include/linux/zlib.h

   1 /* zlib.h -- interface of the 'zlib' general purpose compression library
   2   version 1.1.3, July 9th, 1998
   3
   4   Copyright (C) 1995-1998 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 ftp://ds.internic.net/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 <linux/zconf.h>
  35
  36 #define ZLIB_VERSION "1.1.3"
  37
  38 /*
  39      The 'zlib' compression library provides in-memory compression and
  40   decompression functions, including integrity checks of the uncompressed
  41   data.  This version of the library supports only one compression method
  42   (deflation) but other algorithms will be added later and will have the same
  43   stream interface.
  44
  45      Compression can be done in a single step if the buffers are large
  46   enough (for example if an input file is mmap'ed), or can be done by
  47   repeated calls of the compression function.  In the latter case, the
  48   application must provide more input and/or consume the output
  49   (providing more output space) before each call.
  50
  51      The library also supports reading and writing files in gzip (.gz) format
  52   with an interface similar to that of stdio.
  53
  54      The library does not install any signal handler. The decoder checks
  55   the consistency of the compressed data, so the library should never
  56   crash even in case of corrupted input.
  57 */
  58
  59 struct internal_state;
  60
  61 typedef struct z_stream_s {
  62     Byte    *next_in;   /* next input byte */
  63     uInt     avail_in;  /* number of bytes available at next_in */
  64     uLong    total_in;  /* total nb of input bytes read so far */
  65
  66     Byte    *next_out;  /* next output byte should be put there */
  67     uInt     avail_out; /* remaining free space at next_out */
  68     uLong    total_out; /* total nb of bytes output so far */
  69
  70     char     *msg;      /* last error message, NULL if no error */
  71     struct internal_state *state; /* not visible by applications */
  72
  73     void     *workspace; /* memory allocated for this stream */
  74
  75     int     data_type;  /* best guess about the data type: ascii or binary */
  76     uLong   adler;      /* adler32 value of the uncompressed data */
  77     uLong   reserved;   /* reserved for future use */
  78 } z_stream;
  79
  80 typedef z_stream *z_streamp;
  81
  82 /*
  83    The application must update next_in and avail_in when avail_in has
  84    dropped to zero. It must update next_out and avail_out when avail_out
  85    has dropped to zero. The application must initialize zalloc, zfree and
  86    opaque before calling the init function. All other fields are set by the
  87    compression library and must not be updated by the application.
  88
  89    The opaque value provided by the application will be passed as the first
  90    parameter for calls of zalloc and zfree. This can be useful for custom
  91    memory management. The compression library attaches no meaning to the
  92    opaque value.
  93
  94    zalloc must return NULL if there is not enough memory for the object.
  95    If zlib is used in a multi-threaded application, zalloc and zfree must be
  96    thread safe.
  97
  98    On 16-bit systems, the functions zalloc and zfree must be able to allocate
  99    exactly 65536 bytes, but will not be required to allocate more than this
 100    if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS,
 101    pointers returned by zalloc for objects of exactly 65536 bytes *must*
 102    have their offset normalized to zero. The default allocation function
 103    provided by this library ensures this (see zutil.c). To reduce memory
 104    requirements and avoid any allocation of 64K objects, at the expense of
 105    compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h).
 106
 107    The fields total_in and total_out can be used for statistics or
 108    progress reports. After compression, total_in holds the total size of
 109    the uncompressed data and may be saved for use in the decompressor
 110    (particularly if the decompressor wants to decompress everything in
 111    a single step).
