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  10 <h1> zlib 1.1.4 Manual </h1>
  11 <hr>
  12 <a name="Contents"><h2>Contents</h2>
  13 <ol type="I">
  14 <li> <a href="#Prologue">Prologue</a>
  15 <li> <a href="#Introduction">Introduction</a>
  16 <li> <a href="#Utility functions">Utility functions</a>
  17 <li> <a href="#Basic functions">Basic functions</a>
  18 <li> <a href="#Advanced functions">Advanced functions</a>
  19 <li> <a href="#Constants">Constants</a>
  20 <li> <a href="#struct z_stream_s">struct z_stream_s</a>
  21 <li> <a href="#Checksum functions">Checksum functions</a>
  22 <li> <a href="#Misc">Misc</a>
  23 </ol>
  24 <hr>
  25 <a name="Prologue"><h2> Prologue </h2>
  26   'zlib' general purpose compression library version 1.1.4, March 11th, 2002
  27   <p>
  28   Copyright (C) 1995-2002 Jean-loup Gailly and Mark Adler
  29   <p>
  30   This software is provided 'as-is', without any express or implied
  31   warranty.  In no event will the authors be held liable for any damages
  32   arising from the use of this software.
  33   <p>
  34   Permission is granted to anyone to use this software for any purpose,
  35   including commercial applications, and to alter it and redistribute it
  36   freely, subject to the following restrictions:
  37   <ol>
  38    <li> The origin of this software must not be misrepresented ; you must not
  39      claim that you wrote the original software. If you use this software
  40      in a product, an acknowledgment in the product documentation would be
  41      appreciated but is not required.
  42    <li> Altered source versions must be plainly marked as such, and must not be
  43      misrepresented as being the original software.
  44    <li> This notice may not be removed or altered from any source distribution.
  45   </ol>
  46
  47   <dl>
  48   <dt>Jean-loup Gailly
  49   <dd><a href="mailto:jloup@gzip.org">jloup@gzip.org</a>
  50   <dt>Mark Adler
  51   <dd><a href="mailto:madler@alumni.caltech.edu">madler@alumni.caltech.edu</a>
  52   </dl>
  53
  54   The data format used by the zlib library is described by RFCs (Request for
  55   Comments) 1950 to 1952 in the files
  56   <a href="ftp://ds.internic.net/rfc/rfc1950.txt">
  57   ftp://ds.internic.net/rfc/rfc1950.txt </a>
  58   (zlib format),
  59   <a href="ftp://ds.internic.net/rfc/rfc1951.txt">
  60   rfc1951.txt </a>
  61   (<a href="#deflate">deflate</a> format) and
  62   <a href="ftp://ds.internic.net/rfc/rfc1952.txt">
  63   rfc1952.txt </a>
  64   (gzip format).
  65   <p>
  66   This manual is converted from zlib.h by
  67   <a href="mailto:piaip@csie.ntu.edu.tw"> piaip </a>
  68   <p>
  69   Visit <a href="http://ftp.cdrom.com/pub/infozip/zlib/">
  70   http://ftp.cdrom.com/pub/infozip/zlib/</a>
  71   for the official zlib web page.
  72   <p>
  73
  74 <hr>
  75 <a name="Introduction"><h2> Introduction </h2>
  76      The 'zlib' compression library provides in-memory compression and
  77   decompression functions, including integrity checks of the uncompressed
  78   data.  This version of the library supports only one compression method
  79   (deflation) but other algorithms will be added later and will have the same
  80   stream interface.
  81   <p>
  82
  83      Compression can be done in a single step if the buffers are large
  84   enough (for example if an input file is mmap'ed), or can be done by
  85   repeated calls of the compression function.  In the latter case, the
  86   application must provide more input and/or consume the output
  87   (providing more output space) before each call.
  88   <p>
  89
  90      The library also supports reading and writing files in gzip (.gz) format
  91   with an interface similar to that of stdio.
  92   <p>
  93
  94      The library does not install any signal handler. The decoder checks
  95   the consistency of the compressed data, so the library should never
  96   crash even in case of corrupted input.
  97   <p>
  98
  99 <hr>
 100 <a name="Utility functions"><h2> Utility functions </h2>
 101      The following utility functions are implemented on top of the
 102    <a href="#Basic functions">basic stream-oriented functions</a>.
 103    To simplify the interface, some
 104    default options are assumed (compression level and memory usage,
 105    standard memory allocation functions). The source code of these
 106    utility functions can easily be modified if you need special options.
 107 <h3> Function list </h3>
 108 <ul>
 109 <li> int  <a href="#compress">compress</a> (Bytef *dest,   uLongf *destLen, const Bytef *source, uLong sourceLen);
 110 <li> int  <a href="#compress2">compress2</a> (Bytef *dest,   uLongf *destLen, const Bytef *source, uLong sourceLen, int level);
 111 <li> int  <a href="#uncompress">uncompress</a> (Bytef *dest,   uLongf *destLen, const Bytef *source, uLong sourceLen);
 112 <li> typedef voidp gzFile;
 113 <li>  gzFile  <a href="#gzopen">gzopen</a>  (const char *path, const char *mode);
 114 <li> gzFile  <a href="#gzdopen">gzdopen</a>  (int fd, const char *mode);
 115 <li> int  <a href="#gzsetparams">gzsetparams</a> (gzFile file, int level, int strategy);
 116 <li> int     <a href="#gzread">gzread</a>  (gzFile file, voidp buf, unsigned len);
 117 <li> int     <a href="#gzwrite">gzwrite</a> (gzFile file, const voidp buf, unsigned len);
 118 <li> int VA   <a href="#gzprintf">gzprintf</a> (gzFile file, const char *format, ...);
 119 <li> int  <a href="#gzputs">gzputs</a> (gzFile file, const char *s);
 120 <li> char *  <a href="#gzgets">gzgets</a> (gzFile file, char *buf, int len);
 121 <li> int     <a href="#gzputc">gzputc</a> (gzFile file, int c);
 122 <li> int     <a href="#gzgetc">gzgetc</a> (gzFile file);
 123 <li> int     <a href="#gzflush">gzflush</a> (gzFile file, int flush);
 124 <li> z_off_t     <a href="#gzseek">gzseek</a> (gzFile file, z_off_t offset, int whence);
 125 <li> z_off_t     <a href="#gztell">gztell</a> (gzFile file);
 126 <li> int     <a href="#gzrewind">gzrewind</a> (gzFile file);
 127 <li> int  <a href="#gzeof">gzeof</a> (gzFile file);
 128 <li> int     <a href="#gzclose">gzclose</a> (gzFile file);
 129 <li> const char *  <a href="#gzerror">gzerror</a> (gzFile file, int *errnum);
 130 </ul>
 131 <h3> Function description </h3>
 132 <dl>
 133 <font color="Blue"><dt> int  <a name="compress">compress</a> (Bytef *dest,   uLongf *destLen, const Bytef *source, uLong sourceLen);</font>
 134 <dd>
 135      Compresses the source buffer into the destination buffer.  sourceLen is
 136    the byte length of the source buffer. Upon entry, destLen is the total
 137    size of the destination buffer, which must be at least 0.1% larger than
 138    sourceLen plus 12 bytes. Upon exit, destLen is the actual size of the
 139    compressed buffer.<p>
 140      This function can be used to <a href="#compress">compress</a> a whole file at once if the
 141    input file is mmap'ed.<p>
 142      <a href="#compress">compress</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not
 143    enough memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if there was not enough room in the output
 144    buffer.<p>
 145
 146 <font color="Blue"><dt> int  <a name="compress2">compress2</a> (Bytef *dest,   uLongf *destLen, const Bytef *source, uLong sourceLen, int level);</font>
 147 <dd>
 148      Compresses the source buffer into the destination buffer. The level
 149    parameter has the same meaning as in <a href="#deflateInit">deflateInit</a>.  sourceLen is the byte
 150    length of the source buffer. Upon entry, destLen is the total size of the
 151    destination buffer, which must be at least 0.1% larger than sourceLen plus
 152    12 bytes. Upon exit, destLen is the actual size of the compressed buffer.
