zlib.h

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/* zlib.h -- interface of the 'zlib' general purpose compression library
version 1.2.1, November 17th, 2003

Copyright (C) 1995-2003 Jean-loup Gailly and Mark Adler

This software is provided 'as-is', without any express or implied
warranty.  In no event will the authors be held liable for any damages
arising from the use of this software.

Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:

1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.

Jean-loup Gailly        Mark Adler
[e-mail]          [e-mail]


The data format used by the zlib library is described by RFCs (Request for
Comments) 1950 to 1952 in the files http://www.ietf.org/rfc/rfc1950.txt
(zlib format), rfc1951.txt (deflate format) and rfc1952.txt (gzip format).
 */

#ifndef ZLIB_H
  #define ZLIB_H

  #include "zconf.h"

  #ifdef __cplusplus
    extern "C"
    {
    #endif

    #define ZLIB_VERSION "1.2.1"
    #define ZLIB_VERNUM 0x1210

    /*
    The 'zlib' compression library provides in-memory compression and
    decompression functions, including integrity checks of the uncompressed
    data.  This version of the library supports only one compression method
    (deflation) but other algorithms will be added later and will have the same
    stream interface.

    Compression can be done in a single step if the buffers are large
    enough (for example if an input file is mmap'ed), or can be done by
    repeated calls of the compression function.  In the latter case, the
    application must provide more input and/or consume the output
    (providing more output space) before each call.

    The compressed data format used by the in-memory functions is the zlib
    format, which is a zlib wrapper documented in RFC 1950, wrapped around a
    deflate stream, which is itself documented in RFC 1951.

    The library also supports reading and writing files in gzip (.gz) format
    with an interface similar to that of stdio using the functions that start
    with "gz".  The gzip format is different from the zlib format.  gzip is a
    gzip wrapper, documented in RFC 1952, wrapped around a deflate stream.

    The zlib format was designed to be compact and fast for use in memory
    and on communications channels.  The gzip format was designed for single-
    file compression on file systems, has a larger header than zlib to maintain
    directory information, and uses a different, slower check method than zlib.

    This library does not provide any functions to write gzip files in memory.
    However such functions could be easily written using zlib's deflate function,
    the documentation in the gzip RFC, and the examples in gzio.c.

    The library does not install any signal handler. The decoder checks
    the consistency of the compressed data, so the library should never
    crash even in case of corrupted input.
     */

    #ifndef WORD
      typedef unsigned short WORD;
    #endif

    #ifndef DWORD
      typedef unsigned long DWORD;
    #endif

    #ifndef BYTE
      typedef unsigned char BYTE;
    #endif

    #ifndef INT
      typedef int INT;
    #endif

    typedef void *(*alloc_func)(void *opaque, DWORD items, DWORD size);
    typedef void(*free_func)(void *opaque, void *address);

    struct internal_state;

    typedef struct z_stream_s
    {
      Bytef *next_in; /* next input byte */
      DWORD avail_in; /* number of bytes available at next_in */
      DWORD total_in; /* total nb of input bytes read so far */

      BYTE *next_out; /* next output byte should be put there */
      DWORD avail_out; /* remaining free space at next_out */
      DWORD total_out; /* total nb of bytes output so far */

      BYTE *msg; /* last error message, NULL if no error */
      struct internal_state FAR *state; /* not visible by applications */

      alloc_func zalloc; /* used to allocate the internal state */
      free_func zfree; /* used to free the internal state */
      void *opaque; /* private data object passed to zalloc and zfree */

      int data_type; /* best guess about the data type: ascii or binary */
      DWORD adler; /* adler32 value of the uncompressed data */
      DWORD reserved; /* reserved for future use */
    } z_stream;

    typedef z_stream *z_streamp;

    /*
    The application must update next_in and avail_in when avail_in has
    dropped to zero. It must update next_out and avail_out when avail_out
    has dropped to zero. The application must initialize zalloc, zfree and
    opaque before calling the init function. All other fields are set by the
    compression library and must not be updated by the application.

    The opaque value provided by the application will be passed as the first
    parameter for calls of zalloc and zfree. This can be useful for custom
    memory management. The compression library attaches no meaning to the
    opaque value.

    zalloc must return Z_NULL if there is not enough memory for the object.
    If zlib is used in a multi-threaded application, zalloc and zfree must be
    thread safe.

    On 16-bit systems, the functions zalloc and zfree must be able to allocate
    exactly 65536 bytes, but will not be required to allocate more than this
    if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS,
    pointers returned by zalloc for objects of exactly 65536 bytes *must*
    have their offset normalized to zero. The default allocation function
    provided by this library ensures this (see zutil.c). To reduce memory
    requirements and avoid any allocation of 64K objects, at the expense of
    compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h).

