include/linux/zlib.h

   1 /* zlib.h -- interface of the 'zlib' general purpose compression library
   2
   3   Copyright (C) 1995-2005 Jean-loup Gailly and Mark Adler
   4
   5   This software is provided 'as-is', without any express or implied
   6   warranty.  In no event will the authors be held liable for any damages
   7   arising from the use of this software.
   8
   9   Permission is granted to anyone to use this software for any purpose,
  10   including commercial applications, and to alter it and redistribute it
  11   freely, subject to the following restrictions:
  12
  13   1. The origin of this software must not be misrepresented; you must not
  14      claim that you wrote the original software. If you use this software
  15      in a product, an acknowledgment in the product documentation would be
  16      appreciated but is not required.
  17   2. Altered source versions must be plainly marked as such, and must not be
  18      misrepresented as being the original software.
  19   3. This notice may not be removed or altered from any source distribution.
  20
  21   Jean-loup Gailly        Mark Adler
  22   jloup@gzip.org          madler@alumni.caltech.edu
  23
  24
  25   The data format used by the zlib library is described by RFCs (Request for
  26   Comments) 1950 to 1952 in the files http://www.ietf.org/rfc/rfc1950.txt
  27   (zlib format), rfc1951.txt (deflate format) and rfc1952.txt (gzip format).
  28 */
  29
  30 #ifndef _ZLIB_H
  31 #define _ZLIB_H
  32
  33 #include <linux/zconf.h>
  34
  35 /* zlib deflate based on ZLIB_VERSION "1.1.3" */
  36 /* zlib inflate based on ZLIB_VERSION "1.2.3" */
  37
  38 /*
  39   This is a modified version of zlib for use inside the Linux kernel.
  40   The main changes are to perform all memory allocation in advance.
  41
  42   Inflation Changes:
  43     * Z_PACKET_FLUSH is added and used by ppp_deflate. Before returning
  44       this checks there is no more input data available and the next data
  45       is a STORED block. It also resets the mode to be read for the next
  46       data, all as per PPP requirements.
  47     * Addition of zlib_inflateIncomp which copies incompressible data into
  48       the history window and adjusts the accoutning without calling
  49       zlib_inflate itself to inflate the data.
  50 */
  51
  52 /*
  53      The 'zlib' compression library provides in-memory compression and
  54   decompression functions, including integrity checks of the uncompressed
  55   data.  This version of the library supports only one compression method
  56   (deflation) but other algorithms will be added later and will have the same
  57   stream interface.
  58
  59      Compression can be done in a single step if the buffers are large
  60   enough (for example if an input file is mmap'ed), or can be done by
  61   repeated calls of the compression function.  In the latter case, the
  62   application must provide more input and/or consume the output
  63   (providing more output space) before each call.
  64
  65      The compressed data format used by default by the in-memory functions is
  66   the zlib format, which is a zlib wrapper documented in RFC 1950, wrapped
  67   around a deflate stream, which is itself documented in RFC 1951.
  68
  69      The library also supports reading and writing files in gzip (.gz) format
  70   with an interface similar to that of stdio.
  71
  72      The zlib format was designed to be compact and fast for use in memory
  73   and on communications channels.  The gzip format was designed for single-
  74   file compression on file systems, has a larger header than zlib to maintain
  75   directory information, and uses a different, slower check method than zlib.
  76
  77      The library does not install any signal handler. The decoder checks
  78   the consistency of the compressed data, so the library should never
  79   crash even in case of corrupted input.