 153    <p>
 154
 155      <a href="#compress2">compress2</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not enough
 156    memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if there was not enough room in the output buffer,
 157    <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the level parameter is invalid.
 158    <p>
 159
 160 <font color="Blue"><dt> int  <a name="uncompress">uncompress</a> (Bytef *dest,   uLongf *destLen, const Bytef *source, uLong sourceLen);</font>
 161 <dd>
 162      Decompresses the source buffer into the destination buffer.  sourceLen is
 163    the byte length of the source buffer. Upon entry, destLen is the total
 164    size of the destination buffer, which must be large enough to hold the
 165    entire uncompressed data. (The size of the uncompressed data must have
 166    been saved previously by the compressor and transmitted to the decompressor
 167    by some mechanism outside the scope of this compression library.)
 168    Upon exit, destLen is the actual size of the compressed buffer. <p>
 169      This function can be used to decompress a whole file at once if the
 170    input file is mmap'ed.
 171    <p>
 172
 173      <a href="#uncompress">uncompress</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not
 174    enough memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if there was not enough room in the output
 175    buffer, or <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the input data was corrupted.
 176    <p>
 177
 178 <dt> typedef voidp gzFile;
 179 <dd> <p>
 180
 181 <font color="Blue"><dt>  gzFile  <a name="gzopen">gzopen</a>  (const char *path, const char *mode);</font>
 182 <dd>
 183      Opens a gzip (.gz) file for reading or writing. The mode parameter
 184    is as in fopen ("rb" or "wb") but can also include a compression level
 185    ("wb9") or a strategy: 'f' for filtered data as in "wb6f", 'h' for
 186    Huffman only compression as in "wb1h". (See the description
 187    of <a href="#deflateInit2">deflateInit2</a> for more information about the strategy parameter.)
 188    <p>
 189
 190      <a href="#gzopen">gzopen</a> can be used to read a file which is not in gzip format ; in this
 191    case <a href="#gzread">gzread</a> will directly read from the file without decompression.
 192    <p>
 193
 194      <a href="#gzopen">gzopen</a> returns NULL if the file could not be opened or if there was
 195    insufficient memory to allocate the (de)compression <a href="#state">state</a> ; errno
 196    can be checked to distinguish the two cases (if errno is zero, the
 197    zlib error is <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a>).
 198    <p>
 199
 200 <font color="Blue"><dt> gzFile  <a name="gzdopen">gzdopen</a>  (int fd, const char *mode);</font>
 201 <dd>
 202      <a href="#gzdopen">gzdopen</a>() associates a gzFile with the file descriptor fd.  File
 203    descriptors are obtained from calls like open, dup, creat, pipe or
 204    fileno (in the file has been previously opened with fopen).
 205    The mode parameter is as in <a href="#gzopen">gzopen</a>.
 206    <p>
 207      The next call of <a href="#gzclose">gzclose</a> on the returned gzFile will also close the
 208    file descriptor fd, just like fclose(fdopen(fd), mode) closes the file
 209    descriptor fd. If you want to keep fd open, use <a href="#gzdopen">gzdopen</a>(dup(fd), mode).
 210    <p>
 211      <a href="#gzdopen">gzdopen</a> returns NULL if there was insufficient memory to allocate
 212    the (de)compression <a href="#state">state</a>.
 213    <p>
 214
 215 <font color="Blue"><dt> int  <a name="gzsetparams">gzsetparams</a> (gzFile file, int level, int strategy);</font>
 216 <dd>
 217      Dynamically update the compression level or strategy. See the description
 218    of <a href="#deflateInit2">deflateInit2</a> for the meaning of these parameters.
 219    <p>
 220      <a href="#gzsetparams">gzsetparams</a> returns <a href="#Z_OK">Z_OK</a> if success, or <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the file was not
 221    opened for writing.
 222    <p>
 223
 224 <font color="Blue"><dt> int     <a name="gzread">gzread</a>  (gzFile file, voidp buf, unsigned len);</font>
 225 <dd>
 226      Reads the given number of uncompressed bytes from the compressed file.
 227    If the input file was not in gzip format, <a href="#gzread">gzread</a> copies the given number
 228    of bytes into the buffer.
 229    <p>
 230      <a href="#gzread">gzread</a> returns the number of uncompressed bytes actually read (0 for
 231    end of file, -1 for error).
 232    <p>
 233
 234 <font color="Blue"><dt> int     <a name="gzwrite">gzwrite</a> (gzFile file, const voidp buf, unsigned len);</font>
 235 <dd>
 236      Writes the given number of uncompressed bytes into the compressed file.
 237    <a href="#gzwrite">gzwrite</a> returns the number of uncompressed bytes actually written
 238    (0 in case of error).
 239    <p>
 240
 241 <font color="Blue"><dt> int VA   <a name="gzprintf">gzprintf</a> (gzFile file, const char *format, ...);</font>
 242 <dd>
 243      Converts, formats, and writes the args to the compressed file under
 244    control of the format string, as in fprintf. <a href="#gzprintf">gzprintf</a> returns the number of
 245    uncompressed bytes actually written (0 in case of error).
 246    <p>
 247
 248 <font color="Blue"><dt> int  <a name="gzputs">gzputs</a> (gzFile file, const char *s);</font>
 249 <dd>
 250       Writes the given null-terminated string to the compressed file, excluding
 251    the terminating null character.
 252    <p>
 253       <a href="#gzputs">gzputs</a> returns the number of characters written, or -1 in case of error.
 254       <p>
 255
 256 <font color="Blue"><dt> char *  <a name="gzgets">gzgets</a> (gzFile file, char *buf, int len);</font>
 257 <dd>
 258       Reads bytes from the compressed file until len-1 characters are read, or
 259    a newline character is read and transferred to buf, or an end-of-file
 260    condition is encountered.  The string is then terminated with a null
 261    character.
 262    <p>
 263       <a href="#gzgets">gzgets</a> returns buf, or <a href="#Z_NULL">Z_NULL</a> in case of error.
 264       <p>
 265
 266 <font color="Blue"><dt> int     <a name="gzputc">gzputc</a> (gzFile file, int c);</font>
 267 <dd>
 268       Writes c, converted to an unsigned char, into the compressed file.
 269    <a href="#gzputc">gzputc</a> returns the value that was written, or -1 in case of error.
 270    <p>
 271
 272 <font color="Blue"><dt> int     <a name="gzgetc">gzgetc</a> (gzFile file);</font>
 273 <dd>
 274       Reads one byte from the compressed file. <a href="#gzgetc">gzgetc</a> returns this byte
 275    or -1 in case of end of file or error.
 276    <p>
 277
 278 <font color="Blue"><dt> int     <a name="gzflush">gzflush</a> (gzFile file, int flush);</font>
 279 <dd>
 280      Flushes all pending output into the compressed file. The parameter
 281    flush is as in the <a href="#deflate">deflate</a>() function. The return value is the zlib
 282    error number (see function <a href="#gzerror">gzerror</a> below). <a href="#gzflush">gzflush</a> returns <a href="#Z_OK">Z_OK</a> if
 283    the flush parameter is <a href="#Z_FINISH">Z_FINISH</a> and all output could be flushed.
