).	This  is  a  dangerous
	      and common mistake. It can be easily fixed by adding the default
	      rule * which has the lowest priority, matches any	code unit, and
	      always consumes a	single code unit.

       -Wunreachable-rules
	      Warn about rules that are	shadowed by other rules	and will never
	      match.

       -Wuseless-escape
	      Warn  if	a symbol is escaped when it shouldn't be.  By default,
	      re2java silently ignores such escapes, but this may as well  in-
	      dicate a typo or an error	in the escape sequence.

       -Wnondeterministic-tags
	      Warn  if	a  tag	has  n-th degree of nondeterminism, where n is
	      greater than 1.

       -Wsentinel-in-midrule
	      Warn if the sentinel symbol occurs in the	middle of a  rule  ---
	      this  may	 cause reads past the end of buffer, crashes or	memory
	      corruption in the	generated lexer. This warning is only applica-
	      ble if the sentinel method of checking for the end of  input  is
	      used.   It  is set to an error if	re2c:sentinel configuration is
	      used.

       -Wundefined-syntax-config
	      Warn if the syntax file specified	with --syntax option is	 miss-
	      ing  definitions	of some	configurations.	This helps to maintain
	      user-defined syntax files: if a new release adds configurations,
	      old syntax file will raise a warning, and	the user will be noti-
	      fied. If some configurations are unused and do not need a	defin-
	      ition, they should be explicitly set to <undefined>.

   Syntax files
       Support for different languages in re2c is based	on the idea of	syntax
       files.	A  syntax  file	is a configuration file	that defines syntax of
       the target language -- not the whole language, but a small part	of  it
       that  is	used by	the generated code. Syntax files make re2c very	flexi-
       ble, but	they should not	be used	as a replacement for re2c:  configura-
       tions: their purpose is to define syntax	of the target language,	not to
       customize  one  particular  lexer. All supported	languages have default
       syntax files that are part of the distribution (see include/syntax sub-
       directory); they	are also embedded in the re2java  binary.   Users  may
       provide	a  custom  syntax file that overrides a	few configurations for
       one of supported	languages, or they may choose to redefine all configu-
       rations (in that	case --lang none option	should be used).  Syntax files
       contain configurations of four different	kinds: feature lists, language
       configurations, inplace configurations and code templates.

       Feature lists
	  A few	list configurations define various  features  supported	 by  a
	  given	 backend,  so  that re2java may	give a clear error if the user
	  tries	to enable an unsupported feature:

	  supported_apis
		 A list	of  supported  APIs  with  possible  elements  simple,
		 record, generic.

	  supported_api_styles
		 A  list  of supported API styles with possible	elements func-
		 tions,	free-form.

	  supported_code_models
		 A list	 of  supported	code  models  with  possible  elements
		 goto-label, loop-switch, recursive-functions.

	  supported_targets
		 A  list  of  supported	codegen	targets	with possible elements
		 code, dot, skeleton.

	  supported_features
		 A  list  of  supported	 features   with   possible   elements
		 nested-ifs,  bitmaps,	computed-gotos,	 case-ranges, monadic,
		 unsafe, tags, captures, captvars.

       Language	configurations
	  A few	boolean	configurations describe	features of  the  target  lan-
	  guage	that affect re2java parser and code generator:

	  semicolons
		 Non-zero if the language uses semicolons after	statements.

	  backtick_quoted_strings
		 Non-zero if the language has backtick-quoted strings.

	  single_quoted_strings
		 Non-zero if the language has single-quoted strings.

	  indentation_sensitive
		 Non-zero if the language is indentation sensitive.

	  wrap_blocks_in_braces
		 Non-zero  if  compound	 statements  must  be wrapped in curly
		 braces.

       Inplace configurations
	  Syntax files define initial values of	all re2c:  configurations,  as
	  they	may differ for different languages. See	configurations section
	  for a	full list of all inplace configurations	and their meaning.

       Code templates
	  Code templates define	syntax of the target language. They are	 writ-
	  ten  in  a simple domain-specific language with the following	formal
	  grammar:

	      code-template ::
		    name '=' code-exprs	';'
		  | CODE_TEMPLATE ';'
		  | '<undefined>' ';'

	      code-exprs ::
		    <EMPTY>
		  | code-exprs code-expr

	      code-expr	::
		    STRING
		  | VARIABLE
		  | optional
		  | list

	      optional ::
		    '('	CONDITIONAL '?'	code-exprs ')'
		  | '('	CONDITIONAL '?'	code-exprs ':' code-exprs ')'

	      list ::
		    '['	VARIABLE ':' code-exprs	']'
		  | '['	VARIABLE '{' NUMBER '}'	':' code-exprs ']'
		  | '['	VARIABLE '{' NUMBER ','	NUMBER '}' ':' code-exprs ']'

	  A code template is a sequence	of  string  literals,  variables,  op-
	  tional  elements and lists, or a reference to	another	code template,
	  or a special value <undefined>. Variables are	placeholders that  are
	  substituted  during  code  generation	phase. List variables are spe-
	  cial:	when expanding list templates, re2java repeats expressions the
	  right	hand side of the column	a few times, each time	replacing  oc-
	  currences of the list	variable with a	value specific to this repeti-
	  tion.	 Lists	have optional bounds (negative values are counted from
	  the end, e.g.	-1 means the last element).  Conditional  names	 start
	  with	a  dot.	  Both	conditionals and variables may be either local
	  (specific to the given code template)	or global (allowed in all code
	  templates). When re2java reads syntax	file, it checks	that each code
	  template uses	only the variables and conditionals that  are  allowed
	  in it.

	  For  example,	 the following code template defines if-then-else con-
	  struct for a C-like language:

	      code:if_then_else	=
		  [branch{0}: topindent	"if " cond " {"	nl
		      indent [stmt: stmt] dedent]
		  [branch{1:-1}: topindent "} else" (.cond ? " if " cond) " {" nl
		      indent [stmt: stmt] dedent]
		  topindent "}"	nl;

	  Here branch is a list	 variable:  branch{0}  expands	to  the	 first
	  branch  (which  is  special, as there	is no else part), branch{1:-1}
	  expands to all remaining branches (if	any).  stmt  is	 also  a  list
	  variable:  [stmt:  stmt]  is a nested	list that expands to a list of
	  statements in	the body of the	current	branch.	topindent, indent, de-
	  dent and nl are global variables, and	.cond is a  local  conditional
	  (their meaning is described below). This code	template could produce
	  the following	code:

	      if x {
		  // do	something
	      }	else if	y {
		  // do	something else
	      }	else {
		  // don't do anything
	      }

	  Here's  a list of all	code templates supported by re2java with their
	  local	variables and conditionals. Note that a	particular  definition
	  may, but does	not have to use	local variables	and conditionals.  Any
	  unused code templates	should be set to <undefined>.

	  code:var_local
		 Declaration  or  definition  of  a  local variable. Supported
		 variables: type (the type of the variable), name  (its	 name)
		 and  init  (initial value, if any). Conditionals: .init (true
		 if there is an	initializer).

	  code:var_global
		 Same as code:var_local, except	that it's used in top-level.

	  code:const_local
		 Definition of a local	constant.  Supported  variables:  type
		 (the type of the constant), name (its name) and init (initial
		 value).

	  code:const_global
		 Same as code:const_local, except that it's used in top-level.

	  code:array_local
		 Definition  of	 a  local  array (table). Supported variables:
		 type (the type	of array elements), name  (array  name),  size
		 (its size), row (a list variable that does not	itself produce
		 any  code, but	expands	list expression	as many	times as there
		 are rows in the table)	and elem (a list variable that expands
		 to all	table elements in the current row -- it's meant	to  be
		 nested	in the row list).

	  code:array_global
		 Same as code:array_local, except that it's used in top-level.

	  code:array_elem
		 Reference  to an element of an	array (table). Supported vari-
		 ables:	array (the name	of the array) and index	(index of  the
		 element).

	  code:enum
		 Definition  of	an enumeration (it may be defined using	a spe-
		 cial language construct for enumerations, or simply as	a  few
		 standalone   constants).    Supported	 variables   are  type
		 (user-defined enumeration type	or  type  of  the  constants),
		 elem  (list variable that expands to the name of each member)
		 and init (initializer for each	member).  Conditionals:	 .init
		 (true if there	is an initializer).

	  code:enum_elem
		 Enumeration  element  (a member of a user-defined enumeration
		 type or a name	of a constant, depending on how	 code:enum  is
		 defined).  Supported variables	are name (the name of the ele-
		 ment) and type	(its type).

	  code:assign
		 Assignment  statement.	Supported variables are	lhs (left hand
		 side) and rhs (right hand side).

	  code:type_int
		 Signed	integer	type.

	  code:type_uint
		 Unsigned integer type.

	  code:type_yybm
		 Type of elements in the yybm table.

	  code:type_yytarget
		 Type of elements in the yytarget table.

	  code:cmp_eq
		 Operator "equals".

	  code:cmp_ne
		 Operator "not equals".

	  code:cmp_lt
		 Operator "less	than".

	  code:cmp_gt
		 Operator "greater than"

	  code:cmp_le
		 Operator "less	or equal"

	  code:cmp_ge
		 Operator "greater or equal"

	  code:if_then_else
		 If-then-else statement	with one or more  branches.  Supported
		 variables:  branch (a list variable that does not itself pro-
		 duce any code,	but expands list expression as many  times  as
		 there	are  branches),	cond (condition	of the current branch)
		 and stmt (a list variable that	expands	to all	statements  in
		 the current branch). Conditionals: .cond (true	if the current
		 branch	has a condition), .many	(true if there's more than one
		 branch).

	  code:if_then_else_oneline
		 A  specialization  of code:if_then_else for the case when all
		 branches have one-line	statements. If	this  is  <undefined>,
		 code:if_then_else is used instead.

	  code:switch
		 A  switch  statement  with one	or more	cases. Supported vari-
		 ables:	expr (the switched-on expression)  and	case  (a  list
		 variable  that	 expands  to  all cases-groups with their code
		 blocks).

	  code:switch_cases
		 A group of switch cases that maps to  a  single  code	block.
		 Supported variables are case (a list variable that expands to
		 all  cases  in	this group) and	stmt (a	list variable that ex-
		 pands to all statements in the	code block.

	  code:switch_cases_oneline
		 A specialization of code:switch_cases for the case  when  the
		 code  block  consists of a single one-line statement. If this
		 is <undefined>, code:switch_cases is used instead.

	  code:switch_case_range
		 A single switch case that covers a range of values  (possibly
		 consisting  of	 a  single  value). Supported variable:	val (a
		 list variable that expands to all values in the range).  Sup-
		 ported	 conditionals:	.many  (true  if there's more than one
		 value in the range) and .char_literals	(true  if  this	 is  a
		 switch	 on  character literals	-- some	languages provide spe-
		 cial syntax for this case).

	  code:switch_case_default
		 Default switch	case.

	  code:loop
		 A loop	that runs forever (unless interrupted  from  the  loop
		 body).	 Supported variables: label (loop label), stmt (a list
		 variable that expands to all statements in the	loop body).

	  code:continue
		 Continue  statement.  Supported  variables: label (label from
		 which to continue execution).

	  code:goto
		 Goto statement. Supported variables: label (label of the jump
		 target).

	  code:fndecl
		 Function declaration.	Supported  variables:  name  (function
		 name),	type (return type), arg	(a list	variable that does not
		 itself	 produce  code,	 but  expands  list expression as many
		 times as there	are function arguments), argname (name of  the
		 current  argument),  argtype  (type of	the current argument).
		 Conditional: .type (true if this is a non-void	function).

	  code:fndef
		 Like code:fndecl, but used for	function  definitions,	so  it
		 has  one  additional  list  variable stmt that	expands	to all
		 statements in the function body.

	  code:fncall
		 Function call statement. Supported variables: name  (function
		 name),	 retval	 (l-value where	the return value is stored, if
		 any) and arg (a list variable that expands  to	 all  function
		 arguments).   Conditionals:  .args  (true if the function has
		 arguments) and	.retval	(true if  return  value	 needs	to  be
		 saved).