  80 */
  81
  82 struct internal_state;
  83
  84 typedef struct z_stream_s {
  85     Byte    *next_in;   /* next input byte */
  86     uInt     avail_in;  /* number of bytes available at next_in */
  87     uLong    total_in;  /* total nb of input bytes read so far */
  88
  89     Byte    *next_out;  /* next output byte should be put there */
  90     uInt     avail_out; /* remaining free space at next_out */
  91     uLong    total_out; /* total nb of bytes output so far */
  92
  93     char     *msg;      /* last error message, NULL if no error */
  94     struct internal_state *state; /* not visible by applications */
  95
  96     void     *workspace; /* memory allocated for this stream */
  97
  98     int     data_type;  /* best guess about the data type: ascii or binary */
  99     uLong   adler;      /* adler32 value of the uncompressed data */
 100     uLong   reserved;   /* reserved for future use */
 101 } z_stream;
 102
 103 typedef z_stream *z_streamp;
 104
 105 /*
 106    The application must update next_in and avail_in when avail_in has
 107    dropped to zero. It must update next_out and avail_out when avail_out
 108    has dropped to zero. The application must initialize zalloc, zfree and
 109    opaque before calling the init function. All other fields are set by the
 110    compression library and must not be updated by the application.
 111
 112    The opaque value provided by the application will be passed as the first
 113    parameter for calls of zalloc and zfree. This can be useful for custom
 114    memory management. The compression library attaches no meaning to the
 115    opaque value.
 116
 117    zalloc must return NULL if there is not enough memory for the object.
 118    If zlib is used in a multi-threaded application, zalloc and zfree must be
 119    thread safe.
 120
 121    On 16-bit systems, the functions zalloc and zfree must be able to allocate
 122    exactly 65536 bytes, but will not be required to allocate more than this
 123    if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS,
 124    pointers returned by zalloc for objects of exactly 65536 bytes *must*
 125    have their offset normalized to zero. The default allocation function
 126    provided by this library ensures this (see zutil.c). To reduce memory
 127    requirements and avoid any allocation of 64K objects, at the expense of
 128    compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h).
 129
 130    The fields total_in and total_out can be used for statistics or
 131    progress reports. After compression, total_in holds the total size of
 132    the uncompressed data and may be saved for use in the decompressor
 133    (particularly if the decompressor wants to decompress everything in
 134    a single step).
 135 */
 136
 137                         /* constants */
 138
 139 #define Z_NO_FLUSH      0
 140 #define Z_PARTIAL_FLUSH 1 /* will be removed, use Z_SYNC_FLUSH instead */
 141 #define Z_PACKET_FLUSH  2
 142 #define Z_SYNC_FLUSH    3
 143 #define Z_FULL_FLUSH    4
 144 #define Z_FINISH        5
 145 #define Z_BLOCK         6 /* Only for inflate at present */
 146 /* Allowed flush values; see deflate() and inflate() below for details */
 147
 148 #define Z_OK            0
 149 #define Z_STREAM_END    1
 150 #define Z_NEED_DICT     2
 151 #define Z_ERRNO        (-1)
 152 #define Z_STREAM_ERROR (-2)
 153 #define Z_DATA_ERROR   (-3)
 154 #define Z_MEM_ERROR    (-4)
 155 #define Z_BUF_ERROR    (-5)
 156 #define Z_VERSION_ERROR (-6)
 157 /* Return codes for the compression/decompression functions. Negative
 158  * values are errors, positive values are used for special but normal events.
 159  */
 160
 161 #define Z_NO_COMPRESSION         0
 162 #define Z_BEST_SPEED             1
 163 #define Z_BEST_COMPRESSION       9
 164 #define Z_DEFAULT_COMPRESSION  (-1)
 165 /* compression levels */
 166
 167 #define Z_FILTERED            1
 168 #define Z_HUFFMAN_ONLY        2
 169 #define Z_DEFAULT_STRATEGY    0
 170 /* compression strategy; see deflateInit2() below for details */
 171
 172 #define Z_BINARY   0
 173 #define Z_ASCII    1
 174 #define Z_UNKNOWN  2
 175 /* Possible values of the data_type field */
 176
 177 #define Z_DEFLATED   8
 178 /* The deflate compression method (the only one supported in this version) */
 179
 180                         /* basic functions */
 181
 182 extern int zlib_deflate_workspacesize (void);
 183 /*
 184    Returns the number of bytes that needs to be allocated for a per-
 185    stream workspace.  A pointer to this number of bytes should be
 186    returned in stream->workspace before calling zlib_deflateInit().
