zlib.h

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2019, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */

#pragma once

#include "zconf.h"

#ifdef __cplusplus
extern "C"
{
#endif

#define ZLIB_VERSION "1.2.3"
#define ZLIB_VERNUM 0x1230

    /*
         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 default 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.

         This library can optionally read and write gzip streams in memory as
      well.

         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.

         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.
    */

    typedef voidpf(*alloc_func) OF((voidpf opaque, uInt items, uInt size));
    typedef void(*free_func) OF((voidpf opaque, voidpf address));

    struct internal_state;

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

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

        char* msg; /* last error message, nullptr 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 */
        voidpf opaque; /* private data object passed to zalloc and zfree */

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

    typedef z_stream FAR* z_streamp;

    /*
         gzip header information passed to and from zlib routines.  See RFC 1952
      for more details on the meanings of these fields.
    */
    typedef struct gz_header_s
    {
        int text; /* true if compressed data believed to be text */
        uLong time; /* modification time */
        int xflags; /* extra flags (not used when writing a gzip file) */
        int os; /* operating system */
        Bytef* extra; /* pointer to extra field or Z_NULL if none */
        uInt extra_len; /* extra field length (valid if extra != Z_NULL) */
        uInt extra_max; /* space at extra (only when reading header) */
        Bytef* name; /* pointer to zero-terminated file name or Z_NULL */
        uInt name_max; /* space at name (only when reading header) */
        Bytef* comment; /* pointer to zero-terminated comment or Z_NULL */
        uInt comm_max; /* space at comment (only when reading header) */
        int hcrc; /* true if there was or will be a header crc */
        int done; /* true when done reading gzip header (not used
                     when writing a gzip file) */
    } gz_header;

    typedef gz_header FAR* gz_headerp;

    /*
       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_FIXED 4
#define Z_DEFAULT_STRATEGY 0
    /* compression strategy; see deflateInit2() below for details */

#define Z_BINARY 0
#define Z_TEXT 1
#define Z_ASCII Z_TEXT /* for compatibility with 1.2.2 and earlier */
#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 zlibVersion()
    /* for compatibility with versions < 1.0.2 */

    /* basic functions */

    ZEXTERN const char* ZEXPORT zlibVersion OF((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 OF((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.

        Normally the parameter flush is set to Z_NO_FLUSH, which allows deflate
      to decide how much data to accumualte before producing output, in order to
      maximize compression.

        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 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.

        deflate() sets strm->adler to the adler32 checksum of all input read
      so far (that is, total_in bytes).

        deflate() may update strm->data_type if it can make a good guess about
      the input data type (Z_BINARY or Z_TEXT). In doubt, the data is considered
      binary. This field is only for information purposes and does not affect
      the compression algorithm in any manner.

        deflate() returns Z_OK if some progress has been made (more input
      processed or more output produced), Z_STREAM_END if all input has been
      consumed and all output has been produced (only when flush is set to
      Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for
      example if next_in or next_out was nullptr), Z_BUF_ERROR if no progress is
      possible (for example avail_in or avail_out was zero). Note that
      Z_BUF_ERROR is not fatal, and deflate() can be called again with more
      input and more output space to continue compressing.
    */

    ZEXTERN int ZEXPORT deflateEnd OF((z_streamp strm));
    /*
         All dynamically allocated data structures for this stream are freed.
       This function discards any unprocessed input and does not flush any
       pending output.

         deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
       stream state was inconsistent, Z_DATA_ERROR if the stream was freed
       prematurely (some input or output was discarded). In the error case,
       msg may be set but then points to a static string (which must not be
       deallocated).
    */

    /*
    ZEXTERN int ZEXPORT inflateInit OF((z_streamp strm));

         Initializes the internal stream state for decompression. The fields
       next_in, avail_in, zalloc, zfree and opaque must be initialized before by
       the caller. If next_in is not Z_NULL and avail_in is large enough (the
    exact value depends on the compression method), inflateInit determines the
       compression method from the zlib header and allocates all data structures
       accordingly; otherwise the allocation will be deferred to the first call
    of inflate.  If zalloc and zfree are set to Z_NULL, inflateInit updates them
    to use default allocation functions.

         inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
    enough memory, Z_VERSION_ERROR if the zlib library version is incompatible
    with the version assumed by the caller.  msg is set to null if there is no
    error message. inflateInit does not perform any decompression apart from
    reading the zlib header if present: this will be done by inflate().  (So
    next_in and avail_in may be modified, but next_out and avail_out are
    unchanged.)
    */

    ZEXTERN int ZEXPORT inflate OF((z_streamp strm, int flush));
    /*
        inflate decompresses 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. inflate performs one or both of the
      following actions:

      - Decompress 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 is updated and processing
        will resume at this point for the next call of inflate().

      - Provide more output starting at next_out and update next_out and
      avail_out accordingly.  inflate() provides as much output as possible,
      until there is no more input data or no more space in the output buffer
      (see below about the flush parameter).

      Before the call of inflate(), the application should ensure that at least
      one of the actions is possible, by providing more input and/or consuming
      more output, and updating the next_* and avail_* values accordingly.
      The application can consume the uncompressed output when it wants, for
      example when the output buffer is full (avail_out == 0), or after each
      call of inflate(). If inflate 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.

        The flush parameter of inflate() can be Z_NO_FLUSH, Z_SYNC_FLUSH,
      Z_FINISH, or Z_BLOCK. Z_SYNC_FLUSH requests that inflate() flush as much
      output as possible to the output buffer. Z_BLOCK requests that inflate()
      stop if and when it gets to the next deflate block boundary. When decoding
      the zlib or gzip format, this will cause inflate() to return immediately
      after the header and before the first block. When doing a raw inflate,
      inflate() will go ahead and process the first block, and will return when
      it gets to the end of that block, or when it runs out of data.