 284    <p>
 285      <a href="#gzflush">gzflush</a> should be called only when strictly necessary because it can
 286    degrade compression.
 287    <p>
 288
 289 <font color="Blue"><dt> z_off_t     <a name="gzseek">gzseek</a> (gzFile file, z_off_t offset, int whence);</font>
 290 <dd>
 291       Sets the starting position for the next <a href="#gzread">gzread</a> or <a href="#gzwrite">gzwrite</a> on the
 292    given compressed file. The offset represents a number of bytes in the
 293    uncompressed data stream. The whence parameter is defined as in lseek(2);
 294    the value SEEK_END is not supported.
 295    <p>
 296      If the file is opened for reading, this function is emulated but can be
 297    extremely slow. If the file is opened for writing, only forward seeks are
 298    supported ; <a href="#gzseek">gzseek</a> then compresses a sequence of zeroes up to the new
 299    starting position.
 300    <p>
 301       <a href="#gzseek">gzseek</a> returns the resulting offset location as measured in bytes from
 302    the beginning of the uncompressed stream, or -1 in case of error, in
 303    particular if the file is opened for writing and the new starting position
 304    would be before the current position.
 305    <p>
 306
 307 <font color="Blue"><dt> int     <a name="gzrewind">gzrewind</a> (gzFile file);</font>
 308 <dd>
 309      Rewinds the given file. This function is supported only for reading.
 310      <p>
 311    <a href="#gzrewind">gzrewind</a>(file) is equivalent to (int)<a href="#gzseek">gzseek</a>(file, 0L, SEEK_SET)
 312    <p>
 313
 314 <font color="Blue"><dt> z_off_t     <a name="gztell">gztell</a> (gzFile file);</font>
 315 <dd>
 316      Returns the starting position for the next <a href="#gzread">gzread</a> or <a href="#gzwrite">gzwrite</a> on the
 317    given compressed file. This position represents a number of bytes in the
 318    uncompressed data stream.
 319    <p>
 320
 321    <a href="#gztell">gztell</a>(file) is equivalent to <a href="#gzseek">gzseek</a>(file, 0L, SEEK_CUR)
 322    <p>
 323
 324 <font color="Blue"><dt> int  <a name="gzeof">gzeof</a> (gzFile file);</font>
 325 <dd>
 326      Returns 1 when EOF has previously been detected reading the given
 327    input stream, otherwise zero.
 328    <p>
 329
 330 <font color="Blue"><dt> int     <a name="gzclose">gzclose</a> (gzFile file);</font>
 331 <dd>
 332      Flushes all pending output if necessary, closes the compressed file
 333    and deallocates all the (de)compression <a href="#state">state</a>. The return value is the zlib
 334    error number (see function <a href="#gzerror">gzerror</a> below).
 335    <p>
 336
 337 <font color="Blue"><dt> const char *  <a name="gzerror">gzerror</a> (gzFile file, int *errnum);</font>
 338 <dd>
 339      Returns the error message for the last error which occurred on the
 340    given compressed file. errnum is set to zlib error number. If an
 341    error occurred in the file system and not in the compression library,
 342    errnum is set to <a href="#Z_ERRNO">Z_ERRNO</a> and the application may consult errno
 343    to get the exact error code.
 344    <p>
 345 </dl>
 346 <hr>
 347 <a name="Basic functions"><h2> Basic functions </h2>
 348 <h3> Function list </h3>
 349 <ul>
 350 <li>  const char *  <a href="#zlibVersion">zlibVersion</a> (void);
 351 <li>  int  <a href="#deflateInit">deflateInit</a> (<a href="#z_streamp">z_streamp</a> strm, int level);
 352 <li>  int  <a href="#deflate">deflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush);
 353 <li>  int  <a href="#deflateEnd">deflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm);
 354 <li>  int  <a href="#inflateInit">inflateInit</a> (<a href="#z_streamp">z_streamp</a> strm);
 355 <li>  int  <a href="#inflate">inflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush);
 356 <li>  int  <a href="#inflateEnd">inflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm);
 357 </ul>
 358
 359 <h3> Function description </h3>
 360 <dl>
 361 <font color="Blue"><dt>  const char *  <a name="zlibVersion">zlibVersion</a> (void);</font>
 362 <dd> The application can compare <a href="#zlibVersion">zlibVersion</a> and ZLIB_VERSION for consistency.
 363    If the first character differs, the library code actually used is
 364    not compatible with the zlib.h header file used by the application.
 365    This check is automatically made by <a href="#deflateInit">deflateInit</a> and <a href="#inflateInit">inflateInit</a>.
 366    <p>
 367
 368 <font color="Blue"><dt> int  <a name="deflateInit">deflateInit</a> (<a href="#z_streamp">z_streamp</a> strm, int level);</font>
 369 <dd>
 370      Initializes the internal stream <a href="#state">state</a> for compression. The fields
 371    <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and <a href="#opaque">opaque</a> must be initialized before by the caller.
 372    If <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> are set to <a href="#Z_NULL">Z_NULL</a>, <a href="#deflateInit">deflateInit</a> updates them to
 373    use default allocation functions.
 374    <p>
 375
 376      The compression level must be <a href="#Z_DEFAULT_COMPRESSION">Z_DEFAULT_COMPRESSION</a>, or between 0 and 9:
 377    1 gives best speed, 9 gives best compression, 0 gives no compression at
 378    all (the input data is simply copied a block at a time).
 379    <p>
 380
 381    <a href="#Z_DEFAULT_COMPRESSION">Z_DEFAULT_COMPRESSION</a> requests a default compromise between speed and
 382    compression (currently equivalent to level 6).
 383    <p>
 384
 385      <a href="#deflateInit">deflateInit</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not
 386    enough memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if level is not a valid compression level,
 387    <a href="#Z_VERSION_ERROR">Z_VERSION_ERROR</a> if the zlib library version (<a href="#zlib_version">zlib_version</a>) is incompatible
 388    with the version assumed by the caller (ZLIB_VERSION).
 389    <a href="#msg">msg</a> is set to null if there is no error message.  <a href="#deflateInit">deflateInit</a> does not
 390    perform any compression: this will be done by <a href="#deflate">deflate</a>().
 391    <p>
 392
 393 <font color="Blue"><dt>  int  <a name="deflate">deflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush);</font>
 394 <dd>
 395     <a href="#deflate">deflate</a> compresses as much data as possible, and stops when the input
 396   buffer becomes empty or the output buffer becomes full. It may introduce some
 397   output latency (reading input without producing any output) except when
 398   forced to flush.<p>
 399
 400     The detailed semantics are as follows. <a href="#deflate">deflate</a> performs one or both of the
 401   following actions:
 402
 403   <ul>
 404   <li> Compress more input starting at <a href="#next_in">next_in</a> and update <a href="#next_in">next_in</a> and <a href="#avail_in">avail_in</a>
 405     accordingly. If not all input can be processed (because there is not
 406     enough room in the output buffer), <a href="#next_in">next_in</a> and <a href="#avail_in">avail_in</a> are updated and
 407     processing will resume at this point for the next call of <a href="#deflate">deflate</a>().
 408
 409   <li>
 410     Provide more output starting at <a href="#next_out">next_out</a> and update <a href="#next_out">next_out</a> and <a href="#avail_out">avail_out</a>
 411     accordingly. This action is forced if the parameter flush is non zero.
 412     Forcing flush frequently degrades the compression ratio, so this parameter
 413     should be set only when necessary (in interactive applications).