 187 */
 188
 189 /*
 190 extern int deflateInit (z_streamp strm, int level);
 191
 192      Initializes the internal stream state for compression. The fields
 193    zalloc, zfree and opaque must be initialized before by the caller.
 194    If zalloc and zfree are set to NULL, deflateInit updates them to
 195    use default allocation functions.
 196
 197      The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
 198    1 gives best speed, 9 gives best compression, 0 gives no compression at
 199    all (the input data is simply copied a block at a time).
 200    Z_DEFAULT_COMPRESSION requests a default compromise between speed and
 201    compression (currently equivalent to level 6).
 202
 203      deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
 204    enough memory, Z_STREAM_ERROR if level is not a valid compression level,
 205    Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible
 206    with the version assumed by the caller (ZLIB_VERSION).
 207    msg is set to null if there is no error message.  deflateInit does not
 208    perform any compression: this will be done by deflate().
 209 */
 210
 211
 212 extern int zlib_deflate (z_streamp strm, int flush);
 213 /*
 214     deflate compresses as much data as possible, and stops when the input
 215   buffer becomes empty or the output buffer becomes full. It may introduce some
 216   output latency (reading input without producing any output) except when
 217   forced to flush.
 218
 219     The detailed semantics are as follows. deflate performs one or both of the
 220   following actions:
 221
 222   - Compress more input starting at next_in and update next_in and avail_in
 223     accordingly. If not all input can be processed (because there is not
 224     enough room in the output buffer), next_in and avail_in are updated and
 225     processing will resume at this point for the next call of deflate().
 226
 227   - Provide more output starting at next_out and update next_out and avail_out
 228     accordingly. This action is forced if the parameter flush is non zero.
 229     Forcing flush frequently degrades the compression ratio, so this parameter
 230     should be set only when necessary (in interactive applications).
 231     Some output may be provided even if flush is not set.
 232
 233   Before the call of deflate(), the application should ensure that at least
 234   one of the actions is possible, by providing more input and/or consuming
 235   more output, and updating avail_in or avail_out accordingly; avail_out
 236   should never be zero before the call. The application can consume the
 237   compressed output when it wants, for example when the output buffer is full
 238   (avail_out == 0), or after each call of deflate(). If deflate returns Z_OK
 239   and with zero avail_out, it must be called again after making room in the
 240   output buffer because there might be more output pending.
 241
 242     If the parameter flush is set to Z_SYNC_FLUSH, all pending output is
 243   flushed to the output buffer and the output is aligned on a byte boundary, so
 244   that the decompressor can get all input data available so far. (In particular
 245   avail_in is zero after the call if enough output space has been provided
 246   before the call.)  Flushing may degrade compression for some compression
 247   algorithms and so it should be used only when necessary.
 248
 249     If flush is set to Z_FULL_FLUSH, all output is flushed as with
 250   Z_SYNC_FLUSH, and the compression state is reset so that decompression can
 251   restart from this point if previous compressed data has been damaged or if
 252   random access is desired. Using Z_FULL_FLUSH too often can seriously degrade
 253   the compression.
 254
 255     If deflate returns with avail_out == 0, this function must be called again
 256   with the same value of the flush parameter and more output space (updated
 257   avail_out), until the flush is complete (deflate returns with non-zero
 258   avail_out).
 259
 260     If the parameter flush is set to Z_FINISH, pending input is processed,
 261   pending output is flushed and deflate returns with Z_STREAM_END if there
 262   was enough output space; if deflate returns with Z_OK, this function must be
 263   called again with Z_FINISH and more output space (updated avail_out) but no
 264   more input data, until it returns with Z_STREAM_END or an error. After
 265   deflate has returned Z_STREAM_END, the only possible operations on the
 266   stream are deflateReset or deflateEnd.
 267
 268     Z_FINISH can be used immediately after deflateInit if all the compression
 269   is to be done in a single step. In this case, avail_out must be at least
 270   0.1% larger than avail_in plus 12 bytes.  If deflate does not return
 271   Z_STREAM_END, then it must be called again as described above.
 272
 273     deflate() sets strm->adler to the adler32 checksum of all input read
 274   so far (that is, total_in bytes).