 112 */
 113
 114                         /* constants */
 115
 116 #define Z_NO_FLUSH      0
 117 #define Z_PARTIAL_FLUSH 1 /* will be removed, use Z_SYNC_FLUSH instead */
 118 #define Z_PACKET_FLUSH  2
 119 #define Z_SYNC_FLUSH    3
 120 #define Z_FULL_FLUSH    4
 121 #define Z_FINISH        5
 122 /* Allowed flush values; see deflate() below for details */
 123
 124 #define Z_OK            0
 125 #define Z_STREAM_END    1
 126 #define Z_NEED_DICT     2
 127 #define Z_ERRNO        (-1)
 128 #define Z_STREAM_ERROR (-2)
 129 #define Z_DATA_ERROR   (-3)
 130 #define Z_MEM_ERROR    (-4)
 131 #define Z_BUF_ERROR    (-5)
 132 #define Z_VERSION_ERROR (-6)
 133 /* Return codes for the compression/decompression functions. Negative
 134  * values are errors, positive values are used for special but normal events.
 135  */
 136
 137 #define Z_NO_COMPRESSION         0
 138 #define Z_BEST_SPEED             1
 139 #define Z_BEST_COMPRESSION       9
 140 #define Z_DEFAULT_COMPRESSION  (-1)
 141 /* compression levels */
 142
 143 #define Z_FILTERED            1
 144 #define Z_HUFFMAN_ONLY        2
 145 #define Z_DEFAULT_STRATEGY    0
 146 /* compression strategy; see deflateInit2() below for details */
 147
 148 #define Z_BINARY   0
 149 #define Z_ASCII    1
 150 #define Z_UNKNOWN  2
 151 /* Possible values of the data_type field */
 152
 153 #define Z_DEFLATED   8
 154 /* The deflate compression method (the only one supported in this version) */
 155
 156                         /* basic functions */
 157
 158 extern const char * zlib_zlibVersion (void);
 159 /* The application can compare zlibVersion and ZLIB_VERSION for consistency.
 160    If the first character differs, the library code actually used is
 161    not compatible with the zlib.h header file used by the application.
 162    This check is automatically made by deflateInit and inflateInit.
 163  */
 164
 165 extern int zlib_deflate_workspacesize (void);
 166 /*
 167    Returns the number of bytes that needs to be allocated for a per-
 168    stream workspace.  A pointer to this number of bytes should be
 169    returned in stream->workspace before calling zlib_deflateInit().
 170 */
 171
 172 /*
 173 extern int deflateInit (z_streamp strm, int level);
 174
 175      Initializes the internal stream state for compression. The fields
 176    zalloc, zfree and opaque must be initialized before by the caller.
 177    If zalloc and zfree are set to NULL, deflateInit updates them to
 178    use default allocation functions.
 179
 180      The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
 181    1 gives best speed, 9 gives best compression, 0 gives no compression at
 182    all (the input data is simply copied a block at a time).
 183    Z_DEFAULT_COMPRESSION requests a default compromise between speed and
 184    compression (currently equivalent to level 6).
 185
 186      deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
 187    enough memory, Z_STREAM_ERROR if level is not a valid compression level,
 188    Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible
 189    with the version assumed by the caller (ZLIB_VERSION).
 190    msg is set to null if there is no error message.  deflateInit does not
 191    perform any compression: this will be done by deflate().
 192 */
 193
 194
 195 extern int zlib_deflate (z_streamp strm, int flush);
 196 /*
 197     deflate compresses as much data as possible, and stops when the input
 198   buffer becomes empty or the output buffer becomes full. It may introduce some
 199   output latency (reading input without producing any output) except when
 200   forced to flush.
 201
 202     The detailed semantics are as follows. deflate performs one or both of the
 203   following actions:
 204
 205   - Compress more input starting at next_in and update next_in and avail_in
 206     accordingly. If not all input can be processed (because there is not
 207     enough room in the output buffer), next_in and avail_in are updated and
 208     processing will resume at this point for the next call of deflate().
 209
 210   - Provide more output starting at next_out and update next_out and avail_out
 211     accordingly. This action is forced if the parameter flush is non zero.
 212     Forcing flush frequently degrades the compression ratio, so this parameter
 213     should be set only when necessary (in interactive applications).