        The Z_BLOCK option assists in appending to or combining deflate streams.
      Also to assist in this, on return inflate() will set strm->data_type to
      the number of unused bits in the last byte taken from strm->next_in, plus
      64 if inflate() is currently decoding the last block in the deflate
      stream, plus 128 if inflate() returned immediately after decoding an
      end-of-block code or decoding the complete header up to just before the
      first byte of the deflate stream. The end-of-block will not be indicated
      until all of the uncompressed data from that block has been written to
      strm->next_out.  The number of unused bits may in general be greater than
      seven, except when bit 7 of data_type is set, in which case the number of
      unused bits will be less than eight.

        inflate() should normally be called until it returns Z_STREAM_END or an
      error. However if all decompression is to be performed in a single step
      (a single call of inflate), the parameter flush should be set to
      Z_FINISH. In this case all pending input is processed and all pending
      output is flushed; avail_out must be large enough to hold all the
      uncompressed data. (The size of the uncompressed data may have been saved
      by the compressor for this purpose.) The next operation on this stream
      must be inflateEnd to deallocate the decompression state. The use of
      Z_FINISH is never required, but can be used to inform inflate that a
      faster approach may be used for the single inflate() call.

         In this implementation, inflate() always flushes as much output as
      possible to the output buffer, and always uses the faster approach on the
      first call. So the only effect of the flush parameter in this
      implementation is on the return value of inflate(), as noted below, or
      when it returns early because Z_BLOCK is used.

         If a preset dictionary is needed after this call (see
      inflateSetDictionary below), inflate sets strm->adler to the adler32
      checksum of the dictionary chosen by the compressor and returns
      Z_NEED_DICT; otherwise it sets strm->adler to the adler32 checksum of all
      output produced so far (that is, total_out bytes) and returns Z_OK,
      Z_STREAM_END or an error code as described below. At the end of the
      stream, inflate() checks that its computed adler32 checksum is equal to
      that saved by the compressor and returns Z_STREAM_END only if the checksum
      is correct.

        inflate() will decompress and check either zlib-wrapped or gzip-wrapped
      deflate data.  The header type is detected automatically.  Any information
      contained in the gzip header is not retained, so applications that need
      that information should instead use raw inflate, see inflateInit2() below,
      or inflateBack() and perform their own processing of the gzip header and
      trailer.

        inflate() returns Z_OK if some progress has been made (more input
      processed or more output produced), Z_STREAM_END if the end of the
      compressed data has been reached and all uncompressed output has been
      produced, Z_NEED_DICT if a preset dictionary is needed at this point,
      Z_DATA_ERROR if the input data was corrupted (input stream not conforming
      to the zlib format or incorrect check value), Z_STREAM_ERROR if the stream
      structure was inconsistent (for example if next_in or next_out was
      nullptr), Z_MEM_ERROR if there was not enough memory, Z_BUF_ERROR if no
      progress is possible or if there was not enough room in the output buffer
      when Z_FINISH is used. Note that Z_BUF_ERROR is not fatal, and inflate()
      can be called again with more input and more output space to continue
      decompressing. If Z_DATA_ERROR is returned, the application may then call
      inflateSync() to look for a good compression block if a partial recovery
      of the data is desired.
    */

    ZEXTERN int ZEXPORT inflateEnd OF((z_streamp strm));
    /*
         All dynamically allocated data structures for this stream are freed.
       This function discards any unprocessed input and does not flush any
       pending output.

         inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
       was inconsistent. In the error case, msg may be set but then points to a
       static string (which must not be deallocated).
    */

    /* Advanced functions */

    /*
        The following functions are needed only in some special applications.
    */

    /*
    ZEXTERN int ZEXPORT deflateInit2 OF((z_streamp strm,
                                         int  level,
                                         int  method,
                                         int  windowBits,
                                         int  memLevel,
                                         int  strategy));

         This is another version of deflateInit with more compression options.
    The fields next_in, zalloc, zfree and opaque must be initialized before by
       the caller.

         The method parameter is the compression method. It must be Z_DEFLATED
    in this version of the library.

         The windowBits parameter is the base two logarithm of the window size
       (the size of the history buffer). It should be in the range 8..15 for
    this version of the library. Larger values of this parameter result in
    better compression at the expense of memory usage. The default value is 15
    if deflateInit is used instead.

         windowBits can also be -8..-15 for raw deflate. In this case,
    -windowBits determines the window size. deflate() will then generate raw
    deflate data with no zlib header or trailer, and will not compute an adler32
    check value.

         windowBits can also be greater than 15 for optional gzip encoding. Add
       16 to windowBits to write a simple gzip header and trailer around the
       compressed data instead of a zlib wrapper. The gzip header will have no
       file name, no extra data, no comment, no modification time (set to zero),
       no header crc, and the operating system will be set to 255 (unknown).  If
    a gzip stream is being written, strm->adler is a crc32 instead of an
    adler32.

         The memLevel parameter specifies how much memory should be allocated
       for the internal compression state. memLevel=1 uses minimum memory but
       is slow and reduces compression ratio; memLevel=9 uses maximum memory
       for optimal speed. The default value is 8. See zconf.h for total memory
       usage as a function of windowBits and memLevel.