 275
 276     deflate() may update data_type if it can make a good guess about
 277   the input data type (Z_ASCII or Z_BINARY). In doubt, the data is considered
 278   binary. This field is only for information purposes and does not affect
 279   the compression algorithm in any manner.
 280
 281     deflate() returns Z_OK if some progress has been made (more input
 282   processed or more output produced), Z_STREAM_END if all input has been
 283   consumed and all output has been produced (only when flush is set to
 284   Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
 285   if next_in or next_out was NULL), Z_BUF_ERROR if no progress is possible
 286   (for example avail_in or avail_out was zero).
 287 */
 288
 289
 290 extern int zlib_deflateEnd (z_streamp strm);
 291 /*
 292      All dynamically allocated data structures for this stream are freed.
 293    This function discards any unprocessed input and does not flush any
 294    pending output.
 295
 296      deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
 297    stream state was inconsistent, Z_DATA_ERROR if the stream was freed
 298    prematurely (some input or output was discarded). In the error case,
 299    msg may be set but then points to a static string (which must not be
 300    deallocated).
 301 */
 302
 303
 304 extern int zlib_inflate_workspacesize (void);
 305 /*
 306    Returns the number of bytes that needs to be allocated for a per-
 307    stream workspace.  A pointer to this number of bytes should be
 308    returned in stream->workspace before calling zlib_inflateInit().
 309 */
 310
 311 /*
 312 extern int zlib_inflateInit (z_streamp strm);
 313
 314      Initializes the internal stream state for decompression. The fields
 315    next_in, avail_in, and workspace must be initialized before by
 316    the caller. If next_in is not NULL and avail_in is large enough (the exact
 317    value depends on the compression method), inflateInit determines the
 318    compression method from the zlib header and allocates all data structures
 319    accordingly; otherwise the allocation will be deferred to the first call of
 320    inflate.  If zalloc and zfree are set to NULL, inflateInit updates them to
 321    use default allocation functions.
 322
 323      inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
 324    memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
 325    version assumed by the caller.  msg is set to null if there is no error
 326    message. inflateInit does not perform any decompression apart from reading
 327    the zlib header if present: this will be done by inflate().  (So next_in and
 328    avail_in may be modified, but next_out and avail_out are unchanged.)
 329 */
 330
 331
 332 extern int zlib_inflate (z_streamp strm, int flush);
 333 /*
 334     inflate decompresses as much data as possible, and stops when the input
 335   buffer becomes empty or the output buffer becomes full. It may introduce
 336   some output latency (reading input without producing any output) except when
 337   forced to flush.
 338
 339   The detailed semantics are as follows. inflate performs one or both of the
 340   following actions:
 341
 342   - Decompress more input starting at next_in and update next_in and avail_in
 343     accordingly. If not all input can be processed (because there is not
 344     enough room in the output buffer), next_in is updated and processing
 345     will resume at this point for the next call of inflate().
 346
 347   - Provide more output starting at next_out and update next_out and avail_out
 348     accordingly.  inflate() provides as much output as possible, until there
 349     is no more input data or no more space in the output buffer (see below
 350     about the flush parameter).
 351
 352   Before the call of inflate(), the application should ensure that at least
 353   one of the actions is possible, by providing more input and/or consuming
 354   more output, and updating the next_* and avail_* values accordingly.
 355   The application can consume the uncompressed output when it wants, for
 356   example when the output buffer is full (avail_out == 0), or after each
 357   call of inflate(). If inflate returns Z_OK and with zero avail_out, it
 358   must be called again after making room in the output buffer because there
 359   might be more output pending.