 214     Some output may be provided even if flush is not set.
 215
 216   Before the call of deflate(), the application should ensure that at least
 217   one of the actions is possible, by providing more input and/or consuming
 218   more output, and updating avail_in or avail_out accordingly; avail_out
 219   should never be zero before the call. The application can consume the
 220   compressed output when it wants, for example when the output buffer is full
 221   (avail_out == 0), or after each call of deflate(). If deflate returns Z_OK
 222   and with zero avail_out, it must be called again after making room in the
 223   output buffer because there might be more output pending.
 224
 225     If the parameter flush is set to Z_SYNC_FLUSH, all pending output is
 226   flushed to the output buffer and the output is aligned on a byte boundary, so
 227   that the decompressor can get all input data available so far. (In particular
 228   avail_in is zero after the call if enough output space has been provided
 229   before the call.)  Flushing may degrade compression for some compression
 230   algorithms and so it should be used only when necessary.
 231
 232     If flush is set to Z_FULL_FLUSH, all output is flushed as with
 233   Z_SYNC_FLUSH, and the compression state is reset so that decompression can
 234   restart from this point if previous compressed data has been damaged or if
 235   random access is desired. Using Z_FULL_FLUSH too often can seriously degrade
 236   the compression.
 237
 238     If deflate returns with avail_out == 0, this function must be called again
 239   with the same value of the flush parameter and more output space (updated
 240   avail_out), until the flush is complete (deflate returns with non-zero
 241   avail_out).
 242
 243     If the parameter flush is set to Z_FINISH, pending input is processed,
 244   pending output is flushed and deflate returns with Z_STREAM_END if there
 245   was enough output space; if deflate returns with Z_OK, this function must be
 246   called again with Z_FINISH and more output space (updated avail_out) but no
 247   more input data, until it returns with Z_STREAM_END or an error. After
 248   deflate has returned Z_STREAM_END, the only possible operations on the
 249   stream are deflateReset or deflateEnd.
 250
 251     Z_FINISH can be used immediately after deflateInit if all the compression
 252   is to be done in a single step. In this case, avail_out must be at least
 253   0.1% larger than avail_in plus 12 bytes.  If deflate does not return
 254   Z_STREAM_END, then it must be called again as described above.
 255
 256     deflate() sets strm->adler to the adler32 checksum of all input read
 257   so far (that is, total_in bytes).
 258
 259     deflate() may update data_type if it can make a good guess about
 260   the input data type (Z_ASCII or Z_BINARY). In doubt, the data is considered
 261   binary. This field is only for information purposes and does not affect
 262   the compression algorithm in any manner.
 263
 264     deflate() returns Z_OK if some progress has been made (more input
 265   processed or more output produced), Z_STREAM_END if all input has been
 266   consumed and all output has been produced (only when flush is set to
 267   Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
 268   if next_in or next_out was NULL), Z_BUF_ERROR if no progress is possible
 269   (for example avail_in or avail_out was zero).
 270 */
 271
 272
 273 extern int zlib_deflateEnd (z_streamp strm);
 274 /*
 275      All dynamically allocated data structures for this stream are freed.
 276    This function discards any unprocessed input and does not flush any
 277    pending output.
 278
 279      deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
 280    stream state was inconsistent, Z_DATA_ERROR if the stream was freed
 281    prematurely (some input or output was discarded). In the error case,
 282    msg may be set but then points to a static string (which must not be
 283    deallocated).
 284 */
 285
 286
 287 extern int zlib_inflate_workspacesize (void);
 288 /*
 289    Returns the number of bytes that needs to be allocated for a per-
 290    stream workspace.  A pointer to this number of bytes should be
 291    returned in stream->workspace before calling zlib_inflateInit().
 292 */
 293
 294 /*
 295 extern int zlib_inflateInit (z_streamp strm);
 296
 297      Initializes the internal stream state for decompression. The fields
 298    next_in, avail_in, and workspace must be initialized before by
 299    the caller. If next_in is not NULL and avail_in is large enough (the exact
 300    value depends on the compression method), inflateInit determines the
 301    compression method from the zlib header and allocates all data structures
 302    accordingly; otherwise the allocation will be deferred to the first call of
 303    inflate.  If zalloc and zfree are set to NULL, inflateInit updates them to
 304    use default allocation functions.
