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/* zlib.h -- interface of the 'zlib' general purpose compression library
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version 1.2.8, April 28th, 2013
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Copyright (C) 1995-2013 Jean-loup Gailly and Mark Adler
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This software is provided 'as-is', without any express or implied
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warranty. In no event will the authors be held liable for any damages
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arising from the use of this software.
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Permission is granted to anyone to use this software for any purpose,
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including commercial applications, and to alter it and redistribute it
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freely, subject to the following restrictions:
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1. The origin of this software must not be misrepresented; you must not
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claim that you wrote the original software. If you use this software
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in a product, an acknowledgment in the product documentation would be
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appreciated but is not required.
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2. Altered source versions must be plainly marked as such, and must not be
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misrepresented as being the original software.
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3. This notice may not be removed or altered from any source distribution.
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Jean-loup Gailly Mark Adler
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jloup@gzip.org madler@alumni.caltech.edu
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The data format used by the zlib library is described by RFCs (Request for
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Comments) 1950 to 1952 in the files http://tools.ietf.org/html/rfc1950
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(zlib format), rfc1951 (deflate format) and rfc1952 (gzip format).
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#define ZLIB_VERSION "1.2.8"
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#define ZLIB_VERNUM 0x1280
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#define ZLIB_VER_MAJOR 1
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#define ZLIB_VER_MINOR 2
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#define ZLIB_VER_REVISION 8
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#define ZLIB_VER_SUBREVISION 0
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The 'zlib' compression library provides in-memory compression and
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decompression functions, including integrity checks of the uncompressed data.
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This version of the library supports only one compression method (deflation)
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but other algorithms will be added later and will have the same stream
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Compression can be done in a single step if the buffers are large enough,
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or can be done by repeated calls of the compression function. In the latter
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case, the application must provide more input and/or consume the output
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(providing more output space) before each call.
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The compressed data format used by default by the in-memory functions is
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the zlib format, which is a zlib wrapper documented in RFC 1950, wrapped
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around a deflate stream, which is itself documented in RFC 1951.
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The library also supports reading and writing files in gzip (.gz) format
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with an interface similar to that of stdio using the functions that start
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with "gz". The gzip format is different from the zlib format. gzip is a
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gzip wrapper, documented in RFC 1952, wrapped around a deflate stream.
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This library can optionally read and write gzip streams in memory as well.
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The zlib format was designed to be compact and fast for use in memory
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and on communications channels. The gzip format was designed for single-
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file compression on file systems, has a larger header than zlib to maintain
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directory information, and uses a different, slower check method than zlib.
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The library does not install any signal handler. The decoder checks
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the consistency of the compressed data, so the library should never crash
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even in case of corrupted input.
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typedef voidpf (*alloc_func) OF((voidpf opaque, uInt items, uInt size));
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typedef void (*free_func) OF((voidpf opaque, voidpf address));
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struct internal_state;
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typedef struct z_stream_s {
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z_const Bytef *next_in; /* next input byte */
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uInt avail_in; /* number of bytes available at next_in */
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uLong total_in; /* total number of input bytes read so far */
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Bytef *next_out; /* next output byte should be put there */
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uInt avail_out; /* remaining free space at next_out */
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uLong total_out; /* total number of bytes output so far */
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z_const char *msg; /* last error message, NULL if no error */
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struct internal_state FAR *state; /* not visible by applications */
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alloc_func zalloc; /* used to allocate the internal state */
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free_func zfree; /* used to free the internal state */
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voidpf opaque; /* private data object passed to zalloc and zfree */
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int data_type; /* best guess about the data type: binary or text */
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uLong adler; /* adler32 value of the uncompressed data */
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uLong reserved; /* reserved for future use */
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typedef z_stream FAR *z_streamp;
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gzip header information passed to and from zlib routines. See RFC 1952
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for more details on the meanings of these fields.
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typedef struct gz_header_s {
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int text; /* true if compressed data believed to be text */
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uLong time; /* modification time */
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int xflags; /* extra flags (not used when writing a gzip file) */
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int os; /* operating system */
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Bytef *extra; /* pointer to extra field or Z_NULL if none */
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uInt extra_len; /* extra field length (valid if extra != Z_NULL) */
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uInt extra_max; /* space at extra (only when reading header) */
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Bytef *name; /* pointer to zero-terminated file name or Z_NULL */
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uInt name_max; /* space at name (only when reading header) */
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Bytef *comment; /* pointer to zero-terminated comment or Z_NULL */
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uInt comm_max; /* space at comment (only when reading header) */
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int hcrc; /* true if there was or will be a header crc */
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int done; /* true when done reading gzip header (not used
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when writing a gzip file) */
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typedef gz_header FAR *gz_headerp;
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The application must update next_in and avail_in when avail_in has dropped
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to zero. It must update next_out and avail_out when avail_out has dropped
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to zero. The application must initialize zalloc, zfree and opaque before
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calling the init function. All other fields are set by the compression
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library and must not be updated by the application.
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The opaque value provided by the application will be passed as the first
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parameter for calls of zalloc and zfree. This can be useful for custom
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memory management. The compression library attaches no meaning to the
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zalloc must return Z_NULL if there is not enough memory for the object.
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If zlib is used in a multi-threaded application, zalloc and zfree must be
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On 16-bit systems, the functions zalloc and zfree must be able to allocate
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exactly 65536 bytes, but will not be required to allocate more than this if
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the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS, pointers
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returned by zalloc for objects of exactly 65536 bytes *must* have their
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offset normalized to zero. The default allocation function provided by this
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library ensures this (see zutil.c). To reduce memory requirements and avoid
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any allocation of 64K objects, at the expense of compression ratio, compile
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the library with -DMAX_WBITS=14 (see zconf.h).
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The fields total_in and total_out can be used for statistics or progress
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reports. After compression, total_in holds the total size of the
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uncompressed data and may be saved for use in the decompressor (particularly
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if the decompressor wants to decompress everything in a single step).
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#define Z_PARTIAL_FLUSH 1
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#define Z_SYNC_FLUSH 2
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#define Z_FULL_FLUSH 3
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/* Allowed flush values; see deflate() and inflate() below for details */
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#define Z_STREAM_END 1
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#define Z_NEED_DICT 2
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#define Z_STREAM_ERROR (-2)
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#define Z_DATA_ERROR (-3)
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#define Z_MEM_ERROR (-4)
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#define Z_BUF_ERROR (-5)
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#define Z_VERSION_ERROR (-6)
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/* Return codes for the compression/decompression functions. Negative values
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* are errors, positive values are used for special but normal events.
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#define Z_NO_COMPRESSION 0
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#define Z_BEST_SPEED 1
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#define Z_BEST_COMPRESSION 9
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#define Z_DEFAULT_COMPRESSION (-1)
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/* compression levels */
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#define Z_HUFFMAN_ONLY 2
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#define Z_DEFAULT_STRATEGY 0
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/* compression strategy; see deflateInit2() below for details */
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#define Z_ASCII Z_TEXT /* for compatibility with 1.2.2 and earlier */
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/* Possible values of the data_type field (though see inflate()) */
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/* The deflate compression method (the only one supported in this version) */
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#define Z_NULL 0 /* for initializing zalloc, zfree, opaque */
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#define zlib_version zlibVersion()
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/* for compatibility with versions < 1.0.2 */
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/* basic functions */
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ZEXTERN const char * ZEXPORT zlibVersion OF((void));
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/* The application can compare zlibVersion and ZLIB_VERSION for consistency.
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If the first character differs, the library code actually used is not
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compatible with the zlib.h header file used by the application. This check
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is automatically made by deflateInit and inflateInit.
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ZEXTERN int ZEXPORT deflateInit OF((z_streamp strm, int level));
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Initializes the internal stream state for compression. The fields
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zalloc, zfree and opaque must be initialized before by the caller. If
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zalloc and zfree are set to Z_NULL, deflateInit updates them to use default
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allocation functions.
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The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
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1 gives best speed, 9 gives best compression, 0 gives no compression at all
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(the input data is simply copied a block at a time). Z_DEFAULT_COMPRESSION
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requests a default compromise between speed and compression (currently
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equivalent to level 6).
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deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
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memory, Z_STREAM_ERROR if level is not a valid compression level, or
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Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible
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with the version assumed by the caller (ZLIB_VERSION). msg is set to null
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if there is no error message. deflateInit does not perform any compression:
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this will be done by deflate().
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ZEXTERN int ZEXPORT deflate OF((z_streamp strm, int flush));
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deflate compresses as much data as possible, and stops when the input
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buffer becomes empty or the output buffer becomes full. It may introduce
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some output latency (reading input without producing any output) except when
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The detailed semantics are as follows. deflate performs one or both of the
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- Compress more input starting at next_in and update next_in and avail_in
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accordingly. If not all input can be processed (because there is not
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enough room in the output buffer), next_in and avail_in are updated and
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processing will resume at this point for the next call of deflate().
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- Provide more output starting at next_out and update next_out and avail_out
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accordingly. This action is forced if the parameter flush is non zero.
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Forcing flush frequently degrades the compression ratio, so this parameter
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should be set only when necessary (in interactive applications). Some
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output may be provided even if flush is not set.
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Before the call of deflate(), the application should ensure that at least
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one of the actions is possible, by providing more input and/or consuming more
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output, and updating avail_in or avail_out accordingly; avail_out should
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never be zero before the call. The application can consume the compressed
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output when it wants, for example when the output buffer is full (avail_out
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== 0), or after each call of deflate(). If deflate returns Z_OK and with
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zero avail_out, it must be called again after making room in the output
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buffer because there might be more output pending.