 414     Some output may be provided even if flush is not set.
 415   </ul> <p>
 416
 417   Before the call of <a href="#deflate">deflate</a>(), the application should ensure that at least
 418   one of the actions is possible, by providing more input and/or consuming
 419   more output, and updating <a href="#avail_in">avail_in</a> or <a href="#avail_out">avail_out</a> accordingly ; <a href="#avail_out">avail_out</a>
 420   should never be zero before the call. The application can consume the
 421   compressed output when it wants, for example when the output buffer is full
 422   (<a href="#avail_out">avail_out</a> == 0), or after each call of <a href="#deflate">deflate</a>(). If <a href="#deflate">deflate</a> returns <a href="#Z_OK">Z_OK</a>
 423   and with zero <a href="#avail_out">avail_out</a>, it must be called again after making room in the
 424   output buffer because there might be more output pending.
 425   <p>
 426
 427     If the parameter flush is set to <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>, all pending output is
 428   flushed to the output buffer and the output is aligned on a byte boundary, so
 429   that the decompressor can get all input data available so far. (In particular
 430   <a href="#avail_in">avail_in</a> is zero after the call if enough output space has been provided
 431   before the call.)  Flushing may degrade compression for some compression
 432   algorithms and so it should be used only when necessary.
 433   <p>
 434
 435     If flush is set to <a href="#Z_FULL_FLUSH">Z_FULL_FLUSH</a>, all output is flushed as with
 436   <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>, and the compression <a href="#state">state</a> is reset so that decompression can
 437   restart from this point if previous compressed data has been damaged or if
 438   random access is desired. Using <a href="#Z_FULL_FLUSH">Z_FULL_FLUSH</a> too often can seriously degrade
 439   the compression.
 440   <p>
 441
 442     If <a href="#deflate">deflate</a> returns with <a href="#avail_out">avail_out</a> == 0, this function must be called again
 443   with the same value of the flush parameter and more output space (updated
 444   <a href="#avail_out">avail_out</a>), until the flush is complete (<a href="#deflate">deflate</a> returns with non-zero
 445   <a href="#avail_out">avail_out</a>).
 446   <p>
 447
 448     If the parameter flush is set to <a href="#Z_FINISH">Z_FINISH</a>, pending input is processed,
 449   pending output is flushed and <a href="#deflate">deflate</a> returns with <a href="#Z_STREAM_END">Z_STREAM_END</a> if there
 450   was enough output space ; if <a href="#deflate">deflate</a> returns with <a href="#Z_OK">Z_OK</a>, this function must be
 451   called again with <a href="#Z_FINISH">Z_FINISH</a> and more output space (updated <a href="#avail_out">avail_out</a>) but no
 452   more input data, until it returns with <a href="#Z_STREAM_END">Z_STREAM_END</a> or an error. After
 453   <a href="#deflate">deflate</a> has returned <a href="#Z_STREAM_END">Z_STREAM_END</a>, the only possible operations on the
 454   stream are <a href="#deflateReset">deflateReset</a> or <a href="#deflateEnd">deflateEnd</a>.
 455   <p>
 456
 457     <a href="#Z_FINISH">Z_FINISH</a> can be used immediately after <a href="#deflateInit">deflateInit</a> if all the compression
 458   is to be done in a single step. In this case, <a href="#avail_out">avail_out</a> must be at least
 459   0.1% larger than <a href="#avail_in">avail_in</a> plus 12 bytes.  If <a href="#deflate">deflate</a> does not return
 460   <a href="#Z_STREAM_END">Z_STREAM_END</a>, then it must be called again as described above.
 461   <p>
 462
 463     <a href="#deflate">deflate</a>() sets strm-&gt <a href="#adler">adler</a> to the <a href="#adler32">adler32</a> checksum of all input read
 464   so far (that is, <a href="#total_in">total_in</a> bytes).
 465   <p>
 466
 467     <a href="#deflate">deflate</a>() may update <a href="#data_type">data_type</a> if it can make a good guess about
 468   the input data type (<a href="#Z_ASCII">Z_ASCII</a> or <a href="#Z_BINARY">Z_BINARY</a>). In doubt, the data is considered
 469   binary. This field is only for information purposes and does not affect
 470   the compression algorithm in any manner.
 471   <p>
 472
 473     <a href="#deflate">deflate</a>() returns <a href="#Z_OK">Z_OK</a> if some progress has been made (more input
 474   processed or more output produced), <a href="#Z_STREAM_END">Z_STREAM_END</a> if all input has been
 475   consumed and all output has been produced (only when flush is set to
 476   <a href="#Z_FINISH">Z_FINISH</a>), <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the stream <a href="#state">state</a> was inconsistent (for example
 477   if <a href="#next_in">next_in</a> or <a href="#next_out">next_out</a> was NULL), <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if no progress is possible
 478   (for example <a href="#avail_in">avail_in</a> or <a href="#avail_out">avail_out</a> was zero).
 479   <p>
 480
 481 <font color="Blue"><dt>  int  <a name="deflateEnd">deflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
 482 <dd>
 483      All dynamically allocated data structures for this stream are freed.
 484    This function discards any unprocessed input and does not flush any
 485    pending output.
 486    <p>
 487
 488      <a href="#deflateEnd">deflateEnd</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the
 489    stream <a href="#state">state</a> was inconsistent, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the stream was freed
 490    prematurely (some input or output was discarded). In the error case,
 491    <a href="#msg">msg</a> may be set but then points to a static string (which must not be
 492    deallocated).
 493    <p>
 494
 495 <font color="Blue"><dt>  int  <a name="inflateInit">inflateInit</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
 496 <dd>
 497         Initializes the internal stream <a href="#state">state</a> for decompression. The fields
 498    <a href="#next_in">next_in</a>, <a href="#avail_in">avail_in</a>, <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and <a href="#opaque">opaque</a> must be initialized before by
 499    the caller. If <a href="#next_in">next_in</a> is not <a href="#Z_NULL">Z_NULL</a> and <a href="#avail_in">avail_in</a> is large enough (the exact
 500    value depends on the compression method), <a href="#inflateInit">inflateInit</a> determines the
 501    compression method from the zlib header and allocates all data structures
 502    accordingly ; otherwise the allocation will be deferred to the first call of
 503    <a href="#inflate">inflate</a>.  If <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> are set to <a href="#Z_NULL">Z_NULL</a>, <a href="#inflateInit">inflateInit</a> updates them to
 504    use default allocation functions.
 505    <p>
 506
 507      <a href="#inflateInit">inflateInit</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not enough
 508    memory, <a href="#Z_VERSION_ERROR">Z_VERSION_ERROR</a> if the zlib library version is incompatible with the
 509    version assumed by the caller.  <a href="#msg">msg</a> is set to null if there is no error
 510    message. <a href="#inflateInit">inflateInit</a> does not perform any decompression apart from reading
 511    the zlib header if present: this will be done by <a href="#inflate">inflate</a>().  (So <a href="#next_in">next_in</a> and
 512    <a href="#avail_in">avail_in</a> may be modified, but <a href="#next_out">next_out</a> and <a href="#avail_out">avail_out</a> are unchanged.)
 513    <p>
 514
 515 <font color="Blue"><dt>  int  <a name="inflate">inflate</a> (<a href="#z_streamp">z_streamp</a> strm, int flush);</font>
 516 <dd>
 517     <a href="#inflate">inflate</a> decompresses as much data as possible, and stops when the input
 518   buffer becomes empty or the output buffer becomes full. It may some
 519   introduce some output latency (reading input without producing any output)
 520   except when forced to flush.