 305
 306      inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
 307    memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
 308    version assumed by the caller.  msg is set to null if there is no error
 309    message. inflateInit does not perform any decompression apart from reading
 310    the zlib header if present: this will be done by inflate().  (So next_in and
 311    avail_in may be modified, but next_out and avail_out are unchanged.)
 312 */
 313
 314
 315 extern int zlib_inflate (z_streamp strm, int flush);
 316 /*
 317     inflate decompresses as much data as possible, and stops when the input
 318   buffer becomes empty or the output buffer becomes full. It may some
 319   introduce some output latency (reading input without producing any output)
 320   except when forced to flush.
 321
 322   The detailed semantics are as follows. inflate performs one or both of the
 323   following actions:
 324
 325   - Decompress more input starting at next_in and update next_in and avail_in
 326     accordingly. If not all input can be processed (because there is not
 327     enough room in the output buffer), next_in is updated and processing
 328     will resume at this point for the next call of inflate().
 329
 330   - Provide more output starting at next_out and update next_out and avail_out
 331     accordingly.  inflate() provides as much output as possible, until there
 332     is no more input data or no more space in the output buffer (see below
 333     about the flush parameter).
 334
 335   Before the call of inflate(), the application should ensure that at least
 336   one of the actions is possible, by providing more input and/or consuming
 337   more output, and updating the next_* and avail_* values accordingly.
 338   The application can consume the uncompressed output when it wants, for
 339   example when the output buffer is full (avail_out == 0), or after each
 340   call of inflate(). If inflate returns Z_OK and with zero avail_out, it
 341   must be called again after making room in the output buffer because there
 342   might be more output pending.
 343
 344     If the parameter flush is set to Z_SYNC_FLUSH, inflate flushes as much
 345   output as possible to the output buffer. The flushing behavior of inflate is
 346   not specified for values of the flush parameter other than Z_SYNC_FLUSH
 347   and Z_FINISH, but the current implementation actually flushes as much output
 348   as possible anyway.
 349
 350     inflate() should normally be called until it returns Z_STREAM_END or an
 351   error. However if all decompression is to be performed in a single step
 352   (a single call of inflate), the parameter flush should be set to
 353   Z_FINISH. In this case all pending input is processed and all pending
 354   output is flushed; avail_out must be large enough to hold all the
 355   uncompressed data. (The size of the uncompressed data may have been saved
 356   by the compressor for this purpose.) The next operation on this stream must
 357   be inflateEnd to deallocate the decompression state. The use of Z_FINISH
 358   is never required, but can be used to inform inflate that a faster routine
 359   may be used for the single inflate() call.
 360
 361      If a preset dictionary is needed at this point (see inflateSetDictionary
 362   below), inflate sets strm-adler to the adler32 checksum of the
 363   dictionary chosen by the compressor and returns Z_NEED_DICT; otherwise
 364   it sets strm->adler to the adler32 checksum of all output produced
 365   so far (that is, total_out bytes) and returns Z_OK, Z_STREAM_END or
 366   an error code as described below. At the end of the stream, inflate()
 367   checks that its computed adler32 checksum is equal to that saved by the
 368   compressor and returns Z_STREAM_END only if the checksum is correct.
 369
 370     inflate() returns Z_OK if some progress has been made (more input processed
 371   or more output produced), Z_STREAM_END if the end of the compressed data has
 372   been reached and all uncompressed output has been produced, Z_NEED_DICT if a
 373   preset dictionary is needed at this point, Z_DATA_ERROR if the input data was
 374   corrupted (input stream not conforming to the zlib format or incorrect
 375   adler32 checksum), Z_STREAM_ERROR if the stream structure was inconsistent
 376   (for example if next_in or next_out was NULL), Z_MEM_ERROR if there was not
 377   enough memory, Z_BUF_ERROR if no progress is possible or if there was not
 378   enough room in the output buffer when Z_FINISH is used. In the Z_DATA_ERROR
 379   case, the application may then call inflateSync to look for a good
 380   compression block.