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Normally the parameter flush is set to Z_NO_FLUSH, which allows deflate to
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decide how much data to accumulate before producing output, in order to
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maximize compression.
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If the parameter flush is set to Z_SYNC_FLUSH, all pending output is
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flushed to the output buffer and the output is aligned on a byte boundary, so
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that the decompressor can get all input data available so far. (In
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particular avail_in is zero after the call if enough output space has been
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provided before the call.) Flushing may degrade compression for some
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compression algorithms and so it should be used only when necessary. This
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completes the current deflate block and follows it with an empty stored block
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that is three bits plus filler bits to the next byte, followed by four bytes
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If flush is set to Z_PARTIAL_FLUSH, all pending output is flushed to the
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output buffer, but the output is not aligned to a byte boundary. All of the
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input data so far will be available to the decompressor, as for Z_SYNC_FLUSH.
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This completes the current deflate block and follows it with an empty fixed
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codes block that is 10 bits long. This assures that enough bytes are output
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in order for the decompressor to finish the block before the empty fixed code
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If flush is set to Z_BLOCK, a deflate block is completed and emitted, as
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for Z_SYNC_FLUSH, but the output is not aligned on a byte boundary, and up to
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seven bits of the current block are held to be written as the next byte after
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the next deflate block is completed. In this case, the decompressor may not
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be provided enough bits at this point in order to complete decompression of
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the data provided so far to the compressor. It may need to wait for the next
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block to be emitted. This is for advanced applications that need to control
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the emission of deflate blocks.
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If flush is set to Z_FULL_FLUSH, all output is flushed as with
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Z_SYNC_FLUSH, and the compression state is reset so that decompression can
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restart from this point if previous compressed data has been damaged or if
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random access is desired. Using Z_FULL_FLUSH too often can seriously degrade
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If deflate returns with avail_out == 0, this function must be called again
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with the same value of the flush parameter and more output space (updated
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avail_out), until the flush is complete (deflate returns with non-zero
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avail_out). In the case of a Z_FULL_FLUSH or Z_SYNC_FLUSH, make sure that
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avail_out is greater than six to avoid repeated flush markers due to
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avail_out == 0 on return.
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If the parameter flush is set to Z_FINISH, pending input is processed,
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pending output is flushed and deflate returns with Z_STREAM_END if there was
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enough output space; if deflate returns with Z_OK, this function must be
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called again with Z_FINISH and more output space (updated avail_out) but no
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more input data, until it returns with Z_STREAM_END or an error. After
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deflate has returned Z_STREAM_END, the only possible operations on the stream
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are deflateReset or deflateEnd.
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Z_FINISH can be used immediately after deflateInit if all the compression
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is to be done in a single step. In this case, avail_out must be at least the
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value returned by deflateBound (see below). Then deflate is guaranteed to
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return Z_STREAM_END. If not enough output space is provided, deflate will
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not return Z_STREAM_END, and it must be called again as described above.
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deflate() sets strm->adler to the adler32 checksum of all input read
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so far (that is, total_in bytes).
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deflate() may update strm->data_type if it can make a good guess about
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the input data type (Z_BINARY or Z_TEXT). In doubt, the data is considered
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binary. This field is only for information purposes and does not affect the
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compression algorithm in any manner.
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deflate() returns Z_OK if some progress has been made (more input
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processed or more output produced), Z_STREAM_END if all input has been
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consumed and all output has been produced (only when flush is set to
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Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
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if next_in or next_out was Z_NULL), Z_BUF_ERROR if no progress is possible
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(for example avail_in or avail_out was zero). Note that Z_BUF_ERROR is not
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fatal, and deflate() can be called again with more input and more output
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space to continue compressing.
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ZEXTERN int ZEXPORT deflateEnd OF((z_streamp strm));
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All dynamically allocated data structures for this stream are freed.
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This function discards any unprocessed input and does not flush any pending
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deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
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stream state was inconsistent, Z_DATA_ERROR if the stream was freed
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prematurely (some input or output was discarded). In the error case, msg
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may be set but then points to a static string (which must not be
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ZEXTERN int ZEXPORT inflateInit OF((z_streamp strm));
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Initializes the internal stream state for decompression. The fields
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next_in, avail_in, zalloc, zfree and opaque must be initialized before by
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the caller. If next_in is not Z_NULL and avail_in is large enough (the
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exact value depends on the compression method), inflateInit determines the
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compression method from the zlib header and allocates all data structures
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accordingly; otherwise the allocation will be deferred to the first call of
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inflate. If zalloc and zfree are set to Z_NULL, inflateInit updates them to
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use default allocation functions.
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inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
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memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
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version assumed by the caller, or Z_STREAM_ERROR if the parameters are
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invalid, such as a null pointer to the structure. msg is set to null if
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there is no error message. inflateInit does not perform any decompression
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apart from possibly reading the zlib header if present: actual decompression
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will be done by inflate(). (So next_in and avail_in may be modified, but
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next_out and avail_out are unused and unchanged.) The current implementation
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of inflateInit() does not process any header information -- that is deferred
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until inflate() is called.
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ZEXTERN int ZEXPORT inflate OF((z_streamp strm, int flush));
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inflate decompresses as much data as possible, and stops when the input
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buffer becomes empty or the output buffer becomes full. It may introduce
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some output latency (reading input without producing any output) except when
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The detailed semantics are as follows. inflate performs one or both of the
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- Decompress more input starting at next_in and update next_in and avail_in
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accordingly. If not all input can be processed (because there is not
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enough room in the output buffer), next_in is updated and processing will
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resume at this point for the next call of inflate().
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- Provide more output starting at next_out and update next_out and avail_out
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accordingly. inflate() provides as much output as possible, until there is
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no more input data or no more space in the output buffer (see below about
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the flush parameter).
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Before the call of inflate(), the application should ensure that at least
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one of the actions is possible, by providing more input and/or consuming more
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output, and updating the next_* and avail_* values accordingly. The
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application can consume the uncompressed output when it wants, for example
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when the output buffer is full (avail_out == 0), or after each call of
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inflate(). If inflate returns Z_OK and with zero avail_out, it must be
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called again after making room in the output buffer because there might be
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The flush parameter of inflate() can be Z_NO_FLUSH, Z_SYNC_FLUSH, Z_FINISH,
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Z_BLOCK, or Z_TREES. Z_SYNC_FLUSH requests that inflate() flush as much
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output as possible to the output buffer. Z_BLOCK requests that inflate()
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stop if and when it gets to the next deflate block boundary. When decoding
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the zlib or gzip format, this will cause inflate() to return immediately
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after the header and before the first block. When doing a raw inflate,
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inflate() will go ahead and process the first block, and will return when it
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gets to the end of that block, or when it runs out of data.
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The Z_BLOCK option assists in appending to or combining deflate streams.
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Also to assist in this, on return inflate() will set strm->data_type to the
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number of unused bits in the last byte taken from strm->next_in, plus 64 if
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inflate() is currently decoding the last block in the deflate stream, plus
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128 if inflate() returned immediately after decoding an end-of-block code or
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decoding the complete header up to just before the first byte of the deflate
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stream. The end-of-block will not be indicated until all of the uncompressed
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data from that block has been written to strm->next_out. The number of
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unused bits may in general be greater than seven, except when bit 7 of
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data_type is set, in which case the number of unused bits will be less than
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eight. data_type is set as noted here every time inflate() returns for all
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flush options, and so can be used to determine the amount of currently
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consumed input in bits.
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The Z_TREES option behaves as Z_BLOCK does, but it also returns when the
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end of each deflate block header is reached, before any actual data in that
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block is decoded. This allows the caller to determine the length of the
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deflate block header for later use in random access within a deflate block.
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256 is added to the value of strm->data_type when inflate() returns
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immediately after reaching the end of the deflate block header.
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inflate() should normally be called until it returns Z_STREAM_END or an
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error. However if all decompression is to be performed in a single step (a
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single call of inflate), the parameter flush should be set to Z_FINISH. In
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this case all pending input is processed and all pending output is flushed;
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avail_out must be large enough to hold all of the uncompressed data for the
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operation to complete. (The size of the uncompressed data may have been
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saved by the compressor for this purpose.) The use of Z_FINISH is not
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required to perform an inflation in one step. However it may be used to
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inform inflate that a faster approach can be used for the single inflate()
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call. Z_FINISH also informs inflate to not maintain a sliding window if the
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stream completes, which reduces inflate's memory footprint. If the stream
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does not complete, either because not all of the stream is provided or not
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enough output space is provided, then a sliding window will be allocated and
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inflate() can be called again to continue the operation as if Z_NO_FLUSH had
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In this implementation, inflate() always flushes as much output as
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possible to the output buffer, and always uses the faster approach on the
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first call. So the effects of the flush parameter in this implementation are
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on the return value of inflate() as noted below, when inflate() returns early
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when Z_BLOCK or Z_TREES is used, and when inflate() avoids the allocation of
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memory for a sliding window when Z_FINISH is used.
