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    1 /* zlib.h -- interface of the 'zlib' general purpose compression library
    2   version 1.2.1.1, January 9th, 2004
    3 
    4   Copyright (C) 1995-2004 Jean-loup Gailly and Mark Adler
    5 
    6   This software is provided 'as-is', without any express or implied
    7   warranty.  In no event will the authors be held liable for any damages
    8   arising from the use of this software.
    9 
   10   Permission is granted to anyone to use this software for any purpose,
   11   including commercial applications, and to alter it and redistribute it
   12   freely, subject to the following restrictions:
   13 
   14   1. The origin of this software must not be misrepresented; you must not
   15      claim that you wrote the original software. If you use this software
   16      in a product, an acknowledgment in the product documentation would be
   17      appreciated but is not required.
   18   2. Altered source versions must be plainly marked as such, and must not be
   19      misrepresented as being the original software.
   20   3. This notice may not be removed or altered from any source distribution.
   21 
   22   Jean-loup Gailly        Mark Adler
   23   jloup@gzip.org          madler@alumni.caltech.edu
   24 
   25 
   26   The data format used by the zlib library is described by RFCs (Request for
   27   Comments) 1950 to 1952 in the files http://www.ietf.org/rfc/rfc1950.txt
   28   (zlib format), rfc1951.txt (deflate format) and rfc1952.txt (gzip format).
   29 */
   30 
   31 #ifndef ZLIB_H
   32 #define ZLIB_H
   33 
   34 #include "zconf.h"
   35 
   36 #ifdef __cplusplus
   37 extern "C" {
   38 #endif
   39 
   40 #define ZLIB_VERSION "1.2.1.1"
   41 #define ZLIB_VERNUM 0x1211
   42 
   43 /*
   44      The 'zlib' compression library provides in-memory compression and
   45   decompression functions, including integrity checks of the uncompressed
   46   data.  This version of the library supports only one compression method
   47   (deflation) but other algorithms will be added later and will have the same
   48   stream interface.
   49 
   50      Compression can be done in a single step if the buffers are large
   51   enough (for example if an input file is mmap'ed), or can be done by
   52   repeated calls of the compression function.  In the latter case, the
   53   application must provide more input and/or consume the output
   54   (providing more output space) before each call.
   55 
   56      The compressed data format used by the in-memory functions is the zlib
   57   format, which is a zlib wrapper documented in RFC 1950, wrapped around a
   58   deflate stream, which is itself documented in RFC 1951.
   59 
   60      The library also supports reading and writing files in gzip (.gz) format
   61   with an interface similar to that of stdio using the functions that start
   62   with "gz".  The gzip format is different from the zlib format.  gzip is a
   63   gzip wrapper, documented in RFC 1952, wrapped around a deflate stream.
   64 
   65      The zlib format was designed to be compact and fast for use in memory
   66   and on communications channels.  The gzip format was designed for single-
   67   file compression on file systems, has a larger header than zlib to maintain
   68   directory information, and uses a different, slower check method than zlib.
   69 
   70      This library does not provide any functions to write gzip files in memory.
   71   However such functions could be easily written using zlib's deflate function,
   72   the documentation in the gzip RFC, and the examples in gzio.c.
   73 
   74      The library does not install any signal handler. The decoder checks
   75   the consistency of the compressed data, so the library should never
   76   crash even in case of corrupted input.
   77 */
   78 
   79 typedef voidpf (*alloc_func) OF((voidpf opaque, uInt items, uInt size));
   80 typedef void   (*free_func)  OF((voidpf opaque, voidpf address));
   81 
   82 struct internal_state;
   83 
   84 typedef struct z_stream_s {
   85     Bytef    *next_in;  /* next input byte */
   86     uInt     avail_in;  /* number of bytes available at next_in */
   87     uLong    total_in;  /* total nb of input bytes read so far */
   88 
   89     Bytef    *next_out; /* next output byte should be put there */
   90     uInt     avail_out; /* remaining free space at next_out */
   91     uLong    total_out; /* total nb of bytes output so far */
   92 
   93     char     *msg;      /* last error message, NULL if no error */
   94     struct internal_state FAR *state; /* not visible by applications */
   95 
   96     alloc_func zalloc;  /* used to allocate the internal state */
   97     free_func  zfree;   /* used to free the internal state */
   98     voidpf     opaque;  /* private data object passed to zalloc and zfree */
   99 
  100     int     data_type;  /* best guess about the data type: ascii or binary */
  101     uLong   adler;      /* adler32 value of the uncompressed data */
  102     uLong   reserved;   /* reserved for future use */
  103 } z_stream;
  104 
  105 typedef z_stream FAR *z_streamp;
  106 
  107 /*
  108    The application must update next_in and avail_in when avail_in has
  109    dropped to zero. It must update next_out and avail_out when avail_out
  110    has dropped to zero. The application must initialize zalloc, zfree and
  111    opaque before calling the init function. All other fields are set by the
  112    compression library and must not be updated by the application.
  113 
  114    The opaque value provided by the application will be passed as the first
  115    parameter for calls of zalloc and zfree. This can be useful for custom
  116    memory management. The compression library attaches no meaning to the
  117    opaque value.
  118 
  119    zalloc must return Z_NULL if there is not enough memory for the object.
  120    If zlib is used in a multi-threaded application, zalloc and zfree must be
  121    thread safe.
  122 
  123    On 16-bit systems, the functions zalloc and zfree must be able to allocate
  124    exactly 65536 bytes, but will not be required to allocate more than this
  125    if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS,
  126    pointers returned by zalloc for objects of exactly 65536 bytes *must*
  127    have their offset normalized to zero. The default allocation function
  128    provided by this library ensures this (see zutil.c). To reduce memory
  129    requirements and avoid any allocation of 64K objects, at the expense of
  130    compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h).
  131 
  132    The fields total_in and total_out can be used for statistics or
  133    progress reports. After compression, total_in holds the total size of
  134    the uncompressed data and may be saved for use in the decompressor
  135    (particularly if the decompressor wants to decompress everything in
  136    a single step).
  137 */
  138 
  139                         /* constants */
  140 
  141 #define Z_NO_FLUSH      0
  142 #define Z_PARTIAL_FLUSH 1 /* will be removed, use Z_SYNC_FLUSH instead */
  143 #define Z_SYNC_FLUSH    2
  144 #define Z_FULL_FLUSH    3
  145 #define Z_FINISH        4
  146 #define Z_BLOCK         5
  147 /* Allowed flush values; see deflate() and inflate() below for details */
  148 
  149 #define Z_OK            0
  150 #define Z_STREAM_END    1
  151 #define Z_NEED_DICT     2
  152 #define Z_ERRNO        (-1)
  153 #define Z_STREAM_ERROR (-2)
  154 #define Z_DATA_ERROR   (-3)
  155 #define Z_MEM_ERROR    (-4)
  156 #define Z_BUF_ERROR    (-5)
  157 #define Z_VERSION_ERROR (-6)
  158 /* Return codes for the compression/decompression functions. Negative
  159  * values are errors, positive values are used for special but normal events.