	  code:tailcall
		 Tail  call  statement.	 Supported  variables:	name (function
		 name),	and arg	(a list	variable that expands to all  function
		 arguments).   Conditionals:  .args  (true if the function has
		 arguments) and	.retval	(true if this is a non-void function).

	  code:recursive_functions
		 Program body with --recursive-functions code model. Supported
		 variables: fn (a list variable	that does not  itself  produce
		 any  code, but	expands	list expression	as many	times as there
		 are functions), fndecl	(declaration of	the current  function)
		 and fndef (definition of the current function).

	  code:fingerprint
		 The fingerprint at the	top of the generated output file. Sup-
		 ported	 variables: ver	(re2java version that was used to gen-
		 erate this) and date (generation date).

	  code:line_info
		 The format of line directives (if this	is set to <undefined>,
		 no directives are generated). Supported variables: line (line
		 number) and file (filename).

	  code:abort
		 A statement that aborts program execution.

	  code:yydebug
		 YYDEBUG statement, possibly specialized for  different	 APIs.
		 Supported variables: YYDEBUG, yyrecord, yych (map to the cor-
		 responding re2c: configurations), state (DFA state number).

	  code:yypeek
		 YYPEEK	 statement,  possibly  specialized for different APIs.
		 Supported  variables:	YYPEEK,	 YYCTYPE,  YYINPUT,  YYCURSOR,
		 yyrecord,  yych  (map	to  the	corresponding re2c: configura-
		 tions). Conditionals: .cast (true if re2c:yych:conversion  is
		 set to	non-zero).

	  code:yyskip
		 YYSKIP	 statement,  possibly  specialized for different APIs.
		 Supported variables: YYSKIP, YYCURSOR,	yyrecord (map  to  the
		 corresponding re2c: configurations).

	  code:yybackup
		 YYBACKUP  statement, possibly specialized for different APIs.
		 Supported variables: YYBACKUP,	YYCURSOR,  YYMARKER,  yyrecord
		 (map to the corresponding re2c: configurations).

	  code:yybackupctx
		 YYBACKUPCTX  statement,  possibly  specialized	 for different
		 APIs.	Supported  variables:  YYBACKUPCTX,  YYCURSOR,	YYCTX-
		 MARKER,  yyrecord  (map to the	corresponding re2c: configura-
		 tions).

	  code:yyskip_yypeek
		 Combined code:yyskip and code:yypeek statement	 (defaults  to
		 code:yyskip followed by code:yypeek).

	  code:yypeek_yyskip
		 Combined  code:yypeek	and code:yyskip	statement (defaults to
		 code:yypeek followed by code:yyskip).

	  code:yyskip_yybackup
		 Combined code:yyskip and code:yybackup	statement (defaults to
		 code:yyskip followed by code:yybackup).

	  code:yybackup_yyskip
		 Combined code:yybackup	and code:yyskip	statement (defaults to
		 code:yybackup followed	by code:yyskip).

	  code:yybackup_yypeek
		 Combined code:yybackup	and code:yypeek	statement (defaults to
		 code:yybackup followed	by code:yypeek).

	  code:yyskip_yybackup_yypeek
		 Combined code:yyskip, code:yybackup and code:yypeek statement
		 (defaults to``code:yyskip`` followed  by  code:yybackup  fol-
		 lowed by code:yypeek).

	  code:yybackup_yypeek_yyskip
		 Combined code:yybackup, code:yypeek and code:yyskip statement
		 (defaults  to``code:yybackup``	 followed  by code:yypeek fol-
		 lowed by code:yyskip).

	  code:yyrestore
		 YYRESTORE statement, possibly specialized for different APIs.
		 Supported variables: YYRESTORE, YYCURSOR, YYMARKER,  yyrecord
		 (map to the corresponding re2c: configurations).

	  code:yyrestorectx
		 YYRESTORECTX  statement,  possibly  specialized for different
		 APIs.	Supported variables:  YYRESTORECTX,  YYCURSOR,	YYCTX-
		 MARKER,  yyrecord  (map to the	corresponding re2c: configura-
		 tions).

	  code:yyrestoretag
		 YYRESTORETAG statement, possibly  specialized	for  different
		 APIs.	 Supported variables: YYRESTORETAG, YYCURSOR, yyrecord
		 (map to the corresponding  re2c:  configurations),  tag  (the
		 name of tag variable used to restore position).

	  code:yyshift
		 YYSHIFT  statement,  possibly specialized for different APIs.
		 Supported variables: YYSHIFT, YYCURSOR, yyrecord (map to  the
		 corresponding	re2c:  configurations),	 offset	(the number of
		 code units to shift the current position).

	  code:yyshiftstag
		 YYSHIFTSTAG statement,	 possibly  specialized	for  different
		 APIs.	 Supported  variables: YYSHIFTSTAG, yyrecord, negative
		 (map to the corresponding  re2c:  configurations),  tag  (tag
		 variable  which  needs	 to be shifted), offset	(the number of
		 code units to shift). Conditionals: .nested (true if this  is
		 a  nested  tag	 --  in	 this  case  its  value	 may  equal to
		 re2c:tags:negative, which should not be shifted).

	  code:yyshiftmtag
		 YYSHIFTMTAG statement,	 possibly  specialized	for  different
		 APIs.	 Supported  variables: YYSHIFTMTAG (maps to the	corre-
		 sponding re2c:	configuration),	tag (tag variable which	 needs
		 to be shifted), offset	(the number of code units to shift).

	  code:yystagp
		 YYSTAGP  statement,  possibly specialized for different APIs.
		 Supported variables: YYSTAGP, YYCURSOR, yyrecord (map to  the
		 corresponding	re2c:  configurations),	tag (tag variable that
		 should	be updated).

	  code:yymtagp
		 YYMTAGP statement, possibly specialized for  different	 APIs.
		 Supported variables: YYMTAGP (maps to the corresponding re2c:
		 configuration), tag (tag variable that	should be updated).

	  code:yystagn
		 YYSTAGN  statement,  possibly specialized for different APIs.
		 Supported variables: YYSTAGN, negative, yyrecord (map to  the
		 corresponding	re2c:  configurations),	tag (tag variable that
		 should	be updated).

	  code:yymtagn
		 YYMTAGN statement, possibly specialized for  different	 APIs.
		 Supported variables: YYMTAGN (maps to the corresponding re2c:
		 configuration), tag (tag variable that	should be updated).

	  code:yycopystag
		 YYCOPYSTAG  statement,	 possibly  specialized	for  different
		 APIs.	Supported variables: YYCOPYSTAG, yyrecord (map to  the
		 corresponding re2c: configurations), lhs, rhs (left and right
		 hand side tag variables of the	copy operation).

	  code:yycopymtag
		 YYCOPYMTAG  statement,	 possibly  specialized	for  different
		 APIs.	Supported variables: YYCOPYMTAG, yyrecord (map to  the
		 corresponding re2c: configurations), lhs, rhs (left and right
		 hand side tag variables of the	copy operation).

	  code:yygetaccept
		 YYGETACCEPT  statement,  possibly  specialized	 for different
		 APIs.	Supported variables: YYGETACCEPT, yyrecord (map	to the
		 corresponding re2c: configurations), var (maps	to  re2c:yyac-
		 cept configuration).

	  code:yysetaccept
		 YYSETACCEPT  statement,  possibly  specialized	 for different
		 APIs.	Supported variables: YYSETACCEPT, yyrecord (map	to the
		 corresponding re2c: configurations), var (maps	to  re2c:yyac-
		 cept  configuration)  and  val	(numeric value of the accepted
		 rule).

	  code:yygetcond
		 YYGETCOND statement, possibly specialized for different APIs.
		 Supported variables: YYGETCOND, yyrecord (map to  the	corre-
		 sponding re2c:	configurations), var (maps to re2c:yycond con-
		 figuration).

	  code:yysetcond
		 YYSETCOND statement, possibly specialized for different APIs.
		 Supported  variables:	YYSETCOND, yyrecord (map to the	corre-
		 sponding re2c:	configurations), var (maps to re2c:yycond con-
		 figuration) and val (numeric condition	identifier).

	  code:yygetstate
		 YYGETSTATE  statement,	 possibly  specialized	for  different
		 APIs.	 Supported variables: YYGETSTATE, yyrecord (map	to the
		 corresponding re2c: configurations), var (maps	 to  re2c:yys-
		 tate configuration).

	  code:yysetstate
		 YYSETSTATE  statement,	 possibly  specialized	for  different
		 APIs.	Supported variables: YYSETSTATE, yyrecord (map to  the
		 corresponding	re2c:  configurations),	var (maps to re2c:yys-
		 tate configuration) and val (state number).

	  code:yylessthan
		 YYLESSTHAN  statement,	 possibly  specialized	for  different
		 APIs.	 Supported  variables:	YYLESSTHAN, YYCURSOR, YYLIMIT,
		 yyrecord (map to  the	corresponding  re2c:  configurations),
		 need  (the  number  of	 code  units to	check against).	Condi-
		 tional: .many (true if	the need is more than one).

	  code:yybm_filter
		 Condition that	is used	to filter out yych values that are not
		 covered by the	yybm table (used with --bitmaps	option).  Sup-
		 ported	variable: yych (maps to	re2c:yych configuration).

	  code:yybm_match
		 The format of yybm table check	(generated with	--bitmaps  op-
		 tion).	 Supported  variables:	yybm,  yych (map to the	corre-
		 sponding re2c:	configurations), offset	(offset	 in  the  yybm
		 table that needs to be	added to yych) and mask	(bit mask that
		 should	 be applied to the table entry to retrieve the boolean
		 value that needs to be	checked)

	  Here's a list	of all global variables	that  are  allowed  in	syntax
	  files:

	  nl	 A newline.

	  indent A variable that does not produce any code, but	has a side-ef-
		 fect of increasing indentation	level.

	  dedent A variable that does not produce any code, but	has a side-ef-
		 fect of decreasing indentation	level.

	  topindent
		 Indentation  string  for  the	current	statement. Indentation
		 level is tracked and automatically updated by the code	gener-
		 ator.

	  Here's a list	of all global conditionals that	are allowed in	syntax
	  files:

	  .api.simple
		 True  if  simple API is used (--api simple or re2c:api	= sim-
		 ple).

	  .api.generic
		 True if generic API is	used  (--api  generic  or  re2c:api  =
		 generic).

	  .api.record
		 True  if  record  API	is  used  (--api  record or re2c:api =
		 record).

	  .api_style.functions
		 True if function-like API style  is  used  (re2c:api-style  =
		 functions).

	  .api_style.freeform
		 True  if  free-form  API  style  is  used  (re2c:api-style  =
		 free-form).

	  .case_ranges
		 True if case ranges  feature  is  enabled  (--case-ranges  or
		 re2c:case-ranges = 1).

	  .code_model.goto_label
		 True  if   code model based on	goto/label is used (--goto-la-
		 bel).

	  .code_model.loop_switch
		 True  if  code	  model	  based	  on   loop/switch   is	  used
		 (--loop-switch).

	  .code_model.recursive_functions
		 True  if  code	 model	based  on  recursive functions is used
		 (--recursive-function).

	  .date	 True if the generated fingerprint should  contain  generation
		 date.

	  .loop_label
		 True  if  re2java generated loops must	have a label (re2c:la-
		 bel:yyloop is set to a	nonempty string).

	  .monadic
		 True if the generated code should be monadic (re2c:monadic  =
		 1).  This is only relevant for	pure functional	languages.

	  .start_conditions
		 True if start conditions are enabled (--start-conditions).

	  .storable_state
		 True if storable state	is enabled (--storable-state).

	  .unsafe
		 True if re2java should	use "unsafe" blocks in order to	gener-
		 ate  faster  code  (--unsafe,	re2c:unsafe = 1). This is only
		 relevant for languages	that have "unsafe" feature.

	  .version
		 True if the generated fingerprint should contain re2java ver-
		 sion.