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If a preset dictionary is needed after this call (see inflateSetDictionary
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below), inflate sets strm->adler to the Adler-32 checksum of the dictionary
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chosen by the compressor and returns Z_NEED_DICT; otherwise it sets
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strm->adler to the Adler-32 checksum of all output produced so far (that is,
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total_out bytes) and returns Z_OK, Z_STREAM_END or an error code as described
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below. At the end of the stream, inflate() checks that its computed adler32
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checksum is equal to that saved by the compressor and returns Z_STREAM_END
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only if the checksum is correct.
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inflate() can decompress and check either zlib-wrapped or gzip-wrapped
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deflate data. The header type is detected automatically, if requested when
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initializing with inflateInit2(). Any information contained in the gzip
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header is not retained, so applications that need that information should
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instead use raw inflate, see inflateInit2() below, or inflateBack() and
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perform their own processing of the gzip header and trailer. When processing
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gzip-wrapped deflate data, strm->adler32 is set to the CRC-32 of the output
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producted so far. The CRC-32 is checked against the gzip trailer.
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inflate() returns Z_OK if some progress has been made (more input processed
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or more output produced), Z_STREAM_END if the end of the compressed data has
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been reached and all uncompressed output has been produced, Z_NEED_DICT if a
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preset dictionary is needed at this point, Z_DATA_ERROR if the input data was
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corrupted (input stream not conforming to the zlib format or incorrect check
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value), Z_STREAM_ERROR if the stream structure was inconsistent (for example
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next_in or next_out was Z_NULL), Z_MEM_ERROR if there was not enough memory,
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Z_BUF_ERROR if no progress is possible or if there was not enough room in the
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output buffer when Z_FINISH is used. Note that Z_BUF_ERROR is not fatal, and
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inflate() can be called again with more input and more output space to
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continue decompressing. If Z_DATA_ERROR is returned, the application may
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then call inflateSync() to look for a good compression block if a partial
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recovery of the data is desired.
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ZEXTERN int ZEXPORT inflateEnd OF((z_streamp strm));
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All dynamically allocated data structures for this stream are freed.
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This function discards any unprocessed input and does not flush any pending
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inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
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was inconsistent. In the error case, msg may be set but then points to a
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static string (which must not be deallocated).
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/* Advanced functions */
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The following functions are needed only in some special applications.
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ZEXTERN int ZEXPORT deflateInit2 OF((z_streamp strm,
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This is another version of deflateInit with more compression options. The
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fields next_in, zalloc, zfree and opaque must be initialized before by the
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The method parameter is the compression method. It must be Z_DEFLATED in
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this version of the library.
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The windowBits parameter is the base two logarithm of the window size
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(the size of the history buffer). It should be in the range 8..15 for this
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version of the library. Larger values of this parameter result in better
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compression at the expense of memory usage. The default value is 15 if
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deflateInit is used instead.
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windowBits can also be -8..-15 for raw deflate. In this case, -windowBits
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determines the window size. deflate() will then generate raw deflate data
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with no zlib header or trailer, and will not compute an adler32 check value.
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windowBits can also be greater than 15 for optional gzip encoding. Add
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16 to windowBits to write a simple gzip header and trailer around the
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compressed data instead of a zlib wrapper. The gzip header will have no
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file name, no extra data, no comment, no modification time (set to zero), no
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header crc, and the operating system will be set to 255 (unknown). If a
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gzip stream is being written, strm->adler is a crc32 instead of an adler32.
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The memLevel parameter specifies how much memory should be allocated
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for the internal compression state. memLevel=1 uses minimum memory but is
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slow and reduces compression ratio; memLevel=9 uses maximum memory for
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optimal speed. The default value is 8. See zconf.h for total memory usage
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as a function of windowBits and memLevel.
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The strategy parameter is used to tune the compression algorithm. Use the
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value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a
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filter (or predictor), Z_HUFFMAN_ONLY to force Huffman encoding only (no
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string match), or Z_RLE to limit match distances to one (run-length
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encoding). Filtered data consists mostly of small values with a somewhat
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random distribution. In this case, the compression algorithm is tuned to
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compress them better. The effect of Z_FILTERED is to force more Huffman
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coding and less string matching; it is somewhat intermediate between
572
Z_DEFAULT_STRATEGY and Z_HUFFMAN_ONLY. Z_RLE is designed to be almost as
573
fast as Z_HUFFMAN_ONLY, but give better compression for PNG image data. The
574
strategy parameter only affects the compression ratio but not the
575
correctness of the compressed output even if it is not set appropriately.
576
Z_FIXED prevents the use of dynamic Huffman codes, allowing for a simpler
577
decoder for special applications.
579
deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
580
memory, Z_STREAM_ERROR if any parameter is invalid (such as an invalid
581
method), or Z_VERSION_ERROR if the zlib library version (zlib_version) is
582
incompatible with the version assumed by the caller (ZLIB_VERSION). msg is
583
set to null if there is no error message. deflateInit2 does not perform any
584
compression: this will be done by deflate().
587
ZEXTERN int ZEXPORT deflateSetDictionary OF((z_streamp strm,
588
const Bytef *dictionary,
591
Initializes the compression dictionary from the given byte sequence
592
without producing any compressed output. When using the zlib format, this
593
function must be called immediately after deflateInit, deflateInit2 or
594
deflateReset, and before any call of deflate. When doing raw deflate, this
595
function must be called either before any call of deflate, or immediately
596
after the completion of a deflate block, i.e. after all input has been
597
consumed and all output has been delivered when using any of the flush
598
options Z_BLOCK, Z_PARTIAL_FLUSH, Z_SYNC_FLUSH, or Z_FULL_FLUSH. The
599
compressor and decompressor must use exactly the same dictionary (see
600
inflateSetDictionary).
602
The dictionary should consist of strings (byte sequences) that are likely
603
to be encountered later in the data to be compressed, with the most commonly
604
used strings preferably put towards the end of the dictionary. Using a
605
dictionary is most useful when the data to be compressed is short and can be
606
predicted with good accuracy; the data can then be compressed better than
607
with the default empty dictionary.
609
Depending on the size of the compression data structures selected by
610
deflateInit or deflateInit2, a part of the dictionary may in effect be
611
discarded, for example if the dictionary is larger than the window size
612
provided in deflateInit or deflateInit2. Thus the strings most likely to be
613
useful should be put at the end of the dictionary, not at the front. In
614
addition, the current implementation of deflate will use at most the window
615
size minus 262 bytes of the provided dictionary.
617
Upon return of this function, strm->adler is set to the adler32 value
618
of the dictionary; the decompressor may later use this value to determine
619
which dictionary has been used by the compressor. (The adler32 value
620
applies to the whole dictionary even if only a subset of the dictionary is
621
actually used by the compressor.) If a raw deflate was requested, then the
622
adler32 value is not computed and strm->adler is not set.
624
deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
625
parameter is invalid (e.g. dictionary being Z_NULL) or the stream state is
626
inconsistent (for example if deflate has already been called for this stream
627
or if not at a block boundary for raw deflate). deflateSetDictionary does
628
not perform any compression: this will be done by deflate().
631
ZEXTERN int ZEXPORT deflateCopy OF((z_streamp dest,
634
Sets the destination stream as a complete copy of the source stream.
636
This function can be useful when several compression strategies will be
637
tried, for example when there are several ways of pre-processing the input
638
data with a filter. The streams that will be discarded should then be freed
639
by calling deflateEnd. Note that deflateCopy duplicates the internal
640
compression state which can be quite large, so this strategy is slow and can
641
consume lots of memory.
643
deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
644
enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
645
(such as zalloc being Z_NULL). msg is left unchanged in both source and
649
ZEXTERN int ZEXPORT deflateReset OF((z_streamp strm));
651
This function is equivalent to deflateEnd followed by deflateInit,
652
but does not free and reallocate all the internal compression state. The
653
stream will keep the same compression level and any other attributes that
654
may have been set by deflateInit2.
656
deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
657
stream state was inconsistent (such as zalloc or state being Z_NULL).
660
ZEXTERN int ZEXPORT deflateParams OF((z_streamp strm,
664
Dynamically update the compression level and compression strategy. The
665
interpretation of level and strategy is as in deflateInit2. This can be
666
used to switch between compression and straight copy of the input data, or
667
to switch to a different kind of input data requiring a different strategy.
668
If the compression level is changed, the input available so far is
669
compressed with the old level (and may be flushed); the new level will take
670
effect only at the next call of deflate().
672
Before the call of deflateParams, the stream state must be set as for
673
a call of deflate(), since the currently available input may have to be
674
compressed and flushed. In particular, strm->avail_out must be non-zero.
676
deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source
677
stream state was inconsistent or if a parameter was invalid, Z_BUF_ERROR if
678
strm->avail_out was zero.
681
ZEXTERN int ZEXPORT deflateTune OF((z_streamp strm,
687
Fine tune deflate's internal compression parameters. This should only be
688
used by someone who understands the algorithm used by zlib's deflate for
689
searching for the best matching string, and even then only by the most
690
fanatic optimizer trying to squeeze out the last compressed bit for their
691
specific input data. Read the deflate.c source code for the meaning of the
692
max_lazy, good_length, nice_length, and max_chain parameters.
694
deflateTune() can be called after deflateInit() or deflateInit2(), and
695
returns Z_OK on success, or Z_STREAM_ERROR for an invalid deflate stream.
