linux/include/linux/zlib.h
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   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
  82struct internal_state;
  83
  84typedef struct z_stream_s {
  85    const 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
 103typedef 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
 182extern int zlib_deflate_workspacesize (int windowBits, int memLevel);
 183/*
 184   Returns the number of bytes that needs to be allocated for a per-
 185   stream workspace with the specified parameters.  A pointer to this
 186   number of bytes should be returned in stream->workspace before
 187   you call zlib_deflateInit() or zlib_deflateInit2().  If you call
 188   zlib_deflateInit(), specify windowBits = MAX_WBITS and memLevel =
 189   MAX_MEM_LEVEL here.  If you call zlib_deflateInit2(), the windowBits
 190   and memLevel parameters passed to zlib_deflateInit2() must not
 191   exceed those passed here.
 192*/
 193
 194/* 
 195extern int deflateInit (z_streamp strm, int level);
 196
 197     Initializes the internal stream state for compression. The fields
 198   zalloc, zfree and opaque must be initialized before by the caller.
 199   If zalloc and zfree are set to NULL, deflateInit updates them to
 200   use default allocation functions.
 201
 202     The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
 203   1 gives best speed, 9 gives best compression, 0 gives no compression at
 204   all (the input data is simply copied a block at a time).
 205   Z_DEFAULT_COMPRESSION requests a default compromise between speed and
 206   compression (currently equivalent to level 6).
 207
 208     deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
 209   enough memory, Z_STREAM_ERROR if level is not a valid compression level,
 210   Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible
 211   with the version assumed by the caller (ZLIB_VERSION).
 212   msg is set to null if there is no error message.  deflateInit does not
 213   perform any compression: this will be done by deflate().
 214*/
 215
 216
 217extern int zlib_deflate (z_streamp strm, int flush);
 218/*
 219    deflate compresses as much data as possible, and stops when the input
 220  buffer becomes empty or the output buffer becomes full. It may introduce some
 221  output latency (reading input without producing any output) except when
 222  forced to flush.
 223
 224    The detailed semantics are as follows. deflate performs one or both of the
 225  following actions:
 226
 227  - Compress more input starting at next_in and update next_in and avail_in
 228    accordingly. If not all input can be processed (because there is not
 229    enough room in the output buffer), next_in and avail_in are updated and
 230    processing will resume at this point for the next call of deflate().
 231
 232  - Provide more output starting at next_out and update next_out and avail_out
 233    accordingly. This action is forced if the parameter flush is non zero.
 234    Forcing flush frequently degrades the compression ratio, so this parameter
 235    should be set only when necessary (in interactive applications).
 236    Some output may be provided even if flush is not set.
 237
 238  Before the call of deflate(), the application should ensure that at least
 239  one of the actions is possible, by providing more input and/or consuming
 240  more output, and updating avail_in or avail_out accordingly; avail_out
 241  should never be zero before the call. The application can consume the
 242  compressed output when it wants, for example when the output buffer is full
 243  (avail_out == 0), or after each call of deflate(). If deflate returns Z_OK
 244  and with zero avail_out, it must be called again after making room in the
 245  output buffer because there might be more output pending.
 246
 247    If the parameter flush is set to Z_SYNC_FLUSH, all pending output is
 248  flushed to the output buffer and the output is aligned on a byte boundary, so
 249  that the decompressor can get all input data available so far. (In particular
 250  avail_in is zero after the call if enough output space has been provided
 251  before the call.)  Flushing may degrade compression for some compression
 252  algorithms and so it should be used only when necessary.
 253
 254    If flush is set to Z_FULL_FLUSH, all output is flushed as with
 255  Z_SYNC_FLUSH, and the compression state is reset so that decompression can
 256  restart from this point if previous compressed data has been damaged or if
 257  random access is desired. Using Z_FULL_FLUSH too often can seriously degrade
 258  the compression.