         The strategy parameter is used to tune the compression algorithm. Use
    the value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced
    by a filter (or predictor), Z_HUFFMAN_ONLY to force Huffman encoding only
    (no string match), or Z_RLE to limit match distances to one (run-length
       encoding). Filtered data consists mostly of small values with a somewhat
       random distribution. In this case, the compression algorithm is tuned to
       compress them better. The effect of Z_FILTERED is to force more Huffman
       coding and less string matching; it is somewhat intermediate between
       Z_DEFAULT and Z_HUFFMAN_ONLY. Z_RLE is designed to be almost as fast as
       Z_HUFFMAN_ONLY, but give better compression for PNG image data. The
    strategy parameter only affects the compression ratio but not the
    correctness of the compressed output even if it is not set appropriately.
    Z_FIXED prevents the use of dynamic Huffman codes, allowing for a simpler
    decoder for special applications.

          deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not
    enough memory, Z_STREAM_ERROR if a parameter is invalid (such as an invalid
       method). msg is set to null if there is no error message.  deflateInit2
    does not perform any compression: this will be done by deflate().
    */

    ZEXTERN int ZEXPORT deflateSetDictionary
        OF((z_streamp strm, const Bytef* dictionary, uInt dictLength));
    /*
         Initializes the compression dictionary from the given byte sequence
       without producing any compressed output. This function must be called
       immediately after deflateInit, deflateInit2 or deflateReset, before any
       call of deflate. The compressor and decompressor must use exactly the
       same dictionary (see inflateSetDictionary).

         The dictionary should consist of strings (byte sequences) that are
       likely to be encountered later in the data to be compressed, with the
       most commonly used strings preferably put towards the end of the
       dictionary. Using a dictionary is most useful when the data to be
       compressed is short and can be predicted with good accuracy; the data can
       then be compressed better than with the default empty dictionary.

         Depending on the size of the compression data structures selected by
       deflateInit or deflateInit2, a part of the dictionary may in effect be
       discarded, for example if the dictionary is larger than the window size
       in deflate or deflate2. Thus the strings most likely to be useful should
       be put at the end of the dictionary, not at the front. In addition, the
       current implementation of deflate will use at most the window size minus
       262 bytes of the provided dictionary.

         Upon return of this function, strm->adler is set to the adler32 value
       of the dictionary; the decompressor may later use this value to determine
       which dictionary has been used by the compressor. (The adler32 value
       applies to the whole dictionary even if only a subset of the dictionary
       is actually used by the compressor.) If a raw deflate was requested, then
       the adler32 value is not computed and strm->adler is not set.

         deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
       parameter is invalid (such as nullptr dictionary) or the stream state is
       inconsistent (for example if deflate has already been called for this
       stream or if the compression method is bsort). deflateSetDictionary does
       not perform any compression: this will be done by deflate().
    */

    ZEXTERN int ZEXPORT deflateCopy OF((z_streamp dest, z_streamp source));
    /*
         Sets the destination stream as a complete copy of the source stream.

         This function can be useful when several compression strategies will be
       tried, for example when there are several ways of pre-processing the
       input data with a filter. The streams that will be discarded should then
       be freed by calling deflateEnd.  Note that deflateCopy duplicates the
       internal compression state which can be quite large, so this strategy is
       slow and can consume lots of memory.

         deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
       enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
       (such as zalloc being nullptr). msg is left unchanged in both source and
       destination.
    */

    ZEXTERN int ZEXPORT deflateReset OF((z_streamp strm));
    /*
         This function is equivalent to deflateEnd followed by deflateInit,
       but does not free and reallocate all the internal compression state.
       The stream will keep the same compression level and any other attributes
       that may have been set by deflateInit2.

          deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
       stream state was inconsistent (such as zalloc or state being nullptr).
    */

    ZEXTERN int ZEXPORT deflateParams
        OF((z_streamp strm, int level, int strategy));
    /*
         Dynamically update the compression level and compression strategy.  The
       interpretation of level and strategy is as in deflateInit2.  This can be
       used to switch between compression and straight copy of the input data,
       or to switch to a different kind of input data requiring a different
       strategy. If the compression level is changed, the input available so far
       is compressed with the old level (and may be flushed); the new level will
       take effect only at the next call of deflate().

         Before the call of deflateParams, the stream state must be set as for
       a call of deflate(), since the currently available input may have to
       be compressed and flushed. In particular, strm->avail_out must be
       non-zero.

         deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source
       stream state was inconsistent or if a parameter was invalid, Z_BUF_ERROR
       if strm->avail_out was zero.
    */

    ZEXTERN int ZEXPORT deflateTune
        OF((z_streamp strm, int good_length, int max_lazy, int nice_length,
            int max_chain));
    /*
         Fine tune deflate's internal compression parameters.  This should only
       be used by someone who understands the algorithm used by zlib's deflate
       for searching for the best matching string, and even then only by the
       most fanatic optimizer trying to squeeze out the last compressed bit for
       their specific input data.  Read the deflate.c source code for the
       meaning of the max_lazy, good_length, nice_length, and max_chain
       parameters.

         deflateTune() can be called after deflateInit() or deflateInit2(), and
       returns Z_OK on success, or Z_STREAM_ERROR for an invalid deflate stream.
     */

    ZEXTERN uLong ZEXPORT deflateBound OF((z_streamp strm, uLong sourceLen));
    /*
         deflateBound() returns an upper bound on the compressed size after
       deflation of sourceLen bytes.  It must be called after deflateInit()
       or deflateInit2().  This would be used to allocate an output buffer
       for deflation in a single pass, and so would be called before deflate().
    */

    ZEXTERN int ZEXPORT deflatePrime OF((z_streamp strm, int bits, int value));
    /*
         deflatePrime() inserts bits in the deflate output stream.  The intent
      is that this function is used to start off the deflate output with the
      bits leftover from a previous deflate stream when appending to it.  As
      such, this function can only be used for raw deflate, and must be used
      before the first deflate() call after a deflateInit2() or deflateReset().
      bits must be less than or equal to 16, and that many of the least
      significant bits of value will be inserted in the output.

          deflatePrime returns Z_OK if success, or Z_STREAM_ERROR if the source
       stream state was inconsistent.
    */

    ZEXTERN int ZEXPORT deflateSetHeader OF((z_streamp strm, gz_headerp head));
    /*
          deflateSetHeader() provides gzip header information for when a gzip
       stream is requested by deflateInit2().  deflateSetHeader() may be called
       after deflateInit2() or deflateReset() and before the first call of
       deflate().  The text, time, os, extra field, name, and comment
       information in the provided gz_header structure are written to the gzip
       header (xflag is ignored -- the extra flags are set according to the
       compression level).  The caller must assure that, if not Z_NULL, name and
       comment are terminated with a zero byte, and that if extra is not Z_NULL,
       that extra_len bytes are available there.  If hcrc is true, a gzip header
       crc is included.  Note that the current versions of the command-line
       version of gzip (up through version 1.3.x) do not support header crc's,
       and will report that it is a "multi-part gzip file" and give up.