HANDLING THE END OF INPUT
       One of the main problems	for the	lexer is to know when to stop.	 There
       are a few terminating conditions:

        the  lexer may	match some rule	(including default rule	*) and come to
	 a final state

        the lexer may fail to match any rule and come to a default state

        the lexer may reach the end of	input

       The first two conditions	terminate the lexer in	a  "natural"  way:  it
       comes  to  a state with no outgoing transitions,	and the	matching auto-
       matically stops.	The third condition, end of input,  is	different:  it
       may  happen  in	any  state, and	the lexer should be able to handle it.
       Checking	for the	end of input interrupts	the normal lexer workflow  and
       adds  conditional  branches  to	the generated program, therefore it is
       necessary to minimize the number	of such	checks.	re2java	supports a few
       different methods for handling the end of input.	Which one to  use  de-
       pends on	the complexity of regular expressions, the need	for buffering,
       performance  considerations  and	other factors. Here is a list of meth-
       ods:

        Sentinel.  This method	eliminates the	need  for  the	end  of	 input
	 checks	 altogether.  It  is  simple and efficient, but	limited	to the
	 case when there is a natural "sentinel" character that	can never  oc-
	 cur  in valid input. This character may still occur in	invalid	input,
	 but it	should not be allowed by the regular expressions, except  per-
	 haps as the last character of a rule. The sentinel is appended	at the
	 end  of  input	and serves as a	stop signal: when the lexer reads this
	 character, it is either a syntax error	or the end of input.  In  both
	 cases	the  lexer  should stop. This method is	used if	YYFILL is dis-
	 abled with re2c:yyfill:enable = 0; and	re2c:eof has the default value
	 -1.

        Sentinel with bounds checks.  This method is generic: it  allows  one
	 to  handle any	input without restrictions on the regular expressions.
	 The idea is to	reduce the number of end of input checks by performing
	 them only on certain characters. Similar to  the  "sentinel"  method,
	 one  of  the characters is chosen as a	"sentinel" and appended	at the
	 end of	input. However,	there is no restriction	on where the  sentinel
	 may  occur  (in  fact,	 any  character	can be chosen for a sentinel).
	 When the lexer	reads  this  character,	 it  additionally  performs  a
	 bounds	 check.	  If  the current position is within bounds, the lexer
	 resumes matching and handles the sentinel  as	a  regular  character.
	 Otherwise it invokes YYFILL (unless it	is disabled). If more input is
	 supplied,  the	 lexer will rematch the	last character and continue as
	 if the	sentinel wasn't	there. Otherwise it must be the	 real  end  of
	 input,	 and  the  lexer  stops. This method is	used when re2c:eof has
	 non-negative value (it	should be set to the numeric value of the sen-
	 tinel). YYFILL	is optional.

        Bounds	checks with padding.  This method is generic, and  it  may  be
	 faster	 than the "sentinel with bounds	checks"	method,	but it is also
	 more complex. The idea	is to partition	DFA states into	strongly  con-
	 nected	 components  (SCCs)  and  generate  a single check per SCC for
	 enough	characters to cover the	longest	non-looping path in this  SCC.
	 This  reduces the number of checks, but there is a problem with short
	 lexemes at the	end of input, as the check requires enough  characters
	 to  cover  the	longest	lexeme.	This can be fixed by padding the input
	 with a	few fake characters that do not	form a valid lexeme suffix (so
	 that the lexer	cannot match them). The	length of  padding  should  be
	 YYMAXFILL,  generated with a max block. If there is not enough	input,
	 the lexer invokes YYFILL which	should supply at  least	 the  required
	 number	of characters or not return.  This method is used if YYFILL is
	 enabled and re2c:eof is -1 (this is the default configuration).

        Custom	 checks.   Generic API allows one to override basic operations
	 like reading a	character, which makes	it  possible  to  include  the
	 end-of-input  checks  as  part	of them.  This approach	is error-prone
	 and should be used with caution.  To  use  a  custom  method,	enable
	 generic  API  with --api custom or re2c:api = custom; and disable de-
	 fault bounds checks with re2c:yyfill:enable = 0; or re2c:yyfill:check
	 = 0;.

       The following subsections contain an example of each method.

   Sentinel
       This example uses a sentinel character to handle	the end	of input.  The
       program	counts	space-separated	words in a null-terminated string. The
       sentinel	is null: it is the last	character of each input	string,	and it
       is not allowed in the middle of a lexeme	by any of the rules  (in  par-
       ticular,	 it  is	 not  included in character ranges where it is easy to
       overlook). If a null occurs in the middle of a string, it is  a	syntax
       error  and  the lexer will match	default	rule *,	but it won't read past
       the end of  input  or  crash  (use  -Wsentinel-in-midrule  warning  and
       re2c:sentinel  configuration  to	 verify	 this).	Configuration re2c:yy-
       fill:enable = 0;	suppresses the generation of bounds checks and	YYFILL
       invocations.

	  // re2java $INPUT -o $OUTPUT

	  class	Main {
	      // Expects a null-terminated string.
	      static int lex(String yyinput) {
		  int yycursor = 0;
		  int count = 0;

		  loop:	while (true) {
		      /*!re2c
			  re2c:YYCTYPE = "char";
			  re2c:YYPEEK =	"yyinput.charAt(yycursor)";
			  re2c:yyfill:enable = 0;

			  *	 { return -1; }
			  [\x00] { return count; }
			  [a-z]+ { count += 1; continue	loop; }
			  [ ]+	 { continue loop; }
		      */
		  }
	      }

	      public static void main(String []args) {
		  assert lex("\0") == 0;
		  assert lex("one two three\0")	== 3;
		  assert lex("f0ur\0") == -1;
	      }
	  };

   Sentinel with bounds	checks
       This  example uses sentinel with	bounds checks to handle	the end	of in-
       put (this  method  was  added  in  version  1.2).  The  program	counts
       space-separated	single-quoted strings. The sentinel character is null,
       which is	specified with re2c:eof	= 0; configuration. As in the sentinel
       method, null is the last	character of each input	string,	but it is  al-
       lowed in	the middle of a	rule (for example, 'aaa\0aa'\0 is valid	input,
       but  'aaa\0  is	a  syntax error).  Bounds checks are generated in each
       state that matches an input character,  but  they  are  scoped  to  the
       branch  that handles null. Bounds checks	are of the form	YYLIMIT	<= YY-
       CURSOR or YYLESSTHAN(1) with generic API. If  the  check	 condition  is
       true,  lexer  has  reached  the end of input and	should stop (YYFILL is
       disabled	with re2c:yyfill:enable	=  0;  as  the	input  fits  into  one
       buffer,	see  the YYFILL	with sentinel section for an example that uses
       YYFILL).	Reaching the end of input opens	three  possibilities:  if  the
       lexer  is  in  the initial state	it will	match the end-of-input rule $,
       otherwise it may	fallback to a previously matched rule  (including  de-
       fault	rule	*)    or    go	  to	a   default   state,   causing
       -Wundefined-control-flow.

	  // re2java $INPUT -o $OUTPUT

	  class	Main {
	      // Expects a null-terminated string.
	      static int lex(String yyinput) {
		  int yycursor = 0;
		  int yymarker = 0;
		  int yylimit =	yyinput.length() - 1; // yylimit points	at the terminating null
		  int count = 0;

		  loop:	while (true) {
		      /*!re2c
			  re2c:YYCTYPE = "char";
			  re2c:YYPEEK =	"yyinput.charAt(yycursor)";
			  re2c:yyfill:enable = 0;
			  re2c:eof = 0;

			  str =	['] ([^'\\] | [\\][^])*	['];

			  *    { return	-1; }
			  $    { return	count; }
			  str  { count += 1; continue loop; }
			  [ ]+ { continue loop;	}
		      */
		  }
	      }

	      public static void main(String []args) {
		  assert lex("\0") == 0;
		  assert lex("'qu\0tes'	'are' 'fine: \\'' \0") == 3;
		  assert lex("'unterminated\\'\0") == -1;
	      }
	  };

   Bounds checks with padding
       This example uses bounds	checks with padding to handle the end of input
       (this method is enabled by default). The	program	counts space-separated
       single-quoted strings. There is a padding of YYMAXFILL null  characters
       appended	 at  the  end of input,	where YYMAXFILL	value is autogenerated
       with a max block. It is not necessary to	use null for padding  ---  any
       characters  can be used as long as they do not form a valid lexeme suf-
       fix (in this example padding should not contain single quotes, as  they
       may  be	mistaken  for  a suffix	of a single-quoted string). There is a
       "stop" rule that	matches	the first padding character (null) and	termi-
       nates  the  lexer  (note	 that it checks	if null	is at the beginning of
       padding,	otherwise it is	a syntax error). Bounds	checks	are  generated
       only  in	some states that are determined	by the strongly	connected com-
       ponents of the underlying automaton. Checks have	the  form  (YYLIMIT  -
       YYCURSOR) < n or	YYLESSTHAN(n) with generic API,	where n	is the minimum
       number  of characters that are needed for the lexer to proceed (it also
       means that the next bounds check	will occur in at most  n  characters).
       If  the check condition is true,	the lexer has reached the end of input
       and will	invoke YYFILL(n) that should either supply at  least  n	 input
       characters  or not return. In this example YYFILL always	fails and ter-
       minates the lexer with an error (which is fine because the  input  fits
       into  one  buffer).  See	the YYFILL with	padding	section	for an example
       that refills the	input buffer with YYFILL.

	  // re2java $INPUT -o $OUTPUT

	  class	Main {
	      /*!max:re2c*/

	      // Expects yymaxfill-padded string.
	      static int lex(String str) {
		  // Pad string	with yymaxfill zeroes at the end.
		  byte[] yyinput = new byte[str.length() + YYMAXFILL];
		  System.arraycopy(str.getBytes(), 0, yyinput, 0, str.length());

		  int yycursor = 0;
		  int yylimit =	yyinput.length;
		  int count = 0;

		  loop:	while (true) {
		      /*!re2c
			  re2c:YYCTYPE = "byte";
			  re2c:YYPEEK =	"yyinput[yycursor]";
			  re2c:YYFILL =	"return	-1;";

			  str =	['] ([^'\\] | [\\][^])*	['];

			  [\x00] {
			      // Check that it is the sentinel,	not some unexpected null.
			      return (yycursor - 1 == str.length()) ? count : -1;
			  }
			  str  { count += 1; continue loop; }
			  [ ]+ { continue loop;	}
			  *    { return	-1; }
		      */
		  }
	      }

	      public static void main(String []args) {
		  assert lex("") == 0;
		  assert lex("'qu\0tes'	'are' 'fine: \\'' ") ==	3;
		  assert lex("'unterminated\\'") == -1;
		  assert lex("'unexpected \00 null\\'")	== -1;
	      }
	  };

   Custom checks
       This example uses  a  custom  end-of-input  handling  method  based  on
       generic API.  The program counts	space-separated	single-quoted strings.
       It  is  the  same as the	sentinel example, except that the input	is not
       null-terminated.	To cover up for	the absence of a sentinel character at
       the end of input, YYPEEK	is redefined to	perform	a bounds check	before
       it  reads the next input	character.  This is inefficient	because	checks
       are done	very often. If the check condition fails, YYPEEK  returns  the
       real character, otherwise it returns a fake sentinel character.