698
ZEXTERN uLong ZEXPORT deflateBound OF((z_streamp strm,
701
deflateBound() returns an upper bound on the compressed size after
702
deflation of sourceLen bytes. It must be called after deflateInit() or
703
deflateInit2(), and after deflateSetHeader(), if used. This would be used
704
to allocate an output buffer for deflation in a single pass, and so would be
705
called before deflate(). If that first deflate() call is provided the
706
sourceLen input bytes, an output buffer allocated to the size returned by
707
deflateBound(), and the flush value Z_FINISH, then deflate() is guaranteed
708
to return Z_STREAM_END. Note that it is possible for the compressed size to
709
be larger than the value returned by deflateBound() if flush options other
710
than Z_FINISH or Z_NO_FLUSH are used.
713
ZEXTERN int ZEXPORT deflatePending OF((z_streamp strm,
717
deflatePending() returns the number of bytes and bits of output that have
718
been generated, but not yet provided in the available output. The bytes not
719
provided would be due to the available output space having being consumed.
720
The number of bits of output not provided are between 0 and 7, where they
721
await more bits to join them in order to fill out a full byte. If pending
722
or bits are Z_NULL, then those values are not set.
724
deflatePending returns Z_OK if success, or Z_STREAM_ERROR if the source
725
stream state was inconsistent.
728
ZEXTERN int ZEXPORT deflatePrime OF((z_streamp strm,
732
deflatePrime() inserts bits in the deflate output stream. The intent
733
is that this function is used to start off the deflate output with the bits
734
leftover from a previous deflate stream when appending to it. As such, this
735
function can only be used for raw deflate, and must be used before the first
736
deflate() call after a deflateInit2() or deflateReset(). bits must be less
737
than or equal to 16, and that many of the least significant bits of value
738
will be inserted in the output.
740
deflatePrime returns Z_OK if success, Z_BUF_ERROR if there was not enough
741
room in the internal buffer to insert the bits, or Z_STREAM_ERROR if the
742
source stream state was inconsistent.
745
ZEXTERN int ZEXPORT deflateSetHeader OF((z_streamp strm,
748
deflateSetHeader() provides gzip header information for when a gzip
749
stream is requested by deflateInit2(). deflateSetHeader() may be called
750
after deflateInit2() or deflateReset() and before the first call of
751
deflate(). The text, time, os, extra field, name, and comment information
752
in the provided gz_header structure are written to the gzip header (xflag is
753
ignored -- the extra flags are set according to the compression level). The
754
caller must assure that, if not Z_NULL, name and comment are terminated with
755
a zero byte, and that if extra is not Z_NULL, that extra_len bytes are
756
available there. If hcrc is true, a gzip header crc is included. Note that
757
the current versions of the command-line version of gzip (up through version
758
1.3.x) do not support header crc's, and will report that it is a "multi-part
759
gzip file" and give up.
761
If deflateSetHeader is not used, the default gzip header has text false,
762
the time set to zero, and os set to 255, with no extra, name, or comment
763
fields. The gzip header is returned to the default state by deflateReset().
765
deflateSetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source
766
stream state was inconsistent.
770
ZEXTERN int ZEXPORT inflateInit2 OF((z_streamp strm,
773
This is another version of inflateInit with an extra parameter. The
774
fields next_in, avail_in, zalloc, zfree and opaque must be initialized
775
before by the caller.
777
The windowBits parameter is the base two logarithm of the maximum window
778
size (the size of the history buffer). It should be in the range 8..15 for
779
this version of the library. The default value is 15 if inflateInit is used
780
instead. windowBits must be greater than or equal to the windowBits value
781
provided to deflateInit2() while compressing, or it must be equal to 15 if
782
deflateInit2() was not used. If a compressed stream with a larger window
783
size is given as input, inflate() will return with the error code
784
Z_DATA_ERROR instead of trying to allocate a larger window.
786
windowBits can also be zero to request that inflate use the window size in
787
the zlib header of the compressed stream.
789
windowBits can also be -8..-15 for raw inflate. In this case, -windowBits
790
determines the window size. inflate() will then process raw deflate data,
791
not looking for a zlib or gzip header, not generating a check value, and not
792
looking for any check values for comparison at the end of the stream. This
793
is for use with other formats that use the deflate compressed data format
794
such as zip. Those formats provide their own check values. If a custom
795
format is developed using the raw deflate format for compressed data, it is
796
recommended that a check value such as an adler32 or a crc32 be applied to
797
the uncompressed data as is done in the zlib, gzip, and zip formats. For
798
most applications, the zlib format should be used as is. Note that comments
799
above on the use in deflateInit2() applies to the magnitude of windowBits.
801
windowBits can also be greater than 15 for optional gzip decoding. Add
802
32 to windowBits to enable zlib and gzip decoding with automatic header
803
detection, or add 16 to decode only the gzip format (the zlib format will
804
return a Z_DATA_ERROR). If a gzip stream is being decoded, strm->adler is a
805
crc32 instead of an adler32.
807
inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
808
memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
809
version assumed by the caller, or Z_STREAM_ERROR if the parameters are
810
invalid, such as a null pointer to the structure. msg is set to null if
811
there is no error message. inflateInit2 does not perform any decompression
812
apart from possibly reading the zlib header if present: actual decompression
813
will be done by inflate(). (So next_in and avail_in may be modified, but
814
next_out and avail_out are unused and unchanged.) The current implementation
815
of inflateInit2() does not process any header information -- that is
816
deferred until inflate() is called.
819
ZEXTERN int ZEXPORT inflateSetDictionary OF((z_streamp strm,
820
const Bytef *dictionary,
823
Initializes the decompression dictionary from the given uncompressed byte
824
sequence. This function must be called immediately after a call of inflate,
825
if that call returned Z_NEED_DICT. The dictionary chosen by the compressor
826
can be determined from the adler32 value returned by that call of inflate.
827
The compressor and decompressor must use exactly the same dictionary (see
828
deflateSetDictionary). For raw inflate, this function can be called at any
829
time to set the dictionary. If the provided dictionary is smaller than the
830
window and there is already data in the window, then the provided dictionary
831
will amend what's there. The application must insure that the dictionary
832
that was used for compression is provided.
834
inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
835
parameter is invalid (e.g. dictionary being Z_NULL) or the stream state is
836
inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the
837
expected one (incorrect adler32 value). inflateSetDictionary does not
838
perform any decompression: this will be done by subsequent calls of
842
ZEXTERN int ZEXPORT inflateGetDictionary OF((z_streamp strm,
846
Returns the sliding dictionary being maintained by inflate. dictLength is
847
set to the number of bytes in the dictionary, and that many bytes are copied
848
to dictionary. dictionary must have enough space, where 32768 bytes is
849
always enough. If inflateGetDictionary() is called with dictionary equal to
850
Z_NULL, then only the dictionary length is returned, and nothing is copied.
851
Similary, if dictLength is Z_NULL, then it is not set.
853
inflateGetDictionary returns Z_OK on success, or Z_STREAM_ERROR if the
854
stream state is inconsistent.
857
ZEXTERN int ZEXPORT inflateSync OF((z_streamp strm));
859
Skips invalid compressed data until a possible full flush point (see above
860
for the description of deflate with Z_FULL_FLUSH) can be found, or until all
861
available input is skipped. No output is provided.
863
inflateSync searches for a 00 00 FF FF pattern in the compressed data.
864
All full flush points have this pattern, but not all occurrences of this
865
pattern are full flush points.
867
inflateSync returns Z_OK if a possible full flush point has been found,
868
Z_BUF_ERROR if no more input was provided, Z_DATA_ERROR if no flush point
869
has been found, or Z_STREAM_ERROR if the stream structure was inconsistent.
870
In the success case, the application may save the current current value of
871
total_in which indicates where valid compressed data was found. In the
872
error case, the application may repeatedly call inflateSync, providing more
873
input each time, until success or end of the input data.
876
ZEXTERN int ZEXPORT inflateCopy OF((z_streamp dest,
879
Sets the destination stream as a complete copy of the source stream.
881
This function can be useful when randomly accessing a large stream. The
882
first pass through the stream can periodically record the inflate state,
883
allowing restarting inflate at those points when randomly accessing the
886
inflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
887
enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
888
(such as zalloc being Z_NULL). msg is left unchanged in both source and
892
ZEXTERN int ZEXPORT inflateReset OF((z_streamp strm));
894
This function is equivalent to inflateEnd followed by inflateInit,
895
but does not free and reallocate all the internal decompression state. The
896
stream will keep attributes that may have been set by inflateInit2.
898
inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
899
stream state was inconsistent (such as zalloc or state being Z_NULL).
902
ZEXTERN int ZEXPORT inflateReset2 OF((z_streamp strm,
905
This function is the same as inflateReset, but it also permits changing
906
the wrap and window size requests. The windowBits parameter is interpreted
907
the same as it is for inflateInit2.
909
inflateReset2 returns Z_OK if success, or Z_STREAM_ERROR if the source
910
stream state was inconsistent (such as zalloc or state being Z_NULL), or if
911
the windowBits parameter is invalid.
914
ZEXTERN int ZEXPORT inflatePrime OF((z_streamp strm,
918
This function inserts bits in the inflate input stream. The intent is
919
that this function is used to start inflating at a bit position in the
920
middle of a byte. The provided bits will be used before any bytes are used
921
from next_in. This function should only be used with raw inflate, and
922
should be used before the first inflate() call after inflateInit2() or
923
inflateReset(). bits must be less than or equal to 16, and that many of the
924
least significant bits of value will be inserted in the input.