 360
 361     The flush parameter of inflate() can be Z_NO_FLUSH, Z_SYNC_FLUSH,
 362   Z_FINISH, or Z_BLOCK. Z_SYNC_FLUSH requests that inflate() flush as much
 363   output as possible to the output buffer. Z_BLOCK requests that inflate() stop
 364   if and when it gets to the next deflate block boundary. When decoding the
 365   zlib or gzip format, this will cause inflate() to return immediately after
 366   the header and before the first block. When doing a raw inflate, inflate()
 367   will go ahead and process the first block, and will return when it gets to
 368   the end of that block, or when it runs out of data.
 369
 370     The Z_BLOCK option assists in appending to or combining deflate streams.
 371   Also to assist in this, on return inflate() will set strm->data_type to the
 372   number of unused bits in the last byte taken from strm->next_in, plus 64
 373   if inflate() is currently decoding the last block in the deflate stream,
 374   plus 128 if inflate() returned immediately after decoding an end-of-block
 375   code or decoding the complete header up to just before the first byte of the
 376   deflate stream. The end-of-block will not be indicated until all of the
 377   uncompressed data from that block has been written to strm->next_out.  The
 378   number of unused bits may in general be greater than seven, except when
 379   bit 7 of data_type is set, in which case the number of unused bits will be
 380   less than eight.
 381
 382     inflate() should normally be called until it returns Z_STREAM_END or an
 383   error. However if all decompression is to be performed in a single step
 384   (a single call of inflate), the parameter flush should be set to
 385   Z_FINISH. In this case all pending input is processed and all pending
 386   output is flushed; avail_out must be large enough to hold all the
 387   uncompressed data. (The size of the uncompressed data may have been saved
 388   by the compressor for this purpose.) The next operation on this stream must
 389   be inflateEnd to deallocate the decompression state. The use of Z_FINISH
 390   is never required, but can be used to inform inflate that a faster approach
 391   may be used for the single inflate() call.
 392
 393      In this implementation, inflate() always flushes as much output as
 394   possible to the output buffer, and always uses the faster approach on the
 395   first call. So the only effect of the flush parameter in this implementation
 396   is on the return value of inflate(), as noted below, or when it returns early
 397   because Z_BLOCK is used.
 398
 399      If a preset dictionary is needed after this call (see inflateSetDictionary
 400   below), inflate sets strm->adler to the adler32 checksum of the dictionary
 401   chosen by the compressor and returns Z_NEED_DICT; otherwise it sets
 402   strm->adler to the adler32 checksum of all output produced so far (that is,
 403   total_out bytes) and returns Z_OK, Z_STREAM_END or an error code as described
 404   below. At the end of the stream, inflate() checks that its computed adler32
 405   checksum is equal to that saved by the compressor and returns Z_STREAM_END
 406   only if the checksum is correct.
 407
 408     inflate() will decompress and check either zlib-wrapped or gzip-wrapped
 409   deflate data.  The header type is detected automatically.  Any information
 410   contained in the gzip header is not retained, so applications that need that
 411   information should instead use raw inflate, see inflateInit2() below, or
 412   inflateBack() and perform their own processing of the gzip header and
 413   trailer.
 414
 415     inflate() returns Z_OK if some progress has been made (more input processed
 416   or more output produced), Z_STREAM_END if the end of the compressed data has
 417   been reached and all uncompressed output has been produced, Z_NEED_DICT if a
 418   preset dictionary is needed at this point, Z_DATA_ERROR if the input data was
 419   corrupted (input stream not conforming to the zlib format or incorrect check
 420   value), Z_STREAM_ERROR if the stream structure was inconsistent (for example
 421   if next_in or next_out was NULL), Z_MEM_ERROR if there was not enough memory,
 422   Z_BUF_ERROR if no progress is possible or if there was not enough room in the
 423   output buffer when Z_FINISH is used. Note that Z_BUF_ERROR is not fatal, and
 424   inflate() can be called again with more input and more output space to
 425   continue decompressing. If Z_DATA_ERROR is returned, the application may then
 426   call inflateSync() to look for a good compression block if a partial recovery
 427   of the data is desired.
 428 */
 429
 430
 431 extern int zlib_inflateEnd (z_streamp strm);
 432 /*
 433      All dynamically allocated data structures for this stream are freed.
 434    This function discards any unprocessed input and does not flush any
 435    pending output.