          If deflateSetHeader is not used, the default gzip header has text
       false, the time set to zero, and os set to 255, with no extra, name, or
       comment fields.  The gzip header is returned to the default state by
       deflateReset().

          deflateSetHeader returns Z_OK if success, or Z_STREAM_ERROR if the
       source stream state was inconsistent.
    */

    /*
    ZEXTERN int ZEXPORT inflateInit2 OF((z_streamp strm,
                                         int  windowBits));

         This is another version of inflateInit with an extra parameter. The
       fields next_in, avail_in, zalloc, zfree and opaque must be initialized
       before by the caller.

         The windowBits parameter is the base two logarithm of the maximum
    window size (the size of the history buffer).  It should be in the
    range 8..15 for this version of the library. The default value is 15 if
    inflateInit is used instead. windowBits must be greater than or equal to the
    windowBits value provided to deflateInit2() while compressing, or it must be
    equal to 15 if deflateInit2() was not used. If a compressed stream with a
    larger window size is given as input, inflate() will return with the error
    code Z_DATA_ERROR instead of trying to allocate a larger window.

         windowBits can also be -8..-15 for raw inflate. In this case,
    -windowBits determines the window size. inflate() will then process raw
    deflate data, not looking for a zlib or gzip header, not generating a check
    value, and not looking for any check values for comparison at the end of the
    stream. This is for use with other formats that use the deflate compressed
    data format such as zip.  Those formats provide their own check values. If a
    custom format is developed using the raw deflate format for compressed data,
    it is recommended that a check value such as an adler32 or a crc32 be
    applied to the uncompressed data as is done in the zlib, gzip, and zip
    formats.  For most applications, the zlib format should be used as is. Note
    that comments above on the use in deflateInit2() applies to the magnitude of
    windowBits.

         windowBits can also be greater than 15 for optional gzip decoding. Add
       32 to windowBits to enable zlib and gzip decoding with automatic header
       detection, or add 16 to decode only the gzip format (the zlib format will
       return a Z_DATA_ERROR).  If a gzip stream is being decoded, strm->adler
    is a crc32 instead of an adler32.

         inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not
    enough memory, Z_STREAM_ERROR if a parameter is invalid (such as a null
    strm). msg is set to null if there is no error message.  inflateInit2 does
    not perform any decompression apart from reading the zlib header if present:
    this will be done by inflate(). (So next_in and avail_in may be modified,
    but next_out and avail_out are unchanged.)
    */

    ZEXTERN int ZEXPORT inflateSetDictionary
        OF((z_streamp strm, const Bytef* dictionary, uInt dictLength));
    /*
         Initializes the decompression dictionary from the given uncompressed
       byte sequence. This function must be called immediately after a call of
       inflate, if that call returned Z_NEED_DICT. The dictionary chosen by the
       compressor can be determined from the adler32 value returned by that call
       of inflate. The compressor and decompressor must use exactly the same
       dictionary (see deflateSetDictionary).  For raw inflate, this function
       can be called immediately after inflateInit2() or inflateReset() and
       before any call of inflate() to set the dictionary.  The application must
       insure that the dictionary that was used for compression is provided.

         inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
       parameter is invalid (such as nullptr dictionary) or the stream state is
       inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the
       expected one (incorrect adler32 value). inflateSetDictionary does not
       perform any decompression: this will be done by subsequent calls of
       inflate().
    */

    ZEXTERN int ZEXPORT inflateSync OF((z_streamp strm));
    /*
        Skips invalid compressed data until a full flush point (see above the
      description of deflate with Z_FULL_FLUSH) can be found, or until all
      available input is skipped. No output is provided.

        inflateSync returns Z_OK if a full flush point has been found,
      Z_BUF_ERROR if no more input was provided, Z_DATA_ERROR if no flush point
      has been found, or Z_STREAM_ERROR if the stream structure was
      inconsistent. In the success case, the application may save the current
      current value of total_in which indicates where valid compressed data was
      found. In the error case, the application may repeatedly call inflateSync,
      providing more input each time, until success or end of the input data.
    */

    ZEXTERN int ZEXPORT inflateCopy OF((z_streamp dest, z_streamp source));
    /*
         Sets the destination stream as a complete copy of the source stream.

         This function can be useful when randomly accessing a large stream. The
       first pass through the stream can periodically record the inflate state,
       allowing restarting inflate at those points when randomly accessing the
       stream.

         inflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
       enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
       (such as zalloc being nullptr). msg is left unchanged in both source and
       destination.
    */

    ZEXTERN int ZEXPORT inflateReset OF((z_streamp strm));
    /*
         This function is equivalent to inflateEnd followed by inflateInit,
       but does not free and reallocate all the internal decompression state.
       The stream will keep attributes that may have been set by inflateInit2.

          inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
       stream state was inconsistent (such as zalloc or state being nullptr).
    */

    ZEXTERN int ZEXPORT inflatePrime OF((z_streamp strm, int bits, int value));
    /*
         This function inserts bits in the inflate input stream.  The intent is
      that this function is used to start inflating at a bit position in the
      middle of a byte.  The provided bits will be used before any bytes are
      used from next_in.  This function should only be used with raw inflate,
      and should be used before the first inflate() call after inflateInit2() or
      inflateReset().  bits must be less than or equal to 16, and that many of
      the least significant bits of value will be inserted in the input.

          inflatePrime returns Z_OK if success, or Z_STREAM_ERROR if the source
       stream state was inconsistent.
    */

    ZEXTERN int ZEXPORT inflateGetHeader OF((z_streamp strm, gz_headerp head));
    /*
          inflateGetHeader() requests that gzip header information be stored in
       the provided gz_header structure.  inflateGetHeader() may be called after
       inflateInit2() or inflateReset(), and before the first call of inflate().
       As inflate() processes the gzip stream, head->done is zero until the
       header is completed, at which time head->done is set to one.  If a zlib
       stream is being decoded, then head->done is set to -1 to indicate that
       there will be no gzip header information forthcoming.  Note that Z_BLOCK
       can be used to force inflate() to return immediately after header
       processing is complete and before any actual data is decompressed.