926
If bits is negative, then the input stream bit buffer is emptied. Then
927
inflatePrime() can be called again to put bits in the buffer. This is used
928
to clear out bits leftover after feeding inflate a block description prior
929
to feeding inflate codes.
931
inflatePrime returns Z_OK if success, or Z_STREAM_ERROR if the source
932
stream state was inconsistent.
935
ZEXTERN long ZEXPORT inflateMark OF((z_streamp strm));
937
This function returns two values, one in the lower 16 bits of the return
938
value, and the other in the remaining upper bits, obtained by shifting the
939
return value down 16 bits. If the upper value is -1 and the lower value is
940
zero, then inflate() is currently decoding information outside of a block.
941
If the upper value is -1 and the lower value is non-zero, then inflate is in
942
the middle of a stored block, with the lower value equaling the number of
943
bytes from the input remaining to copy. If the upper value is not -1, then
944
it is the number of bits back from the current bit position in the input of
945
the code (literal or length/distance pair) currently being processed. In
946
that case the lower value is the number of bytes already emitted for that
949
A code is being processed if inflate is waiting for more input to complete
950
decoding of the code, or if it has completed decoding but is waiting for
951
more output space to write the literal or match data.
953
inflateMark() is used to mark locations in the input data for random
954
access, which may be at bit positions, and to note those cases where the
955
output of a code may span boundaries of random access blocks. The current
956
location in the input stream can be determined from avail_in and data_type
957
as noted in the description for the Z_BLOCK flush parameter for inflate.
959
inflateMark returns the value noted above or -1 << 16 if the provided
960
source stream state was inconsistent.
963
ZEXTERN int ZEXPORT inflateGetHeader OF((z_streamp strm,
966
inflateGetHeader() requests that gzip header information be stored in the
967
provided gz_header structure. inflateGetHeader() may be called after
968
inflateInit2() or inflateReset(), and before the first call of inflate().
969
As inflate() processes the gzip stream, head->done is zero until the header
970
is completed, at which time head->done is set to one. If a zlib stream is
971
being decoded, then head->done is set to -1 to indicate that there will be
972
no gzip header information forthcoming. Note that Z_BLOCK or Z_TREES can be
973
used to force inflate() to return immediately after header processing is
974
complete and before any actual data is decompressed.
976
The text, time, xflags, and os fields are filled in with the gzip header
977
contents. hcrc is set to true if there is a header CRC. (The header CRC
978
was valid if done is set to one.) If extra is not Z_NULL, then extra_max
979
contains the maximum number of bytes to write to extra. Once done is true,
980
extra_len contains the actual extra field length, and extra contains the
981
extra field, or that field truncated if extra_max is less than extra_len.
982
If name is not Z_NULL, then up to name_max characters are written there,
983
terminated with a zero unless the length is greater than name_max. If
984
comment is not Z_NULL, then up to comm_max characters are written there,
985
terminated with a zero unless the length is greater than comm_max. When any
986
of extra, name, or comment are not Z_NULL and the respective field is not
987
present in the header, then that field is set to Z_NULL to signal its
988
absence. This allows the use of deflateSetHeader() with the returned
989
structure to duplicate the header. However if those fields are set to
990
allocated memory, then the application will need to save those pointers
991
elsewhere so that they can be eventually freed.
993
If inflateGetHeader is not used, then the header information is simply
994
discarded. The header is always checked for validity, including the header
995
CRC if present. inflateReset() will reset the process to discard the header
996
information. The application would need to call inflateGetHeader() again to
997
retrieve the header from the next gzip stream.
999
inflateGetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source
1000
stream state was inconsistent.
1004
ZEXTERN int ZEXPORT inflateBackInit OF((z_streamp strm, int windowBits,
1005
unsigned char FAR *window));
1007
Initialize the internal stream state for decompression using inflateBack()
1008
calls. The fields zalloc, zfree and opaque in strm must be initialized
1009
before the call. If zalloc and zfree are Z_NULL, then the default library-
1010
derived memory allocation routines are used. windowBits is the base two
1011
logarithm of the window size, in the range 8..15. window is a caller
1012
supplied buffer of that size. Except for special applications where it is
1013
assured that deflate was used with small window sizes, windowBits must be 15
1014
and a 32K byte window must be supplied to be able to decompress general
1017
See inflateBack() for the usage of these routines.
1019
inflateBackInit will return Z_OK on success, Z_STREAM_ERROR if any of
1020
the parameters are invalid, Z_MEM_ERROR if the internal state could not be
1021
allocated, or Z_VERSION_ERROR if the version of the library does not match
1022
the version of the header file.
1025
typedef unsigned (*in_func) OF((void FAR *,
1026
z_const unsigned char FAR * FAR *));
1027
typedef int (*out_func) OF((void FAR *, unsigned char FAR *, unsigned));
1029
ZEXTERN int ZEXPORT inflateBack OF((z_streamp strm,
1030
in_func in, void FAR *in_desc,
1031
out_func out, void FAR *out_desc));
1033
inflateBack() does a raw inflate with a single call using a call-back
1034
interface for input and output. This is potentially more efficient than
1035
inflate() for file i/o applications, in that it avoids copying between the
1036
output and the sliding window by simply making the window itself the output
1037
buffer. inflate() can be faster on modern CPUs when used with large
1038
buffers. inflateBack() trusts the application to not change the output
1039
buffer passed by the output function, at least until inflateBack() returns.
1041
inflateBackInit() must be called first to allocate the internal state
1042
and to initialize the state with the user-provided window buffer.
1043
inflateBack() may then be used multiple times to inflate a complete, raw
1044
deflate stream with each call. inflateBackEnd() is then called to free the
1047
A raw deflate stream is one with no zlib or gzip header or trailer.
1048
This routine would normally be used in a utility that reads zip or gzip
1049
files and writes out uncompressed files. The utility would decode the
1050
header and process the trailer on its own, hence this routine expects only
1051
the raw deflate stream to decompress. This is different from the normal
1052
behavior of inflate(), which expects either a zlib or gzip header and
1053
trailer around the deflate stream.
1055
inflateBack() uses two subroutines supplied by the caller that are then
1056
called by inflateBack() for input and output. inflateBack() calls those
1057
routines until it reads a complete deflate stream and writes out all of the
1058
uncompressed data, or until it encounters an error. The function's
1059
parameters and return types are defined above in the in_func and out_func
1060
typedefs. inflateBack() will call in(in_desc, &buf) which should return the
1061
number of bytes of provided input, and a pointer to that input in buf. If
1062
there is no input available, in() must return zero--buf is ignored in that
1063
case--and inflateBack() will return a buffer error. inflateBack() will call
1064
out(out_desc, buf, len) to write the uncompressed data buf[0..len-1]. out()
1065
should return zero on success, or non-zero on failure. If out() returns
1066
non-zero, inflateBack() will return with an error. Neither in() nor out()
1067
are permitted to change the contents of the window provided to
1068
inflateBackInit(), which is also the buffer that out() uses to write from.
1069
The length written by out() will be at most the window size. Any non-zero
1070
amount of input may be provided by in().
1072
For convenience, inflateBack() can be provided input on the first call by
1073
setting strm->next_in and strm->avail_in. If that input is exhausted, then
1074
in() will be called. Therefore strm->next_in must be initialized before
1075
calling inflateBack(). If strm->next_in is Z_NULL, then in() will be called
1076
immediately for input. If strm->next_in is not Z_NULL, then strm->avail_in
1077
must also be initialized, and then if strm->avail_in is not zero, input will
1078
initially be taken from strm->next_in[0 .. strm->avail_in - 1].
1080
The in_desc and out_desc parameters of inflateBack() is passed as the
1081
first parameter of in() and out() respectively when they are called. These
1082
descriptors can be optionally used to pass any information that the caller-
1083
supplied in() and out() functions need to do their job.
1085
On return, inflateBack() will set strm->next_in and strm->avail_in to
1086
pass back any unused input that was provided by the last in() call. The
1087
return values of inflateBack() can be Z_STREAM_END on success, Z_BUF_ERROR
1088
if in() or out() returned an error, Z_DATA_ERROR if there was a format error
1089
in the deflate stream (in which case strm->msg is set to indicate the nature
1090
of the error), or Z_STREAM_ERROR if the stream was not properly initialized.
1091
In the case of Z_BUF_ERROR, an input or output error can be distinguished
1092
using strm->next_in which will be Z_NULL only if in() returned an error. If
1093
strm->next_in is not Z_NULL, then the Z_BUF_ERROR was due to out() returning
1094
non-zero. (in() will always be called before out(), so strm->next_in is
1095
assured to be defined if out() returns non-zero.) Note that inflateBack()
1099
ZEXTERN int ZEXPORT inflateBackEnd OF((z_streamp strm));
1101
All memory allocated by inflateBackInit() is freed.
1103
inflateBackEnd() returns Z_OK on success, or Z_STREAM_ERROR if the stream
1104
state was inconsistent.
1107
ZEXTERN uLong ZEXPORT zlibCompileFlags OF((void));
1108
/* Return flags indicating compile-time options.