 381 */
 382
 383
 384 extern int zlib_inflateEnd (z_streamp strm);
 385 /*
 386      All dynamically allocated data structures for this stream are freed.
 387    This function discards any unprocessed input and does not flush any
 388    pending output.
 389
 390      inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
 391    was inconsistent. In the error case, msg may be set but then points to a
 392    static string (which must not be deallocated).
 393 */
 394
 395                         /* Advanced functions */
 396
 397 /*
 398     The following functions are needed only in some special applications.
 399 */
 400
 401 /*
 402 extern int deflateInit2 (z_streamp strm,
 403                                      int  level,
 404                                      int  method,
 405                                      int  windowBits,
 406                                      int  memLevel,
 407                                      int  strategy);
 408
 409      This is another version of deflateInit with more compression options. The
 410    fields next_in, zalloc, zfree and opaque must be initialized before by
 411    the caller.
 412
 413      The method parameter is the compression method. It must be Z_DEFLATED in
 414    this version of the library.
 415
 416      The windowBits parameter is the base two logarithm of the window size
 417    (the size of the history buffer).  It should be in the range 8..15 for this
 418    version of the library. Larger values of this parameter result in better
 419    compression at the expense of memory usage. The default value is 15 if
 420    deflateInit is used instead.
 421
 422      The memLevel parameter specifies how much memory should be allocated
 423    for the internal compression state. memLevel=1 uses minimum memory but
 424    is slow and reduces compression ratio; memLevel=9 uses maximum memory
 425    for optimal speed. The default value is 8. See zconf.h for total memory
 426    usage as a function of windowBits and memLevel.
 427
 428      The strategy parameter is used to tune the compression algorithm. Use the
 429    value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a
 430    filter (or predictor), or Z_HUFFMAN_ONLY to force Huffman encoding only (no
 431    string match).  Filtered data consists mostly of small values with a
 432    somewhat random distribution. In this case, the compression algorithm is
 433    tuned to compress them better. The effect of Z_FILTERED is to force more
 434    Huffman coding and less string matching; it is somewhat intermediate
 435    between Z_DEFAULT and Z_HUFFMAN_ONLY. The strategy parameter only affects
 436    the compression ratio but not the correctness of the compressed output even
 437    if it is not set appropriately.
 438
 439       deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
 440    memory, Z_STREAM_ERROR if a parameter is invalid (such as an invalid
 441    method). msg is set to null if there is no error message.  deflateInit2 does
 442    not perform any compression: this will be done by deflate().
 443 */
 444
 445 #if 0
 446 extern int zlib_deflateSetDictionary (z_streamp strm,
 447                                                      const Byte *dictionary,
 448                                                      uInt  dictLength);
 449 #endif
 450 /*
 451      Initializes the compression dictionary from the given byte sequence
 452    without producing any compressed output. This function must be called
 453    immediately after deflateInit, deflateInit2 or deflateReset, before any
 454    call of deflate. The compressor and decompressor must use exactly the same
 455    dictionary (see inflateSetDictionary).
 456
 457      The dictionary should consist of strings (byte sequences) that are likely
 458    to be encountered later in the data to be compressed, with the most commonly
 459    used strings preferably put towards the end of the dictionary. Using a
 460    dictionary is most useful when the data to be compressed is short and can be
 461    predicted with good accuracy; the data can then be compressed better than
 462    with the default empty dictionary.
 463
 464      Depending on the size of the compression data structures selected by
 465    deflateInit or deflateInit2, a part of the dictionary may in effect be
 466    discarded, for example if the dictionary is larger than the window size in
 467    deflate or deflate2. Thus the strings most likely to be useful should be
 468    put at the end of the dictionary, not at the front.
 469
 470      Upon return of this function, strm->adler is set to the Adler32 value
 471    of the dictionary; the decompressor may later use this value to determine
 472    which dictionary has been used by the compressor. (The Adler32 value
 473    applies to the whole dictionary even if only a subset of the dictionary is
 474    actually used by the compressor.)