 259
 260    If deflate returns with avail_out == 0, this function must be called again
 261  with the same value of the flush parameter and more output space (updated
 262  avail_out), until the flush is complete (deflate returns with non-zero
 263  avail_out).
 264
 265    If the parameter flush is set to Z_FINISH, pending input is processed,
 266  pending output is flushed and deflate returns with Z_STREAM_END if there
 267  was enough output space; if deflate returns with Z_OK, this function must be
 268  called again with Z_FINISH and more output space (updated avail_out) but no
 269  more input data, until it returns with Z_STREAM_END or an error. After
 270  deflate has returned Z_STREAM_END, the only possible operations on the
 271  stream are deflateReset or deflateEnd.
 272  
 273    Z_FINISH can be used immediately after deflateInit if all the compression
 274  is to be done in a single step. In this case, avail_out must be at least
 275  0.1% larger than avail_in plus 12 bytes.  If deflate does not return
 276  Z_STREAM_END, then it must be called again as described above.
 277
 278    deflate() sets strm->adler to the adler32 checksum of all input read
 279  so far (that is, total_in bytes).
 280
 281    deflate() may update data_type if it can make a good guess about
 282  the input data type (Z_ASCII or Z_BINARY). In doubt, the data is considered
 283  binary. This field is only for information purposes and does not affect
 284  the compression algorithm in any manner.
 285
 286    deflate() returns Z_OK if some progress has been made (more input
 287  processed or more output produced), Z_STREAM_END if all input has been
 288  consumed and all output has been produced (only when flush is set to
 289  Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
 290  if next_in or next_out was NULL), Z_BUF_ERROR if no progress is possible
 291  (for example avail_in or avail_out was zero).
 292*/
 293
 294
 295extern int zlib_deflateEnd (z_streamp strm);
 296/*
 297     All dynamically allocated data structures for this stream are freed.
 298   This function discards any unprocessed input and does not flush any
 299   pending output.
 300
 301     deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
 302   stream state was inconsistent, Z_DATA_ERROR if the stream was freed
 303   prematurely (some input or output was discarded). In the error case,
 304   msg may be set but then points to a static string (which must not be
 305   deallocated).
 306*/
 307
 308
 309extern int zlib_inflate_workspacesize (void);
 310/*
 311   Returns the number of bytes that needs to be allocated for a per-
 312   stream workspace.  A pointer to this number of bytes should be
 313   returned in stream->workspace before calling zlib_inflateInit().
 314*/
 315
 316/* 
 317extern int zlib_inflateInit (z_streamp strm);
 318
 319     Initializes the internal stream state for decompression. The fields
 320   next_in, avail_in, and workspace must be initialized before by
 321   the caller. If next_in is not NULL and avail_in is large enough (the exact
 322   value depends on the compression method), inflateInit determines the
 323   compression method from the zlib header and allocates all data structures
 324   accordingly; otherwise the allocation will be deferred to the first call of
 325   inflate.  If zalloc and zfree are set to NULL, inflateInit updates them to
 326   use default allocation functions.
 327
 328     inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
 329   memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
 330   version assumed by the caller.  msg is set to null if there is no error
 331   message. inflateInit does not perform any decompression apart from reading
 332   the zlib header if present: this will be done by inflate().  (So next_in and
 333   avail_in may be modified, but next_out and avail_out are unchanged.)
 334*/
 335
 336
 337extern int zlib_inflate (z_streamp strm, int flush);
 338/*
 339    inflate decompresses as much data as possible, and stops when the input
 340  buffer becomes empty or the output buffer becomes full. It may introduce
 341  some output latency (reading input without producing any output) except when
 342  forced to flush.
 343
 344  The detailed semantics are as follows. inflate performs one or both of the
 345  following actions:
 346
 347  - Decompress more input starting at next_in and update next_in and avail_in
 348    accordingly. If not all input can be processed (because there is not
 349    enough room in the output buffer), next_in is updated and processing
 350    will resume at this point for the next call of inflate().