  160  */
  161 
  162 #define Z_NO_COMPRESSION         0
  163 #define Z_BEST_SPEED             1
  164 #define Z_BEST_COMPRESSION       9
  165 #define Z_DEFAULT_COMPRESSION  (-1)
  166 /* compression levels */
  167 
  168 #define Z_FILTERED            1
  169 #define Z_HUFFMAN_ONLY        2
  170 #define Z_RLE                 3
  171 #define Z_DEFAULT_STRATEGY    0
  172 /* compression strategy; see deflateInit2() below for details */
  173 
  174 #define Z_BINARY   0
  175 #define Z_ASCII    1
  176 #define Z_UNKNOWN  2
  177 /* Possible values of the data_type field (though see inflate()) */
  178 
  179 #define Z_DEFLATED   8
  180 /* The deflate compression method (the only one supported in this version) */
  181 
  182 #define Z_NULL  0  /* for initializing zalloc, zfree, opaque */
  183 
  184 #define zlib_version zlibVersion()
  185 /* for compatibility with versions < 1.0.2 */
  186 
  187                         /* basic functions */
  188 
  189 ZEXTERN const char * ZEXPORT zlibVersion OF((void));
  190 /* The application can compare zlibVersion and ZLIB_VERSION for consistency.
  191    If the first character differs, the library code actually used is
  192    not compatible with the zlib.h header file used by the application.
  193    This check is automatically made by deflateInit and inflateInit.
  194  */
  195 
  196 /*
  197 ZEXTERN int ZEXPORT deflateInit OF((z_streamp strm, int level));
  198 
  199      Initializes the internal stream state for compression. The fields
  200    zalloc, zfree and opaque must be initialized before by the caller.
  201    If zalloc and zfree are set to Z_NULL, deflateInit updates them to
  202    use default allocation functions.
  203 
  204      The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
  205    1 gives best speed, 9 gives best compression, 0 gives no compression at
  206    all (the input data is simply copied a block at a time).
  207    Z_DEFAULT_COMPRESSION requests a default compromise between speed and
  208    compression (currently equivalent to level 6).
  209 
  210      deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
  211    enough memory, Z_STREAM_ERROR if level is not a valid compression level,
  212    Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible
  213    with the version assumed by the caller (ZLIB_VERSION).
  214    msg is set to null if there is no error message.  deflateInit does not
  215    perform any compression: this will be done by deflate().
  216 */
  217 
  218 
  219 ZEXTERN int ZEXPORT deflate OF((z_streamp strm, int flush));
  220 /*
  221     deflate compresses as much data as possible, and stops when the input
  222   buffer becomes empty or the output buffer becomes full. It may introduce some
  223   output latency (reading input without producing any output) except when
  224   forced to flush.
  225 
  226     The detailed semantics are as follows. deflate performs one or both of the
  227   following actions:
  228 
  229   - Compress more input starting at next_in and update next_in and avail_in
  230     accordingly. If not all input can be processed (because there is not
  231     enough room in the output buffer), next_in and avail_in are updated and
  232     processing will resume at this point for the next call of deflate().
  233 
  234   - Provide more output starting at next_out and update next_out and avail_out
  235     accordingly. This action is forced if the parameter flush is non zero.
  236     Forcing flush frequently degrades the compression ratio, so this parameter
  237     should be set only when necessary (in interactive applications).
  238     Some output may be provided even if flush is not set.
  239 
  240   Before the call of deflate(), the application should ensure that at least
  241   one of the actions is possible, by providing more input and/or consuming
  242   more output, and updating avail_in or avail_out accordingly; avail_out
  243   should never be zero before the call. The application can consume the
  244   compressed output when it wants, for example when the output buffer is full
  245   (avail_out == 0), or after each call of deflate(). If deflate returns Z_OK
  246   and with zero avail_out, it must be called again after making room in the
  247   output buffer because there might be more output pending.
  248 
  249     If the parameter flush is set to Z_SYNC_FLUSH, all pending output is
  250   flushed to the output buffer and the output is aligned on a byte boundary, so
  251   that the decompressor can get all input data available so far. (In particular
  252   avail_in is zero after the call if enough output space has been provided
  253   before the call.)  Flushing may degrade compression for some compression
  254   algorithms and so it should be used only when necessary.
  255 
  256     If flush is set to Z_FULL_FLUSH, all output is flushed as with
  257   Z_SYNC_FLUSH, and the compression state is reset so that decompression can
  258   restart from this point if previous compressed data has been damaged or if
  259   random access is desired. Using Z_FULL_FLUSH too often can seriously degrade
  260   the compression.
  261 
  262     If deflate returns with avail_out == 0, this function must be called again
  263   with the same value of the flush parameter and more output space (updated
  264   avail_out), until the flush is complete (deflate returns with non-zero
  265   avail_out). In the case of a Z_FULL_FLUSH or Z_SYNC_FLUSH, make sure that
  266   avail_out is greater than six to avoid repeated flush markers due to
  267   avail_out == 0 on return.
  268 
  269     If the parameter flush is set to Z_FINISH, pending input is processed,
  270   pending output is flushed and deflate returns with Z_STREAM_END if there
  271   was enough output space; if deflate returns with Z_OK, this function must be
  272   called again with Z_FINISH and more output space (updated avail_out) but no
  273   more input data, until it returns with Z_STREAM_END or an error. After
  274   deflate has returned Z_STREAM_END, the only possible operations on the
  275   stream are deflateReset or deflateEnd.
  276 
  277     Z_FINISH can be used immediately after deflateInit if all the compression
  278   is to be done in a single step. In this case, avail_out must be at least
  279   the value returned by deflateBound (see below). If deflate does not return
  280   Z_STREAM_END, then it must be called again as described above.
  281 
  282     deflate() sets strm->adler to the adler32 checksum of all input read
  283   so far (that is, total_in bytes).
  284 
  285     deflate() may update data_type if it can make a good guess about
  286   the input data type (Z_ASCII or Z_BINARY). In doubt, the data is considered
  287   binary. This field is only for information purposes and does not affect
  288   the compression algorithm in any manner.
  289 
  290     deflate() returns Z_OK if some progress has been made (more input
  291   processed or more output produced), Z_STREAM_END if all input has been
  292   consumed and all output has been produced (only when flush is set to
  293   Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
  294   if next_in or next_out was NULL), Z_BUF_ERROR if no progress is possible
  295   (for example avail_in or avail_out was zero). Note that Z_BUF_ERROR is not
  296   fatal, and deflate() can be called again with more input and more output
  297   space to continue compressing.
  298 */
  299 
  300 
  301 ZEXTERN int ZEXPORT deflateEnd OF((z_streamp strm));
  302 /*
  303      All dynamically allocated data structures for this stream are freed.
  304    This function discards any unprocessed input and does not flush any
  305    pending output.
  306 
  307      deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
  308    stream state was inconsistent, Z_DATA_ERROR if the stream was freed
  309    prematurely (some input or output was discarded). In the error case,
  310    msg may be set but then points to a static string (which must not be
  311    deallocated).