	  // re2java $INPUT -o $OUTPUT

	  class	Main {
	      // Expects a string without terminating null.
	      static int lex(String str) {
		  byte[] yyinput = str.getBytes();
		  int yycursor = 0;
		  int count = 0;

		  loop:	while (true) {
		      /*!re2c
			  re2c:api = generic;
			  re2c:YYCTYPE = "byte";
			  re2c:YYPEEK =	"(yycursor < yyinput.length) ? yyinput[yycursor] : 0";
			  re2c:YYSKIP =	"yycursor += 1;";
			  re2c:yyfill:enable = 0;

			  *	 { return -1; }
			  [\x00] { return count; }
			  [a-z]+ { count += 1; continue	loop; }
			  [ ]+	 { continue loop; }
		      */
		  }
	      }

	      public static void main(String []args) {
		  assert lex("") == 0;
		  assert lex("one two three") == 3;
		  assert lex("f0ur") ==	-1;
	      }
	  };

BUFFER REFILLING
       The need	for buffering arises when the input cannot be mapped in	memory
       all at once: either it is too large, or it comes	in a streaming fashion
       (like  reading  from a socket). The usual technique in such cases is to
       allocate	a fixed-sized memory buffer and	process	input in  chunks  that
       fit  into  the buffer. When the current chunk is	processed, it is moved
       out and new data	is moved in. In	practice it is somewhat	more  complex,
       because	lexer state consists not of a single input position, but a set
       of interrelated positions:

        cursor: the next input	character to be	read (YYCURSOR	in  C  pointer
	 API or	YYSKIP/YYPEEK in generic API)

        limit:	the position after the last available input character (YYLIMIT
	 in C pointer API, implicitly handled by YYLESSTHAN in generic API)

        marker:  the  position	 of the	most recent match, if any (YYMARKER in
	 default API or	YYBACKUP/YYRESTORE in generic API)

        token:	the start of the current lexeme	(implicit in re2java  API,  as
	 it  is	 not  needed for the normal lexer operation and	can be defined
	 and updated by	the user)

        context marker: the position of the trailing context (YYCTXMARKER  in
	 C pointer API or YYBACKUPCTX/YYRESTORECTX in generic API)

        tag  variables:  submatch  positions  (defined	 with  stags and mtags
	 blocks	and generic API	primitives YYSTAGP/YYSTAGN/YYMTAGP/YYMTAGN)

       Not all these are used in every case, but if used, they must be updated
       by YYFILL. All active positions are contained in	 the  segment  between
       token  and  cursor, therefore everything	between	buffer start and token
       can be discarded, the segment from token	and  up	 to  limit  should  be
       moved  to  the  beginning  of  buffer, and the free space at the	end of
       buffer should be	filled with new	data.  In order	to avoid frequent  YY-
       FILL  calls  it is best to fill in as many input	characters as possible
       (even though fewer characters might suffice to resume the  lexer).  The
       details	of  YYFILL  implementation are slightly	different depending on
       which EOF handling method is used: the case of  EOF  rule  is  somewhat
       simpler	than  the case of bounds-checking with padding.	Also note that
       if -f --storable-state option is	used, YYFILL  has  slightly  different
       semantics (described in the section about storable state).

   YYFILL with sentinel
       If  EOF	rule is	used, YYFILL is	a function-like	primitive that accepts
       no arguments and	returns	a value	which is checked against zero.	YYFILL
       invocation  is  triggered by condition YYLIMIT <= YYCURSOR in C pointer
       API and YYLESSTHAN() in generic API. A non-zero return value means that
       YYFILL has failed. A successful YYFILL call must	supply	at  least  one
       character  and adjust input positions accordingly. Limit	must always be
       set to one after	the last input position	in buffer, and	the  character
       at the limit position must be the sentinel symbol specified by re2c:eof
       configuration.  The pictures below show the relative locations of input
       positions in buffer before and after YYFILL call	 (sentinel  symbol  is
       marked  with #, and the second picture shows the	case when there	is not
       enough input to fill the	whole buffer).

			 <-- shift -->
		       >-A------------B---------C-------------D#-----------E->
		       buffer	    token    marker	    limit,
							    cursor
	  >-A------------B---------C-------------D------------E#->
		       buffer,	marker	      cursor	    limit
		       token

			 <-- shift -->
		       >-A------------B---------C-------------D#--E (EOF)
		       buffer	    token    marker	    limit,
							    cursor
	  >-A------------B---------C-------------D---E#........
		       buffer,	marker	     cursor limit
		       token

       Here is an example of a program that  reads  input  file	 input.txt  in
       chunks of 4096 bytes and	uses EOF rule.

	  // re2java $INPUT -o $OUTPUT

	  import java.io.*;
	  import java.nio.file.*;

	  class	Lexer {
	      public static final int BUFSIZE =	4096;

	      private BufferedInputStream stream;
	      private byte[] yyinput;
	      private int yycursor;
	      private int yymarker;
	      private int yylimit;
	      private int token;
	      private boolean eof;

	      public Lexer(File	file) throws FileNotFoundException {
		  stream = new BufferedInputStream(new FileInputStream(file));
		  // Sentinel at `yylimit` offset is set to zero, which	triggers YYFILL.
		  yyinput = new	byte[BUFSIZE + 1];
		  yycursor = yymarker =	yylimit	= token	= BUFSIZE;
		  eof =	false;
	      }

	      private int fill() throws	IOException {
		  if (eof) { return -1;	} // unexpected	EOF

		  // Error: lexeme too long. In	real life can reallocate a larger buffer.
		  if (token < 1) { return -2; }

		  // Shift buffer contents (discard everything up to the current token).
		  System.arraycopy(yyinput, token, yyinput, 0, yylimit - token);
		  yycursor -= token;
		  yymarker -= token;
		  yylimit -= token;
		  token	= 0;

		  // Fill free space at	the end	of buffer with new data	from file.
		  yylimit += stream.read(yyinput, yylimit, BUFSIZE - yylimit);
		  yyinput[yylimit] = 0;	// append sentinel symbol

		  // If	read less than expected, this is the end of input.
		  eof =	yylimit	< BUFSIZE;

		  return 0;
	      }

	      // Expects a null-terminated string.
	      public int lex() throws IOException {
		  int count = 0;
		  loop:	while (true) {
		      token = yycursor;
		      /*!re2c
			  re2c:YYCTYPE = "byte";
			  re2c:YYPEEK =	"yyinput[yycursor]";
			  re2c:YYFILL =	"fill()	== 0";
			  re2c:eof = 0;

			  str =	['] ([^'\\] | [\\][^])*	['];

			  *    { return	-1; }
			  $    { return	count; }
			  str  { count += 1; continue loop; }
			  [ ]+ { continue loop;	}
		      */
		  }
	      }

	      public static void main(String []args) throws FileNotFoundException, IOException {
		  String fname = "input";
		  String content = "'qu\0tes' 'are' 'fine: \\''	".repeat(Lexer.BUFSIZE);

		  // Prepare input file: a few times the size of the buffer, containing
		  // strings with zeroes and escaped quotes.
		  Files.writeString(Paths.get(fname), content);

		  int count = 3	* Lexer.BUFSIZE; // number of quoted strings written to	file

		  // Prepare lexer state: all offsets are at the end of	buffer.
		  File file = new File(".", fname);
		  Lexer	lexer =	new Lexer(file);

		  // Run the lexer.
		  int n	= lexer.lex();
		  assert n == count;

		  // Cleanup: remove input file.
		  file.delete();
	      }
	  };

   YYFILL with padding
       In  the	default	 case  (when  EOF  rule	is not used) YYFILL is a func-
       tion-like primitive that	accepts	a single argument and does not	return
       any  value.  YYFILL invocation is triggered by condition	(YYLIMIT - YY-
       CURSOR) < n in C	pointer	API and	YYLESSTHAN(n) in generic API. The  ar-
       gument  passed  to YYFILL is the	minimal	number of characters that must
       be supplied. If it fails	to do so, YYFILL must not return to the	 lexer
       (for  that  reason  it is best implemented as a macro that returns from
       the calling function on failure).  In case of a successful YYFILL invo-
       cation the limit	position must be set either to one after the last  in-
       put position in buffer, or to the end of	YYMAXFILL padding (in case YY-
       FILL  has  successfully	read  at least n characters, but not enough to
       fill the	entire buffer).	The pictures below show	the relative locations
       of input	positions in buffer before and after YYFILL invocation (YYMAX-
       FILL padding on the second picture is marked with # symbols).

			 <-- shift -->		       <-- need	-->
		       >-A------------B---------C-----D-------E---F--------G->
		       buffer	    token    marker cursor  limit

	  >-A------------B---------C-----D-------E---F--------G->
		       buffer,	marker cursor		    limit
		       token

			 <-- shift -->		       <-- need	-->
		       >-A------------B---------C-----D-------E-F	 (EOF)
		       buffer	    token    marker cursor  limit

	  >-A------------B---------C-----D-------E-F###############
		       buffer,	marker cursor			limit
		       token			    <- YYMAXFILL ->

       Here is an example of a program that  reads  input  file	 input.txt  in
       chunks of 4096 bytes and	uses bounds-checking with padding.

	  // re2java $INPUT -o $OUTPUT

	  import java.io.*;
	  import java.nio.file.*;
	  import java.util.Arrays;

	  class	Lexer {
	      /*!max:re2c*/
	      public static final int BUFSIZE =	4096;

	      private BufferedInputStream stream;
	      private byte[] yyinput;
	      private int yycursor;
	      private int yylimit;
	      private int token;
	      private boolean eof;

	      public Lexer(File	file) throws FileNotFoundException {
		  stream = new BufferedInputStream(new FileInputStream(file));
		  // Prepare lexer state: all offsets are at the end of	buffer.
		  // This immediately triggers YYFILL, as the YYLESSTHAN condition is true.
		  yyinput = new	byte[BUFSIZE + YYMAXFILL];
		  yycursor = yylimit = token = BUFSIZE;
		  eof =	false;
	      }

	      private int fill(int need) throws	IOException {
		  if (eof) { return -1;	} // unexpected	EOF

		  // Error: lexeme too long. In	real life can reallocate a larger buffer.
		  if (token < need) { return -2; }

		  // Shift buffer contents (discard everything up to the current token).
		  System.arraycopy(yyinput, token, yyinput, 0, yylimit - token);
		  yycursor -= token;
		  yylimit -= token;
		  token	= 0;

		  // Fill free space at	the end	of buffer with new data	from file.
		  yylimit += stream.read(yyinput, yylimit, BUFSIZE - yylimit);
		  yyinput[yylimit] = 0;	// append sentinel symbol

		  // If	read less than expected, this is the end of input.
		  if (yylimit <	BUFSIZE) {
		      eof = true;
		      Arrays.fill(yyinput, yylimit, yylimit + YYMAXFILL, (byte)0);
		      yylimit += YYMAXFILL;
		  }

		  return 0;
	      }

	      // Expects a null-terminated string.
	      public int lex() throws IOException {
		  int count = 0;
		  loop:	while (true) {
		      token = yycursor;
		      /*!re2c
			  re2c:YYCTYPE = "byte";
			  re2c:YYPEEK =	"yyinput[yycursor]";
			  re2c:YYFILL =	"if (fill(@@) != 0) { return -2; }";

			  str =	['] ([^'\\] | [\\][^])*	['];

			  [\x00] {
			      // Check that it is the sentinel,	not some unexpected null.
			      return (token == yylimit - YYMAXFILL) ? count : -1;
			  }
			  str  { count += 1; continue loop; }
			  [ ]+ { continue loop;	}
			  *    { return	-1; }
		      */
		  }
	      }

	      public static void main(String []args) throws FileNotFoundException, IOException {
		  String fname = "input";
		  String content = "'qu\0tes' 'are' 'fine: \\''	".repeat(Lexer.BUFSIZE);

		  // Prepare input file: a few times the size of the buffer, containing
		  // strings with zeroes and escaped quotes.
		  Files.writeString(Paths.get(fname), content);

		  int count = 3	* Lexer.BUFSIZE; // number of quoted strings written to	file

		  // Prepare lexer state: all offsets are at the end of	buffer.
		  File file = new File(".", fname);
		  Lexer	lexer =	new Lexer(file);

		  // Run the lexer.
		  int n	= lexer.lex();
		  assert n == count;

		  // Cleanup: remove input file.
		  file.delete();
	      }
	  };

FEATURES
   Multiple blocks
       Sometimes it is necessary to have multiple interrelated lexers (for ex-
       ample,  if there	is a high-level	state machine that transitions between
       lexer modes). This can be implemented using multiple connected  re2java
       blocks. Another option is to use	start conditions.