 521   <p>
 522
 523   The detailed semantics are as follows. <a href="#inflate">inflate</a> performs one or both of the
 524   following actions:
 525
 526   <ul>
 527   <li> Decompress more input starting at <a href="#next_in">next_in</a> and update <a href="#next_in">next_in</a> and <a href="#avail_in">avail_in</a>
 528     accordingly. If not all input can be processed (because there is not
 529     enough room in the output buffer), <a href="#next_in">next_in</a> is updated and processing
 530     will resume at this point for the next call of <a href="#inflate">inflate</a>().
 531
 532   <li> Provide more output starting at <a href="#next_out">next_out</a> and update <a href="#next_out">next_out</a> and
 533     <a href="#avail_out">avail_out</a> accordingly.  <a href="#inflate">inflate</a>() provides as much output as possible,
 534     until there is no more input data or no more space in the output buffer
 535     (see below about the flush parameter).
 536   </ul> <p>
 537
 538   Before the call of <a href="#inflate">inflate</a>(), the application should ensure that at least
 539   one of the actions is possible, by providing more input and/or consuming
 540   more output, and updating the next_* and avail_* values accordingly.
 541   The application can consume the uncompressed output when it wants, for
 542   example when the output buffer is full (<a href="#avail_out">avail_out</a> == 0), or after each
 543   call of <a href="#inflate">inflate</a>(). If <a href="#inflate">inflate</a> returns <a href="#Z_OK">Z_OK</a> and with zero <a href="#avail_out">avail_out</a>, it
 544   must be called again after making room in the output buffer because there
 545   might be more output pending.
 546   <p>
 547
 548     If the parameter flush is set to <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>, <a href="#inflate">inflate</a> flushes as much
 549   output as possible to the output buffer. The flushing behavior of <a href="#inflate">inflate</a> is
 550   not specified for values of the flush parameter other than <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>
 551   and <a href="#Z_FINISH">Z_FINISH</a>, but the current implementation actually flushes as much output
 552   as possible anyway.
 553   <p>
 554
 555     <a href="#inflate">inflate</a>() should normally be called until it returns <a href="#Z_STREAM_END">Z_STREAM_END</a> or an
 556   error. However if all decompression is to be performed in a single step
 557   (a single call of <a href="#inflate">inflate</a>), the parameter flush should be set to
 558   <a href="#Z_FINISH">Z_FINISH</a>. In this case all pending input is processed and all pending
 559   output is flushed ; <a href="#avail_out">avail_out</a> must be large enough to hold all the
 560   uncompressed data. (The size of the uncompressed data may have been saved
 561   by the compressor for this purpose.) The next operation on this stream must
 562   be <a href="#inflateEnd">inflateEnd</a> to deallocate the decompression <a href="#state">state</a>. The use of <a href="#Z_FINISH">Z_FINISH</a>
 563   is never required, but can be used to inform <a href="#inflate">inflate</a> that a faster routine
 564   may be used for the single <a href="#inflate">inflate</a>() call.
 565   <p>
 566
 567      If a preset dictionary is needed at this point (see <a href="#inflateSetDictionary">inflateSetDictionary</a>
 568   below), <a href="#inflate">inflate</a> sets strm-<a href="#adler">adler</a> to the <a href="#adler32">adler32</a> checksum of the
 569   dictionary chosen by the compressor and returns <a href="#Z_NEED_DICT">Z_NEED_DICT</a> ; otherwise
 570   it sets strm-&gt <a href="#adler">adler</a> to the <a href="#adler32">adler32</a> checksum of all output produced
 571   so far (that is, <a href="#total_out">total_out</a> bytes) and returns <a href="#Z_OK">Z_OK</a>, <a href="#Z_STREAM_END">Z_STREAM_END</a> or
 572   an error code as described below. At the end of the stream, <a href="#inflate">inflate</a>()
 573   checks that its computed <a href="#adler32">adler32</a> checksum is equal to that saved by the
 574   compressor and returns <a href="#Z_STREAM_END">Z_STREAM_END</a> only if the checksum is correct.
 575   <p>
 576
 577     <a href="#inflate">inflate</a>() returns <a href="#Z_OK">Z_OK</a> if some progress has been made (more input processed
 578   or more output produced), <a href="#Z_STREAM_END">Z_STREAM_END</a> if the end of the compressed data has
 579   been reached and all uncompressed output has been produced, <a href="#Z_NEED_DICT">Z_NEED_DICT</a> if a
 580   preset dictionary is needed at this point, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the input data was
 581   corrupted (input stream not conforming to the zlib format or incorrect
 582   <a href="#adler32">adler32</a> checksum), <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the stream structure was inconsistent
 583   (for example if <a href="#next_in">next_in</a> or <a href="#next_out">next_out</a> was NULL), <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not
 584   enough memory, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a> if no progress is possible or if there was not
 585   enough room in the output buffer when <a href="#Z_FINISH">Z_FINISH</a> is used. In the <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a>
 586   case, the application may then call <a href="#inflateSync">inflateSync</a> to look for a good
 587   compression block.
 588   <p>
 589
 590 <font color="Blue"><dt>  int  <a name="inflateEnd">inflateEnd</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
 591 <dd>
 592      All dynamically allocated data structures for this stream are freed.
 593    This function discards any unprocessed input and does not flush any
 594    pending output.
 595    <p>
 596
 597      <a href="#inflateEnd">inflateEnd</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the stream <a href="#state">state</a>
 598    was inconsistent. In the error case, <a href="#msg">msg</a> may be set but then points to a
 599    static string (which must not be deallocated).