  312 */
  313 
  314 
  315 /*
  316 ZEXTERN int ZEXPORT inflateInit OF((z_streamp strm));
  317 
  318      Initializes the internal stream state for decompression. The fields
  319    next_in, avail_in, zalloc, zfree and opaque must be initialized before by
  320    the caller. If next_in is not Z_NULL and avail_in is large enough (the exact
  321    value depends on the compression method), inflateInit determines the
  322    compression method from the zlib header and allocates all data structures
  323    accordingly; otherwise the allocation will be deferred to the first call of
  324    inflate.  If zalloc and zfree are set to Z_NULL, inflateInit updates them to
  325    use default allocation functions.
  326 
  327      inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
  328    memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
  329    version assumed by the caller.  msg is set to null if there is no error
  330    message. inflateInit does not perform any decompression apart from reading
  331    the zlib header if present: this will be done by inflate().  (So next_in and
  332    avail_in may be modified, but next_out and avail_out are unchanged.)
  333 */
  334 
  335 
  336 ZEXTERN int ZEXPORT inflate OF((z_streamp strm, int flush));
  337 /*
  338     inflate decompresses as much data as possible, and stops when the input
  339   buffer becomes empty or the output buffer becomes full. It may introduce
  340   some output latency (reading input without producing any output) except when
  341   forced to flush.
  342 
  343   The detailed semantics are as follows. inflate performs one or both of the
  344   following actions:
  345 
  346   - Decompress more input starting at next_in and update next_in and avail_in
  347     accordingly. If not all input can be processed (because there is not
  348     enough room in the output buffer), next_in is updated and processing
  349     will resume at this point for the next call of inflate().
  350 
  351   - Provide more output starting at next_out and update next_out and avail_out
  352     accordingly.  inflate() provides as much output as possible, until there
  353     is no more input data or no more space in the output buffer (see below
  354     about the flush parameter).
  355 
  356   Before the call of inflate(), the application should ensure that at least
  357   one of the actions is possible, by providing more input and/or consuming
  358   more output, and updating the next_* and avail_* values accordingly.
  359   The application can consume the uncompressed output when it wants, for
  360   example when the output buffer is full (avail_out == 0), or after each
  361   call of inflate(). If inflate returns Z_OK and with zero avail_out, it
  362   must be called again after making room in the output buffer because there
  363   might be more output pending.
  364 
  365     The flush parameter of inflate() can be Z_NO_FLUSH, Z_SYNC_FLUSH,
  366   Z_FINISH, or Z_BLOCK. Z_SYNC_FLUSH requests that inflate() flush as much
  367   output as possible to the output buffer. Z_BLOCK requests that inflate() stop
  368   if and when it get to the next deflate block boundary. When decoding the zlib
  369   or gzip format, this will cause inflate() to return immediately after the
  370   header and before the first block. When doing a raw inflate, inflate() will
  371   go ahead and process the first block, and will return when it gets to the end
  372   of that block, or when it runs out of data.
  373 
  374     The Z_BLOCK option assists in appending to or combining deflate streams.
  375   Also to assist in this, on return inflate() will set strm->data_type to the
  376   number of unused bits in the last byte taken from strm->next_in, plus 64
  377   if inflate() is currently decoding the last block in the deflate stream,
  378   plus 128 if inflate() returned immediately after decoding an end-of-block
  379   code or decoding the complete header up to just before the first byte of the
  380   deflate stream. The end-of-block will not be indicated until all of the
  381   uncompressed data from that block has been written to strm->next_out.  The
  382   number of unused bits may in general be greater than seven, except when
  383   bit 7 of data_type is set, in which case the number of unused bits will be
  384   less than eight.
  385 
  386     inflate() should normally be called until it returns Z_STREAM_END or an
  387   error. However if all decompression is to be performed in a single step
  388   (a single call of inflate), the parameter flush should be set to
  389   Z_FINISH. In this case all pending input is processed and all pending
  390   output is flushed; avail_out must be large enough to hold all the
  391   uncompressed data. (The size of the uncompressed data may have been saved
  392   by the compressor for this purpose.) The next operation on this stream must
  393   be inflateEnd to deallocate the decompression state. The use of Z_FINISH
  394   is never required, but can be used to inform inflate that a faster approach
  395   may be used for the single inflate() call.
  396 
  397      In this implementation, inflate() always flushes as much output as
  398   possible to the output buffer, and always uses the faster approach on the
  399   first call. So the only effect of the flush parameter in this implementation
  400   is on the return value of inflate(), as noted below, or when it returns early
  401   because Z_BLOCK is used.
  402 
  403      If a preset dictionary is needed after this call (see inflateSetDictionary
  404   below), inflate sets strm-adler to the adler32 checksum of the dictionary
  405   chosen by the compressor and returns Z_NEED_DICT; otherwise it sets
  406   strm->adler to the adler32 checksum of all output produced so far (that is,
  407   total_out bytes) and returns Z_OK, Z_STREAM_END or an error code as described
  408   below. At the end of the stream, inflate() checks that its computed adler32
  409   checksum is equal to that saved by the compressor and returns Z_STREAM_END
  410   only if the checksum is correct.
  411 
  412     inflate() will decompress and check either zlib-wrapped or gzip-wrapped
  413   deflate data.  The header type is detected automatically.  Any information
  414   contained in the gzip header is not retained, so applications that need that
  415   information should instead use raw inflate, see inflateInit2() below, or
  416   inflateBack() and perform their own processing of the gzip header and
  417   trailer.
  418 
  419     inflate() returns Z_OK if some progress has been made (more input processed
  420   or more output produced), Z_STREAM_END if the end of the compressed data has
  421   been reached and all uncompressed output has been produced, Z_NEED_DICT if a
  422   preset dictionary is needed at this point, Z_DATA_ERROR if the input data was
  423   corrupted (input stream not conforming to the zlib format or incorrect check
  424   value), Z_STREAM_ERROR if the stream structure was inconsistent (for example
  425   if next_in or next_out was NULL), Z_MEM_ERROR if there was not enough memory,
  426   Z_BUF_ERROR if no progress is possible or if there was not enough room in the
  427   output buffer when Z_FINISH is used. Note that Z_BUF_ERROR is not fatal, and
  428   inflate() can be called again with more input and more output space to
  429   continue decompressing. If Z_DATA_ERROR is returned, the application may then
  430   call inflateSync() to look for a good compression block if a partial recovery
  431   of the data is desired.
  432 */
  433 
  434 
  435 ZEXTERN int ZEXPORT inflateEnd OF((z_streamp strm));
  436 /*
  437      All dynamically allocated data structures for this stream are freed.
  438    This function discards any unprocessed input and does not flush any
  439    pending output.
  440 
  441      inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
  442    was inconsistent. In the error case, msg may be set but then points to a
  443    static string (which must not be deallocated).
  444 */
  445 
  446                         /* Advanced functions */
  447 
  448 /*
  449     The following functions are needed only in some special applications.
  450 */
  451 
  452 /*
  453 ZEXTERN int ZEXPORT deflateInit2 OF((z_streamp strm,
  454                                      int  level,
  455                                      int  method,
  456                                      int  windowBits,
  457                                      int  memLevel,
  458                                      int  strategy));
  459 
  460      This is another version of deflateInit with more compression options. The
  461    fields next_in, zalloc, zfree and opaque must be initialized before by
  462    the caller.
  463 
  464      The method parameter is the compression method. It must be Z_DEFLATED in
  465    this version of the library.