          The text, time, xflags, and os fields are filled in with the gzip
       header contents.  hcrc is set to true if there is a header CRC.  (The
       header CRC was valid if done is set to one.)  If extra is not Z_NULL,
       then extra_max contains the maximum number of bytes to write to extra.
       Once done is true, extra_len contains the actual extra field length, and
       extra contains the extra field, or that field truncated if extra_max is
       less than extra_len. If name is not Z_NULL, then up to name_max
       characters are written there, terminated with a zero unless the length is
       greater than name_max.  If comment is not Z_NULL, then up to comm_max
       characters are written there, terminated with a zero unless the length is
       greater than comm_max.  When any of extra, name, or comment are not
       Z_NULL and the respective field is not present in the header, then that
       field is set to Z_NULL to signal its absence.  This allows the use of
       deflateSetHeader() with the returned structure to duplicate the header.
       However if those fields are set to allocated memory, then the application
       will need to save those pointers elsewhere so that they can be eventually
       freed.

          If inflateGetHeader is not used, then the header information is simply
       discarded.  The header is always checked for validity, including the
       header CRC if present.  inflateReset() will reset the process to discard
       the header information.  The application would need to call
       inflateGetHeader() again to retrieve the header from the next gzip
       stream.

          inflateGetHeader returns Z_OK if success, or Z_STREAM_ERROR if the
       source stream state was inconsistent.
    */

    /*
    ZEXTERN int ZEXPORT inflateBackInit OF((z_streamp strm, int windowBits,
                                            unsigned char FAR *window));

         Initialize the internal stream state for decompression using
    inflateBack() calls.  The fields zalloc, zfree and opaque in strm must be
    initialized before the call.  If zalloc and zfree are Z_NULL, then the
    default library- derived memory allocation routines are used.  windowBits is
    the base two logarithm of the window size, in the range 8..15.  window is a
    caller supplied buffer of that size.  Except for special applications where
    it is assured that deflate was used with small window sizes, windowBits must
    be 15 and a 32K byte window must be supplied to be able to decompress
    general deflate streams.

         See inflateBack() for the usage of these routines.

         inflateBackInit will return Z_OK on success, Z_STREAM_ERROR if any of
       the paramaters are invalid, Z_MEM_ERROR if the internal state could not
       be allocated, or Z_VERSION_ERROR if the version of the library does not
       match the version of the header file.
    */

    typedef unsigned(*in_func) OF((void FAR*, unsigned char FAR* FAR*));
    typedef int(*out_func) OF((void FAR*, unsigned char FAR*, unsigned));

    ZEXTERN int ZEXPORT inflateBack
        OF((z_streamp strm, in_func in, void FAR* in_desc, out_func out,
            void FAR* out_desc));
    /*
         inflateBack() does a raw inflate with a single call using a call-back
       interface for input and output.  This is more efficient than inflate()
       for file i/o applications in that it avoids copying between the output
       and the sliding window by simply making the window itself the output
       buffer.  This function trusts the application to not change the output
       buffer passed by the output function, at least until inflateBack()
       returns.

         inflateBackInit() must be called first to allocate the internal state
       and to initialize the state with the user-provided window buffer.
       inflateBack() may then be used multiple times to inflate a complete, raw
       deflate stream with each call.  inflateBackEnd() is then called to free
       the allocated state.

         A raw deflate stream is one with no zlib or gzip header or trailer.
       This routine would normally be used in a utility that reads zip or gzip
       files and writes out uncompressed files.  The utility would decode the
       header and process the trailer on its own, hence this routine expects
       only the raw deflate stream to decompress.  This is different from the
       normal behavior of inflate(), which expects either a zlib or gzip header
       and trailer around the deflate stream.

         inflateBack() uses two subroutines supplied by the caller that are then
       called by inflateBack() for input and output.  inflateBack() calls those
       routines until it reads a complete deflate stream and writes out all of
       the uncompressed data, or until it encounters an error.  The function's
       parameters and return types are defined above in the in_func and out_func
       typedefs.  inflateBack() will call in(in_desc, &buf) which should return
       the number of bytes of provided input, and a pointer to that input in
       buf.  If there is no input available, in() must return zero--buf is
       ignored in that case--and inflateBack() will return a buffer error.
       inflateBack() will call out(out_desc, buf, len) to write the uncompressed
       data buf[0..len-1].  out() should return zero on success, or non-zero on
       failure.  If out() returns non-zero, inflateBack() will return with an
       error.  Neither in() nor out() are permitted to change the contents of
       the window provided to inflateBackInit(), which is also the buffer that
       out() uses to write from. The length written by out() will be at most the
       window size.  Any non-zero amount of input may be provided by in().

         For convenience, inflateBack() can be provided input on the first call
       by setting strm->next_in and strm->avail_in.  If that input is exhausted,
       then in() will be called.  Therefore strm->next_in must be initialized
       before calling inflateBack().  If strm->next_in is Z_NULL, then in() will
       be called immediately for input.  If strm->next_in is not Z_NULL, then
       strm->avail_in must also be initialized, and then if strm->avail_in is
       not zero, input will initially be taken from strm->next_in[0 ..
       strm->avail_in - 1].