1110
Type sizes, two bits each, 00 = 16 bits, 01 = 32, 10 = 64, 11 = other:
1113
5.4: size of voidpf (pointer)
1114
7.6: size of z_off_t
1116
Compiler, assembler, and debug options:
1118
9: ASMV or ASMINF -- use ASM code
1119
10: ZLIB_WINAPI -- exported functions use the WINAPI calling convention
1122
One-time table building (smaller code, but not thread-safe if true):
1123
12: BUILDFIXED -- build static block decoding tables when needed
1124
13: DYNAMIC_CRC_TABLE -- build CRC calculation tables when needed
1127
Library content (indicates missing functionality):
1128
16: NO_GZCOMPRESS -- gz* functions cannot compress (to avoid linking
1129
deflate code when not needed)
1130
17: NO_GZIP -- deflate can't write gzip streams, and inflate can't detect
1131
and decode gzip streams (to avoid linking crc code)
1134
Operation variations (changes in library functionality):
1135
20: PKZIP_BUG_WORKAROUND -- slightly more permissive inflate
1136
21: FASTEST -- deflate algorithm with only one, lowest compression level
1139
The sprintf variant used by gzprintf (zero is best):
1140
24: 0 = vs*, 1 = s* -- 1 means limited to 20 arguments after the format
1141
25: 0 = *nprintf, 1 = *printf -- 1 means gzprintf() not secure!
1142
26: 0 = returns value, 1 = void -- 1 means inferred string length returned
1150
/* utility functions */
1153
The following utility functions are implemented on top of the basic
1154
stream-oriented functions. To simplify the interface, some default options
1155
are assumed (compression level and memory usage, standard memory allocation
1156
functions). The source code of these utility functions can be modified if
1157
you need special options.
1160
ZEXTERN int ZEXPORT compress OF((Bytef *dest, uLongf *destLen,
1161
const Bytef *source, uLong sourceLen));
1163
Compresses the source buffer into the destination buffer. sourceLen is
1164
the byte length of the source buffer. Upon entry, destLen is the total size
1165
of the destination buffer, which must be at least the value returned by
1166
compressBound(sourceLen). Upon exit, destLen is the actual size of the
1169
compress returns Z_OK if success, Z_MEM_ERROR if there was not
1170
enough memory, Z_BUF_ERROR if there was not enough room in the output
1174
ZEXTERN int ZEXPORT compress2 OF((Bytef *dest, uLongf *destLen,
1175
const Bytef *source, uLong sourceLen,
1178
Compresses the source buffer into the destination buffer. The level
1179
parameter has the same meaning as in deflateInit. sourceLen is the byte
1180
length of the source buffer. Upon entry, destLen is the total size of the
1181
destination buffer, which must be at least the value returned by
1182
compressBound(sourceLen). Upon exit, destLen is the actual size of the
1185
compress2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
1186
memory, Z_BUF_ERROR if there was not enough room in the output buffer,
1187
Z_STREAM_ERROR if the level parameter is invalid.
1190
ZEXTERN uLong ZEXPORT compressBound OF((uLong sourceLen));
1192
compressBound() returns an upper bound on the compressed size after
1193
compress() or compress2() on sourceLen bytes. It would be used before a
1194
compress() or compress2() call to allocate the destination buffer.
1197
ZEXTERN int ZEXPORT uncompress OF((Bytef *dest, uLongf *destLen,
1198
const Bytef *source, uLong sourceLen));
1200
Decompresses the source buffer into the destination buffer. sourceLen is
1201
the byte length of the source buffer. Upon entry, destLen is the total size
1202
of the destination buffer, which must be large enough to hold the entire
1203
uncompressed data. (The size of the uncompressed data must have been saved
1204
previously by the compressor and transmitted to the decompressor by some
1205
mechanism outside the scope of this compression library.) Upon exit, destLen
1206
is the actual size of the uncompressed buffer.
1208
uncompress returns Z_OK if success, Z_MEM_ERROR if there was not
1209
enough memory, Z_BUF_ERROR if there was not enough room in the output
1210
buffer, or Z_DATA_ERROR if the input data was corrupted or incomplete. In
1211
the case where there is not enough room, uncompress() will fill the output
1212
buffer with the uncompressed data up to that point.
1215
/* gzip file access functions */
1218
This library supports reading and writing files in gzip (.gz) format with
1219
an interface similar to that of stdio, using the functions that start with
1220
"gz". The gzip format is different from the zlib format. gzip is a gzip
1221
wrapper, documented in RFC 1952, wrapped around a deflate stream.
1224
typedef struct gzFile_s *gzFile; /* semi-opaque gzip file descriptor */
1227
ZEXTERN gzFile ZEXPORT gzopen OF((const char *path, const char *mode));
1229
Opens a gzip (.gz) file for reading or writing. The mode parameter is as
1230
in fopen ("rb" or "wb") but can also include a compression level ("wb9") or
1231
a strategy: 'f' for filtered data as in "wb6f", 'h' for Huffman-only
1232
compression as in "wb1h", 'R' for run-length encoding as in "wb1R", or 'F'
1233
for fixed code compression as in "wb9F". (See the description of
1234
deflateInit2 for more information about the strategy parameter.) 'T' will
1235
request transparent writing or appending with no compression and not using
1238
"a" can be used instead of "w" to request that the gzip stream that will
1239
be written be appended to the file. "+" will result in an error, since
1240
reading and writing to the same gzip file is not supported. The addition of
1241
"x" when writing will create the file exclusively, which fails if the file
1242
already exists. On systems that support it, the addition of "e" when
1243
reading or writing will set the flag to close the file on an execve() call.
1245
These functions, as well as gzip, will read and decode a sequence of gzip
1246
streams in a file. The append function of gzopen() can be used to create
1247
such a file. (Also see gzflush() for another way to do this.) When
1248
appending, gzopen does not test whether the file begins with a gzip stream,
1249
nor does it look for the end of the gzip streams to begin appending. gzopen
1250
will simply append a gzip stream to the existing file.
1252
gzopen can be used to read a file which is not in gzip format; in this
1253
case gzread will directly read from the file without decompression. When
1254
reading, this will be detected automatically by looking for the magic two-
1257
gzopen returns NULL if the file could not be opened, if there was
1258
insufficient memory to allocate the gzFile state, or if an invalid mode was
1259
specified (an 'r', 'w', or 'a' was not provided, or '+' was provided).
1260
errno can be checked to determine if the reason gzopen failed was that the
1261
file could not be opened.
1264
ZEXTERN gzFile ZEXPORT gzdopen OF((int fd, const char *mode));
1266
gzdopen associates a gzFile with the file descriptor fd. File descriptors
1267
are obtained from calls like open, dup, creat, pipe or fileno (if the file
1268
has been previously opened with fopen). The mode parameter is as in gzopen.
1270
The next call of gzclose on the returned gzFile will also close the file
1271
descriptor fd, just like fclose(fdopen(fd, mode)) closes the file descriptor
1272
fd. If you want to keep fd open, use fd = dup(fd_keep); gz = gzdopen(fd,
1273
mode);. The duplicated descriptor should be saved to avoid a leak, since
1274
gzdopen does not close fd if it fails. If you are using fileno() to get the
1275
file descriptor from a FILE *, then you will have to use dup() to avoid
1276
double-close()ing the file descriptor. Both gzclose() and fclose() will
1277
close the associated file descriptor, so they need to have different file
1280
gzdopen returns NULL if there was insufficient memory to allocate the
1281
gzFile state, if an invalid mode was specified (an 'r', 'w', or 'a' was not
1282
provided, or '+' was provided), or if fd is -1. The file descriptor is not
1283
used until the next gz* read, write, seek, or close operation, so gzdopen
1284
will not detect if fd is invalid (unless fd is -1).
1287
ZEXTERN int ZEXPORT gzbuffer OF((gzFile file, unsigned size));
1289
Set the internal buffer size used by this library's functions. The
1290
default buffer size is 8192 bytes. This function must be called after
1291
gzopen() or gzdopen(), and before any other calls that read or write the
1292
file. The buffer memory allocation is always deferred to the first read or
1293
write. Two buffers are allocated, either both of the specified size when
1294
writing, or one of the specified size and the other twice that size when
1295
reading. A larger buffer size of, for example, 64K or 128K bytes will
1296
noticeably increase the speed of decompression (reading).
1298
The new buffer size also affects the maximum length for gzprintf().
1300
gzbuffer() returns 0 on success, or -1 on failure, such as being called
1304
ZEXTERN int ZEXPORT gzsetparams OF((gzFile file, int level, int strategy));
1306
Dynamically update the compression level or strategy. See the description
1307
of deflateInit2 for the meaning of these parameters.
1309
gzsetparams returns Z_OK if success, or Z_STREAM_ERROR if the file was not
1313
ZEXTERN int ZEXPORT gzread OF((gzFile file, voidp buf, unsigned len));
1315
Reads the given number of uncompressed bytes from the compressed file. If
1316
the input file is not in gzip format, gzread copies the given number of
1317
bytes into the buffer directly from the file.
1319
After reaching the end of a gzip stream in the input, gzread will continue
1320
to read, looking for another gzip stream. Any number of gzip streams may be
1321
concatenated in the input file, and will all be decompressed by gzread().
1322
If something other than a gzip stream is encountered after a gzip stream,
1323
that remaining trailing garbage is ignored (and no error is returned).
1325
gzread can be used to read a gzip file that is being concurrently written.