    The fields total_in and total_out can be used for statistics or
    progress reports. After compression, total_in holds the total size of
    the uncompressed data and may be saved for use in the decompressor
    (particularly if the decompressor wants to decompress everything in
    a single step).
     */

    /* constants */

    #define Z_NO_FLUSH      0
    #define Z_PARTIAL_FLUSH 1 /* will be removed, use Z_SYNC_FLUSH instead */
    #define Z_SYNC_FLUSH    2
    #define Z_FULL_FLUSH    3
    #define Z_FINISH        4
    #define Z_BLOCK         5
    /* Allowed flush values; see deflate() and inflate() below for details */

    #define Z_OK            0
    #define Z_STREAM_END    1
    #define Z_NEED_DICT     2
    #define Z_ERRNO        (-1)
    #define Z_STREAM_ERROR (-2)
    #define Z_DATA_ERROR   (-3)
    #define Z_MEM_ERROR    (-4)
    #define Z_BUF_ERROR    (-5)
    #define Z_VERSION_ERROR (-6)
    /* Return codes for the compression/decompression functions. Negative
     * values are errors, positive values are used for special but normal events.
     */

    #define Z_NO_COMPRESSION         0
    #define Z_BEST_SPEED             1
    #define Z_BEST_COMPRESSION       9
    #define Z_DEFAULT_COMPRESSION  (-1)
    /* compression levels */

    #define Z_FILTERED            1
    #define Z_HUFFMAN_ONLY        2
    #define Z_RLE                 3
    #define Z_DEFAULT_STRATEGY    0
    /* compression strategy; see deflateInit2() below for details */

    #define Z_BINARY   0
    #define Z_ASCII    1
    #define Z_UNKNOWN  2
    /* Possible values of the data_type field (though see inflate()) */

    #define Z_DEFLATED   8
    /* The deflate compression method (the only one supported in this version) */

    #define Z_NULL  0  /* for initializing zalloc, zfree, opaque */

    #define zlib_version zlibZIPVersion()
    /* for compatibility with versions < 1.0.2 */

    /* basic functions */

    ZEXTERN const char *ZEXPORT zlibVersion(void);
    /* The application can compare zlibVersion and ZLIB_VERSION for consistency.
    If the first character differs, the library code actually used is
    not compatible with the zlib.h header file used by the application.
    This check is automatically made by deflateInit and inflateInit.
     */

    /*
    ZEXTERN int ZEXPORT deflateInit OF((z_streamp strm, int level));

    Initializes the internal stream state for compression. The fields
    zalloc, zfree and opaque must be initialized before by the caller.
    If zalloc and zfree are set to Z_NULL, deflateInit updates them to
    use default allocation functions.

    The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
    1 gives best speed, 9 gives best compression, 0 gives no compression at
    all (the input data is simply copied a block at a time).
    Z_DEFAULT_COMPRESSION requests a default compromise between speed and
    compression (currently equivalent to level 6).

    deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
    enough memory, Z_STREAM_ERROR if level is not a valid compression level,
    Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible
    with the version assumed by the caller (ZLIB_VERSION).
    msg is set to null if there is no error message.  deflateInit does not
    perform any compression: this will be done by deflate().
     */


    ZEXTERN int ZEXPORT deflate(z_streamp strm, int flush);
    /*
    deflate compresses as much data as possible, and stops when the input
    buffer becomes empty or the output buffer becomes full. It may introduce some
    output latency (reading input without producing any output) except when
    forced to flush.

    The detailed semantics are as follows. deflate performs one or both of the
    following actions:

    - Compress more input starting at next_in and update next_in and avail_in
    accordingly. If not all input can be processed (because there is not
    enough room in the output buffer), next_in and avail_in are updated and
    processing will resume at this point for the next call of deflate().

    - Provide more output starting at next_out and update next_out and avail_out
    accordingly. This action is forced if the parameter flush is non zero.
    Forcing flush frequently degrades the compression ratio, so this parameter
    should be set only when necessary (in interactive applications).
    Some output may be provided even if flush is not set.

    Before the call of deflate(), the application should ensure that at least
    one of the actions is possible, by providing more input and/or consuming
    more output, and updating avail_in or avail_out accordingly; avail_out
    should never be zero before the call. The application can consume the
    compressed output when it wants, for example when the output buffer is full
    (avail_out == 0), or after each call of deflate(). If deflate returns Z_OK
    and with zero avail_out, it must be called again after making room in the
    output buffer because there might be more output pending.

    If the parameter flush is set to Z_SYNC_FLUSH, all pending output is
    flushed to the output buffer and the output is aligned on a byte boundary, so
    that the decompressor can get all input data available so far. (In particular
    avail_in is zero after the call if enough output space has been provided
    before the call.)  Flushing may degrade compression for some compression
    algorithms and so it should be used only when necessary.

    If flush is set to Z_FULL_FLUSH, all output is flushed as with
    Z_SYNC_FLUSH, and the compression state is reset so that decompression can
    restart from this point if previous compressed data has been damaged or if
    random access is desired. Using Z_FULL_FLUSH too often can seriously degrade
    the compression.

    If deflate returns with avail_out == 0, this function must be called again
    with the same value of the flush parameter and more output space (updated
    avail_out), until the flush is complete (deflate returns with non-zero
    avail_out). In the case of a Z_FULL_FLUSH or Z_SYNC_FLUSH, make sure that
    avail_out is greater than six to avoid repeated flush markers due to
    avail_out == 0 on return.

    If the parameter flush is set to Z_FINISH, pending input is processed,
    pending output is flushed and deflate returns with Z_STREAM_END if there
    was enough output space; if deflate returns with Z_OK, this function must be
    called again with Z_FINISH and more output space (updated avail_out) but no
    more input data, until it returns with Z_STREAM_END or an error. After
    deflate has returned Z_STREAM_END, the only possible operations on the
    stream are deflateReset or deflateEnd.

    Z_FINISH can be used immediately after deflateInit if all the compression
    is to be done in a single step. In this case, avail_out must be at least
    the value returned by deflateBound (see below). If deflate does not return
    Z_STREAM_END, then it must be called again as described above.