 436
 437      inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
 438    was inconsistent. In the error case, msg may be set but then points to a
 439    static string (which must not be deallocated).
 440 */
 441
 442                         /* Advanced functions */
 443
 444 /*
 445     The following functions are needed only in some special applications.
 446 */
 447
 448 /*
 449 extern int deflateInit2 (z_streamp strm,
 450                                      int  level,
 451                                      int  method,
 452                                      int  windowBits,
 453                                      int  memLevel,
 454                                      int  strategy);
 455
 456      This is another version of deflateInit with more compression options. The
 457    fields next_in, zalloc, zfree and opaque must be initialized before by
 458    the caller.
 459
 460      The method parameter is the compression method. It must be Z_DEFLATED in
 461    this version of the library.
 462
 463      The windowBits parameter is the base two logarithm of the window size
 464    (the size of the history buffer).  It should be in the range 8..15 for this
 465    version of the library. Larger values of this parameter result in better
 466    compression at the expense of memory usage. The default value is 15 if
 467    deflateInit is used instead.
 468
 469      The memLevel parameter specifies how much memory should be allocated
 470    for the internal compression state. memLevel=1 uses minimum memory but
 471    is slow and reduces compression ratio; memLevel=9 uses maximum memory
 472    for optimal speed. The default value is 8. See zconf.h for total memory
 473    usage as a function of windowBits and memLevel.
 474
 475      The strategy parameter is used to tune the compression algorithm. Use the
 476    value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a
 477    filter (or predictor), or Z_HUFFMAN_ONLY to force Huffman encoding only (no
 478    string match).  Filtered data consists mostly of small values with a
 479    somewhat random distribution. In this case, the compression algorithm is
 480    tuned to compress them better. The effect of Z_FILTERED is to force more
 481    Huffman coding and less string matching; it is somewhat intermediate
 482    between Z_DEFAULT and Z_HUFFMAN_ONLY. The strategy parameter only affects
 483    the compression ratio but not the correctness of the compressed output even
 484    if it is not set appropriately.
 485
 486       deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
 487    memory, Z_STREAM_ERROR if a parameter is invalid (such as an invalid
 488    method). msg is set to null if there is no error message.  deflateInit2 does
 489    not perform any compression: this will be done by deflate().
 490 */
 491
 492 #if 0
 493 extern int zlib_deflateSetDictionary (z_streamp strm,
 494                                                      const Byte *dictionary,
 495                                                      uInt  dictLength);
 496 #endif
 497 /*
 498      Initializes the compression dictionary from the given byte sequence
 499    without producing any compressed output. This function must be called
 500    immediately after deflateInit, deflateInit2 or deflateReset, before any
 501    call of deflate. The compressor and decompressor must use exactly the same
 502    dictionary (see inflateSetDictionary).
 503
 504      The dictionary should consist of strings (byte sequences) that are likely
 505    to be encountered later in the data to be compressed, with the most commonly
 506    used strings preferably put towards the end of the dictionary. Using a
 507    dictionary is most useful when the data to be compressed is short and can be
 508    predicted with good accuracy; the data can then be compressed better than
 509    with the default empty dictionary.
 510
 511      Depending on the size of the compression data structures selected by
 512    deflateInit or deflateInit2, a part of the dictionary may in effect be
 513    discarded, for example if the dictionary is larger than the window size in
 514    deflate or deflate2. Thus the strings most likely to be useful should be
 515    put at the end of the dictionary, not at the front.
 516
 517      Upon return of this function, strm->adler is set to the Adler32 value
 518    of the dictionary; the decompressor may later use this value to determine
 519    which dictionary has been used by the compressor. (The Adler32 value
 520    applies to the whole dictionary even if only a subset of the dictionary is
 521    actually used by the compressor.)
 522
 523      deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
 524    parameter is invalid (such as NULL dictionary) or the stream state is
 525    inconsistent (for example if deflate has already been called for this stream
 526    or if the compression method is bsort). deflateSetDictionary does not
 527    perform any compression: this will be done by deflate().