         The in_desc and out_desc parameters of inflateBack() is passed as the
       first parameter of in() and out() respectively when they are called.
       These descriptors can be optionally used to pass any information that the
       caller- supplied in() and out() functions need to do their job.

         On return, inflateBack() will set strm->next_in and strm->avail_in to
       pass back any unused input that was provided by the last in() call.  The
       return values of inflateBack() can be Z_STREAM_END on success,
       Z_BUF_ERROR if in() or out() returned an error, Z_DATA_ERROR if there was
       a format error in the deflate stream (in which case strm->msg is set to
       indicate the nature of the error), or Z_STREAM_ERROR if the stream was
       not properly initialized.  In the case of Z_BUF_ERROR, an input or output
       error can be distinguished using strm->next_in which will be Z_NULL only
       if in() returned an error.  If strm->next is not Z_NULL, then the
       Z_BUF_ERROR was due to out() returning non-zero.  (in() will always be
       called before out(), so strm->next_in is assured to be defined if out()
       returns non-zero.)  Note that inflateBack() cannot return Z_OK.
    */

    ZEXTERN int ZEXPORT inflateBackEnd OF((z_streamp strm));
    /*
         All memory allocated by inflateBackInit() is freed.

         inflateBackEnd() returns Z_OK on success, or Z_STREAM_ERROR if the
       stream state was inconsistent.
    */

    ZEXTERN uLong ZEXPORT zlibCompileFlags OF((void));
    /* Return flags indicating compile-time options.

        Type sizes, two bits each, 00 = 16 bits, 01 = 32, 10 = 64, 11 = other:
         1.0: size of uInt
         3.2: size of uLong
         5.4: size of voidpf (pointer)
         7.6: size of z_off_t

        Compiler, assembler, and debug options:
         8: DEBUG
         9: ASMV or ASMINF -- use ASM code
         10: ZLIB_WINAPI -- exported functions use the WINAPI calling convention
         11: 0 (reserved)

        One-time table building (smaller code, but not thread-safe if true):
         12: BUILDFIXED -- build static block decoding tables when needed
         13: DYNAMIC_CRC_TABLE -- build CRC calculation tables when needed
         14,15: 0 (reserved)

        Library content (indicates missing functionality):
         16: NO_GZCOMPRESS -- gz* functions cannot compress (to avoid linking
                              deflate code when not needed)
         17: NO_GZIP -- deflate can't write gzip streams, and inflate can't
       detect and decode gzip streams (to avoid linking crc code) 18-19: 0
       (reserved)

        Operation variations (changes in library functionality):
         20: PKZIP_BUG_WORKAROUND -- slightly more permissive inflate
         21: FASTEST -- deflate algorithm with only one, lowest compression
       level 22,23: 0 (reserved)

        The sprintf variant used by gzprintf (zero is best):
         24: 0 = vs*, 1 = s* -- 1 means limited to 20 arguments after the format
         25: 0 = *nprintf, 1 = *printf -- 1 means gzprintf() not secure!
         26: 0 = returns value, 1 = void -- 1 means inferred string length
       returned

        Remainder:
         27-31: 0 (reserved)
     */

    /* utility functions */

    /*
         The following utility functions are implemented on top of the
       basic stream-oriented functions. To simplify the interface, some
       default options are assumed (compression level and memory usage,
       standard memory allocation functions). The source code of these
       utility functions can easily be modified if you need special options.
    */

    ZEXTERN int ZEXPORT compress OF(
        (Bytef * dest, uLongf* destLen, const Bytef* source, uLong sourceLen));
    /*
         Compresses the source buffer into the destination buffer.  sourceLen is
       the byte length of the source buffer. Upon entry, destLen is the total
       size of the destination buffer, which must be at least the value returned
       by compressBound(sourceLen). Upon exit, destLen is the actual size of the
       compressed buffer.
         This function can be used to compress a whole file at once if the
       input file is mmap'ed.
         compress returns Z_OK if success, Z_MEM_ERROR if there was not
       enough memory, Z_BUF_ERROR if there was not enough room in the output
       buffer.
    */

    ZEXTERN int ZEXPORT compress2
        OF((Bytef * dest, uLongf* destLen, const Bytef* source, uLong sourceLen,
            int level));
    /*
         Compresses the source buffer into the destination buffer. The level
       parameter has the same meaning as in deflateInit.  sourceLen is the byte
       length of the source buffer. Upon entry, destLen is the total size of the
       destination buffer, which must be at least the value returned by
       compressBound(sourceLen). Upon exit, destLen is the actual size of the
       compressed buffer.

         compress2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
       memory, Z_BUF_ERROR if there was not enough room in the output buffer,
       Z_STREAM_ERROR if the level parameter is invalid.
    */

    ZEXTERN uLong ZEXPORT compressBound OF((uLong sourceLen));
    /*
         compressBound() returns an upper bound on the compressed size after
       compress() or compress2() on sourceLen bytes.  It would be used before
       a compress() or compress2() call to allocate the destination buffer.
    */

    ZEXTERN int ZEXPORT uncompress OF(
        (Bytef * dest, uLongf* destLen, const Bytef* source, uLong sourceLen));
    /*
         Decompresses the source buffer into the destination buffer.  sourceLen
       is the byte length of the source buffer. Upon entry, destLen is the total
       size of the destination buffer, which must be large enough to hold the
       entire uncompressed data. (The size of the uncompressed data must have
       been saved previously by the compressor and transmitted to the
       decompressor by some mechanism outside the scope of this compression
       library.) Upon exit, destLen is the actual size of the compressed buffer.
         This function can be used to decompress a whole file at once if the
       input file is mmap'ed.

         uncompress returns Z_OK if success, Z_MEM_ERROR if there was not
       enough memory, Z_BUF_ERROR if there was not enough room in the output
       buffer, or Z_DATA_ERROR if the input data was corrupted or incomplete.
    */

    typedef voidp gzFile;