       The  implementation of connections between blocks depends on the	target
       language.  In languages that have goto statement	(such as C/C++ and Go)
       one can have all	blocks in one function,	each of	them prefixed  with  a
       label.  Transition from one block to another is a simple	goto.  In lan-
       guages that do not have goto (such as Rust) it is necessary  to	use  a
       loop  with  a  switch  on  a  state  variable,  similar	to the yystate
       loop/switch generated by	re2java, or else wrap each block in a function
       and use function	calls.

       The example below uses multiple blocks to parse binary, octal,  decimal
       and hexadecimal numbers.	Each base has its own block. The initial block
       determines  base	 and dispatches	to other blocks. Common	configurations
       are defined in a	separate block at the beginning	of the	program;  they
       are inherited by	the other blocks.

	  // re2java $INPUT -o $OUTPUT

	  class	Parser {
	      private String yyinput;
	      private int yycursor;
	      private int yymarker;
	      private int number;

	      private void add_digit(int base, int offset) throws ArithmeticException {
		  number = Math.addExact(
		      Math.multiplyExact(number, base),
		      yyinput.charAt(yycursor -	1) - offset);
	      }

	      public int parse(String str) throws ArithmeticException, IllegalArgumentException	{
		  yyinput = str;
		  yycursor = 0;
		  number = 0;

		  try {
		      /*!re2c
			  re2c:YYCTYPE = "char";
			  re2c:YYPEEK =	"yyinput.charAt(yycursor)";
			  re2c:yyfill:enable = 0;

			  end =	"\x00";

			  '0b' / [01]	     { return parse_bin(); }
			  "0"		     { return parse_oct(); }
			  ""   / [1-9]	     { return parse_dec(); }
			  '0x' / [0-9a-fA-F] { return parse_hex(); }
			  *		     { throw new IllegalArgumentException("not a number"); }
		      */
		  } catch (Exception e)	{
		      return -1;
		  }
	      }

	      private int parse_bin() throws ArithmeticException, IllegalArgumentException {
		  /*!re2c
		      end   { return number; }
		      [01]  { add_digit(2, 48);	return parse_bin(); }
		      *	    { throw new	IllegalArgumentException("ill-formed binary number"); }
		  */
	      }

	      private int parse_oct() throws ArithmeticException, IllegalArgumentException {
		  /*!re2c
		      end   { return number; }
		      [0-7] { add_digit(8, 48);	return parse_oct(); }
		      *	    { throw new	IllegalArgumentException("ill-formed octal number"); }
		  */
	      }

	      private int parse_dec() throws ArithmeticException, IllegalArgumentException {
		  /*!re2c
		      end   { return number; }
		      [0-9] { add_digit(10, 48); return	parse_dec(); }
		      *	    { throw new	IllegalArgumentException("ill-formed decimal number"); }
		  */
	      }

	      private int parse_hex() throws ArithmeticException, IllegalArgumentException {
		  /*!re2c
		      end   { return number; }
		      [0-9] { add_digit(16, 48); return	parse_hex(); }
		      [a-f] { add_digit(16, 87); return	parse_hex(); }
		      [A-F] { add_digit(16, 55); return	parse_hex(); }
		      *	    { throw new	IllegalArgumentException("ill-formed hexadecimal number"); }
		  */
	      }

	      public static void main(String []args) {
		  Parser parser	= new Parser();
		  assert parser.parse("1234567890\0") == 1234567890;
		  assert parser.parse("0b1101\0") == 0b1101;
		  assert parser.parse("0x007Fe\0") == 0x7fe;
		  assert parser.parse("0644\0")	== 0644;
		  assert parser.parse("9999999999\0") == -1;
		  assert parser.parse("123??\0") == -1;
	      }
	  };

   Start conditions
       Start  conditions are enabled with --start-conditions option. They pro-
       vide a way to encode multiple interrelated  automata  within  the  same
       re2java block.

       Each  condition corresponds to a	single automaton and has a unique name
       specified by the	user and a unique internal number defined by  re2java.
       The  numbers  are used to switch	between	conditions: the	generated code
       uses YYGETCOND and YYSETCOND primitives to get the current condition or
       set it to the given number. Use conditions block,  --header  option  or
       re2c:header  configuration  to  generate	numeric	condition identifiers.
       Configuration re2c:cond:enumprefix specifies the	 generated  identifier
       prefix.

       In condition mode every rule must be prefixed with a list of comma-sep-
       arated  condition  names	in angle brackets, or a	wildcard <*> to	denote
       all conditions. The rule	syntax is extended as follows:

	  < condition-list > regular-expression	code
		 A rule	that is	 merged	 to  every  condition  on  the	condi-
		 tion-list.   It  matches  regular-expression and executes the
		 associated code.

	  < condition-list > regular-expression	=> condition code
		 A rule	that is	 merged	 to  every  condition  on  the	condi-
		 tion-list.   It  matches regular-expression, sets the current
		 condition to condition	and executes the associated code.

	  < condition-list > regular-expression	:=> condition
		 A rule	that is	 merged	 to  every  condition  on  the	condi-
		 tion-list.   It  matches  regular-expression  and immediately
		 transitions to	condition (there is no semantic	action).

	  < condition-list > !action code
		 A rule	that binds code	to the	place  defined	by  action  in
		 every	condition  on the condition-list (see the actions sec-
		 tion for various types	of actions).

	  <! condition-list > code
		 A rule	that prepends code to semantic actions	of  all	 rules
		 for  every  condition	on  the	condition-list.	This syntax is
		 deprecated and	the !pre_rule action should  be	 used  instead
		 (it does exactly the same).

	  < > code
		 A  rule  that	creates	 a special entry condition with	number
		 zero and name "0" that	executes code before jumping to	 other
		 conditions.  This syntax is deprecated, and the !entry	action
		 should	 be used instead (it provides a	more fine-grained con-
		 trol, as the code can be specified on a per-condition	basis,
		 and  one  can	jump directly to condition start without going
		 through condition dispatch).

	  < > => condition code
		 Same as the previous rule, except that	it sets	the next  con-
		 dition.

	  < > :=> condition
		 Same  as  the previous	rule, except that it has no associated
		 code and immediately jumps to condition.

       The code	re2java	generates for conditions depends  on  whether  re2java
       uses  goto/label	 approach  or  loop/switch  approach to	encode the au-
       tomata.

       In languages that have goto statement (such as C/C++ and	Go) conditions
       are naturally implemented as blocks of code prefixed with labels	of the
       form yyc_<cond>,	where cond is a	condition name (label  prefix  can  be
       changed	with re2c:cond:prefix).	Transitions between conditions are im-
       plemented using	goto  and  condition  labels.  Before  all  conditions
       re2java	generates  an  initial	switch on YYGETSTATE that jumps	to the
       start state of the current condition.  The shortcut  rules  :=>	bypass
       the  initial  switch  and  jump	directly  to  the  specified condition
       (re2c:cond:goto can be used to change the default behavior). The	 rules
       with  semantic actions do not automatically jump	to the next condition;
       this should be done by the user-defined action code.

       In languages that do not	have goto (such	as Rust)  re2java  reuses  the
       yystate	variable to store condition numbers. Each condition gets a nu-
       meric identifier	equal to the number of its start state,	and  a	switch
       between	conditions is no different than	a switch between DFA states of
       a single	condition. There is no need for	a separate  initial  condition
       switch.	(Since the same	approach is used to implement storable states,
       YYGETCOND/YYSETCOND  are	 redundant  if both storable states and	condi-
       tions are used).

       The program below uses start conditions to parse	binary,	octal, decimal
       and hexadecimal numbers.	There is a single block	where  each  base  has
       its  own	 condition,  and  the initial condition	is connected to	all of
       them. User-defined variable cond	stores the current  condition  number;
       it is initialized to the	number of the initial condition	generated with
       conditions block.

	  // re2java $INPUT -o $OUTPUT -c

	  class	Parser {
	      /*!conditions:re2c*/
	      private String yyinput;
	      private int yycursor;
	      private int yymarker;
	      private int number;

	      private void add_digit(int base, int offset) throws ArithmeticException {
		  number = Math.addExact(
		      Math.multiplyExact(number, base),
		      yyinput.charAt(yycursor -	1) - offset);
	      }

	      public int parse(String str) throws ArithmeticException, IllegalArgumentException	{
		  yyinput = str;
		  yycursor = 0;
		  int yycond = YYC_init;

		  number = 0;
		  try {
		      loop: while (true) {
		      /*!re2c
			  re2c:YYCTYPE = "char";
			  re2c:YYPEEK =	"yyinput.charAt(yycursor)";
			  re2c:yyfill:enable = 0;

			  <*> *	{ throw	new IllegalArgumentException("ill-formed number"); }

			  <init> '0b' /	[01]	    :=>	bin
			  <init> "0"		    :=>	oct
			  <init> ""   /	[1-9]	    :=>	dec
			  <init> '0x' /	[0-9a-fA-F] :=>	hex

			  <bin,	oct, dec, hex> "\x00" {	return number; }

			  <bin>	[01]  {	add_digit(2, 48); continue loop; }
			  <oct>	[0-7] {	add_digit(8, 48); continue loop; }
			  <dec>	[0-9] {	add_digit(10, 48); continue loop; }
			  <hex>	[0-9] {	add_digit(16, 48); continue loop; }
			  <hex>	[a-f] {	add_digit(16, 87); continue loop; }
			  <hex>	[A-F] {	add_digit(16, 55); continue loop; }
		      */
		      }
		  } catch (Exception e)	{
		      return -1;
		  }
	      }

	      public static void main(String []args) {
		  Parser parser	= new Parser();
		  assert parser.parse("1234567890\0") == 1234567890;
		  assert parser.parse("0b1101\0") == 0b1101;
		  assert parser.parse("0x007Fe\0") == 0x7fe;
		  assert parser.parse("0644\0")	== 0644;
		  assert parser.parse("9999999999\0") == -1;
		  assert parser.parse("123??\0") == -1;
	      }
	  };

   Storable state
       With  --storable-state  option re2java generates	a lexer	that can store
       its current state, return to the	caller,	and  later  resume  operations
       exactly	where it left off. The default mode of operation in re2java is
       a "pull"	model, in which	the lexer "pulls" more input whenever it needs
       it. This	may be unacceptable in cases when the input becomes  available
       piece  by piece (for example, if	the lexer is invoked by	the parser, or
       if the lexer program communicates via a socket protocol with some other
       program that must wait for a reply from the lexer before	 it  transmits
       the  next message). Storable state feature is intended exactly for such
       cases: it allows	one to generate	lexers that work in  a	"push"	model.
       When the	lexer needs more input,	it stores its state and	returns	to the
       caller.	Later,	when  more input becomes available, the	caller resumes
       the lexer exactly where it stopped. There are a few  changes  necessary
       compared	to the "pull" model:

        Define	YYSETSTATE() and YYGETSTATE(state) primitives.

        Define	yych, yyaccept (if used) and state variables as	a part of per-
	 sistent lexer state. The state	variable should	be initialized to -1.

        YYFILL	should return to the outer program instead of trying to	supply
	 more input. Return code should	indicate that lexer needs more input.

        The  outer  program should recognize situations when lexer needs more
	 input and respond appropriately.

        Optionally use	getstate block to generate YYGETSTATE switch  detached
	 from  the  main  lexer.  This only works for languages	that have goto
	 (not in --loop-switch mode).

        Use re2c:eof and the sentinel with bounds checks method to handle the
	 end of	input. Padding-based method may	not work because it is unclear
	 when to append	padding: the current end of input may not be the ulti-
	 mate end of input, and	appending padding too early may	cut off	a par-
	 tially	read greedy lexeme.  Furthermore, due  to  high-level  program
	 logic	getting	 more input may	depend on processing the lexeme	at the
	 end of	buffer (which already is blocked due to	the end-of-input  con-
	 dition).