  466 
  467      The windowBits parameter is the base two logarithm of the window size
  468    (the size of the history buffer). It should be in the range 8..15 for this
  469    version of the library. Larger values of this parameter result in better
  470    compression at the expense of memory usage. The default value is 15 if
  471    deflateInit is used instead.
  472 
  473      windowBits can also be -8..-15 for raw deflate. In this case, -windowBits
  474    determines the window size. deflate() will then generate raw deflate data
  475    with no zlib header or trailer, and will not compute an adler32 check value.
  476 
  477      windowBits can also be greater than 15 for optional gzip encoding. Add
  478    16 to windowBits to write a simple gzip header and trailer around the
  479    compressed data instead of a zlib wrapper. The gzip header will have no
  480    file name, no extra data, no comment, no modification time (set to zero),
  481    no header crc, and the operating system will be set to 255 (unknown).
  482 
  483      The memLevel parameter specifies how much memory should be allocated
  484    for the internal compression state. memLevel=1 uses minimum memory but
  485    is slow and reduces compression ratio; memLevel=9 uses maximum memory
  486    for optimal speed. The default value is 8. See zconf.h for total memory
  487    usage as a function of windowBits and memLevel.
  488 
  489      The strategy parameter is used to tune the compression algorithm. Use the
  490    value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a
  491    filter (or predictor), Z_HUFFMAN_ONLY to force Huffman encoding only (no
  492    string match), or Z_RLE to limit match distances to one (run-length
  493    encoding). Filtered data consists mostly of small values with a somewhat
  494    random distribution. In this case, the compression algorithm is tuned to
  495    compress them better. The effect of Z_FILTERED is to force more Huffman
  496    coding and less string matching; it is somewhat intermediate between
  497    Z_DEFAULT and Z_HUFFMAN_ONLY. Z_RLE is designed to be almost as fast as
  498    Z_HUFFMAN_ONLY, but give better compression for PNG image data. The strategy
  499    parameter only affects the compression ratio but not the correctness of the
  500    compressed output even if it is not set appropriately.
  501 
  502       deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
  503    memory, Z_STREAM_ERROR if a parameter is invalid (such as an invalid
  504    method). msg is set to null if there is no error message.  deflateInit2 does
  505    not perform any compression: this will be done by deflate().
  506 */
  507 
  508 ZEXTERN int ZEXPORT deflateSetDictionary OF((z_streamp strm,
  509                                              const Bytef *dictionary,
  510                                              uInt  dictLength));
  511 /*
  512      Initializes the compression dictionary from the given byte sequence
  513    without producing any compressed output. This function must be called
  514    immediately after deflateInit, deflateInit2 or deflateReset, before any
  515    call of deflate. The compressor and decompressor must use exactly the same
  516    dictionary (see inflateSetDictionary).
  517 
  518      The dictionary should consist of strings (byte sequences) that are likely
  519    to be encountered later in the data to be compressed, with the most commonly
  520    used strings preferably put towards the end of the dictionary. Using a
  521    dictionary is most useful when the data to be compressed is short and can be
  522    predicted with good accuracy; the data can then be compressed better than
  523    with the default empty dictionary.
  524 
  525      Depending on the size of the compression data structures selected by
  526    deflateInit or deflateInit2, a part of the dictionary may in effect be
  527    discarded, for example if the dictionary is larger than the window size in
  528    deflate or deflate2. Thus the strings most likely to be useful should be
  529    put at the end of the dictionary, not at the front.
  530 
  531      Upon return of this function, strm->adler is set to the adler32 value
  532    of the dictionary; the decompressor may later use this value to determine
  533    which dictionary has been used by the compressor. (The adler32 value
  534    applies to the whole dictionary even if only a subset of the dictionary is
  535    actually used by the compressor.) If a raw deflate was requested, then the
  536    adler32 value is not computed and strm->adler is not set.
  537 
  538      deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
  539    parameter is invalid (such as NULL dictionary) or the stream state is
  540    inconsistent (for example if deflate has already been called for this stream
  541    or if the compression method is bsort). deflateSetDictionary does not
  542    perform any compression: this will be done by deflate().
  543 */
  544 
  545 ZEXTERN int ZEXPORT deflateCopy OF((z_streamp dest,
  546                                     z_streamp source));
  547 /*
  548      Sets the destination stream as a complete copy of the source stream.
  549 
  550      This function can be useful when several compression strategies will be
  551    tried, for example when there are several ways of pre-processing the input
  552    data with a filter. The streams that will be discarded should then be freed
  553    by calling deflateEnd.  Note that deflateCopy duplicates the internal
  554    compression state which can be quite large, so this strategy is slow and
  555    can consume lots of memory.
  556 
  557      deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
  558    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
  559    (such as zalloc being NULL). msg is left unchanged in both source and
  560    destination.
  561 */
  562 
  563 ZEXTERN int ZEXPORT deflateReset OF((z_streamp strm));
  564 /*
  565      This function is equivalent to deflateEnd followed by deflateInit,
  566    but does not free and reallocate all the internal compression state.
  567    The stream will keep the same compression level and any other attributes
  568    that may have been set by deflateInit2.
  569 
  570       deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
  571    stream state was inconsistent (such as zalloc or state being NULL).
  572 */
  573 
  574 ZEXTERN int ZEXPORT deflateParams OF((z_streamp strm,
  575                                       int level,
  576                                       int strategy));
  577 /*
  578      Dynamically update the compression level and compression strategy.  The
  579    interpretation of level and strategy is as in deflateInit2.  This can be
  580    used to switch between compression and straight copy of the input data, or
  581    to switch to a different kind of input data requiring a different
  582    strategy. If the compression level is changed, the input available so far
  583    is compressed with the old level (and may be flushed); the new level will
  584    take effect only at the next call of deflate().
  585 
  586      Before the call of deflateParams, the stream state must be set as for
  587    a call of deflate(), since the currently available input may have to
  588    be compressed and flushed. In particular, strm->avail_out must be non-zero.
  589 
  590      deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source
  591    stream state was inconsistent or if a parameter was invalid, Z_BUF_ERROR
  592    if strm->avail_out was zero.
  593 */
  594 
  595 ZEXTERN uLong ZEXPORT deflateBound OF((z_streamp strm,
  596                                        uLong sourceLen));
  597 /*
  598      deflateBound() returns an upper bound on the compressed size after
  599    deflation of sourceLen bytes.  It must be called after deflateInit()
  600    or deflateInit2().  This would be used to allocate an output buffer
  601    for deflation in a single pass, and so would be called before deflate().
  602 */
  603 
  604 ZEXTERN int ZEXPORT deflatePrime OF((z_streamp strm,
  605                                      int bits,
  606                                      int value));
  607 /*
  608      deflatePrime() inserts bits in the deflate output stream.  The intent
  609   is that this function is used to start off the deflate output with the
  610   bits leftover from a previous deflate stream when appending to it.  As such,
  611   this function can only be used for raw deflate, and must be used before the
  612   first deflate() call after a deflateInit2() or deflateReset().  bits must be
  613   less than or equal to 16, and that many of the least significant bits of
  614   value will be inserted in the output.
  615 
  616       deflatePrime returns Z_OK if success, or Z_STREAM_ERROR if the source
  617    stream state was inconsistent.
