FreeBSD/Linux Kernel Cross Reference
sys/lib/libz/zlib.h

     /* $NetBSD: zlib.h,v 1.6 2005/02/26 22:58:57 perry Exp $ */
     
     /* zlib.h -- interface of the 'zlib' general purpose compression library
       version 1.1.4, March 11th, 2002
     
       Copyright (C) 1995-2002 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
      jloup@gzip.org          madler@alumni.caltech.edu
    
    
      The data format used by the zlib library is described by RFCs (Request for
      Comments) 1950 to 1952 in the files ftp://ds.internic.net/rfc/rfc1950.txt
      (zlib format), rfc1951.txt (deflate format) and rfc1952.txt (gzip format).
    */
    
    #ifndef _ZLIB_H
    #define _ZLIB_H
    
    #ifdef __NetBSD__
    #include <sys/cdefs.h>
    #endif
    
    #include "zconf.h"
    
    #ifdef __cplusplus
    extern "C" {
    #endif
    
    #define ZLIB_VERSION "1.1.4"
    
    /*
         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 library also supports reading and writing files in gzip (.gz) format
      with an interface similar to that of stdio.
    
         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) __P((voidpf opaque, unsigned items, unsigned size));
    typedef void   (*free_func)  __P((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, 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 */
        voidpf     opaque;  /* private data object passed to zalloc and zfree */
    
        int     data_type;  /* best guess about the data type: ascii or binary */
        uLong   reserved;   /* reserved for future use */
    } z_stream;
    
    typedef z_stream FAR *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
   /* Allowed flush values; see deflate() 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_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 */
   
   #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 __P((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 __P((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 __P((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).
   
       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
     0.1% larger than avail_in plus 12 bytes.  If deflate does not return
     Z_STREAM_END, then it must be called again as described above.
   
       deflate() may update data_type if it can make a good guess about
     the input data type (Z_ASCII or Z_BINARY). 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 NULL), Z_BUF_ERROR if no progress is possible
     (for example avail_in or avail_out was zero).
   */
   
   
   ZEXTERN int ZEXPORT deflateEnd __P((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 __P((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 __P((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 some
     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.
   
       If the parameter flush is set to Z_SYNC_FLUSH, inflate flushes as much
     output as possible to the output buffer. The flushing behavior of inflate is
     not specified for values of the flush parameter other than Z_SYNC_FLUSH
     and Z_FINISH, but the current implementation actually flushes as much output
     as possible anyway.
   
       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 routine
     may be used for the single inflate() call.
   
       inflate returns Z_OK, Z_STREAM_END or
     an error code as described below. At the end of the stream, inflate()
     returns Z_STREAM_END.
   
       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),
     Z_STREAM_ERROR if the stream structure was inconsistent
     (for example if next_in or next_out was NULL), 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. In the Z_DATA_ERROR
     case, the application may then call inflateSync to look for a good
     compression block.
   */
   
   
   ZEXTERN int ZEXPORT inflateEnd __P((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 __P((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.
   
        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), or Z_HUFFMAN_ONLY to force Huffman encoding only (no
      string match).  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. The strategy parameter only affects
      the compression ratio but not the correctness of the compressed output even
      if it is not set appropriately.
   
         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 __P((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.
   
        deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
      parameter is invalid (such as NULL 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 __P((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 NULL). msg is left unchanged in both source and
      destination.
   */
   
   ZEXTERN int ZEXPORT deflateReset __P((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 NULL).
   */
   
   ZEXTERN int ZEXPORT deflateParams __P((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 inflateInit2 __P((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. 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.
   
         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 negative
      memLevel). 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 __P((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 this call returned Z_NEED_DICT. The dictionary chosen by the compressor
      can be determined from the Adler32 value returned by this call of
      inflate. The compressor and decompressor must use exactly the same
      dictionary (see deflateSetDictionary).
   
        inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
      parameter is invalid (such as NULL 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 inflateReset __P((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 NULL).
   */
   
   
                           /* 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 __P((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 0.1% larger than
      sourceLen plus 12 bytes. 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 __P((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 0.1% larger than sourceLen plus
      12 bytes. 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 int ZEXPORT uncompress __P((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.
   */
   
   
   typedef voidp gzFile;
   
   ZEXTERN gzFile ZEXPORT gzopen  __P((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". (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 NULL 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  __P((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 NULL if there was insufficient memory to allocate
      the (de)compression state.
   */
   
   ZEXTERN int ZEXPORT gzsetparams __P((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  __P((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 __P((gzFile file,
                                      const voidp 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 __P((gzFile file, const char *format, ...))
                   __attribute__((__format__(__printf__, 2, 3)));
   /*
        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).
   */
   
   ZEXTERN int ZEXPORT gzputs __P((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 __P((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 __P((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 __P((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    gzflush __P((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.
   
   */
   
   /*
    * NetBSD note:
    * "long" gzseek has been there till Oct 1999 (1.4L), which was wrong.
    */
   ZEXTERN z_off_t ZEXPORT    gzseek __P((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 __P((gzFile file));
   /*
        Rewinds the given file. This function is supported only for reading.
   
      gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET)
   */
   
   /*
    * NetBSD note:
    * "long" gztell has been there till Oct 1999 (1.4L), which was wrong.
    */
   ZEXTERN z_off_t ZEXPORT    gztell __P((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 __P((gzFile file));
   /*
        Returns 1 when EOF has previously been detected reading the given
      input stream, otherwise zero.
   */
   
   ZEXTERN int ZEXPORT    gzclose __P((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 __P((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.
   */
   
                           /* 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 crc32   __P((uLong crc, const Bytef *buf, uInt len));
   /*
        Update a running crc with the bytes buf[0..len-1] and return the updated
      crc. If buf is NULL, this function returns the required initial value
      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();
   */
   
   
                           /* 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_ __P((z_streamp strm, int level,
                                        const char *version, int stream_size));
   ZEXTERN int ZEXPORT inflateInit_ __P((z_streamp strm,
                                        const char *version, int stream_size));
   ZEXTERN int ZEXPORT deflateInit2_ __P((z_streamp strm, int  level, int  method,
                                         int windowBits, int memLevel,
                                         int strategy, const char *version,
                                         int stream_size));
   ZEXTERN int ZEXPORT inflateInit2_ __P((z_streamp strm, int  windowBits,
                                         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))
   
   
   #if !defined(_Z_UTIL_H) && !defined(NO_DUMMY_DECL)
       struct internal_state {int dummy;}; /* hack for buggy compilers */
   #endif
   
   ZEXTERN const char   * ZEXPORT zError           __P((int err));
   
   #ifdef __cplusplus
   }
   #endif
   
   #endif /* _ZLIB_H */

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