1326
Upon reaching the end of the input, gzread will return with the available
1327
data. If the error code returned by gzerror is Z_OK or Z_BUF_ERROR, then
1328
gzclearerr can be used to clear the end of file indicator in order to permit
1329
gzread to be tried again. Z_OK indicates that a gzip stream was completed
1330
on the last gzread. Z_BUF_ERROR indicates that the input file ended in the
1331
middle of a gzip stream. Note that gzread does not return -1 in the event
1332
of an incomplete gzip stream. This error is deferred until gzclose(), which
1333
will return Z_BUF_ERROR if the last gzread ended in the middle of a gzip
1334
stream. Alternatively, gzerror can be used before gzclose to detect this
1337
gzread returns the number of uncompressed bytes actually read, less than
1338
len for end of file, or -1 for error.
1341
ZEXTERN int ZEXPORT gzwrite OF((gzFile file,
1342
voidpc buf, unsigned len));
1344
Writes the given number of uncompressed bytes into the compressed file.
1345
gzwrite returns the number of uncompressed bytes written or 0 in case of
1349
ZEXTERN int ZEXPORTVA gzprintf Z_ARG((gzFile file, const char *format, ...));
1351
Converts, formats, and writes the arguments to the compressed file under
1352
control of the format string, as in fprintf. gzprintf returns the number of
1353
uncompressed bytes actually written, or 0 in case of error. The number of
1354
uncompressed bytes written is limited to 8191, or one less than the buffer
1355
size given to gzbuffer(). The caller should assure that this limit is not
1356
exceeded. If it is exceeded, then gzprintf() will return an error (0) with
1357
nothing written. In this case, there may also be a buffer overflow with
1358
unpredictable consequences, which is possible only if zlib was compiled with
1359
the insecure functions sprintf() or vsprintf() because the secure snprintf()
1360
or vsnprintf() functions were not available. This can be determined using
1364
ZEXTERN int ZEXPORT gzputs OF((gzFile file, const char *s));
1366
Writes the given null-terminated string to the compressed file, excluding
1367
the terminating null character.
1369
gzputs returns the number of characters written, or -1 in case of error.
1372
ZEXTERN char * ZEXPORT gzgets OF((gzFile file, char *buf, int len));
1374
Reads bytes from the compressed file until len-1 characters are read, or a
1375
newline character is read and transferred to buf, or an end-of-file
1376
condition is encountered. If any characters are read or if len == 1, the
1377
string is terminated with a null character. If no characters are read due
1378
to an end-of-file or len < 1, then the buffer is left untouched.
1380
gzgets returns buf which is a null-terminated string, or it returns NULL
1381
for end-of-file or in case of error. If there was an error, the contents at
1382
buf are indeterminate.
1385
ZEXTERN int ZEXPORT gzputc OF((gzFile file, int c));
1387
Writes c, converted to an unsigned char, into the compressed file. gzputc
1388
returns the value that was written, or -1 in case of error.
1391
ZEXTERN int ZEXPORT gzgetc OF((gzFile file));
1393
Reads one byte from the compressed file. gzgetc returns this byte or -1
1394
in case of end of file or error. This is implemented as a macro for speed.
1395
As such, it does not do all of the checking the other functions do. I.e.
1396
it does not check to see if file is NULL, nor whether the structure file
1397
points to has been clobbered or not.
1400
ZEXTERN int ZEXPORT gzungetc OF((int c, gzFile file));
1402
Push one character back onto the stream to be read as the first character
1403
on the next read. At least one character of push-back is allowed.
1404
gzungetc() returns the character pushed, or -1 on failure. gzungetc() will
1405
fail if c is -1, and may fail if a character has been pushed but not read
1406
yet. If gzungetc is used immediately after gzopen or gzdopen, at least the
1407
output buffer size of pushed characters is allowed. (See gzbuffer above.)
1408
The pushed character will be discarded if the stream is repositioned with
1409
gzseek() or gzrewind().
1412
ZEXTERN int ZEXPORT gzflush OF((gzFile file, int flush));
1414
Flushes all pending output into the compressed file. The parameter flush
1415
is as in the deflate() function. The return value is the zlib error number
1416
(see function gzerror below). gzflush is only permitted when writing.
1418
If the flush parameter is Z_FINISH, the remaining data is written and the
1419
gzip stream is completed in the output. If gzwrite() is called again, a new
1420
gzip stream will be started in the output. gzread() is able to read such
1421
concatented gzip streams.
1423
gzflush should be called only when strictly necessary because it will
1424
degrade compression if called too often.
1428
ZEXTERN z_off_t ZEXPORT gzseek OF((gzFile file,
1429
z_off_t offset, int whence));
1431
Sets the starting position for the next gzread or gzwrite on the given
1432
compressed file. The offset represents a number of bytes in the
1433
uncompressed data stream. The whence parameter is defined as in lseek(2);
1434
the value SEEK_END is not supported.
1436
If the file is opened for reading, this function is emulated but can be
1437
extremely slow. If the file is opened for writing, only forward seeks are
1438
supported; gzseek then compresses a sequence of zeroes up to the new
1441
gzseek returns the resulting offset location as measured in bytes from
1442
the beginning of the uncompressed stream, or -1 in case of error, in
1443
particular if the file is opened for writing and the new starting position
1444
would be before the current position.
1447
ZEXTERN int ZEXPORT gzrewind OF((gzFile file));
1449
Rewinds the given file. This function is supported only for reading.
1451
gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET)
1455
ZEXTERN z_off_t ZEXPORT gztell OF((gzFile file));
1457
Returns the starting position for the next gzread or gzwrite on the given
1458
compressed file. This position represents a number of bytes in the
1459
uncompressed data stream, and is zero when starting, even if appending or
1460
reading a gzip stream from the middle of a file using gzdopen().
1462
gztell(file) is equivalent to gzseek(file, 0L, SEEK_CUR)
1466
ZEXTERN z_off_t ZEXPORT gzoffset OF((gzFile file));
1468
Returns the current offset in the file being read or written. This offset
1469
includes the count of bytes that precede the gzip stream, for example when
1470
appending or when using gzdopen() for reading. When reading, the offset
1471
does not include as yet unused buffered input. This information can be used
1472
for a progress indicator. On error, gzoffset() returns -1.
1475
ZEXTERN int ZEXPORT gzeof OF((gzFile file));
1477
Returns true (1) if the end-of-file indicator has been set while reading,
1478
false (0) otherwise. Note that the end-of-file indicator is set only if the
1479
read tried to go past the end of the input, but came up short. Therefore,
1480
just like feof(), gzeof() may return false even if there is no more data to
1481
read, in the event that the last read request was for the exact number of
1482
bytes remaining in the input file. This will happen if the input file size
1483
is an exact multiple of the buffer size.
1485
If gzeof() returns true, then the read functions will return no more data,
1486
unless the end-of-file indicator is reset by gzclearerr() and the input file
1487
has grown since the previous end of file was detected.
1490
ZEXTERN int ZEXPORT gzdirect OF((gzFile file));
1492
Returns true (1) if file is being copied directly while reading, or false
1493
(0) if file is a gzip stream being decompressed.
1495
If the input file is empty, gzdirect() will return true, since the input
1496
does not contain a gzip stream.
1498
If gzdirect() is used immediately after gzopen() or gzdopen() it will
1499
cause buffers to be allocated to allow reading the file to determine if it
1500
is a gzip file. Therefore if gzbuffer() is used, it should be called before
1503
When writing, gzdirect() returns true (1) if transparent writing was
1504
requested ("wT" for the gzopen() mode), or false (0) otherwise. (Note:
1505
gzdirect() is not needed when writing. Transparent writing must be
1506
explicitly requested, so the application already knows the answer. When
1507
linking statically, using gzdirect() will include all of the zlib code for
1508
gzip file reading and decompression, which may not be desired.)
1511
ZEXTERN int ZEXPORT gzclose OF((gzFile file));
1513
Flushes all pending output if necessary, closes the compressed file and
1514
deallocates the (de)compression state. Note that once file is closed, you
1515
cannot call gzerror with file, since its structures have been deallocated.
1516
gzclose must not be called more than once on the same file, just as free
1517
must not be called more than once on the same allocation.
1519
gzclose will return Z_STREAM_ERROR if file is not valid, Z_ERRNO on a
1520
file operation error, Z_MEM_ERROR if out of memory, Z_BUF_ERROR if the
1521
last read ended in the middle of a gzip stream, or Z_OK on success.
1524
ZEXTERN int ZEXPORT gzclose_r OF((gzFile file));
1525
ZEXTERN int ZEXPORT gzclose_w OF((gzFile file));
1527
Same as gzclose(), but gzclose_r() is only for use when reading, and
1528
gzclose_w() is only for use when writing or appending. The advantage to
1529
using these instead of gzclose() is that they avoid linking in zlib
1530
compression or decompression code that is not used when only reading or only
1531
writing respectively. If gzclose() is used, then both compression and
1532
decompression code will be included the application when linking to a static
1536
ZEXTERN const char * ZEXPORT gzerror OF((gzFile file, int *errnum));
1538
Returns the error message for the last error which occurred on the given
1539
compressed file. errnum is set to zlib error number. If an error occurred
1540
in the file system and not in the compression library, errnum is set to
1541
Z_ERRNO and the application may consult errno to get the exact error code.
1543
The application must not modify the returned string. Future calls to
1544
this function may invalidate the previously returned string. If file is
1545
closed, then the string previously returned by gzerror will no longer be
1548
gzerror() should be used to distinguish errors from end-of-file for those
1549
functions above that do not distinguish those cases in their return values.