  618 */
  619 
  620 /*
  621 ZEXTERN int ZEXPORT inflateInit2 OF((z_streamp strm,
  622                                      int  windowBits));
  623 
  624      This is another version of inflateInit with an extra parameter. The
  625    fields next_in, avail_in, zalloc, zfree and opaque must be initialized
  626    before by the caller.
  627 
  628      The windowBits parameter is the base two logarithm of the maximum window
  629    size (the size of the history buffer).  It should be in the range 8..15 for
  630    this version of the library. The default value is 15 if inflateInit is used
  631    instead. windowBits must be greater than or equal to the windowBits value
  632    provided to deflateInit2() while compressing, or it must be equal to 15 if
  633    deflateInit2() was not used. If a compressed stream with a larger window
  634    size is given as input, inflate() will return with the error code
  635    Z_DATA_ERROR instead of trying to allocate a larger window.
  636 
  637      windowBits can also be -8..-15 for raw inflate. In this case, -windowBits
  638    determines the window size. inflate() will then process raw deflate data,
  639    not looking for a zlib or gzip header, not generating a check value, and not
  640    looking for any check values for comparison at the end of the stream. This
  641    is for use with other formats that use the deflate compressed data format
  642    such as zip.  Those formats provide their own check values. If a custom
  643    format is developed using the raw deflate format for compressed data, it is
  644    recommended that a check value such as an adler32 or a crc32 be applied to
  645    the uncompressed data as is done in the zlib, gzip, and zip formats.  For
  646    most applications, the zlib format should be used as is. Note that comments
  647    above on the use in deflateInit2() applies to the magnitude of windowBits.
  648 
  649      windowBits can also be greater than 15 for optional gzip decoding. Add
  650    32 to windowBits to enable zlib and gzip decoding with automatic header
  651    detection, or add 16 to decode only the gzip format (the zlib format will
  652    return a Z_DATA_ERROR).
  653 
  654      inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
  655    memory, Z_STREAM_ERROR if a parameter is invalid (such as a negative
  656    memLevel). msg is set to null if there is no error message.  inflateInit2
  657    does not perform any decompression apart from reading the zlib header if
  658    present: this will be done by inflate(). (So next_in and avail_in may be
  659    modified, but next_out and avail_out are unchanged.)
  660 */
  661 
  662 ZEXTERN int ZEXPORT inflateSetDictionary OF((z_streamp strm,
  663                                              const Bytef *dictionary,
  664                                              uInt  dictLength));
  665 /*
  666      Initializes the decompression dictionary from the given uncompressed byte
  667    sequence. This function must be called immediately after a call of inflate
  668    if this call returned Z_NEED_DICT. The dictionary chosen by the compressor
  669    can be determined from the adler32 value returned by this call of
  670    inflate. The compressor and decompressor must use exactly the same
  671    dictionary (see deflateSetDictionary).
  672 
  673      inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
  674    parameter is invalid (such as NULL dictionary) or the stream state is
  675    inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the
  676    expected one (incorrect adler32 value). inflateSetDictionary does not
  677    perform any decompression: this will be done by subsequent calls of
  678    inflate().
  679 */
  680 
  681 ZEXTERN int ZEXPORT inflateSync OF((z_streamp strm));
  682 /*
  683     Skips invalid compressed data until a full flush point (see above the
  684   description of deflate with Z_FULL_FLUSH) can be found, or until all
  685   available input is skipped. No output is provided.
  686 
  687     inflateSync returns Z_OK if a full flush point has been found, Z_BUF_ERROR
  688   if no more input was provided, Z_DATA_ERROR if no flush point has been found,
  689   or Z_STREAM_ERROR if the stream structure was inconsistent. In the success
  690   case, the application may save the current current value of total_in which
  691   indicates where valid compressed data was found. In the error case, the
  692   application may repeatedly call inflateSync, providing more input each time,
  693   until success or end of the input data.
  694 */
  695 
  696 ZEXTERN int ZEXPORT inflateCopy OF((z_streamp dest,
  697                                     z_streamp source));
  698 /*
  699      Sets the destination stream as a complete copy of the source stream.
  700 
  701      This function can be useful when randomly accessing a large stream.  The
  702    first pass through the stream can periodically record the inflate state,
  703    allowing restarting inflate at those points when randomly accessing the
  704    stream.
  705 
  706      inflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
  707    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
  708    (such as zalloc being NULL). msg is left unchanged in both source and
  709    destination.
  710 */
  711 
  712 ZEXTERN int ZEXPORT inflateReset OF((z_streamp strm));
  713 /*
  714      This function is equivalent to inflateEnd followed by inflateInit,
  715    but does not free and reallocate all the internal decompression state.
  716    The stream will keep attributes that may have been set by inflateInit2.
  717 
  718       inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
  719    stream state was inconsistent (such as zalloc or state being NULL).
  720 */
  721 
  722 /*
  723 ZEXTERN int ZEXPORT inflateBackInit OF((z_stream FAR *strm, int windowBits,
  724                                         unsigned char FAR *window));
  725 
  726      Initialize the internal stream state for decompression using inflateBack()
  727    calls.  The fields zalloc, zfree and opaque in strm must be initialized
  728    before the call.  If zalloc and zfree are Z_NULL, then the default library-
  729    derived memory allocation routines are used.  windowBits is the base two
  730    logarithm of the window size, in the range 8..15.  window is a caller
  731    supplied buffer of that size.  Except for special applications where it is
  732    assured that deflate was used with small window sizes, windowBits must be 15
  733    and a 32K byte window must be supplied to be able to decompress general
  734    deflate streams.
  735 
  736      See inflateBack() for the usage of these routines.
  737 
  738      inflateBackInit will return Z_OK on success, Z_STREAM_ERROR if any of
  739    the paramaters are invalid, Z_MEM_ERROR if the internal state could not
  740    be allocated, or Z_VERSION_ERROR if the version of the library does not
  741    match the version of the header file.
  742 */
  743 
  744 typedef unsigned (*in_func) OF((void FAR *, unsigned char FAR * FAR *));
  745 typedef int (*out_func) OF((void FAR *, unsigned char FAR *, unsigned));
  746 
  747 ZEXTERN int ZEXPORT inflateBack OF((z_stream FAR *strm,
  748                                     in_func in, void FAR *in_desc,
  749                                     out_func out, void FAR *out_desc));
  750 /*
  751      inflateBack() does a raw inflate with a single call using a call-back
  752    interface for input and output.  This is more efficient than inflate() for
  753    file i/o applications in that it avoids copying between the output and the
  754    sliding window by simply making the window itself the output buffer.  This
  755    function trusts the application to not change the output buffer passed by
  756    the output function, at least until inflateBack() returns.
  757 
  758      inflateBackInit() must be called first to allocate the internal state
  759    and to initialize the state with the user-provided window buffer.
  760    inflateBack() may then be used multiple times to inflate a complete, raw
  761    deflate stream with each call.  inflateBackEnd() is then called to free
  762    the allocated state.
  763 
  764      A raw deflate stream is one with no zlib or gzip header or trailer.
  765    This routine would normally be used in a utility that reads zip or gzip
  766    files and writes out uncompressed files.  The utility would decode the
  767    header and process the trailer on its own, hence this routine expects
  768    only the raw deflate stream to decompress.  This is different from the
  769    normal behavior of inflate(), which expects either a zlib or gzip header and
  770    trailer around the deflate stream.