 600 </dl>
 601 <hr>
 602 <a name="Advanced functions"><h2> Advanced functions </h2>
 603     The following functions are needed only in some special applications.
 604 <h3> Function list </h3>
 605 <ul>
 606 <li>  int  <a href="#deflateInit2">deflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm,
 607 <li> int  <a href="#deflateSetDictionary">deflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt  dictLength);
 608 <li> int  <a href="#deflateCopy">deflateCopy</a> (<a href="#z_streamp">z_streamp</a> dest, <a href="#z_streamp">z_streamp</a> source);
 609 <li> int  <a href="#deflateReset">deflateReset</a> (<a href="#z_streamp">z_streamp</a> strm);
 610 <li> int  <a href="#deflateParams">deflateParams</a> (<a href="#z_streamp">z_streamp</a> strm, int level, int strategy);
 611 <li> int  <a href="#inflateInit2">inflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm, int  windowBits);
 612 <li>  int  <a href="#inflateSetDictionary">inflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt  dictLength);
 613 <li> int  <a href="#inflateSync">inflateSync</a> (<a href="#z_streamp">z_streamp</a> strm);
 614 <li> int  <a href="#inflateReset">inflateReset</a> (<a href="#z_streamp">z_streamp</a> strm);
 615
 616 </ul>
 617 <h3> Function description </h3>
 618 <dl>
 619 <font color="Blue"><dt>  int  <a name="deflateInit2">deflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm, int  level, int  method, int  windowBits, int  memLevel, int  strategy);</font>
 620
 621 <dd> This is another version of <a href="#deflateInit">deflateInit</a> with more compression options. The
 622    fields <a href="#next_in">next_in</a>, <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and <a href="#opaque">opaque</a> must be initialized before by
 623    the caller.<p>
 624
 625      The method parameter is the compression method. It must be <a href="#Z_DEFLATED">Z_DEFLATED</a> in
 626    this version of the library.<p>
 627
 628      The windowBits parameter is the base two logarithm of the window size
 629    (the size of the history buffer).  It should be in the range 8..15 for this
 630    version of the library. Larger values of this parameter result in better
 631    compression at the expense of memory usage. The default value is 15 if
 632    <a href="#deflateInit">deflateInit</a> is used instead.<p>
 633
 634      The memLevel parameter specifies how much memory should be allocated
 635    for the internal compression <a href="#state">state</a>. memLevel=1 uses minimum memory but
 636    is slow and reduces compression ratio ; memLevel=9 uses maximum memory
 637    for optimal speed. The default value is 8. See zconf.h for total memory
 638    usage as a function of windowBits and memLevel.<p>
 639
 640      The strategy parameter is used to tune the compression algorithm. Use the
 641    value <a href="#Z_DEFAULT_STRATEGY">Z_DEFAULT_STRATEGY</a> for normal data, <a href="#Z_FILTERED">Z_FILTERED</a> for data produced by a
 642    filter (or predictor), or <a href="#Z_HUFFMAN_ONLY">Z_HUFFMAN_ONLY</a> to force Huffman encoding only (no
 643    string match).  Filtered data consists mostly of small values with a
 644    somewhat random distribution. In this case, the compression algorithm is
 645    tuned to <a href="#compress">compress</a> them better. The effect of <a href="#Z_FILTERED">Z_FILTERED</a> is to force more
 646    Huffman coding and less string matching ; it is somewhat intermediate
 647    between Z_DEFAULT and <a href="#Z_HUFFMAN_ONLY">Z_HUFFMAN_ONLY</a>. The strategy parameter only affects
 648    the compression ratio but not the correctness of the compressed output even
 649    if it is not set appropriately.<p>
 650
 651       <a href="#deflateInit2">deflateInit2</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not enough
 652    memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if a parameter is invalid (such as an invalid
 653    method). <a href="#msg">msg</a> is set to null if there is no error message.  <a href="#deflateInit2">deflateInit2</a> does
 654    not perform any compression: this will be done by <a href="#deflate">deflate</a>().<p>
 655
 656 <font color="Blue"><dt> int  <a name="deflateSetDictionary">deflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt  dictLength);</font>
 657 <dd>
 658      Initializes the compression dictionary from the given byte sequence
 659    without producing any compressed output. This function must be called
 660    immediately after <a href="#deflateInit">deflateInit</a>, <a href="#deflateInit2">deflateInit2</a> or <a href="#deflateReset">deflateReset</a>, before any
 661    call of <a href="#deflate">deflate</a>. The compressor and decompressor must use exactly the same
 662    dictionary (see <a href="#inflateSetDictionary">inflateSetDictionary</a>).<p>
 663
 664      The dictionary should consist of strings (byte sequences) that are likely
 665    to be encountered later in the data to be compressed, with the most commonly
 666    used strings preferably put towards the end of the dictionary. Using a
 667    dictionary is most useful when the data to be compressed is short and can be
 668    predicted with good accuracy ; the data can then be compressed better than
 669    with the default empty dictionary.<p>
 670
 671      Depending on the size of the compression data structures selected by
 672    <a href="#deflateInit">deflateInit</a> or <a href="#deflateInit2">deflateInit2</a>, a part of the dictionary may in effect be
 673    discarded, for example if the dictionary is larger than the window size in
 674    <a href="#deflate">deflate</a> or deflate2. Thus the strings most likely to be useful should be
 675    put at the end of the dictionary, not at the front.<p>
 676
 677      Upon return of this function, strm-&gt <a href="#adler">adler</a> is set to the Adler32 value
 678    of the dictionary ; the decompressor may later use this value to determine
 679    which dictionary has been used by the compressor. (The Adler32 value
 680    applies to the whole dictionary even if only a subset of the dictionary is
 681    actually used by the compressor.)<p>
 682
 683      <a href="#deflateSetDictionary">deflateSetDictionary</a> returns <a href="#Z_OK">Z_OK</a> if success, or <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if a
 684    parameter is invalid (such as NULL dictionary) or the stream <a href="#state">state</a> is
 685    inconsistent (for example if <a href="#deflate">deflate</a> has already been called for this stream
 686    or if the compression method is bsort). <a href="#deflateSetDictionary">deflateSetDictionary</a> does not
 687    perform any compression: this will be done by <a href="#deflate">deflate</a>().<p>
 688
 689 <font color="Blue"><dt> int  <a name="deflateCopy">deflateCopy</a> (<a href="#z_streamp">z_streamp</a> dest, <a href="#z_streamp">z_streamp</a> source);</font>
 690 <dd>
 691      Sets the destination stream as a complete copy of the source stream.<p>
 692
 693      This function can be useful when several compression strategies will be
 694    tried, for example when there are several ways of pre-processing the input
 695    data with a filter. The streams that will be discarded should then be freed
 696    by calling <a href="#deflateEnd">deflateEnd</a>.  Note that <a href="#deflateCopy">deflateCopy</a> duplicates the internal
 697    compression <a href="#state">state</a> which can be quite large, so this strategy is slow and
 698    can consume lots of memory.<p>
 699
 700      <a href="#deflateCopy">deflateCopy</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not
 701    enough memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the source stream <a href="#state">state</a> was inconsistent
 702    (such as <a href="#zalloc">zalloc</a> being NULL). <a href="#msg">msg</a> is left unchanged in both source and
 703    destination.<p>
 704
 705 <font color="Blue"><dt> int  <a name="deflateReset">deflateReset</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
 706 <dd>     This function is equivalent to <a href="#deflateEnd">deflateEnd</a> followed by <a href="#deflateInit">deflateInit</a>,
 707    but does not free and reallocate all the internal compression <a href="#state">state</a>.