 475
 476      deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
 477    parameter is invalid (such as NULL dictionary) or the stream state is
 478    inconsistent (for example if deflate has already been called for this stream
 479    or if the compression method is bsort). deflateSetDictionary does not
 480    perform any compression: this will be done by deflate().
 481 */
 482
 483 #if 0
 484 extern int zlib_deflateCopy (z_streamp dest, z_streamp source);
 485 #endif
 486
 487 /*
 488      Sets the destination stream as a complete copy of the source stream.
 489
 490      This function can be useful when several compression strategies will be
 491    tried, for example when there are several ways of pre-processing the input
 492    data with a filter. The streams that will be discarded should then be freed
 493    by calling deflateEnd.  Note that deflateCopy duplicates the internal
 494    compression state which can be quite large, so this strategy is slow and
 495    can consume lots of memory.
 496
 497      deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
 498    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
 499    (such as zalloc being NULL). msg is left unchanged in both source and
 500    destination.
 501 */
 502
 503 extern int zlib_deflateReset (z_streamp strm);
 504 /*
 505      This function is equivalent to deflateEnd followed by deflateInit,
 506    but does not free and reallocate all the internal compression state.
 507    The stream will keep the same compression level and any other attributes
 508    that may have been set by deflateInit2.
 509
 510       deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
 511    stream state was inconsistent (such as zalloc or state being NULL).
 512 */
 513
 514 static inline unsigned long deflateBound(unsigned long s)
 515 {
 516         return s + ((s + 7) >> 3) + ((s + 63) >> 6) + 11;
 517 }
 518
 519 #if 0
 520 extern int zlib_deflateParams (z_streamp strm, int level, int strategy);
 521 #endif
 522 /*
 523      Dynamically update the compression level and compression strategy.  The
 524    interpretation of level and strategy is as in deflateInit2.  This can be
 525    used to switch between compression and straight copy of the input data, or
 526    to switch to a different kind of input data requiring a different
 527    strategy. If the compression level is changed, the input available so far
 528    is compressed with the old level (and may be flushed); the new level will
 529    take effect only at the next call of deflate().
 530
 531      Before the call of deflateParams, the stream state must be set as for
 532    a call of deflate(), since the currently available input may have to
 533    be compressed and flushed. In particular, strm->avail_out must be non-zero.
 534
 535      deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source
 536    stream state was inconsistent or if a parameter was invalid, Z_BUF_ERROR
 537    if strm->avail_out was zero.
 538 */
 539
 540 /*
 541 extern int inflateInit2 (z_streamp strm, int  windowBits);
 542
 543      This is another version of inflateInit with an extra parameter. The
 544    fields next_in, avail_in, zalloc, zfree and opaque must be initialized
 545    before by the caller.
 546
 547      The windowBits parameter is the base two logarithm of the maximum window
 548    size (the size of the history buffer).  It should be in the range 8..15 for
 549    this version of the library. The default value is 15 if inflateInit is used
 550    instead. If a compressed stream with a larger window size is given as
 551    input, inflate() will return with the error code Z_DATA_ERROR instead of
 552    trying to allocate a larger window.
 553
 554       inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
 555    memory, Z_STREAM_ERROR if a parameter is invalid (such as a negative
 556    memLevel). msg is set to null if there is no error message.  inflateInit2
 557    does not perform any decompression apart from reading the zlib header if
 558    present: this will be done by inflate(). (So next_in and avail_in may be
 559    modified, but next_out and avail_out are unchanged.)
 560 */
 561
 562 extern int zlib_inflateSetDictionary (z_streamp strm,
 563                                                      const Byte *dictionary,
 564                                                      uInt  dictLength);
 565 /*
 566      Initializes the decompression dictionary from the given uncompressed byte
 567    sequence. This function must be called immediately after a call of inflate
 568    if this call returned Z_NEED_DICT. The dictionary chosen by the compressor
 569    can be determined from the Adler32 value returned by this call of
 570    inflate. The compressor and decompressor must use exactly the same
 571    dictionary (see deflateSetDictionary).
