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MTBL_READER(3)							MTBL_READER(3)

NAME
       mtbl_reader - read an MTBL file

SYNOPSIS
       #include	<mtbl.h>

       Reader objects:

       struct mtbl_reader *
       mtbl_reader_init(const char *fname, const struct	mtbl_reader_options *ropt);

       struct mtbl_reader *
       mtbl_reader_init_fd(int fd, const struct	mtbl_reader_options *ropt);

       void
       mtbl_reader_destroy(struct mtbl_reader **r);

       const struct mtbl_source	*
       mtbl_reader_source(struct mtbl_reader *r);

       const struct mtbl_metadata *
       mtbl_reader_metadata(struct mtbl_reader *r);

       Reader options:

       struct mtbl_reader_options *
       mtbl_reader_options_init(void);

       void
       mtbl_reader_options_destroy(struct mtbl_reader_options **ropt);

       void
       mtbl_reader_options_set_verify_checksums(
	       struct mtbl_reader_options *ropt,
	       bool verify_checksums);

       void
       mtbl_reader_options_set_madvise_random(
	       struct mtbl_reader_options *ropt,
	       bool madvise_random);

DESCRIPTION
       MTBL files are accessed by creating an mtbl_reader object, calling
       mtbl_reader_source() to obtain an mtbl_source handle, and using the
       mtbl_source(3) interface	to read	entries.

       mtbl_reader objects may be created by calling mtbl_reader_init()	with
       an fname	argument specifying the	filename to be opened, or
       mtbl_reader_init_fd() may be called with	an fd argument specifying an
       open, readable file descriptor. Since MTBL files	are immutable, the
       same MTBL file may be opened and	read from concurrently by independent
       threads or processes.

       If the ropt parameter to	mtbl_reader_init() or mtbl_reader_init_fd() is
       non-NULL, the parameters	specified in the mtbl_reader_options object
       will be configured into the mtbl_reader object.

       File-level metadata may be accessed using the mtbl_metadata(3)
       interface, using	the object returned by mtbl_reader_metadata(). Note
       that the	metadata object	is valid only as long as the reader object
       exists.

   Reader options
       verify_checksums

	   Specifies whether or	not the	CRC32C checksum	on the index block and
	   each	data block should be verified or not. If verify_checksums is
	   enabled, a checksum mismatch	will cause a fatal runtime error. The
	   default is to not verify index or data block	checksums.

       madvise_random

	   Specifies whether the kernel	should be advised if the data access
	   patterns are	expected to be random or not. This may hurt some
	   workloads but help others. The default is to	not set	this advisory
	   information.

	   This	option can be explicitly overridden by setting the environment
	   variable MTBL_READER_MADVISE_RANDOM to the string "0" (force
	   disable) or "1" (force enable).

	   This	option only has	any effect on systems that have	the
	   posix_madvise or madvise system calls.

RETURN VALUE
       mtbl_reader_init() and mtbl_reader_init_fd() return NULL	on failure,
       and non-NULL on success.

				  11/14/2022			MTBL_READER(3)

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