       Here is an example of a "push" model lexer that simulates reading pack-
       ets from	a socket. The lexer loops until	it encounters the end of input
       and returns to the calling function. The	calling	function provides more
       input  by  "sending"  the  next packet and resumes lexing. This process
       stops when all the packets have been sent, or when there	is an error.

	  // re2java $INPUT -o $OUTPUT -f

	  import java.io.IOException;
	  import java.nio.ByteBuffer;
	  import java.nio.channels.Pipe;

	  class	Lexer {
	      enum Status {
		  END,
		  READY,
		  WAITING,
		  BIG_PACKET,
		  BAD_PACKET
	      };

	      // Use a small buffer to cover the case when a lexeme doesn't fit.
	      // In real world use a larger buffer.
	      public static final int BUFSIZE =	10;

	      public static class State	{
		  Pipe.SourceChannel source;
		  byte[] yyinput;
		  int yycursor;
		  int yymarker;
		  int yylimit;
		  int token;
		  int yystate;
		  int received;

		  public State(Pipe pipe) {
		      source = pipe.source();
		      // Sentinel at `yylimit` offset is set to	zero, which triggers YYFILL.
		      yyinput =	new byte[BUFSIZE + 1];
		      yycursor = yymarker = yylimit = token = BUFSIZE;
		      yystate =	-1;
		      received = 0;
		  }
	      }

	      private static void log(String format, Object... args) {
		  if (false) { System.out.printf(format	+ "\n",	args); }
	      }

	      private static Status fill(State st) throws IOException {
		  // Error: lexeme too long. In	real life can reallocate a larger buffer.
		  if (st.token < 1) { return Status.BIG_PACKET;	}

		  // Shift buffer contents (discard everything up to the current token).
		  System.arraycopy(st.yyinput, st.token, st.yyinput, 0,	st.yylimit - st.token);
		  st.yycursor -= st.token;
		  st.yymarker -= st.token;
		  st.yylimit -=	st.token;
		  st.token = 0;

		  // Fill free space at	the end	of buffer with new data	from file.
		  ByteBuffer buffer = ByteBuffer.wrap(st.yyinput, st.yylimit, BUFSIZE -	st.yylimit);
		  int have = st.source.read(buffer);
		  if (have != -1) st.yylimit +=	have; // -1 means that pipe is closed
		  st.yyinput[st.yylimit] = 0; // append	sentinel symbol

		  return Status.READY;
	      }

	      private static Status lex(State yyrecord)	{
		  byte yych;
		  loop:	while (true) {
		      yyrecord.token = yyrecord.yycursor;
		      /*!re2c
			  re2c:api = record;
			  re2c:YYCTYPE = "byte";
			  re2c:YYPEEK =	"yyrecord.yyinput[yyrecord.yycursor]";
			  re2c:YYFILL =	"return	Status.WAITING;";
			  re2c:eof = 0;

			  packet = [a-z]+[;];

			  *	 { return Status.BAD_PACKET; }
			  $	 { return Status.END; }
			  packet { yyrecord.received +=	1; continue loop; }
		      */
		  }
	      }

	      public static void test(String[] packets,	Status expect) throws IOException {
		  // Create a pipe.
		  Pipe pipe = Pipe.open();
		  Pipe.SinkChannel sink	= pipe.sink();

		  // Initialize	lexer state
		  Lexer.State st = new Lexer.State(pipe);

		  // Main loop.	The buffer contains incomplete data which appears packet by
		  // packet. When the lexer needs more input it	saves its internal state and
		  // returns to	the caller which should	provide	more input and resume lexing.
		  int send = 0;
		  Status status;
		  while	(true) {
		      status = lex(st);

		      if (status == Status.END)	{
			  log("done: got %d packets", st.received);
			  break;
		      }	else if	(status	== Status.WAITING) {
			  log("waiting...");

			  if (send < packets.length) {
			      log("sent	packet %d: %s",	send, packets[send]);
			      ByteBuffer buffer	= ByteBuffer.wrap(packets[send].getBytes());
			      sink.write(buffer);
			      send += 1;
			  } else {
			      sink.close();
			  }

			  status = fill(st);
			  if (status ==	Status.BIG_PACKET) {
			      log("error: packet too big");
			      break;
			  }
			  assert status	== Status.READY;
		      }	else {
			  assert status	== Status.BAD_PACKET;
			  log("error: ill-formed packet");
			  break;
		      }
		  }

		  // Check results.
		  assert status	== expect;
		  if (status ==	Status.END) {
		      assert send == st.received;
		  }
	      }

	      public static void main(String []args) throws IOException	{
		  test(new String[]{}, Status.END);
		  test(new String[]{"zero;", "one;", "two;", "three;", "four;"}, Status.END);
		  test(new String[]{"zer0;"}, Status.BAD_PACKET);
		  test(new String[]{"goooooooooogle;"},	Status.BIG_PACKET);
	      }
	  };

   Reusable blocks
       Reusable	 blocks	 of  the  form	/*!rules:re2c[:<name>]	 ...   */   or
       %{rules[:<name>]	 ... %}	can be reused any number of times and combined
       with other re2java blocks. The <name> is	optional. A rules block	can be
       used in a use block or directive. The code for a	rules block is	gener-
       ated at every point of use.

       Use   blocks   are   defined   with   /*!use:re2c[:<name>]  ...	*/  or
       %{use[:<name>] ... %}. The <name> is optional: if it's  not  specified,
       the associated rules block is the most recent one (whether named	or un-
       named).	 A  use	 block	can  add named definitions, configurations and
       rules of	its own.  An important use case	for use	blocks is a lexer that
       supports	multiple input encodings: the same rules block is reused  mul-
       tiple  times with encoding-specific configurations (see the example be-
       low).

       In-block	use directive !use:<name>;  can	 be  used  from	 inside	 of  a
       re2java	block.	It merges the referenced block <name> into the current
       one. If some of the merged rules	and configurations  overlap  with  the
       previously  defined  ones, conflicts are	resolved in the	usual way: the
       earliest	rule takes priority, and latest	configuration  overrides  pre-
       ceding ones. One	exception are the special rules	*, $ and (in condition
       mode)  <!>,  for	which a	block-local definition overrides any inherited
       ones. Use directive allows one to combine different re2java blocks  to-
       gether in one block (see	the example below).

       Named  blocks  and in-block use directive were added in re2java version
       2.2.  Since that	version	reusable blocks	are  allowed  by  default  (no
       special	option	is  needed). Before version 2.2	reuse mode was enabled
       with -r --reusable option. Before version 1.2 reusable blocks could not
       be mixed	with normal blocks.

   Example of a	!use directive
	  // re2java $INPUT -o $OUTPUT

	  // This example shows	how to combine reusable	re2c blocks: two blocks
	  // ('colors' and 'fish') are merged into one.	The 'salmon' rule occurs
	  // in	both blocks; the 'fish'	block takes priority because it	is used
	  // earlier. Default rule * occurs in all three blocks; the local (not
	  // inherited)	definition takes priority.

	  /*!rules:re2c:colors
	      *				   { throw new IllegalArgumentException("ah"); }
	      "red" | "salmon" | "magenta" { return Ans.COLOR; }
	  */

	  /*!rules:re2c:fish
	      *				   { throw new IllegalArgumentException("oh"); }
	      "haddock"	| "salmon" | "eel" { return Ans.FISH; }
	  */

	  class	Main {
	      enum Ans {COLOR, FISH, DUNNO};

	      static Ans lex(String yyinput) { // no-throw, as '*' rules are overridden
		  int yycursor = 0;
		  int yymarker = 0;

		  /*!re2c
		      re2c:yyfill:enable = 0;
		      re2c:YYCTYPE = "char";
		      re2c:YYPEEK = "yyinput.charAt(yycursor)";

		      !use:fish;
		      !use:colors;
		      *	{ return Ans.DUNNO; } // overrides inherited '*' rules
		  */
	      }

	      public static void main(String []args) {
		  assert lex("salmon") == Ans.FISH;
		  assert lex("what?") == Ans.DUNNO;
	      }
	  };

   Example of a	/*!use:re2c ...	*/ block
	  // re2java $INPUT -o $OUTPUT --input-encoding	utf8

	  // This example supports multiple input encodings: UTF-8 and UTF-32.
	  // Both lexers are generated from the	same rules block, and the use
	  // blocks add	only encoding-specific configurations.

	  /*!rules:re2c
	      re2c:yyfill:enable = 0;
	      re2c:YYPEEK = "yyinput[yycursor]";
	      re2c:indent:top =	1;

	      "x y" { return true; }
	      *	      {	return false; }
	  */

	  class	Main {
	      static boolean lex_utf8(int[] yyinput) {
		  int yycursor = 0;
		  int yymarker = 0;
		  /*!use:re2c
		      re2c:YYCTYPE = "int"; // should be `byte`, but it's signed in Java
		      re2c:encoding:utf8 = 1;
		  */
	      }

	      static boolean lex_utf32(int[] yyinput) {
		  int yycursor = 0;
		  int yymarker = 0;
		  /*!use:re2c
		      re2c:YYCTYPE = "int";
		      re2c:encoding:utf32 = 1;
		  */
	      }

	      public static void main(String []args) {
		  // we	have to	use `int`, because `byte`in Java cannot	represent values greater than 127
		  int[]	s_utf8 = new int[]{0xe2, 0x88, 0x80, 0x78, 0x20, 0xe2, 0x88, 0x83, 0x79};
		  assert lex_utf8(s_utf8);

		  int[]	s_utf32	= new int[]{0x2200, 0x78, 0x20,	0x2203,	0x79};
		  assert lex_utf32(s_utf32);
	      }
	  };

   Submatch extraction
       re2java has two options for submatch extraction.

       Tags   The first	option is to use standalone tags of the	form @stag  or
	      #mtag,  where  stag  and	mtag are arbitrary used-defined	names.
	      Tags are enabled with -T --tags option or	re2c:tags = 1 configu-
	      ration. Semantically tags	are position markers: they can be  in-
	      serted  anywhere	in  a regular expression, and they bind	to the
	      corresponding position (or  multiple  positions)	in  the	 input
	      string.	S-tags	bind to	the last matching position, and	m-tags
	      bind to a	list of	positions (they	 may  be  used	in  repetition
	      subexpressions,  where a single position in a regular expression
	      corresponds to multiple positions	in the input string). All tags
	      should be	defined	by the user, either manually or	with the  help
	      of  svars	 and  mvars blocks. If there is	more than one way tags
	      can be matched against the input,	ambiguity  is  resolved	 using
	      leftmost greedy disambiguation strategy.

       Captures
	      The  second  option is to	use capturing groups. They are enabled
	      with --captures option or	re2c:captures =	1 configuration. There
	      are two flavours for different disambiguation policies,  --left-
	      most-captures  (the default) is for leftmost greedy policy, and,
	      --posix-captures is for POSIX longest-match policy. In this mode
	      all  parenthesized  subexpressions  are	considered   capturing
	      groups,  and a bang can be used to mark non-capturing groups: (!
	      ... ). With --invert-captures option or re2c:invert-captures = 1
	      configuration the	meaning	of bang	is inverted.   The  number  of
	      groups  for  the	matching rule is stored	in a variable yynmatch
	      (the whole regular expression is group number  zero),  and  sub-
	      match  results  are  stored in yypmatch array. Both yynmatch and
	      yypmatch should be defined by the	user, and yypmatch  size  must
	      be  at  least [yynmatch *	2]. Use	maxnmatch block	to  define YY-
	      MAXNMATCH, a constant that equals	to the maximum value  of  yyn-
	      match among all rules.

       Captvars
	      Another  way to use capturing groups is the --captvars option or
	      re2c:captvars = 1	configuration. The only	difference with	--cap-
	      tures is in the way the generated	code stores submatch  results:
	      instead  of  yynmatch  and  yypmatch re2java generates variables
	      yytl<k> and yytr<k> for k-th capturing group  (the  user	should
	      declare  these  using  an	 svars block). Captures	with variables
	      support  two  disambiguation  policies:  --leftmost-captvars  or
	      re2c:leftmost-captvars  =	 1 for leftmost	greedy policy (the de-
	      fault one) and --posix-captvars or re2c:posix-captvars for POSIX
	      longest-match policy.

