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std::strstr...strstreambuf(3) C++ Standard Libarystd::strstr...strstreambuf(3)

NAME
       std::strstreambuf::strstreambuf - std::strstreambuf::strstreambuf

Synopsis
	  explicit    strstreambuf(    std::streamsize	  alsize    =	0   );
       (until C++11)
	  strstreambuf()	    :		 strstreambuf(0)	    {}
       (since C++11)
	  explicit strstreambuf( std::streamsize alsize	);
	  strstreambuf(	       void*	    (*palloc)(std::size_t),	  void
       (2)
	  (*pfree)(void*) );
	  strstreambuf(	 char*	gnext,	std::streamsize	 n,  char*  pbeg  =  0
       (3)
	  );								 (1)
	  strstreambuf(	  signed   char*   gnext,  std::streamsize  n,	signed
       (4)
	  char*	pbeg = 0 );
	  strstreambuf(	  unsigned    char*    gnext,	 std::streamsize    n,
       (5)
	  unsigned char* pbeg =	0 );
	  strstreambuf(	   const    char*    gnext,   std::streamsize	n   );
       (6)
	  strstreambuf(	 const	signed	char*	gnext,	 std::streamsize   n);
       (7)
	  strstreambuf(	 const	unsigned  char*	 gnext,	 std::streamsize  n );
       (8)

	  1) Constructs	a std::strstreambuf object: initializes	the base class
       by calling the
	  default constructor of std::streambuf, initializes the buffer	 state
       to "dynamic"
	  (the buffer will be allocated	as needed), initializes	allocated size
       to the provided
	  alsize, initializes the allocation and the deallocation functions to
       null (will use
	  new[]	and delete[])
	  2) Constructs	a std::strstreambuf object: initializes	the base class
       by calling the
	  default  constructor of std::streambuf, initializes the buffer state
       to "dynamic"
	  (the buffer will be allocated	as needed), initializes	allocated size
       to unspecified
	  value, initializes the allocation function to	palloc and the deallo-
       cation function
	  to pfree
	  3-5) Constructs a std::strstreambuf object in	following steps:
	  a) Initializes the base class	by calling the default constructor  of
       std::streambuf
	  b) Initializes the buffer state to "constant"	(the buffer is a user-
       provided
	  fixed-size buffer)
	  c)  Determines  the number of	elements in the	user-provided array as
       follows:	if n is
	  greater than zero, n is used.	If n is	 zero,	std::strlen(gnext)  is
       executed	to
	  determine the	buffer size. If	n is negative, INT_MAX is used.
	  d)  Configures the std::basic_streambuf pointers as follows: If pbeg
       is a null
	  pointer, calls setg(gnext, gnext, gnext + N).	If pbeg	is not a  null
       pointer,
	  executes setg(gnext, gnext, pbeg) and	setp(pbeg, pbeg+N), where N is
       the number of
	  elements in the array	as determined earlier.
	  6-8)	Same  as  strstreambuf((char*)gnext, n), except	the "constant"
       bit is set in the
	  buffer state bitmask (output to this buffer is not allowed)

Parameters
	  alsize - the initial size of the dynamically allocated buffer
	  palloc - pointer to user-provided allocation function
	  pfree	 - pointer to user-provided deallocation function
	  gnext	 - pointer to the start	of the get area	in  the	 user-provided
       array
	  pbeg	  -  pointer to	the start of the put area in the user-provided
       array
	  n	 - the number of bytes in the get area (if pbeg	is null) or in
       the put area
		   (if pbeg is not null) of the	user-provided array

Notes
	  These	constructors are  typically  called  by	 the  constructors  of
       std::strstream

	 Defect	reports

	  The following	behavior-changing defect reports were applied retroac-
       tively to
	  previously published C++ standards.

	    DR	  Applied to	  Behavior as published	      Correct behavior
	  P0935R0 C++11	     default constructor was explicit made implicit

Example
       // Run this code

	#include <strstream>
	#include <iostream>

	int main()
	{
	    std::strstreambuf dyn; // dynamic
	    std::strstream dyn_s; // equivalent	stream
	    dyn_s << 1.23 << std::ends;
	    std::cout << dyn_s.str() <<	'\n';
	    dyn_s.freeze(false);

	    char buf[10];
	    std::strstreambuf  user(buf,  10,  buf);  //  user-provided	output
       buffer
	    std::ostrstream user_s(buf,	10); //	equivalent stream
	    user_s << 1.23 << std::ends;
	    std::cout << buf <<	'\n';

	    std::strstreambuf lit("1 2 3", 5); // constant
	    std::istrstream lit_s("1 2 3"); // equivalent stream
	    int	i, j, k;
	    lit_s >> i >> j >> k;
	    std::cout << i << '	' << j << ' ' << k << '\n';
	}

Output:
	1.23
	1.23
	1 2 3

See also
	  constructor	constructs an  strstream,  optionally  allocating  the
       buffer
			(public	member function	of std::strstream)

http://cppreference.com		  2022.07.31	 std::strstr...strstreambuf(3)

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