 528 */
 529
 530 #if 0
 531 extern int zlib_deflateCopy (z_streamp dest, z_streamp source);
 532 #endif
 533
 534 /*
 535      Sets the destination stream as a complete copy of the source stream.
 536
 537      This function can be useful when several compression strategies will be
 538    tried, for example when there are several ways of pre-processing the input
 539    data with a filter. The streams that will be discarded should then be freed
 540    by calling deflateEnd.  Note that deflateCopy duplicates the internal
 541    compression state which can be quite large, so this strategy is slow and
 542    can consume lots of memory.
 543
 544      deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
 545    enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
 546    (such as zalloc being NULL). msg is left unchanged in both source and
 547    destination.
 548 */
 549
 550 extern int zlib_deflateReset (z_streamp strm);
 551 /*
 552      This function is equivalent to deflateEnd followed by deflateInit,
 553    but does not free and reallocate all the internal compression state.
 554    The stream will keep the same compression level and any other attributes
 555    that may have been set by deflateInit2.
 556
 557       deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
 558    stream state was inconsistent (such as zalloc or state being NULL).
 559 */
 560
 561 static inline unsigned long deflateBound(unsigned long s)
 562 {
 563         return s + ((s + 7) >> 3) + ((s + 63) >> 6) + 11;
 564 }
 565
 566 #if 0
 567 extern int zlib_deflateParams (z_streamp strm, int level, int strategy);
 568 #endif
 569 /*
 570      Dynamically update the compression level and compression strategy.  The
 571    interpretation of level and strategy is as in deflateInit2.  This can be
 572    used to switch between compression and straight copy of the input data, or
 573    to switch to a different kind of input data requiring a different
 574    strategy. If the compression level is changed, the input available so far
 575    is compressed with the old level (and may be flushed); the new level will
 576    take effect only at the next call of deflate().
 577
 578      Before the call of deflateParams, the stream state must be set as for
 579    a call of deflate(), since the currently available input may have to
 580    be compressed and flushed. In particular, strm->avail_out must be non-zero.
 581
 582      deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source
 583    stream state was inconsistent or if a parameter was invalid, Z_BUF_ERROR
 584    if strm->avail_out was zero.
 585 */
 586
 587 /*
 588 extern int inflateInit2 (z_streamp strm, int  windowBits);
 589
 590      This is another version of inflateInit with an extra parameter. The
 591    fields next_in, avail_in, zalloc, zfree and opaque must be initialized
 592    before by the caller.
 593
 594      The windowBits parameter is the base two logarithm of the maximum window
 595    size (the size of the history buffer).  It should be in the range 8..15 for
 596    this version of the library. The default value is 15 if inflateInit is used
 597    instead. windowBits must be greater than or equal to the windowBits value
 598    provided to deflateInit2() while compressing, or it must be equal to 15 if
 599    deflateInit2() was not used. If a compressed stream with a larger window
 600    size is given as input, inflate() will return with the error code
 601    Z_DATA_ERROR instead of trying to allocate a larger window.
 602
 603      windowBits can also be -8..-15 for raw inflate. In this case, -windowBits
 604    determines the window size. inflate() will then process raw deflate data,
 605    not looking for a zlib or gzip header, not generating a check value, and not
 606    looking for any check values for comparison at the end of the stream. This
 607    is for use with other formats that use the deflate compressed data format
 608    such as zip.  Those formats provide their own check values. If a custom
 609    format is developed using the raw deflate format for compressed data, it is
 610    recommended that a check value such as an adler32 or a crc32 be applied to
 611    the uncompressed data as is done in the zlib, gzip, and zip formats.  For
 612    most applications, the zlib format should be used as is. Note that comments
 613    above on the use in deflateInit2() applies to the magnitude of windowBits.