  771 
  772      inflateBack() uses two subroutines supplied by the caller that are then
  773    called by inflateBack() for input and output.  inflateBack() calls those
  774    routines until it reads a complete deflate stream and writes out all of the
  775    uncompressed data, or until it encounters an error.  The function's
  776    parameters and return types are defined above in the in_func and out_func
  777    typedefs.  inflateBack() will call in(in_desc, &buf) which should return the
  778    number of bytes of provided input, and a pointer to that input in buf.  If
  779    there is no input available, in() must return zero--buf is ignored in that
  780    case--and inflateBack() will return a buffer error.  inflateBack() will call
  781    out(out_desc, buf, len) to write the uncompressed data buf[0..len-1].  out()
  782    should return zero on success, or non-zero on failure.  If out() returns
  783    non-zero, inflateBack() will return with an error.  Neither in() nor out()
  784    are permitted to change the contents of the window provided to
  785    inflateBackInit(), which is also the buffer that out() uses to write from.
  786    The length written by out() will be at most the window size.  Any non-zero
  787    amount of input may be provided by in().
  788 
  789      For convenience, inflateBack() can be provided input on the first call by
  790    setting strm->next_in and strm->avail_in.  If that input is exhausted, then
  791    in() will be called.  Therefore strm->next_in must be initialized before
  792    calling inflateBack().  If strm->next_in is Z_NULL, then in() will be called
  793    immediately for input.  If strm->next_in is not Z_NULL, then strm->avail_in
  794    must also be initialized, and then if strm->avail_in is not zero, input will
  795    initially be taken from strm->next_in[0 .. strm->avail_in - 1].
  796 
  797      The in_desc and out_desc parameters of inflateBack() is passed as the
  798    first parameter of in() and out() respectively when they are called.  These
  799    descriptors can be optionally used to pass any information that the caller-
  800    supplied in() and out() functions need to do their job.
  801 
  802      On return, inflateBack() will set strm->next_in and strm->avail_in to
  803    pass back any unused input that was provided by the last in() call.  The
  804    return values of inflateBack() can be Z_STREAM_END on success, Z_BUF_ERROR
  805    if in() or out() returned an error, Z_DATA_ERROR if there was a format
  806    error in the deflate stream (in which case strm->msg is set to indicate the
  807    nature of the error), or Z_STREAM_ERROR if the stream was not properly
  808    initialized.  In the case of Z_BUF_ERROR, an input or output error can be
  809    distinguished using strm->next_in which will be Z_NULL only if in() returned
  810    an error.  If strm->next is not Z_NULL, then the Z_BUF_ERROR was due to
  811    out() returning non-zero.  (in() will always be called before out(), so
  812    strm->next_in is assured to be defined if out() returns non-zero.)  Note
  813    that inflateBack() cannot return Z_OK.
  814 */
  815 
  816 ZEXTERN int ZEXPORT inflateBackEnd OF((z_stream FAR *strm));
  817 /*
  818      All memory allocated by inflateBackInit() is freed.
  819 
  820      inflateBackEnd() returns Z_OK on success, or Z_STREAM_ERROR if the stream
  821    state was inconsistent.
  822 */
  823 
  824 ZEXTERN uLong ZEXPORT zlibCompileFlags OF((void));
  825 /* Return flags indicating compile-time options.
  826 
  827     Type sizes, two bits each, 00 = 16 bits, 01 = 32, 10 = 64, 11 = other:
  828      1.0: size of uInt
  829      3.2: size of uLong
  830      5.4: size of voidpf (pointer)
  831      7.6: size of z_off_t
  832 
  833     Compiler, assembler, and debug options:
  834      8: DEBUG
  835      9: ASMV or ASMINF -- use ASM code
  836      10: ZLIB_WINAPI -- exported functions use the WINAPI calling convention
  837      11: 0 (reserved)
  838 
  839     One-time table building (smaller code, but not thread-safe if true):
  840      12: BUILDFIXED -- build static block decoding tables when needed
  841      13: DYNAMIC_CRC_TABLE -- build CRC calculation tables when needed
  842      14,15: 0 (reserved)
  843 
  844     Library content (indicates missing functionality):
  845      16: NO_GZCOMPRESS -- gz* functions cannot compress (to avoid linking
  846                           deflate code when not needed)
  847      17: NO_GZIP -- deflate can't write gzip streams, and inflate can't detect
  848                     and decode gzip streams (to avoid linking crc code)
  849      18-19: 0 (reserved)
  850 
  851     Operation variations (changes in library functionality):
  852      20: PKZIP_BUG_WORKAROUND -- slightly more permissive inflate
  853      21: FASTEST -- deflate algorithm with only one, lowest compression level
  854      22,23: 0 (reserved)
  855 
  856     The sprintf variant used by gzprintf (zero is best):
  857      24: 0 = vs*, 1 = s* -- 1 means limited to 20 arguments after the format
  858      25: 0 = *nprintf, 1 = *printf -- 1 means gzprintf() not secure!
  859      26: 0 = returns value, 1 = void -- 1 means inferred string length returned
  860 
  861     Remainder:
  862      27-31: 0 (reserved)
  863  */
  864 
  865 
  866                         /* utility functions */
  867 
  868 /*
  869      The following utility functions are implemented on top of the
  870    basic stream-oriented functions. To simplify the interface, some
  871    default options are assumed (compression level and memory usage,
  872    standard memory allocation functions). The source code of these
  873    utility functions can easily be modified if you need special options.
  874 */
  875 
  876 ZEXTERN int ZEXPORT compress OF((Bytef *dest,   uLongf *destLen,
  877                                  const Bytef *source, uLong sourceLen));
  878 /*
  879      Compresses the source buffer into the destination buffer.  sourceLen is
  880    the byte length of the source buffer. Upon entry, destLen is the total
  881    size of the destination buffer, which must be at least the value returned
  882    by compressBound(sourceLen). Upon exit, destLen is the actual size of the
  883    compressed buffer.
  884      This function can be used to compress a whole file at once if the
  885    input file is mmap'ed.
  886      compress returns Z_OK if success, Z_MEM_ERROR if there was not
  887    enough memory, Z_BUF_ERROR if there was not enough room in the output
  888    buffer.
  889 */
  890 
  891 ZEXTERN int ZEXPORT compress2 OF((Bytef *dest,   uLongf *destLen,
  892                                   const Bytef *source, uLong sourceLen,
  893                                   int level));
  894 /*
  895      Compresses the source buffer into the destination buffer. The level
  896    parameter has the same meaning as in deflateInit.  sourceLen is the byte
  897    length of the source buffer. Upon entry, destLen is the total size of the
  898    destination buffer, which must be at least the value returned by
  899    compressBound(sourceLen). Upon exit, destLen is the actual size of the
  900    compressed buffer.
  901 
  902      compress2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
  903    memory, Z_BUF_ERROR if there was not enough room in the output buffer,
  904    Z_STREAM_ERROR if the level parameter is invalid.
  905 */
  906 
  907 ZEXTERN uLong ZEXPORT compressBound OF((uLong sourceLen));
  908 /*
  909      compressBound() returns an upper bound on the compressed size after
  910    compress() or compress2() on sourceLen bytes.  It would be used before
  911    a compress() or compress2() call to allocate the destination buffer.