1552
ZEXTERN void ZEXPORT gzclearerr OF((gzFile file));
1554
Clears the error and end-of-file flags for file. This is analogous to the
1555
clearerr() function in stdio. This is useful for continuing to read a gzip
1556
file that is being written concurrently.
1559
#endif /* !Z_SOLO */
1561
/* checksum functions */
1564
These functions are not related to compression but are exported
1565
anyway because they might be useful in applications using the compression
1569
ZEXTERN uLong ZEXPORT adler32 OF((uLong adler, const Bytef *buf, uInt len));
1571
Update a running Adler-32 checksum with the bytes buf[0..len-1] and
1572
return the updated checksum. If buf is Z_NULL, this function returns the
1573
required initial value for the checksum.
1575
An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
1580
uLong adler = adler32(0L, Z_NULL, 0);
1582
while (read_buffer(buffer, length) != EOF) {
1583
adler = adler32(adler, buffer, length);
1585
if (adler != original_adler) error();
1589
ZEXTERN uLong ZEXPORT adler32_combine OF((uLong adler1, uLong adler2,
1592
Combine two Adler-32 checksums into one. For two sequences of bytes, seq1
1593
and seq2 with lengths len1 and len2, Adler-32 checksums were calculated for
1594
each, adler1 and adler2. adler32_combine() returns the Adler-32 checksum of
1595
seq1 and seq2 concatenated, requiring only adler1, adler2, and len2. Note
1596
that the z_off_t type (like off_t) is a signed integer. If len2 is
1597
negative, the result has no meaning or utility.
1600
ZEXTERN uLong ZEXPORT crc32 OF((uLong crc, const Bytef *buf, uInt len));
1602
Update a running CRC-32 with the bytes buf[0..len-1] and return the
1603
updated CRC-32. If buf is Z_NULL, this function returns the required
1604
initial value for the crc. Pre- and post-conditioning (one's complement) is
1605
performed within this function so it shouldn't be done by the application.
1609
uLong crc = crc32(0L, Z_NULL, 0);
1611
while (read_buffer(buffer, length) != EOF) {
1612
crc = crc32(crc, buffer, length);
1614
if (crc != original_crc) error();
1618
ZEXTERN uLong ZEXPORT crc32_combine OF((uLong crc1, uLong crc2, z_off_t len2));
1620
Combine two CRC-32 check values into one. For two sequences of bytes,
1621
seq1 and seq2 with lengths len1 and len2, CRC-32 check values were
1622
calculated for each, crc1 and crc2. crc32_combine() returns the CRC-32
1623
check value of seq1 and seq2 concatenated, requiring only crc1, crc2, and
1628
/* various hacks, don't look :) */
1630
/* deflateInit and inflateInit are macros to allow checking the zlib version
1631
* and the compiler's view of z_stream:
1633
ZEXTERN int ZEXPORT deflateInit_ OF((z_streamp strm, int level,
1634
const char *version, int stream_size));
1635
ZEXTERN int ZEXPORT inflateInit_ OF((z_streamp strm,
1636
const char *version, int stream_size));
1637
ZEXTERN int ZEXPORT deflateInit2_ OF((z_streamp strm, int level, int method,
1638
int windowBits, int memLevel,
1639
int strategy, const char *version,
1641
ZEXTERN int ZEXPORT inflateInit2_ OF((z_streamp strm, int windowBits,
1642
const char *version, int stream_size));
1643
ZEXTERN int ZEXPORT inflateBackInit_ OF((z_streamp strm, int windowBits,
1644
unsigned char FAR *window,
1645
const char *version,
1647
#define deflateInit(strm, level) \
1648
deflateInit_((strm), (level), ZLIB_VERSION, (int)sizeof(z_stream))
1649
#define inflateInit(strm) \
1650
inflateInit_((strm), ZLIB_VERSION, (int)sizeof(z_stream))
1651
#define deflateInit2(strm, level, method, windowBits, memLevel, strategy) \
1652
deflateInit2_((strm),(level),(method),(windowBits),(memLevel),\
1653
(strategy), ZLIB_VERSION, (int)sizeof(z_stream))
1654
#define inflateInit2(strm, windowBits) \
1655
inflateInit2_((strm), (windowBits), ZLIB_VERSION, \
1656
(int)sizeof(z_stream))
1657
#define inflateBackInit(strm, windowBits, window) \
1658
inflateBackInit_((strm), (windowBits), (window), \
1659
ZLIB_VERSION, (int)sizeof(z_stream))
1663
/* gzgetc() macro and its supporting function and exposed data structure. Note
1664
* that the real internal state is much larger than the exposed structure.
1665
* This abbreviated structure exposes just enough for the gzgetc() macro. The
1666
* user should not mess with these exposed elements, since their names or
1667
* behavior could change in the future, perhaps even capriciously. They can
1668
* only be used by the gzgetc() macro. You have been warned.
1672
unsigned char *next;
1675
ZEXTERN int ZEXPORT gzgetc_ OF((gzFile file)); /* backward compatibility */
1678
# define z_gzgetc(g) \
1679
((g)->have ? ((g)->have--, (g)->pos++, *((g)->next)++) : gzgetc(g))
1681
# define gzgetc(g) \
1682
((g)->have ? ((g)->have--, (g)->pos++, *((g)->next)++) : gzgetc(g))
1685
/* provide 64-bit offset functions if _LARGEFILE64_SOURCE defined, and/or
1686
* change the regular functions to 64 bits if _FILE_OFFSET_BITS is 64 (if
1687
* both are true, the application gets the *64 functions, and the regular
1688
* functions are changed to 64 bits) -- in case these are set on systems
1689
* without large file support, _LFS64_LARGEFILE must also be true
1692
ZEXTERN gzFile ZEXPORT gzopen64 OF((const char *, const char *));
1693
ZEXTERN z_off64_t ZEXPORT gzseek64 OF((gzFile, z_off64_t, int));
1694
ZEXTERN z_off64_t ZEXPORT gztell64 OF((gzFile));
1695
ZEXTERN z_off64_t ZEXPORT gzoffset64 OF((gzFile));
1696
ZEXTERN uLong ZEXPORT adler32_combine64 OF((uLong, uLong, z_off64_t));
1697
ZEXTERN uLong ZEXPORT crc32_combine64 OF((uLong, uLong, z_off64_t));
1700
#if !defined(ZLIB_INTERNAL) && defined(Z_WANT64)
1701
# ifdef Z_PREFIX_SET
1702
# define z_gzopen z_gzopen64
1703
# define z_gzseek z_gzseek64
1704
# define z_gztell z_gztell64
1705
# define z_gzoffset z_gzoffset64
1706
# define z_adler32_combine z_adler32_combine64
1707
# define z_crc32_combine z_crc32_combine64
1709
# define gzopen gzopen64
1710
# define gzseek gzseek64
1711
# define gztell gztell64
1712
# define gzoffset gzoffset64
1713
# define adler32_combine adler32_combine64
1714
# define crc32_combine crc32_combine64
1717
ZEXTERN gzFile ZEXPORT gzopen64 OF((const char *, const char *));
1718
ZEXTERN z_off_t ZEXPORT gzseek64 OF((gzFile, z_off_t, int));
1719
ZEXTERN z_off_t ZEXPORT gztell64 OF((gzFile));
1720
ZEXTERN z_off_t ZEXPORT gzoffset64 OF((gzFile));
1721
ZEXTERN uLong ZEXPORT adler32_combine64 OF((uLong, uLong, z_off_t));
1722
ZEXTERN uLong ZEXPORT crc32_combine64 OF((uLong, uLong, z_off_t));
1725
ZEXTERN gzFile ZEXPORT gzopen OF((const char *, const char *));
1726
ZEXTERN z_off_t ZEXPORT gzseek OF((gzFile, z_off_t, int));
1727
ZEXTERN z_off_t ZEXPORT gztell OF((gzFile));
1728
ZEXTERN z_off_t ZEXPORT gzoffset OF((gzFile));
1729
ZEXTERN uLong ZEXPORT adler32_combine OF((uLong, uLong, z_off_t));
1730
ZEXTERN uLong ZEXPORT crc32_combine OF((uLong, uLong, z_off_t));
1735
ZEXTERN uLong ZEXPORT adler32_combine OF((uLong, uLong, z_off_t));
1736
ZEXTERN uLong ZEXPORT crc32_combine OF((uLong, uLong, z_off_t));
1738
#endif /* !Z_SOLO */
1740
/* hack for buggy compilers */
1741
#if !defined(ZUTIL_H) && !defined(NO_DUMMY_DECL)
1742
struct internal_state {int dummy;};
1745
/* undocumented functions */
1746
ZEXTERN const char * ZEXPORT zError OF((int));
1747
ZEXTERN int ZEXPORT inflateSyncPoint OF((z_streamp));
1748
ZEXTERN const z_crc_t FAR * ZEXPORT get_crc_table OF((void));
1749
ZEXTERN int ZEXPORT inflateUndermine OF((z_streamp, int));
1750
ZEXTERN int ZEXPORT inflateResetKeep OF((z_streamp));
1751
ZEXTERN int ZEXPORT deflateResetKeep OF((z_streamp));
1752
#if defined(_WIN32) && !defined(Z_SOLO)
1753
ZEXTERN gzFile ZEXPORT gzopen_w OF((const wchar_t *path,
1756
#if defined(STDC) || defined(Z_HAVE_STDARG_H)
1758
ZEXTERN int ZEXPORTVA gzvprintf Z_ARG((gzFile file,