 614
 615      windowBits can also be greater than 15 for optional gzip decoding. Add
 616    32 to windowBits to enable zlib and gzip decoding with automatic header
 617    detection, or add 16 to decode only the gzip format (the zlib format will
 618    return a Z_DATA_ERROR).  If a gzip stream is being decoded, strm->adler is
 619    a crc32 instead of an adler32.
 620
 621      inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
 622    memory, Z_STREAM_ERROR if a parameter is invalid (such as a null strm). msg
 623    is set to null if there is no error message.  inflateInit2 does not perform
 624    any decompression apart from reading the zlib header if present: this will
 625    be done by inflate(). (So next_in and avail_in may be modified, but next_out
 626    and avail_out are unchanged.)
 627 */
 628
 629 extern int zlib_inflateSetDictionary (z_streamp strm,
 630                                                      const Byte *dictionary,
 631                                                      uInt  dictLength);
 632 /*
 633      Initializes the decompression dictionary from the given uncompressed byte
 634    sequence. This function must be called immediately after a call of inflate,
 635    if that call returned Z_NEED_DICT. The dictionary chosen by the compressor
 636    can be determined from the adler32 value returned by that call of inflate.
 637    The compressor and decompressor must use exactly the same dictionary (see
 638    deflateSetDictionary).  For raw inflate, this function can be called
 639    immediately after inflateInit2() or inflateReset() and before any call of
 640    inflate() to set the dictionary.  The application must insure that the
 641    dictionary that was used for compression is provided.
 642
 643      inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
 644    parameter is invalid (such as NULL dictionary) or the stream state is
 645    inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the
 646    expected one (incorrect adler32 value). inflateSetDictionary does not
 647    perform any decompression: this will be done by subsequent calls of
 648    inflate().
 649 */
 650
 651 #if 0
 652 extern int zlib_inflateSync (z_streamp strm);
 653 #endif
 654 /*
 655     Skips invalid compressed data until a full flush point (see above the
 656   description of deflate with Z_FULL_FLUSH) can be found, or until all
 657   available input is skipped. No output is provided.
 658
 659     inflateSync returns Z_OK if a full flush point has been found, Z_BUF_ERROR
 660   if no more input was provided, Z_DATA_ERROR if no flush point has been found,
 661   or Z_STREAM_ERROR if the stream structure was inconsistent. In the success
 662   case, the application may save the current current value of total_in which
 663   indicates where valid compressed data was found. In the error case, the
 664   application may repeatedly call inflateSync, providing more input each time,
 665   until success or end of the input data.
 666 */
 667
 668 extern int zlib_inflateReset (z_streamp strm);
 669 /*
 670      This function is equivalent to inflateEnd followed by inflateInit,
 671    but does not free and reallocate all the internal decompression state.
 672    The stream will keep attributes that may have been set by inflateInit2.
 673
 674       inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
 675    stream state was inconsistent (such as zalloc or state being NULL).
 676 */
 677
 678 extern int zlib_inflateIncomp (z_stream *strm);
 679 /*
 680      This function adds the data at next_in (avail_in bytes) to the output
 681    history without performing any output.  There must be no pending output,
 682    and the decompressor must be expecting to see the start of a block.
 683    Calling this function is equivalent to decompressing a stored block
 684    containing the data at next_in (except that the data is not output).
 685 */
 686
 687 #define zlib_deflateInit(strm, level) \
 688         zlib_deflateInit2((strm), (level), Z_DEFLATED, MAX_WBITS, \
 689                               DEF_MEM_LEVEL, Z_DEFAULT_STRATEGY)
 690 #define zlib_inflateInit(strm) \
 691         zlib_inflateInit2((strm), DEF_WBITS)
 692
 693 extern int zlib_deflateInit2(z_streamp strm, int  level, int  method,
 694                                       int windowBits, int memLevel,
 695                                       int strategy);
 696 extern int zlib_inflateInit2(z_streamp strm, int  windowBits);
 697
 698 #if !defined(_Z_UTIL_H) && !defined(NO_DUMMY_DECL)
 699     struct internal_state {int dummy;}; /* hack for buggy compilers */
 700 #endif
 701
 702 #endif /* _ZLIB_H */