 708    The stream will keep the same compression level and any other attributes
 709    that may have been set by <a href="#deflateInit2">deflateInit2</a>.<p>
 710
 711       <a href="#deflateReset">deflateReset</a> returns <a href="#Z_OK">Z_OK</a> if success, or <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the source
 712    stream <a href="#state">state</a> was inconsistent (such as <a href="#zalloc">zalloc</a> or <a href="#state">state</a> being NULL).<p>
 713
 714 <font color="Blue"><dt> int  <a name="deflateParams">deflateParams</a> (<a href="#z_streamp">z_streamp</a> strm, int level, int strategy);</font>
 715 <dd>
 716      Dynamically update the compression level and compression strategy.  The
 717    interpretation of level and strategy is as in <a href="#deflateInit2">deflateInit2</a>.  This can be
 718    used to switch between compression and straight copy of the input data, or
 719    to switch to a different kind of input data requiring a different
 720    strategy. If the compression level is changed, the input available so far
 721    is compressed with the old level (and may be flushed); the new level will
 722    take effect only at the next call of <a href="#deflate">deflate</a>().<p>
 723
 724      Before the call of <a href="#deflateParams">deflateParams</a>, the stream <a href="#state">state</a> must be set as for
 725    a call of <a href="#deflate">deflate</a>(), since the currently available input may have to
 726    be compressed and flushed. In particular, strm-&gt <a href="#avail_out">avail_out</a> must be
 727    non-zero.<p>
 728
 729      <a href="#deflateParams">deflateParams</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the source
 730    stream <a href="#state">state</a> was inconsistent or if a parameter was invalid, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a>
 731    if strm-&gtavail_out was zero.<p>
 732
 733 <font color="Blue"><dt> int  <a name="inflateInit2">inflateInit2</a> (<a href="#z_streamp">z_streamp</a> strm, int  windowBits);</font>
 734
 735 <dd>     This is another version of <a href="#inflateInit">inflateInit</a> with an extra parameter. The
 736    fields <a href="#next_in">next_in</a>, <a href="#avail_in">avail_in</a>, <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and <a href="#opaque">opaque</a> must be initialized
 737    before by the caller.<p>
 738
 739      The windowBits parameter is the base two logarithm of the maximum window
 740    size (the size of the history buffer).  It should be in the range 8..15 for
 741    this version of the library. The default value is 15 if <a href="#inflateInit">inflateInit</a> is used
 742    instead. If a compressed stream with a larger window size is given as
 743    input, <a href="#inflate">inflate</a>() will return with the error code <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> instead of
 744    trying to allocate a larger window.<p>
 745
 746       <a href="#inflateInit2">inflateInit2</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_MEM_ERROR">Z_MEM_ERROR</a> if there was not enough
 747    memory, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if a parameter is invalid (such as a negative
 748    memLevel). <a href="#msg">msg</a> is set to null if there is no error message.  <a href="#inflateInit2">inflateInit2</a>
 749    does not perform any decompression apart from reading the zlib header if
 750    present: this will be done by <a href="#inflate">inflate</a>(). (So <a href="#next_in">next_in</a> and <a href="#avail_in">avail_in</a> may be
 751    modified, but <a href="#next_out">next_out</a> and <a href="#avail_out">avail_out</a> are unchanged.)<p>
 752
 753 <font color="Blue"><dt>  int  <a name="inflateSetDictionary">inflateSetDictionary</a> (<a href="#z_streamp">z_streamp</a> strm, const Bytef *dictionary, uInt  dictLength);</font>
 754 <dd>
 755      Initializes the decompression dictionary from the given uncompressed byte
 756    sequence. This function must be called immediately after a call of <a href="#inflate">inflate</a>
 757    if this call returned <a href="#Z_NEED_DICT">Z_NEED_DICT</a>. The dictionary chosen by the compressor
 758    can be determined from the Adler32 value returned by this call of
 759    <a href="#inflate">inflate</a>. The compressor and decompressor must use exactly the same
 760    dictionary (see <a href="#deflateSetDictionary">deflateSetDictionary</a>).<p>
 761
 762      <a href="#inflateSetDictionary">inflateSetDictionary</a> returns <a href="#Z_OK">Z_OK</a> if success, <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if a
 763    parameter is invalid (such as NULL dictionary) or the stream <a href="#state">state</a> is
 764    inconsistent, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if the given dictionary doesn't match the
 765    expected one (incorrect Adler32 value). <a href="#inflateSetDictionary">inflateSetDictionary</a> does not
 766    perform any decompression: this will be done by subsequent calls of
 767    <a href="#inflate">inflate</a>().<p>
 768
 769 <font color="Blue"><dt> int  <a name="inflateSync">inflateSync</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
 770
 771 <dd>    Skips invalid compressed data until a full flush point (see above the
 772   description of <a href="#deflate">deflate</a> with <a href="#Z_FULL_FLUSH">Z_FULL_FLUSH</a>) can be found, or until all
 773   available input is skipped. No output is provided.<p>
 774
 775     <a href="#inflateSync">inflateSync</a> returns <a href="#Z_OK">Z_OK</a> if a full flush point has been found, <a href="#Z_BUF_ERROR">Z_BUF_ERROR</a>
 776   if no more input was provided, <a href="#Z_DATA_ERROR">Z_DATA_ERROR</a> if no flush point has been found,
 777   or <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the stream structure was inconsistent. In the success
 778   case, the application may save the current current value of <a href="#total_in">total_in</a> which
 779   indicates where valid compressed data was found. In the error case, the
 780   application may repeatedly call <a href="#inflateSync">inflateSync</a>, providing more input each time,
 781   until success or end of the input data.<p>
 782
 783 <font color="Blue"><dt> int  <a name="inflateReset">inflateReset</a> (<a href="#z_streamp">z_streamp</a> strm);</font>
 784 <dd>
 785      This function is equivalent to <a href="#inflateEnd">inflateEnd</a> followed by <a href="#inflateInit">inflateInit</a>,
 786    but does not free and reallocate all the internal decompression <a href="#state">state</a>.
 787    The stream will keep attributes that may have been set by <a href="#inflateInit2">inflateInit2</a>.
 788    <p>
 789
 790       <a href="#inflateReset">inflateReset</a> returns <a href="#Z_OK">Z_OK</a> if success, or <a href="#Z_STREAM_ERROR">Z_STREAM_ERROR</a> if the source
 791    stream <a href="#state">state</a> was inconsistent (such as <a href="#zalloc">zalloc</a> or <a href="#state">state</a> being NULL).
 792    <p>
 793 </dl>
 794
 795 <hr>
 796 <a name="Checksum functions"><h2> Checksum functions </h2>
 797      These functions are not related to compression but are exported
 798    anyway because they might be useful in applications using the
 799    compression library.
 800 <h3> Function list </h3>
 801 <ul>
 802 <li> uLong  <a href="#adler32">adler32</a> (uLong <a href="#adler">adler</a>, const Bytef *buf, uInt len);
 803 <li> uLong  <a href="#crc32">crc32</a>   (uLong crc, const Bytef *buf, uInt len);
 804 </ul>
 805 <h3> Function description </h3>
 806 <dl>
 807 <font color="Blue"><dt> uLong  <a name="adler32">adler32</a> (uLong <a href="#adler">adler</a>, const Bytef *buf, uInt len);</font>
 808 <dd>
 809      Update a running Adler-32 checksum with the bytes buf[0..len-1] and
 810    return the updated checksum. If buf is NULL, this function returns
 811    the required initial value for the checksum.
 812    <p>
 813    An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
 814    much faster. Usage example:
 815    <pre>
 816
 817      uLong <a href="#adler">adler</a> = <a href="#adler32">adler32</a>(0L, <a href="#Z_NULL">Z_NULL</a>, 0);
 818
 819      while (read_buffer(buffer, length) != EOF) {
 820        <a href="#adler">adler</a> = <a href="#adler32">adler32</a>(<a href="#adler">adler</a>, buffer, length);
 821      }
 822      if (<a href="#adler">adler</a> != original_adler) error();
 823    </pre>
 824
 825 <font color="Blue"><dt> uLong  <a name="crc32">crc32</a>   (uLong crc, const Bytef *buf, uInt len);</font>
 826 <dd>
 827      Update a running crc with the bytes buf[0..len-1] and return the updated
 828    crc. If buf is NULL, this function returns the required initial value
 829    for the crc. Pre- and post-conditioning (one's complement) is performed
 830    within this function so it shouldn't be done by the application.