 351
 352  - Provide more output starting at next_out and update next_out and avail_out
 353    accordingly.  inflate() provides as much output as possible, until there
 354    is no more input data or no more space in the output buffer (see below
 355    about the flush parameter).
 356
 357  Before the call of inflate(), the application should ensure that at least
 358  one of the actions is possible, by providing more input and/or consuming
 359  more output, and updating the next_* and avail_* values accordingly.
 360  The application can consume the uncompressed output when it wants, for
 361  example when the output buffer is full (avail_out == 0), or after each
 362  call of inflate(). If inflate returns Z_OK and with zero avail_out, it
 363  must be called again after making room in the output buffer because there
 364  might be more output pending.
 365
 366    The flush parameter of inflate() can be Z_NO_FLUSH, Z_SYNC_FLUSH,
 367  Z_FINISH, or Z_BLOCK. Z_SYNC_FLUSH requests that inflate() flush as much
 368  output as possible to the output buffer. Z_BLOCK requests that inflate() stop
 369  if and when it gets to the next deflate block boundary. When decoding the
 370  zlib or gzip format, this will cause inflate() to return immediately after
 371  the header and before the first block. When doing a raw inflate, inflate()
 372  will go ahead and process the first block, and will return when it gets to
 373  the end of that block, or when it runs out of data.
 374
 375    The Z_BLOCK option assists in appending to or combining deflate streams.
 376  Also to assist in this, on return inflate() will set strm->data_type to the
 377  number of unused bits in the last byte taken from strm->next_in, plus 64
 378  if inflate() is currently decoding the last block in the deflate stream,
 379  plus 128 if inflate() returned immediately after decoding an end-of-block
 380  code or decoding the complete header up to just before the first byte of the
 381  deflate stream. The end-of-block will not be indicated until all of the
 382  uncompressed data from that block has been written to strm->next_out.  The
 383  number of unused bits may in general be greater than seven, except when
 384  bit 7 of data_type is set, in which case the number of unused bits will be
 385  less than eight.
 386
 387    inflate() should normally be called until it returns Z_STREAM_END or an
 388  error. However if all decompression is to be performed in a single step
 389  (a single call of inflate), the parameter flush should be set to
 390  Z_FINISH. In this case all pending input is processed and all pending
 391  output is flushed; avail_out must be large enough to hold all the
 392  uncompressed data. (The size of the uncompressed data may have been saved
 393  by the compressor for this purpose.) The next operation on this stream must
 394  be inflateEnd to deallocate the decompression state. The use of Z_FINISH
 395  is never required, but can be used to inform inflate that a faster approach
 396  may be used for the single inflate() call.
 397
 398     In this implementation, inflate() always flushes as much output as
 399  possible to the output buffer, and always uses the faster approach on the
 400  first call. So the only effect of the flush parameter in this implementation
 401  is on the return value of inflate(), as noted below, or when it returns early
 402  because Z_BLOCK is used.
 403
 404     If a preset dictionary is needed after this call (see inflateSetDictionary
 405  below), inflate sets strm->adler to the adler32 checksum of the dictionary
 406  chosen by the compressor and returns Z_NEED_DICT; otherwise it sets
 407  strm->adler to the adler32 checksum of all output produced so far (that is,
 408  total_out bytes) and returns Z_OK, Z_STREAM_END or an error code as described
 409  below. At the end of the stream, inflate() checks that its computed adler32
 410  checksum is equal to that saved by the compressor and returns Z_STREAM_END
 411  only if the checksum is correct.
 412
 413    inflate() will decompress and check either zlib-wrapped or gzip-wrapped
 414  deflate data.  The header type is detected automatically.  Any information
 415  contained in the gzip header is not retained, so applications that need that
 416  information should instead use raw inflate, see inflateInit2() below, or
 417  inflateBack() and perform their own processing of the gzip header and
 418  trailer.