  912 */
  913 
  914 ZEXTERN int ZEXPORT uncompress OF((Bytef *dest,   uLongf *destLen,
  915                                    const Bytef *source, uLong sourceLen));
  916 /*
  917      Decompresses the source buffer into the destination buffer.  sourceLen is
  918    the byte length of the source buffer. Upon entry, destLen is the total
  919    size of the destination buffer, which must be large enough to hold the
  920    entire uncompressed data. (The size of the uncompressed data must have
  921    been saved previously by the compressor and transmitted to the decompressor
  922    by some mechanism outside the scope of this compression library.)
  923    Upon exit, destLen is the actual size of the compressed buffer.
  924      This function can be used to decompress a whole file at once if the
  925    input file is mmap'ed.
  926 
  927      uncompress returns Z_OK if success, Z_MEM_ERROR if there was not
  928    enough memory, Z_BUF_ERROR if there was not enough room in the output
  929    buffer, or Z_DATA_ERROR if the input data was corrupted or incomplete.
  930 */
  931 
  932 
  933 typedef voidp gzFile;
  934 
  935 ZEXTERN gzFile ZEXPORT gzopen  OF((const char *path, const char *mode));
  936 /*
  937      Opens a gzip (.gz) file for reading or writing. The mode parameter
  938    is as in fopen ("rb" or "wb") but can also include a compression level
  939    ("wb9") or a strategy: 'f' for filtered data as in "wb6f", 'h' for
  940    Huffman only compression as in "wb1h", or 'R' for run-length encoding
  941    as in "wb1R". (See the description of deflateInit2 for more information
  942    about the strategy parameter.)
  943 
  944      gzopen can be used to read a file which is not in gzip format; in this
  945    case gzread will directly read from the file without decompression.
  946 
  947      gzopen returns NULL if the file could not be opened or if there was
  948    insufficient memory to allocate the (de)compression state; errno
  949    can be checked to distinguish the two cases (if errno is zero, the
  950    zlib error is Z_MEM_ERROR).  */
  951 
  952 ZEXTERN gzFile ZEXPORT gzdopen  OF((int fd, const char *mode));
  953 /*
  954      gzdopen() associates a gzFile with the file descriptor fd.  File
  955    descriptors are obtained from calls like open, dup, creat, pipe or
  956    fileno (in the file has been previously opened with fopen).
  957    The mode parameter is as in gzopen.
  958      The next call of gzclose on the returned gzFile will also close the
  959    file descriptor fd, just like fclose(fdopen(fd), mode) closes the file
  960    descriptor fd. If you want to keep fd open, use gzdopen(dup(fd), mode).
  961      gzdopen returns NULL if there was insufficient memory to allocate
  962    the (de)compression state.
  963 */
  964 
  965 ZEXTERN int ZEXPORT gzsetparams OF((gzFile file, int level, int strategy));
  966 /*
  967      Dynamically update the compression level or strategy. See the description
  968    of deflateInit2 for the meaning of these parameters.
  969      gzsetparams returns Z_OK if success, or Z_STREAM_ERROR if the file was not
  970    opened for writing.
  971 */
  972 
  973 ZEXTERN int ZEXPORT    gzread  OF((gzFile file, voidp buf, unsigned len));
  974 /*
  975      Reads the given number of uncompressed bytes from the compressed file.
  976    If the input file was not in gzip format, gzread copies the given number
  977    of bytes into the buffer.
  978      gzread returns the number of uncompressed bytes actually read (0 for
  979    end of file, -1 for error). */
  980 #if 0
  981 ZEXTERN int ZEXPORT    gzwrite OF((gzFile file,
  982                                    voidpc buf, unsigned len));
  983 #endif
  984 /*
  985      Writes the given number of uncompressed bytes into the compressed file.
  986    gzwrite returns the number of uncompressed bytes actually written
  987    (0 in case of error).
  988 */
  989 
  990 ZEXTERN int ZEXPORTVA   gzprintf OF((gzFile file, const char *format, ...));
  991 /*
  992      Converts, formats, and writes the args to the compressed file under
  993    control of the format string, as in fprintf. gzprintf returns the number of
  994    uncompressed bytes actually written (0 in case of error).  The number of
  995    uncompressed bytes written is limited to 4095. The caller should assure that
  996    this limit is not exceeded. If it is exceeded, then gzprintf() will return
  997    return an error (0) with nothing written. In this case, there may also be a
  998    buffer overflow with unpredictable consequences, which is possible only if
  999    zlib was compiled with the insecure functions sprintf() or vsprintf()
 1000    because the secure snprintf() or vsnprintf() functions were not available.
 1001 */
 1002 
 1003 ZEXTERN int ZEXPORT gzputs OF((gzFile file, const char *s));
 1004 /*
 1005       Writes the given null-terminated string to the compressed file, excluding
 1006    the terminating null character.
 1007       gzputs returns the number of characters written, or -1 in case of error.
 1008 */
 1009 
 1010 ZEXTERN char * ZEXPORT gzgets OF((gzFile file, char *buf, int len));
 1011 /*
 1012       Reads bytes from the compressed file until len-1 characters are read, or
 1013    a newline character is read and transferred to buf, or an end-of-file
 1014    condition is encountered.  The string is then terminated with a null
 1015    character.
 1016       gzgets returns buf, or Z_NULL in case of error.
 1017 */
 1018 
 1019 ZEXTERN int ZEXPORT    gzputc OF((gzFile file, int c));
 1020 /*
 1021       Writes c, converted to an unsigned char, into the compressed file.
 1022    gzputc returns the value that was written, or -1 in case of error.
 1023 */
 1024 
 1025 ZEXTERN int ZEXPORT    gzgetc OF((gzFile file));
 1026 /*
 1027       Reads one byte from the compressed file. gzgetc returns this byte
 1028    or -1 in case of end of file or error.
 1029 */
 1030 
 1031 ZEXTERN int ZEXPORT    gzungetc OF((int c, gzFile file));
 1032 /*
 1033       Push one character back onto the stream to be read again later.
 1034    Only one character of push-back is allowed.  gzungetc() returns the
 1035    character pushed, or -1 on failure.  gzungetc() will fail if a
 1036    character has been pushed but not read yet, or if c is -1. The pushed
 1037    character will be discarded if the stream is repositioned with gzseek()
 1038    or gzrewind().
 1039 */
 1040 
 1041 ZEXTERN int ZEXPORT    gzflush OF((gzFile file, int flush));
 1042 /*
 1043      Flushes all pending output into the compressed file. The parameter
 1044    flush is as in the deflate() function. The return value is the zlib
 1045    error number (see function gzerror below). gzflush returns Z_OK if
 1046    the flush parameter is Z_FINISH and all output could be flushed.
 1047      gzflush should be called only when strictly necessary because it can
 1048    degrade compression.