 831    Usage example:
 832    <pre>
 833
 834      uLong crc = <a href="#crc32">crc32</a>(0L, <a href="#Z_NULL">Z_NULL</a>, 0);
 835
 836      while (read_buffer(buffer, length) != EOF) {
 837        crc = <a href="#crc32">crc32</a>(crc, buffer, length);
 838      }
 839      if (crc != original_crc) error();
 840    </pre>
 841 </dl>
 842 <hr>
 843 <a name="struct z_stream_s"><h2> struct z_stream_s </h2>
 844 <font color="Blue">
 845 <a name="z_stream_s">
 846 <pre>
 847 typedef struct z_stream_s {
 848     Bytef    *<a name="next_in">next_in</a>;  /* next input byte */
 849     uInt     <a name="avail_in">avail_in</a>;  /* number of bytes available at <a href="#next_in">next_in</a> */
 850     uLong    <a name="total_in">total_in</a>;  /* total nb of input bytes read so far */
 851
 852     Bytef    *<a name="next_out">next_out</a>; /* next output byte should be put there */
 853     uInt     <a name="avail_out">avail_out</a>; /* remaining free space at <a href="#next_out">next_out</a> */
 854     uLong    <a name="total_out">total_out</a>; /* total nb of bytes output so far */
 855
 856     char     *<a name="msg">msg</a>;      /* last error message, NULL if no error */
 857     struct internal_state FAR *<a name="state">state</a>; /* not visible by applications */
 858
 859     alloc_func <a name="zalloc">zalloc</a>;  /* used to allocate the internal <a href="#state">state</a> */
 860     free_func  <a name="zfree">zfree</a>;   /* used to free the internal <a href="#state">state</a> */
 861     voidpf     <a name="opaque">opaque</a>;  /* private data object passed to <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> */
 862
 863     int     <a name="data_type">data_type</a>;  /* best guess about the data type: ascii or binary */
 864     uLong   <a name="adler">adler</a>;      /* <a href="#adler32">adler32</a> value of the uncompressed data */
 865     uLong   <a name="reserved">reserved</a>;   /* <a href="#reserved">reserved</a> for future use */
 866 } <a href="#z_stream_s">z_stream</a> ;
 867
 868 typedef <a href="#z_stream_s">z_stream</a> FAR * <a name="z_streamp">z_streamp</a>;  ÿ
 869 </pre>
 870 </font>
 871    The application must update <a href="#next_in">next_in</a> and <a href="#avail_in">avail_in</a> when <a href="#avail_in">avail_in</a> has
 872    dropped to zero. It must update <a href="#next_out">next_out</a> and <a href="#avail_out">avail_out</a> when <a href="#avail_out">avail_out</a>
 873    has dropped to zero. The application must initialize <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a> and
 874    <a href="#opaque">opaque</a> before calling the init function. All other fields are set by the
 875    compression library and must not be updated by the application. <p>
 876
 877    The <a href="#opaque">opaque</a> value provided by the application will be passed as the first
 878    parameter for calls of <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a>. This can be useful for custom
 879    memory management. The compression library attaches no meaning to the
 880    <a href="#opaque">opaque</a> value. <p>
 881
 882    <a href="#zalloc">zalloc</a> must return <a href="#Z_NULL">Z_NULL</a> if there is not enough memory for the object.
 883    If zlib is used in a multi-threaded application, <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> must be
 884    thread safe. <p>
 885
 886    On 16-bit systems, the functions <a href="#zalloc">zalloc</a> and <a href="#zfree">zfree</a> must be able to allocate
 887    exactly 65536 bytes, but will not be required to allocate more than this
 888    if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS,
 889    pointers returned by <a href="#zalloc">zalloc</a> for objects of exactly 65536 bytes *must*
 890    have their offset normalized to zero. The default allocation function
 891    provided by this library ensures this (see zutil.c). To reduce memory
 892    requirements and avoid any allocation of 64K objects, at the expense of
 893    compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h).
 894    <p>
 895
 896    The fields <a href="#total_in">total_in</a> and <a href="#total_out">total_out</a> can be used for statistics or
 897    progress reports. After compression, <a href="#total_in">total_in</a> holds the total size of
 898    the uncompressed data and may be saved for use in the decompressor
 899    (particularly if the decompressor wants to decompress everything in
 900    a single step). <p>
 901
 902 <hr>
 903 <a name="Constants"><h2> Constants </h2>
 904 <font color="Blue">
 905 <pre>
 906 #define <a name="Z_NO_FLUSH">Z_NO_FLUSH</a>      0
 907 #define <a name="Z_PARTIAL_FLUSH">Z_PARTIAL_FLUSH</a> 1
 908         /* will be removed, use <a href="#Z_SYNC_FLUSH">Z_SYNC_FLUSH</a> instead */
 909 #define <a name="Z_SYNC_FLUSH">Z_SYNC_FLUSH</a>    2
 910 #define <a name="Z_FULL_FLUSH">Z_FULL_FLUSH</a>    3
 911 #define <a name="Z_FINISH">Z_FINISH</a>        4
 912 /* Allowed flush values ; see <a href="#deflate">deflate</a>() below for details */
 913
 914 #define <a name="Z_OK">Z_OK</a>            0
 915 #define <a name="Z_STREAM_END">Z_STREAM_END</a>    1
 916 #define <a name="Z_NEED_DICT">Z_NEED_DICT</a>     2
 917 #define <a name="Z_ERRNO">Z_ERRNO</a>        (-1)
 918 #define <a name="Z_STREAM_ERROR">Z_STREAM_ERROR</a> (-2)
 919 #define <a name="Z_DATA_ERROR">Z_DATA_ERROR</a>   (-3)
 920 #define <a name="Z_MEM_ERROR">Z_MEM_ERROR</a>    (-4)
 921 #define <a name="Z_BUF_ERROR">Z_BUF_ERROR</a>    (-5)
 922 #define <a name="Z_VERSION_ERROR">Z_VERSION_ERROR</a> (-6)
 923 /* Return codes for the compression/decompression functions. Negative
 924  * values are errors, positive values are used for special but normal events.
 925  */
 926
 927 #define <a name="Z_NO_COMPRESSION">Z_NO_COMPRESSION</a>         0
 928 #define <a name="Z_BEST_SPEED">Z_BEST_SPEED</a>             1
 929 #define <a name="Z_BEST_COMPRESSION">Z_BEST_COMPRESSION</a>       9
 930 #define <a name="Z_DEFAULT_COMPRESSION">Z_DEFAULT_COMPRESSION</a>  (-1)
 931 /* compression levels */
 932
 933 #define <a name="Z_FILTERED">Z_FILTERED</a>            1
 934 #define <a name="Z_HUFFMAN_ONLY">Z_HUFFMAN_ONLY</a>        2
 935 #define <a name="Z_DEFAULT_STRATEGY">Z_DEFAULT_STRATEGY</a>    0
 936 /* compression strategy ; see <a href="#deflateInit2">deflateInit2</a>() below for details */
 937
 938 #define <a name="Z_BINARY">Z_BINARY</a>   0
 939 #define <a name="Z_ASCII">Z_ASCII</a>    1
 940 #define <a name="Z_UNKNOWN">Z_UNKNOWN</a>  2
 941 /* Possible values of the <a href="#data_type">data_type</a> field */
 942
 943 #define <a name="Z_DEFLATED">Z_DEFLATED</a>   8
 944 /* The <a href="#deflate">deflate</a> compression method (the only one supported in this version) */
 945
 946 #define <a name="Z_NULL">Z_NULL</a>  0  /* for initializing <a href="#zalloc">zalloc</a>, <a href="#zfree">zfree</a>, <a href="#opaque">opaque</a> */
 947
 948 #define <a name="zlib_version">zlib_version</a> <a href="#zlibVersion">zlibVersion</a>()
 949 /* for compatibility with versions less than 1.0.2 */
 950 </pre>
 951 </font>
 952
 953 <hr>
 954 <a name="Misc"><h2> Misc </h2>
 955  <a href="#deflateInit">deflateInit</a> and <a href="#inflateInit">inflateInit</a> are macros to allow checking the zlib version
 956  and the compiler's view of <a href="#z_stream_s">z_stream</a>.
 957  <p>
 958  Other functions:
 959  <dl>
 960  <font color="Blue"><dt> const char   *  <a name="zError">zError</a>           (int err);</font>
 961  <font color="Blue"><dt> int             <a name="inflateSyncPoint">inflateSyncPoint</a> (<a href="#z_streamp">z_streamp</a> z);</font>
 962  <font color="Blue"><dt> const uLongf *  <a name="get_crc_table">get_crc_table</a>    (void);</font>
 963  </dl>
 964  <hr>
 965  <font size="-1">
 966  Last update: Wed Oct 13 20:42:34 1999<br>
 967  piapi@csie.ntu.edu.tw
 968  </font>
 969
 970 </body>
 971 </html>