 419
 420    inflate() returns Z_OK if some progress has been made (more input processed
 421  or more output produced), Z_STREAM_END if the end of the compressed data has
 422  been reached and all uncompressed output has been produced, Z_NEED_DICT if a
 423  preset dictionary is needed at this point, Z_DATA_ERROR if the input data was
 424  corrupted (input stream not conforming to the zlib format or incorrect check
 425  value), Z_STREAM_ERROR if the stream structure was inconsistent (for example
 426  if next_in or next_out was NULL), Z_MEM_ERROR if there was not enough memory,
 427  Z_BUF_ERROR if no progress is possible or if there was not enough room in the
 428  output buffer when Z_FINISH is used. Note that Z_BUF_ERROR is not fatal, and
 429  inflate() can be called again with more input and more output space to
 430  continue decompressing. If Z_DATA_ERROR is returned, the application may then
 431  call inflateSync() to look for a good compression block if a partial recovery
 432  of the data is desired.
 433*/
 434
 435
 436extern int zlib_inflateEnd (z_streamp strm);
 437/*
 438     All dynamically allocated data structures for this stream are freed.
 439   This function discards any unprocessed input and does not flush any
 440   pending output.
 441
 442     inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
 443   was inconsistent. In the error case, msg may be set but then points to a
 444   static string (which must not be deallocated).
 445*/
 446
 447                        /* Advanced functions */
 448
 449/*
 450    The following functions are needed only in some special applications.
 451*/
 452
 453/*   
 454extern int deflateInit2 (z_streamp strm,
 455                                     int  level,
 456                                     int  method,
 457                                     int  windowBits,
 458                                     int  memLevel,
 459                                     int  strategy);
 460
 461     This is another version of deflateInit with more compression options. The
 462   fields next_in, zalloc, zfree and opaque must be initialized before by
 463   the caller.
 464
 465     The method parameter is the compression method. It must be Z_DEFLATED in
 466   this version of the library.
 467
 468     The windowBits parameter is the base two logarithm of the window size
 469   (the size of the history buffer).  It should be in the range 8..15 for this
 470   version of the library. Larger values of this parameter result in better
 471   compression at the expense of memory usage. The default value is 15 if
 472   deflateInit is used instead.
 473
 474     The memLevel parameter specifies how much memory should be allocated
 475   for the internal compression state. memLevel=1 uses minimum memory but
 476   is slow and reduces compression ratio; memLevel=9 uses maximum memory
 477   for optimal speed. The default value is 8. See zconf.h for total memory
 478   usage as a function of windowBits and memLevel.
 479
 480     The strategy parameter is used to tune the compression algorithm. Use the
 481   value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a
 482   filter (or predictor), or Z_HUFFMAN_ONLY to force Huffman encoding only (no
 483   string match).  Filtered data consists mostly of small values with a
 484   somewhat random distribution. In this case, the compression algorithm is
 485   tuned to compress them better. The effect of Z_FILTERED is to force more
 486   Huffman coding and less string matching; it is somewhat intermediate
 487   between Z_DEFAULT and Z_HUFFMAN_ONLY. The strategy parameter only affects
 488   the compression ratio but not the correctness of the compressed output even
 489   if it is not set appropriately.
 490
 491      deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
 492   memory, Z_STREAM_ERROR if a parameter is invalid (such as an invalid
 493   method). msg is set to null if there is no error message.  deflateInit2 does
 494   not perform any compression: this will be done by deflate().
 495*/
 496                            
 497#if 0
 498extern int zlib_deflateSetDictionary (z_streamp strm,
 499                                                     const Byte *dictionary,
 500                                                     uInt  dictLength);
 501#endif
 502/*
 503     Initializes the compression dictionary from the given byte sequence
 504   without producing any compressed output. This function must be called
 505   immediately after deflateInit, deflateInit2 or deflateReset, before any
 506   call of deflate. The compressor and decompressor must use exactly the same
 507   dictionary (see inflateSetDictionary).
 508
 509     The dictionary should consist of strings (byte sequences) that are likely
 510   to be encountered later in the data to be compressed, with the most commonly
 511   used strings preferably put towards the end of the dictionary. Using a
 512   dictionary is most useful when the data to be compressed is short and can be
 513   predicted with good accuracy; the data can then be compressed better than
 514   with the default empty dictionary.