       Under the hood all these	options	translate into tags and	Tagged	Deter-
       ministic	 Finite	 Automata with Lookahead.  The core idea of TDFA is to
       minimize	the overhead on	 submatch  extraction.	 In  the  extreme,  if
       there're	 no  tags or captures in a regular expression, TDFA is just an
       ordinary	DFA. If	the number of tags is moderate,	the overhead is	barely
       noticeable. The generated TDFA uses a number of tag variables which  do
       not  map	 directly to tags: a single variable may be used for different
       tags, and a tag may require multiple variables to hold all its possible
       values. Eventually ambiguity is resolved, and only one  final  variable
       per  tag	survives. Tag variables	should be defined using	stags or mtags
       blocks. If lexer	state is stored, tag variables should be part  of  it.
       They also need to be updated  by	YYFILL.

       S-tags support the following operations:

        save input position to	an s-tag: t = YYCURSOR with C pointer API or a
	 user-defined operation	YYSTAGP(t) with	generic	API

        save  default	value  to  an  s-tag: t	= NULL with C pointer API or a
	 user-defined operation	YYSTAGN(t) with	generic	API

        copy one s-tag	to another: t1 = t2

       M-tags support the following operations:

        append	input position to an  m-tag:  a	 user-defined  operation  YYM-
	 TAGP(t) with both default and generic API

        append	default	value to an m-tag: a user-defined operation YYMTAGN(t)
	 with both default and generic API

        copy one m-tag	to another: t1 = t2

       S-tags  can  be	implemented  as	 scalar	 values	(pointers or offsets).
       M-tags need a more complex representation, as they need to store	a  se-
       quence  of tag values. The most naive and inefficient representation of
       an m-tag	is a list (array, vector) of tag values; a more	efficient rep-
       resentation is to store all m-tags in a prefix-tree represented as  ar-
       ray  of nodes (v, p), where v is	tag value and p	is a pointer to	parent
       node.

       Here is a simple	example	of using s-tags	 to  parse  semantic  versions
       consisting of three numeric components: major, minor, patch (the	latter
       is optional).  See below	for a more complex example that	uses YYFILL.

	  // re2java $INPUT -o $OUTPUT

	  import java.util.Optional;

	  class	Main {
	      static class SemVer {
		  int major;
		  int minor;
		  int patch;

		  public SemVer(int m, int n, int k) {
		      major = m;
		      minor = n;
		      patch = k;
		  }

		  public boolean equals(SemVer v) {
		      return major == v.major && minor == v.minor && patch == v.patch;
		  }
	      };

	      static Optional<SemVer> parse(String yyinput) {
		  int yycursor = 0;
		  int yymarker = 0;

		  // Final tag variables available in semantic action.
		  /*!svars:re2c	format = "int @@;"; */

		  // Intermediate tag variables	used by	the lexer (must	be autogenerated).
		  /*!stags:re2c	format = "int @@ = -1;"; */

		  /*!re2c
		      re2c:YYCTYPE = "char";
		      re2c:YYPEEK = "yyinput.charAt(yycursor)";
		      re2c:yyfill:enable = 0;
		      re2c:tags	= 1;

		      num = [0-9]+;

		      @t1 num @t2 "." @t3 num @t4 ("." @t5 num)? [\x00]	{
			  int major = Integer.valueOf(yyinput.substring(t1, t2));
			  int minor = Integer.valueOf(yyinput.substring(t3, t4));
			  int patch = (t5 == -1) ? 0 : Integer.valueOf(yyinput.substring(t5, yycursor -	1));
			  return Optional.of(new SemVer(major, minor, patch));
		      }
		      *	{ return Optional.empty(); }
		  */
	      }

	      public static void main(String []args) {
		  assert parse("23.34\0").get().equals(new SemVer(23, 34, 0));
		  assert parse("1.2.99999\0").get().equals(new SemVer(1, 2, 99999));
		  assert !parse("1.a\0").isPresent();
	      }
	  };

       Here  is	 a more	complex	example	of using s-tags	with YYFILL to parse a
       file with newline-separated semantic versions. Tag variables  are  part
       of  the	lexer  state, and they are adjusted in YYFILL like other input
       positions.  Note	that it	is necessary for s-tags	because	 their	values
       are invalidated after shifting buffer contents. It may not be necessary
       in  a  custom implementation where tag variables	store offsets relative
       to the start of the input string	rather than the	buffer,	which  may  be
       the case	with m-tags.

	  // re2java $INPUT -o $OUTPUT

	  import java.io.*;
	  import java.nio.file.*;
	  import java.util.*;

	  class	Lexer {
	      static class SemVer {
		  int major;
		  int minor;
		  int patch;

		  public SemVer(int m, int n, int k) {
		      major = m;
		      minor = n;
		      patch = k;
		  }

		  public boolean equals(SemVer v) {
		      return major == v.major && minor == v.minor && patch == v.patch;
		  }
	      };

	      public static final int BUFSIZE =	4096;

	      private BufferedInputStream stream;
	      private byte[] yyinput;
	      private int yycursor;
	      private int yymarker;
	      private int yylimit;
	      private int token;
	      // Intermediate tag variables used by the	lexer (must be autogenerated).
	      /*!stags:re2c format = "private int @@;\n"; */
	      private boolean eof;

	      public Lexer(File	file) throws FileNotFoundException {
		  stream = new BufferedInputStream(new FileInputStream(file));
		  // Sentinel at `yylimit` offset is set to zero, which	triggers YYFILL.
		  yyinput = new	byte[BUFSIZE + 1];
		  yycursor = yymarker =	yylimit	= token	= BUFSIZE;
		  /*!stags:re2c	format = "@@ = -1;\n"; */
		  eof =	false;
	      }

	      private int fill() throws	IOException {
		  if (eof) { return -1;	} // unexpected	EOF

		  // Error: lexeme too long. In	real life can reallocate a larger buffer.
		  if (token < 1) { return -2; }

		  // Shift buffer contents (discard everything up to the current token).
		  System.arraycopy(yyinput, token, yyinput, 0, yylimit - token);
		  yycursor -= token;
		  yymarker -= token;
		  yylimit -= token;
		  /*!stags:re2c	format = "if (@@ != -1)	{@@ -= token;}\n"; */
		  token	= 0;

		  // Fill free space at	the end	of buffer with new data	from file.
		  yylimit += stream.read(yyinput, yylimit, BUFSIZE - yylimit);
		  yyinput[yylimit] = 0;	// append sentinel symbol

		  // If	read less than expected, this is the end of input.
		  eof =	yylimit	< BUFSIZE;

		  return 0;
	      }

	      private int readInt(int tag1, int	tag2) {
		  int n	= 0;
		  for (int i = tag1; i < tag2; ++i) { n	= n * 10 + (yyinput[i] - 48); }
		  return n;
	      }

	      public Optional<ArrayList<SemVer>> lex() throws IOException {
		  ArrayList<SemVer> vers = new ArrayList<SemVer>();

		  // Final tag variables available in semantic action.
		  /*!svars:re2c	format = "int @@;"; */

		  loop:	while (true) {
		      token = yycursor;
		      /*!re2c
			  re2c:YYCTYPE = "byte";
			  re2c:YYPEEK =	"yyinput[yycursor]";
			  re2c:YYFILL =	"fill()	== 0";
			  re2c:eof = 0;
			  re2c:tags = 1;

			  num =	[0-9]+;

			  @t1 num @t2 "." @t3 num @t4 ("." @t5 num)? [\n] {
			      int major	= readInt(t1, t2);
			      int minor	= readInt(t3, t4);
			      int patch	= (t5 == -1) ? 0 : readInt(t5, yycursor	- 1);
			      vers.add(new SemVer(major, minor,	patch));
			      continue loop;
			  }
			  $ { return Optional.of(vers);	}
			  * { return Optional.empty(); }
		      */
		  }
	      }

	      public static void main(String []args) throws FileNotFoundException, IOException {
		  String fname = "input";
		  String content = "1.22.333\n".repeat(Lexer.BUFSIZE);

		  // Prepare input file: a few times the size of the buffer, containing
		  // strings with zeroes and escaped quotes.
		  Files.writeString(Paths.get(fname), content);

		  // Prepare lexer state: all offsets are at the end of	buffer.
		  File file = new File(".", fname);
		  Lexer	lexer =	new Lexer(file);

		  // Run the lexer.
		  Optional<ArrayList<SemVer>> vers = lexer.lex();

		  // Check resuts.
		  assert vers.isPresent() && vers.get().size() == BUFSIZE;
		  SemVer v = new SemVer(1, 22, 333);
		  for (int i = 0; i < BUFSIZE; ++i) {
		      assert vers.get().get(i).equals(v);
		  }

		  // Cleanup: remove input file.
		  file.delete();
	      }
	  };

       Here  is	 an  example  of using capturing groups	to parse semantic ver-
       sions.

	  // re2java $INPUT -o $OUTPUT

	  import java.util.Optional;

	  class	Main {
	      static class SemVer {
		  int major;
		  int minor;
		  int patch;

		  public SemVer(int m, int n, int k) {
		      major = m;
		      minor = n;
		      patch = k;
		  }

		  public boolean equals(SemVer v) {
		      return major == v.major && minor == v.minor && patch == v.patch;
		  }
	      };

	      static Optional<SemVer> parse(String yyinput) {
		  int yycursor = 0;
		  int yymarker = 0;

		  // Final tag variables available in semantic action.
		  /*!svars:re2c	format = "int @@;"; */

		  // Intermediate tag variables	used by	the lexer (must	be autogenerated).
		  /*!stags:re2c	format = "int @@ = -1;"; */

		  /*!re2c
		      re2c:YYCTYPE = "char";
		      re2c:YYPEEK = "yyinput.charAt(yycursor)";
		      re2c:yyfill:enable = 0;
		      re2c:captvars = 1;

		      num = [0-9]+;

		      (num) "."	(num) ("." num)? [\x00]	{
			  int major = Integer.valueOf(yyinput.substring(yytl1, yytr1));
			  int minor = Integer.valueOf(yyinput.substring(yytl2, yytr2));
			  int patch = (yytl3 ==	-1) ? 0
				  : Integer.valueOf(yyinput.substring(yytl3 + 1, yytr3));
			  return Optional.of(new SemVer(major, minor, patch));
		      }
		      *	{ return Optional.empty(); }
		  */
	      }

	      public static void main(String []args) {
		  assert parse("23.34\0").get().equals(new SemVer(23, 34, 0));
		  assert parse("1.2.99999\0").get().equals(new SemVer(1, 2, 99999));
		  assert !parse("1.a\0").isPresent();
	      }
	  };

       Here is an example of using m-tags to parse a version with  a  variable
       number of components. Tag variables are stored in a trie.