 1049 */
 1050 
 1051 ZEXTERN z_off_t ZEXPORT    gzseek OF((gzFile file,
 1052                                       z_off_t offset, int whence));
 1053 /*
 1054       Sets the starting position for the next gzread or gzwrite on the
 1055    given compressed file. The offset represents a number of bytes in the
 1056    uncompressed data stream. The whence parameter is defined as in lseek(2);
 1057    the value SEEK_END is not supported.
 1058      If the file is opened for reading, this function is emulated but can be
 1059    extremely slow. If the file is opened for writing, only forward seeks are
 1060    supported; gzseek then compresses a sequence of zeroes up to the new
 1061    starting position.
 1062 
 1063       gzseek returns the resulting offset location as measured in bytes from
 1064    the beginning of the uncompressed stream, or -1 in case of error, in
 1065    particular if the file is opened for writing and the new starting position
 1066    would be before the current position.
 1067 */
 1068 
 1069 ZEXTERN int ZEXPORT    gzrewind OF((gzFile file));
 1070 /*
 1071      Rewinds the given file. This function is supported only for reading.
 1072 
 1073    gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET)
 1074 */
 1075 
 1076 ZEXTERN z_off_t ZEXPORT    gztell OF((gzFile file));
 1077 /*
 1078      Returns the starting position for the next gzread or gzwrite on the
 1079    given compressed file. This position represents a number of bytes in the
 1080    uncompressed data stream.
 1081 
 1082    gztell(file) is equivalent to gzseek(file, 0L, SEEK_CUR)
 1083 */
 1084 
 1085 ZEXTERN int ZEXPORT gzeof OF((gzFile file));
 1086 /*
 1087      Returns 1 when EOF has previously been detected reading the given
 1088    input stream, otherwise zero.
 1089 */
 1090 
 1091 ZEXTERN int ZEXPORT    gzclose OF((gzFile file));
 1092 /*
 1093      Flushes all pending output if necessary, closes the compressed file
 1094    and deallocates all the (de)compression state. The return value is the zlib
 1095    error number (see function gzerror below).
 1096 */
 1097 
 1098 ZEXTERN const char * ZEXPORT gzerror OF((gzFile file, int *errnum));
 1099 /*
 1100      Returns the error message for the last error which occurred on the
 1101    given compressed file. errnum is set to zlib error number. If an
 1102    error occurred in the file system and not in the compression library,
 1103    errnum is set to Z_ERRNO and the application may consult errno
 1104    to get the exact error code.
 1105 */
 1106 
 1107 ZEXTERN void ZEXPORT gzclearerr OF((gzFile file));
 1108 /*
 1109      Clears the error and end-of-file flags for file. This is analogous to the
 1110    clearerr() function in stdio. This is useful for continuing to read a gzip
 1111    file that is being written concurrently.
 1112 */
 1113 
 1114                         /* checksum functions */
 1115 
 1116 /*
 1117      These functions are not related to compression but are exported
 1118    anyway because they might be useful in applications using the
 1119    compression library.
 1120 */
 1121 
 1122 ZEXTERN uLong ZEXPORT adler32 OF((uLong adler, const Bytef *buf, uInt len));
 1123 
 1124 /*
 1125      Update a running Adler-32 checksum with the bytes buf[0..len-1] and
 1126    return the updated checksum. If buf is NULL, this function returns
 1127    the required initial value for the checksum.
 1128    An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
 1129    much faster. Usage example:
 1130 
 1131      uLong adler = adler32(0L, Z_NULL, 0);
 1132 
 1133      while (read_buffer(buffer, length) != EOF) {
 1134        adler = adler32(adler, buffer, length);
 1135      }
 1136      if (adler != original_adler) error();
 1137 */
 1138 
 1139 ZEXTERN uLong ZEXPORT crc32   OF((uLong crc, const Bytef *buf, uInt len));
 1140 /*
 1141      Update a running crc with the bytes buf[0..len-1] and return the updated
 1142    crc. If buf is NULL, this function returns the required initial value
 1143    for the crc. Pre- and post-conditioning (one's complement) is performed
 1144    within this function so it shouldn't be done by the application.
 1145    Usage example:
 1146 
 1147      uLong crc = crc32(0L, Z_NULL, 0);
 1148 
 1149      while (read_buffer(buffer, length) != EOF) {
 1150        crc = crc32(crc, buffer, length);
 1151      }
 1152      if (crc != original_crc) error();
 1153 */
 1154 
 1155 ZEXTERN int ZEXPORT updatewindow OF((z_streamp strm, unsigned out));
 1156 ZEXTERN void ZEXPORT inflate_advance OF((z_streamp strm, int zoffset, int b, int s));
 1157 
 1158                         /* various hacks, don't look :) */
 1159 
 1160 /* deflateInit and inflateInit are macros to allow checking the zlib version
 1161  * and the compiler's view of z_stream:
 1162  */
 1163 ZEXTERN int ZEXPORT deflateInit_ OF((z_streamp strm, int level,
 1164                                      const char *version, int stream_size));
 1165 ZEXTERN int ZEXPORT inflateInit_ OF((z_streamp strm,
 1166                                      const char *version, int stream_size));
 1167 ZEXTERN int ZEXPORT deflateInit2_ OF((z_streamp strm, int  level, int  method,
 1168                                       int windowBits, int memLevel,
 1169                                       int strategy, const char *version,
 1170                                       int stream_size));
 1171 ZEXTERN int ZEXPORT inflateInit2_ OF((z_streamp strm, int  windowBits,
 1172                                       const char *version, int stream_size));
 1173 ZEXTERN int ZEXPORT inflateBackInit_ OF((z_stream FAR *strm, int windowBits,
 1174                                          unsigned char FAR *window,
 1175                                          const char *version,
 1176                                          int stream_size));
 1177 #define deflateInit(strm, level) \
 1178         deflateInit_((strm), (level),       ZLIB_VERSION, sizeof(z_stream))
 1179 #define inflateInit(strm) \
 1180         inflateInit_((strm),                ZLIB_VERSION, sizeof(z_stream))
 1181 #define deflateInit2(strm, level, method, windowBits, memLevel, strategy) \
 1182         deflateInit2_((strm),(level),(method),(windowBits),(memLevel),\
 1183                       (strategy),           ZLIB_VERSION, sizeof(z_stream))
 1184 #define inflateInit2(strm, windowBits) \
 1185         inflateInit2_((strm), (windowBits), ZLIB_VERSION, sizeof(z_stream))
 1186 #define inflateBackInit(strm, windowBits, window) \
 1187         inflateBackInit_((strm), (windowBits), (window), \
 1188         ZLIB_VERSION, sizeof(z_stream))
 1189 
 1190 
 1191 #if !defined(ZUTIL_H) && !defined(NO_DUMMY_DECL)
 1192     struct internal_state {int dummy;}; /* hack for buggy compilers */
 1193 #endif
 1194 
 1195 ZEXTERN const char   * ZEXPORT zError           OF((int err));
 1196 ZEXTERN int            ZEXPORT inflateSyncPoint OF((z_streamp z));
 1197 ZEXTERN int            ZEXPORT inflateSafePoint OF((z_streamp z));
 1198 ZEXTERN const uLongf * ZEXPORT get_crc_table    OF((void));
 1199 
 1200 #ifdef __cplusplus
 1201 }
 1202 #endif
 1203 
 1204 #endif /* ZLIB_H */