 515
 516     Depending on the size of the compression data structures selected by
 517   deflateInit or deflateInit2, a part of the dictionary may in effect be
 518   discarded, for example if the dictionary is larger than the window size in
 519   deflate or deflate2. Thus the strings most likely to be useful should be
 520   put at the end of the dictionary, not at the front.
 521
 522     Upon return of this function, strm->adler is set to the Adler32 value
 523   of the dictionary; the decompressor may later use this value to determine
 524   which dictionary has been used by the compressor. (The Adler32 value
 525   applies to the whole dictionary even if only a subset of the dictionary is
 526   actually used by the compressor.)
 527
 528     deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
 529   parameter is invalid (such as NULL dictionary) or the stream state is
 530   inconsistent (for example if deflate has already been called for this stream
 531   or if the compression method is bsort). deflateSetDictionary does not
 532   perform any compression: this will be done by deflate().
 533*/
 534
 535#if 0
 536extern int zlib_deflateCopy (z_streamp dest, z_streamp source);
 537#endif
 538
 539/*
 540     Sets the destination stream as a complete copy of the source stream.
 541
 542     This function can be useful when several compression strategies will be
 543   tried, for example when there are several ways of pre-processing the input
 544   data with a filter. The streams that will be discarded should then be freed
 545   by calling deflateEnd.  Note that deflateCopy duplicates the internal
 546   compression state which can be quite large, so this strategy is slow and
 547   can consume lots of memory.
 548
 549     deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
 550   enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
 551   (such as zalloc being NULL). msg is left unchanged in both source and
 552   destination.
 553*/
 554
 555extern int zlib_deflateReset (z_streamp strm);
 556/*
 557     This function is equivalent to deflateEnd followed by deflateInit,
 558   but does not free and reallocate all the internal compression state.
 559   The stream will keep the same compression level and any other attributes
 560   that may have been set by deflateInit2.
 561
 562      deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
 563   stream state was inconsistent (such as zalloc or state being NULL).
 564*/
 565
 566static inline unsigned long deflateBound(unsigned long s)
 567{
 568        return s + ((s + 7) >> 3) + ((s + 63) >> 6) + 11;
 569}
 570
 571#if 0
 572extern int zlib_deflateParams (z_streamp strm, int level, int strategy);
 573#endif
 574/*
 575     Dynamically update the compression level and compression strategy.  The
 576   interpretation of level and strategy is as in deflateInit2.  This can be
 577   used to switch between compression and straight copy of the input data, or
 578   to switch to a different kind of input data requiring a different
 579   strategy. If the compression level is changed, the input available so far
 580   is compressed with the old level (and may be flushed); the new level will
 581   take effect only at the next call of deflate().
 582
 583     Before the call of deflateParams, the stream state must be set as for
 584   a call of deflate(), since the currently available input may have to
 585   be compressed and flushed. In particular, strm->avail_out must be non-zero.
 586
 587     deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source
 588   stream state was inconsistent or if a parameter was invalid, Z_BUF_ERROR
 589   if strm->avail_out was zero.
 590*/
 591
 592/*   
 593extern int inflateInit2 (z_streamp strm, int  windowBits);
 594
 595     This is another version of inflateInit with an extra parameter. The
 596   fields next_in, avail_in, zalloc, zfree and opaque must be initialized
 597   before by the caller.