	  // re2java $INPUT -o $OUTPUT

	  import java.util.*;

	  class	Main {
	      static Optional<int[]> parse(String yyinput) {
		  int yycursor = 0;
		  int yymarker = 0;

		  // Final tag variables available in semantic action.
		  /*!svars:re2c	format = "int @@;"; */
		  /*!mvars:re2c	format = "List<Integer>	@@;"; */

		  // Intermediate tag variables	used by	the lexer (must	be autogenerated).
		  /*!stags:re2c	format = "int @@ = -1;"; */
		  /*!mtags:re2c	format = "List<Integer>	@@ = new ArrayList<>();"; */

		  /*!re2c
		      re2c:YYCTYPE = "char";
		      re2c:YYPEEK = "yyinput.charAt(yycursor)";
		      re2c:YYMTAGP = "@@.add(yycursor);";
		      re2c:YYMTAGN = ""; // do nothing
		      re2c:yyfill:enable = 0;
		      re2c:tags	= 1;

		      num = [0-9]+;

		      @t1 num @t2 ("." #t3 num #t4)* [\x00] {
			  int[]	vers = new int[t3.size() + 1];
			  vers[0] = Integer.valueOf(yyinput.substring(t1, t2));
			  for (int i = 0; i < t3.size(); ++i) {
			      vers[i + 1] = Integer.valueOf(yyinput.substring(t3.get(i), t4.get(i)));
			  }
			  return Optional.of(vers);
		      }
		      *	{ return Optional.empty(); }
		  */
	      }

	      public static void main(String []args) {
		  assert Arrays.equals(parse("1\0").get(), new int[]{1});
		  assert Arrays.equals(parse("1.2.3.4.5.6.7\0").get(), new int[]{1, 2, 3, 4, 5,	6, 7});
		  assert !parse("1.2.\0").isPresent();
	      }
	  };

   Encoding support
       It  is  necessary  to understand	the difference between code points and
       code units. A code point	is a numeric identifier	of a  symbol.  A  code
       unit is the smallest unit of storage in the encoded text. A single code
       point may be represented	with one or more code units. In	a fixed-length
       encoding	 all  code points are represented with the same	number of code
       units. In a variable-length encoding code  points  may  be  represented
       with  a	different  number of code units.  Note that the	"any" rule [^]
       matches any code	point, but not necessarily any code unit (the only way
       to match	any code unit regardless of the	encoding is the	 default  rule
       *).  The	generated lexer	works with a stream of code units: yych	stores
       a code unit, and	YYCTYPE	is the code unit type. Regular expressions, on
       the  other  hand,  are  specified in terms of code points. When re2java
       compiles	regular	expressions to automata	it translates code  points  to
       code  units. This is generally not a simple mapping: in variable-length
       encodings a single code point range may get  translated	to  a  complex
       code unit graph.	 The following encodings are supported:

        ASCII	(enabled  by default). It is a fixed-length encoding with code
	 space [0-255] and 1-byte code points and code units.

        EBCDIC	(enabled with  --ebcdic	 or  re2c:encoding:ebcdic).  It	 is  a
	 fixed-length  encoding	with code space	[0-255]	and 1-byte code	points
	 and code units.

        UCS2  (enabled	 with  --ucs2  or   re2c:encoding:ucs2).   It	is   a
	 fixed-length  encoding	 with  code  space  [0-0xFFFF] and 2-byte code
	 points	and code units.

        UTF8 (enabled with --utf8  or	re2c:encoding:utf8).  It  is  a	 vari-
	 able-length  Unicode  encoding. Code unit size	is 1 byte. Code	points
	 are represented with 1	-- 4 code units.

        UTF16 (enabled	with --utf16 or	re2c:encoding:utf16). It  is  a	 vari-
	 able-length  Unicode encoding.	Code unit size is 2 bytes. Code	points
	 are represented with 1	-- 2 code units.

        UTF32	(enabled  with	--utf32	 or  re2c:encoding:utf32).  It	is   a
	 fixed-length Unicode encoding with code space [0-0x10FFFF] and	4-byte
	 code points and code units.

       Include file include/unicode_categories.re provides re2java definitions
       for the standard	Unicode	categories.

       Option  --input-encoding	 specifies  source file	encoding, which	can be
       used to enable Unicode literals in  regular  expressions.  For  example
       --input-encoding	utf8 tells re2java that	the source file	is in UTF8 (it
       differs	from  --utf8  which sets input text encoding). Option --encod-
       ing-policy specifies the	way re2java handles Unicode  surrogates	 (code
       points in range [0xD800-0xDFFF]).

       Below is	an example of a	lexer for UTF8 encoded Unicode identifiers.

	  // re2java $INPUT -o $OUTPUT --utf8 -s

	  /*!include:re2c "unicode_categories.re" */

	  class	Main {
	      static boolean lex(String	yyinput) {
		  int yycursor = 0;
		  int yymarker = 0;

		  /*!re2c
		      re2c:YYCTYPE = "char";
		      re2c:YYPEEK = "yyinput.charAt(yycursor)";
		      re2c:yyfill:enable = 0;

		      // Simplified "Unicode Identifier	and Pattern Syntax"
		      // (see https://unicode.org/reports/tr31)
		      id_start	  = L |	Nl | [$_];
		      id_continue = id_start | Mn | Mc | Nd | Pc | [\u200D\u05F3];
		      identifier  = id_start+;
		      // It should be `id_start	id_continue*`, but that	causes `error: code too	large`

		      identifier { return true;	}
		      *		 { return false; }
		  */
	      }

	      public static void main(String []args) {
		  assert lex("_\0");
	      }
	  };

   Include files
       re2java	allows	one  to	 include other files using a block of the form
       /*!include:re2c FILE */ or %{include FILE %}, or	an in-block  directive
       !include	 FILE  ;,  where  FILE	is  a path to the file to be included.
       re2java looks for include files in the directory	of the including  file
       and  in	include	 locations, which can be specified with	the -I option.
       Include blocks/directives in re2java work in the	same way as C/C++ #in-
       clude: FILE contents are	copy-pasted verbatim in	place of the block/di-
       rective.	Include	files may have further	includes  of  their  own.  Use
       --depfile  option to track build	dependencies of	the output file	on in-
       clude files.  re2java provides some predefined include files  that  can
       be  found in the	include/ subdirectory of the project. These files con-
       tain definitions	that may be useful to other projects (such as  Unicode
       categories) and form something like a standard library for re2java. Be-
       low is an example of using include files.

   Include file	1 (definitions.java)
	  /*!re2c
	      number = [1-9][0-9]*;
	  */

   Include file	2 (extra_rules.re.inc)
	  // floating-point numbers
	  frac	= [0-9]* "." [0-9]+ | [0-9]+ ".";
	  exp	= 'e' [+-]? [0-9]+;
	  float	= frac exp? | [0-9]+ exp;

	  float	{ return Num.FLOAT; }

   Input file
	  // re2java $INPUT -o $OUTPUT

	  /*!include:re2c "definitions.java" */

	  class	Main {
	      enum Num {INT, FLOAT, NAN};

	      static Num lex(String yyinput) {
		  int yycursor = 0;
		  int yymarker = 0;

		  /*!re2c
		      re2c:YYCTYPE = "char";
		      re2c:YYPEEK = "yyinput.charAt(yycursor)";
		      re2c:yyfill:enable = 0;

		      *	     { return Num.NAN; }
		      number { return Num.INT; }
		      !include "extra_rules.re.inc";
		  */
	      }

	      public static void main(String []args) {
		  assert lex("123\0") == Num.INT;
		  assert lex("123.4567\0") == Num.FLOAT;
	      }
	  };

   Header files
       re2java	allows one to generate header file from	the input .re file us-
       ing --header option or re2c:header configuration	and block pairs	of the
       form /*!header:re2c:on*/	and /*!header:re2c:off*/, or %{header:on%} and
       %{header:off%}. The first block marks the beginning of header file, and
       the second block	marks the end of it. Everything	between	 these	blocks
       is  processed by	re2java, and the generated code	is written to the file
       specified with --header option or re2c:header configuration (or	stdout
       if neither option nor configuration is used). Autogenerated header file
       may  be	needed	in  cases when re2java is used to generate definitions
       that must be visible from other translation units.

       Here is an example of generating	a header file that contains definition
       of the lexer state with tag variables (the number variables depends  on
       the regular grammar and is unknown to the programmer).

   Input file
	  // re2java $INPUT -o $OUTPUT --header	lexer/state.java

	  package headers;

	  import headers.lexer.State;

	  /*!header:re2c:on*/
	  package headers.lexer;

	  public class State {
	      public String yyinput;
	      public int yycursor;
	      /*!stags:re2c format = "public int @@;\n"; */

	      public State(String str) {
		  yyinput = str;
		  yycursor = 0;
		  /*!stags:re2c	format = "@@ = 0;\n"; */
	      }
	  };
	  /*!header:re2c:off*/

	  class	Main {
	      static int lex(String str) {
		  State	yyrecord = new State(str);
		  int t;
		  /*!re2c
		      re2c:api = record;
		      re2c:tags	= 1;
		      re2c:yyfill:enable = 0;
		      re2c:YYCTYPE = "char";
		      re2c:YYPEEK = "yyrecord.yyinput.charAt(yyrecord.yycursor)";
		      re2c:header = "lexer/state.java";

		      [a]* @t [b]* { return t; }
		  */
	      }

	      public static void main(String []args) {
		  assert lex("ab\0") ==	1;
	      }
	  };

   Header file
	  // Generated by re2c

	  package headers.lexer;

	  public class State {
	      public String yyinput;
	      public int yycursor;
	      public int yyt1;

	      public State(String str) {
		  yyinput = str;
		  yycursor = 0;
		  yyt1 = 0;

	      }
	  };

   Skeleton programs
       With  the  -S,  --skeleton option, re2java ignores all non-re2java code
       and generates a self-contained C	program	that can be  further  compiled
       and  executed.	The program consists of	lexer code and input data. For
       each constructed	DFA (block or condition) re2java  generates  a	stand-
       alone lexer and two files: an .input file with strings derived from the
       DFA and a .keys file with expected match	results. The program runs each
       lexer  on  the  corresponding .input file and compares results with the
       expectations.  Skeleton programs	are very useful	for a number  of  rea-
       sons:

        They can check	correctness of various re2java optimizations (the data
	 is  generated	early  in  the process,	before any DFA transformations
	 have taken place).

        Generating a set of input data	with good coverage may be  useful  for
	 both testing and benchmarking.

        Generating self-contained executable programs allows one to get mini-
	 mized test cases (the original	code may be large or have a lot	of de-
	 pendencies).

       The  difficulty with generating input data is that for all but the most
       trivial cases the number	of possible input strings is too  large	 (even
       if  the	string	length	is limited). re2java solves this difficulty by
       generating sufficiently many strings to cover almost  all  DFA  transi-
       tions. It uses the following algorithm. First, it constructs a skeleton
       of  the	DFA.  For encodings with 1-byte	code unit size (such as	ASCII,
       UTF-8 and EBCDIC) skeleton is just an exact copy	of the	original  DFA.
       For  encodings with multibyte code units	skeleton is a copy of DFA with
       certain transitions omitted: namely, re2java takes  at  most  256  code
       units  for  each	 disjoint  continuous  range that corresponds to a DFA
       transition.  The	chosen values are evenly distributed and include range
       bounds. Instead of trying to cover all possible paths in	 the  skeleton
       (which  is  infeasible)	re2java	 generates  sufficiently many paths to
       cover all skeleton transitions, and thus	trigger	the corresponding con-
       ditional	jumps in the lexer.  The algorithm implementation  is  limited
       by  ~1Gb	of transitions and consumes constant amount of memory (re2java
       writes data to file as soon as it is generated).

   Visualization and debug
       With the	-D, --emit-dot option, re2java does  not  generate  code.  In-
       stead,  it dumps	the generated DFA in DOT format.  One can convert this
       dump to an image	of the DFA using Graphviz or  another  library.	  Note
       that this option	shows the final	DFA after it has gone through a	number
       of optimizations	and transformations. Earlier stages can	be dumped with
       various debug options, such as --dump-nfa, --dump-dfa-raw etc. (see the
       full list of options).

SEE ALSO
       You  can	 find  more  information  about	 re2c at the official website:
       http://re2c.org.	  Similar  programs  are   flex(1),   lex(1),	quex(-
       http://quex.sourceforge.net).

AUTHORS
       re2java	  was	 originally    written	  by	Peter	 Bumbulis   (-
       peter@csg.uwaterloo.ca) in 1993.	 Marcus	Boerger	and Dan	 Nuffer	 spent
       several	years  to  turn	the original idea into a production ready code
       generator. Since	then it	has been maintained and	developed by  multiple
       volunteers,   most   notably,  Brian  Young  (bayoung@acm.org),	Marcus
       Boerger,	Dan Nuffer (nuffer@users.sourceforge.net), Ulya	Trofimovich (-
       skvadrik@gmail.com), Serghei Iakovlev, Sergei Trofimovich, Petr Skocik,
       ligfx raekye and	PolarGoose.

								    RE2JAVA(1)

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