    ZEXTERN gzFile ZEXPORT gzopen OF((const char* path, const char* mode));
    /*
         Opens a gzip (.gz) file for reading or writing. The mode parameter
       is as in fopen ("rb" or "wb") but can also include a compression level
       ("wb9") or a strategy: 'f' for filtered data as in "wb6f", 'h' for
       Huffman only compression as in "wb1h", or 'R' for run-length encoding
       as in "wb1R". (See the description of deflateInit2 for more information
       about the strategy parameter.)

         gzopen can be used to read a file which is not in gzip format; in this
       case gzread will directly read from the file without decompression.

         gzopen returns nullptr if the file could not be opened or if there was
       insufficient memory to allocate the (de)compression state; errno
       can be checked to distinguish the two cases (if errno is zero, the
       zlib error is Z_MEM_ERROR).  */

    ZEXTERN gzFile ZEXPORT gzdopen OF((int fd, const char* mode));
    /*
         gzdopen() associates a gzFile with the file descriptor fd.  File
       descriptors are obtained from calls like open, dup, creat, pipe or
       fileno (in the file has been previously opened with fopen).
       The mode parameter is as in gzopen.
         The next call of gzclose on the returned gzFile will also close the
       file descriptor fd, just like fclose(fdopen(fd), mode) closes the file
       descriptor fd. If you want to keep fd open, use gzdopen(dup(fd), mode).
         gzdopen returns nullptr if there was insufficient memory to allocate
       the (de)compression state.
    */

    ZEXTERN int ZEXPORT gzsetparams OF((gzFile file, int level, int strategy));
    /*
         Dynamically update the compression level or strategy. See the
       description of deflateInit2 for the meaning of these parameters.
         gzsetparams returns Z_OK if success, or Z_STREAM_ERROR if the file was
       not opened for writing.
    */

    ZEXTERN int ZEXPORT gzread OF((gzFile file, voidp buf, unsigned len));
    /*
         Reads the given number of uncompressed bytes from the compressed file.
       If the input file was not in gzip format, gzread copies the given number
       of bytes into the buffer.
         gzread returns the number of uncompressed bytes actually read (0 for
       end of file, -1 for error). */

    ZEXTERN int ZEXPORT gzwrite OF((gzFile file, voidpc buf, unsigned len));
    /*
         Writes the given number of uncompressed bytes into the compressed file.
       gzwrite returns the number of uncompressed bytes actually written
       (0 in case of error).
    */

    ZEXTERN int ZEXPORTVA gzprintf OF((gzFile file, const char* format, ...));
    /*
         Converts, formats, and writes the args to the compressed file under
       control of the format string, as in fprintf. gzprintf returns the number
       of uncompressed bytes actually written (0 in case of error).  The number
       of uncompressed bytes written is limited to 4095. The caller should
       assure that this limit is not exceeded. If it is exceeded, then
       gzprintf() will return return an error (0) with nothing written. In this
       case, there may also be a buffer overflow with unpredictable
       consequences, which is possible only if zlib was compiled with the
       insecure functions sprintf() or vsprintf() because the secure snprintf()
       or vsnprintf() functions were not available.
    */

    ZEXTERN int ZEXPORT gzputs OF((gzFile file, const char* s));
    /*
          Writes the given null-terminated string to the compressed file,
       excluding the terminating null character. gzputs returns the number of
       characters written, or -1 in case of error.
    */

    ZEXTERN char* ZEXPORT gzgets OF((gzFile file, char* buf, int len));
    /*
          Reads bytes from the compressed file until len-1 characters are read,
       or a newline character is read and transferred to buf, or an end-of-file
       condition is encountered.  The string is then terminated with a null
       character.
          gzgets returns buf, or Z_NULL in case of error.
    */

    ZEXTERN int ZEXPORT gzputc OF((gzFile file, int c));
    /*
          Writes c, converted to an unsigned char, into the compressed file.
       gzputc returns the value that was written, or -1 in case of error.
    */

    ZEXTERN int ZEXPORT gzgetc OF((gzFile file));
    /*
          Reads one byte from the compressed file. gzgetc returns this byte
       or -1 in case of end of file or error.
    */

    ZEXTERN int ZEXPORT gzungetc OF((int c, gzFile file));
    /*
          Push one character back onto the stream to be read again later.
       Only one character of push-back is allowed.  gzungetc() returns the
       character pushed, or -1 on failure.  gzungetc() will fail if a
       character has been pushed but not read yet, or if c is -1. The pushed
       character will be discarded if the stream is repositioned with gzseek()
       or gzrewind().
    */

    ZEXTERN int ZEXPORT gzflush OF((gzFile file, int flush));
    /*
         Flushes all pending output into the compressed file. The parameter
       flush is as in the deflate() function. The return value is the zlib
       error number (see function gzerror below). gzflush returns Z_OK if
       the flush parameter is Z_FINISH and all output could be flushed.
         gzflush should be called only when strictly necessary because it can
       degrade compression.
    */

    ZEXTERN z_off_t ZEXPORT gzseek
        OF((gzFile file, z_off_t offset, int whence));
    /*
          Sets the starting position for the next gzread or gzwrite on the
       given compressed file. The offset represents a number of bytes in the
       uncompressed data stream. The whence parameter is defined as in lseek(2);
       the value SEEK_END is not supported.
         If the file is opened for reading, this function is emulated but can be
       extremely slow. If the file is opened for writing, only forward seeks are
       supported; gzseek then compresses a sequence of zeroes up to the new
       starting position.

          gzseek returns the resulting offset location as measured in bytes from
       the beginning of the uncompressed stream, or -1 in case of error, in
       particular if the file is opened for writing and the new starting
       position would be before the current position.
    */

    ZEXTERN int ZEXPORT gzrewind OF((gzFile file));
    /*
         Rewinds the given file. This function is supported only for reading.

       gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET)
    */

    ZEXTERN z_off_t ZEXPORT gztell OF((gzFile file));
    /*
         Returns the starting position for the next gzread or gzwrite on the
       given compressed file. This position represents a number of bytes in the
       uncompressed data stream.

       gztell(file) is equivalent to gzseek(file, 0L, SEEK_CUR)
    */

    ZEXTERN int ZEXPORT gzeof OF((gzFile file));
    /*
         Returns 1 when EOF has previously been detected reading the given
       input stream, otherwise zero.
    */

    ZEXTERN int ZEXPORT gzdirect OF((gzFile file));
    /*
         Returns 1 if file is being read directly without decompression,
       otherwise zero.
    */

    ZEXTERN int ZEXPORT gzclose OF((gzFile file));
    /*
         Flushes all pending output if necessary, closes the compressed file
       and deallocates all the (de)compression state. The return value is the
       zlib error number (see function gzerror below).
    */

    ZEXTERN const char* ZEXPORT gzerror OF((gzFile file, int* errnum));
    /*
         Returns the error message for the last error which occurred on the
       given compressed file. errnum is set to zlib error number. If an
       error occurred in the file system and not in the compression library,
       errnum is set to Z_ERRNO and the application may consult errno
       to get the exact error code.
    */

    ZEXTERN void ZEXPORT gzclearerr OF((gzFile file));
    /*
         Clears the error and end-of-file flags for file. This is analogous to
       the clearerr() function in stdio. This is useful for continuing to read a
       gzip file that is being written concurrently.
    */

    /* checksum functions */

    /*
         These functions are not related to compression but are exported
       anyway because they might be useful in applications using the
       compression library.
    */

    ZEXTERN uLong ZEXPORT adler32 OF((uLong adler, const Bytef* buf, uInt len));
    /*
         Update a running Adler-32 checksum with the bytes buf[0..len-1] and
       return the updated checksum. If buf is nullptr, this function returns
       the required initial value for the checksum.
       An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
       much faster. Usage example:

         uLong adler = adler32(0L, Z_NULL, 0);

         while (read_buffer(buffer, length) != EOF) {
           adler = adler32(adler, buffer, length);
         }
         if (adler != original_adler) error();
    */

    ZEXTERN uLong ZEXPORT adler32_combine
        OF((uLong adler1, uLong adler2, z_off_t len2));
    /*
         Combine two Adler-32 checksums into one.  For two sequences of bytes,
       seq1 and seq2 with lengths len1 and len2, Adler-32 checksums were
       calculated for each, adler1 and adler2.  adler32_combine() returns the
       Adler-32 checksum of seq1 and seq2 concatenated, requiring only adler1,
       adler2, and len2.
    */

    ZEXTERN uLong ZEXPORT crc32 OF((uLong crc, const Bytef* buf, uInt len));
    /*
         Update a running CRC-32 with the bytes buf[0..len-1] and return the
       updated CRC-32. If buf is nullptr, this function returns the required
       initial value for the for the crc. Pre- and post-conditioning (one's
       complement) is performed within this function so it shouldn't be done by
       the application. Usage example:

         uLong crc = crc32(0L, Z_NULL, 0);

         while (read_buffer(buffer, length) != EOF) {
           crc = crc32(crc, buffer, length);
         }
         if (crc != original_crc) error();
    */

    ZEXTERN uLong ZEXPORT crc32_combine
        OF((uLong crc1, uLong crc2, z_off_t len2));

    /*
         Combine two CRC-32 check values into one.  For two sequences of bytes,
       seq1 and seq2 with lengths len1 and len2, CRC-32 check values were
       calculated for each, crc1 and crc2.  crc32_combine() returns the CRC-32
       check value of seq1 and seq2 concatenated, requiring only crc1, crc2, and
       len2.
    */

    /* various hacks, don't look :) */

    /* deflateInit and inflateInit are macros to allow checking the zlib version
     * and the compiler's view of z_stream:
     */
    ZEXTERN int ZEXPORT deflateInit_
        OF((z_streamp strm, int level, const char* version, int stream_size));
    ZEXTERN int ZEXPORT inflateInit_
        OF((z_streamp strm, const char* version, int stream_size));
    ZEXTERN int ZEXPORT deflateInit2_
        OF((z_streamp strm, int level, int method, int windowBits, int memLevel,
            int strategy, const char* version, int stream_size));
    ZEXTERN int ZEXPORT inflateInit2_ OF(
        (z_streamp strm, int windowBits, const char* version, int stream_size));
    ZEXTERN int ZEXPORT inflateBackInit_
        OF((z_streamp strm, int windowBits, unsigned char FAR* window,
            const char* version, int stream_size));
#define deflateInit(strm, level) \
    deflateInit_((strm), (level), ZLIB_VERSION, sizeof(z_stream))
#define inflateInit(strm) inflateInit_((strm), ZLIB_VERSION, sizeof(z_stream))
#define deflateInit2(strm, level, method, windowBits, memLevel, strategy) \
    deflateInit2_(                                                        \
        (strm), (level), (method), (windowBits), (memLevel), (strategy),  \
        ZLIB_VERSION, sizeof(z_stream))
#define inflateInit2(strm, windowBits) \
    inflateInit2_((strm), (windowBits), ZLIB_VERSION, sizeof(z_stream))
#define inflateBackInit(strm, windowBits, window) \
    inflateBackInit_(                             \
        (strm), (windowBits), (window), ZLIB_VERSION, sizeof(z_stream))

#if !defined(ZUTIL_H) && !defined(NO_DUMMY_DECL)
    struct internal_state
    {
        int dummy;
    }; /* hack for buggy compilers */
#endif

    ZEXTERN const char* ZEXPORT zError OF((int));
    ZEXTERN int ZEXPORT inflateSyncPoint OF((z_streamp z));
    ZEXTERN const uLongf* ZEXPORT get_crc_table OF((void));

#ifdef __cplusplus
}
#endif