 572
 573      inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
 574    parameter is invalid (such as NULL dictionary) or the stream state is
 575    inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the
 576    expected one (incorrect Adler32 value). inflateSetDictionary does not
 577    perform any decompression: this will be done by subsequent calls of
 578    inflate().
 579 */
 580
 581 #if 0
 582 extern int zlib_inflateSync (z_streamp strm);
 583 #endif
 584 /*
 585     Skips invalid compressed data until a full flush point (see above the
 586   description of deflate with Z_FULL_FLUSH) can be found, or until all
 587   available input is skipped. No output is provided.
 588
 589     inflateSync returns Z_OK if a full flush point has been found, Z_BUF_ERROR
 590   if no more input was provided, Z_DATA_ERROR if no flush point has been found,
 591   or Z_STREAM_ERROR if the stream structure was inconsistent. In the success
 592   case, the application may save the current current value of total_in which
 593   indicates where valid compressed data was found. In the error case, the
 594   application may repeatedly call inflateSync, providing more input each time,
 595   until success or end of the input data.
 596 */
 597
 598 extern int zlib_inflateReset (z_streamp strm);
 599 /*
 600      This function is equivalent to inflateEnd followed by inflateInit,
 601    but does not free and reallocate all the internal decompression state.
 602    The stream will keep attributes that may have been set by inflateInit2.
 603
 604       inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
 605    stream state was inconsistent (such as zalloc or state being NULL).
 606 */
 607
 608 extern int zlib_inflateIncomp (z_stream *strm);
 609 /*
 610      This function adds the data at next_in (avail_in bytes) to the output
 611    history without performing any output.  There must be no pending output,
 612    and the decompressor must be expecting to see the start of a block.
 613    Calling this function is equivalent to decompressing a stored block
 614    containing the data at next_in (except that the data is not output).
 615 */
 616
 617                         /* various hacks, don't look :) */
 618
 619 /* deflateInit and inflateInit are macros to allow checking the zlib version
 620  * and the compiler's view of z_stream:
 621  */
 622 extern int zlib_deflateInit_ (z_streamp strm, int level,
 623                                      const char *version, int stream_size);
 624 extern int zlib_inflateInit_ (z_streamp strm,
 625                                      const char *version, int stream_size);
 626 extern int zlib_deflateInit2_ (z_streamp strm, int  level, int  method,
 627                                       int windowBits, int memLevel,
 628                                       int strategy, const char *version,
 629                                       int stream_size);
 630 extern int zlib_inflateInit2_ (z_streamp strm, int  windowBits,
 631                                       const char *version, int stream_size);
 632 #define zlib_deflateInit(strm, level) \
 633         zlib_deflateInit_((strm), (level), ZLIB_VERSION, sizeof(z_stream))
 634 #define zlib_inflateInit(strm) \
 635         zlib_inflateInit_((strm), ZLIB_VERSION, sizeof(z_stream))
 636 #define zlib_deflateInit2(strm, level, method, windowBits, memLevel, strategy) \
 637         zlib_deflateInit2_((strm),(level),(method),(windowBits),(memLevel),\
 638                       (strategy), ZLIB_VERSION, sizeof(z_stream))
 639 #define zlib_inflateInit2(strm, windowBits) \
 640         zlib_inflateInit2_((strm), (windowBits), ZLIB_VERSION, sizeof(z_stream))
 641
 642
 643 #if !defined(_Z_UTIL_H) && !defined(NO_DUMMY_DECL)
 644     struct internal_state {int dummy;}; /* hack for buggy compilers */
 645 #endif
 646
 647 extern const char  * zlib_zError           (int err);
 648 #if 0
 649 extern int           zlib_inflateSyncPoint (z_streamp z);
 650 #endif
 651 extern const uLong * zlib_get_crc_table    (void);
 652
 653 #endif /* _ZLIB_H */