 598
 599     The windowBits parameter is the base two logarithm of the maximum window
 600   size (the size of the history buffer).  It should be in the range 8..15 for
 601   this version of the library. The default value is 15 if inflateInit is used
 602   instead. windowBits must be greater than or equal to the windowBits value
 603   provided to deflateInit2() while compressing, or it must be equal to 15 if
 604   deflateInit2() was not used. If a compressed stream with a larger window
 605   size is given as input, inflate() will return with the error code
 606   Z_DATA_ERROR instead of trying to allocate a larger window.
 607
 608     windowBits can also be -8..-15 for raw inflate. In this case, -windowBits
 609   determines the window size. inflate() will then process raw deflate data,
 610   not looking for a zlib or gzip header, not generating a check value, and not
 611   looking for any check values for comparison at the end of the stream. This
 612   is for use with other formats that use the deflate compressed data format
 613   such as zip.  Those formats provide their own check values. If a custom
 614   format is developed using the raw deflate format for compressed data, it is
 615   recommended that a check value such as an adler32 or a crc32 be applied to
 616   the uncompressed data as is done in the zlib, gzip, and zip formats.  For
 617   most applications, the zlib format should be used as is. Note that comments
 618   above on the use in deflateInit2() applies to the magnitude of windowBits.
 619
 620     windowBits can also be greater than 15 for optional gzip decoding. Add
 621   32 to windowBits to enable zlib and gzip decoding with automatic header
 622   detection, or add 16 to decode only the gzip format (the zlib format will
 623   return a Z_DATA_ERROR).  If a gzip stream is being decoded, strm->adler is
 624   a crc32 instead of an adler32.
 625
 626     inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
 627   memory, Z_STREAM_ERROR if a parameter is invalid (such as a null strm). msg
 628   is set to null if there is no error message.  inflateInit2 does not perform
 629   any decompression apart from reading the zlib header if present: this will
 630   be done by inflate(). (So next_in and avail_in may be modified, but next_out
 631   and avail_out are unchanged.)
 632*/
 633
 634extern int zlib_inflateSetDictionary (z_streamp strm,
 635                                                     const Byte *dictionary,
 636                                                     uInt  dictLength);
 637/*
 638     Initializes the decompression dictionary from the given uncompressed byte
 639   sequence. This function must be called immediately after a call of inflate,
 640   if that call returned Z_NEED_DICT. The dictionary chosen by the compressor
 641   can be determined from the adler32 value returned by that call of inflate.
 642   The compressor and decompressor must use exactly the same dictionary (see
 643   deflateSetDictionary).  For raw inflate, this function can be called
 644   immediately after inflateInit2() or inflateReset() and before any call of
 645   inflate() to set the dictionary.  The application must insure that the
 646   dictionary that was used for compression is provided.
 647
 648     inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
 649   parameter is invalid (such as NULL dictionary) or the stream state is
 650   inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the
 651   expected one (incorrect adler32 value). inflateSetDictionary does not
 652   perform any decompression: this will be done by subsequent calls of
 653   inflate().
 654*/
 655
 656#if 0
 657extern int zlib_inflateSync (z_streamp strm);
 658#endif
 659/* 
 660    Skips invalid compressed data until a full flush point (see above the
 661  description of deflate with Z_FULL_FLUSH) can be found, or until all
 662  available input is skipped. No output is provided.
 663
 664    inflateSync returns Z_OK if a full flush point has been found, Z_BUF_ERROR
 665  if no more input was provided, Z_DATA_ERROR if no flush point has been found,
 666  or Z_STREAM_ERROR if the stream structure was inconsistent. In the success
 667  case, the application may save the current current value of total_in which
 668  indicates where valid compressed data was found. In the error case, the
 669  application may repeatedly call inflateSync, providing more input each time,
 670  until success or end of the input data.
 671*/
 672
 673extern int zlib_inflateReset (z_streamp strm);
 674/*
 675     This function is equivalent to inflateEnd followed by inflateInit,
 676   but does not free and reallocate all the internal decompression state.
 677   The stream will keep attributes that may have been set by inflateInit2.
 678
 679      inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
 680   stream state was inconsistent (such as zalloc or state being NULL).
 681*/
 682
 683extern int zlib_inflateIncomp (z_stream *strm);
 684/*
 685     This function adds the data at next_in (avail_in bytes) to the output
 686   history without performing any output.  There must be no pending output,
 687   and the decompressor must be expecting to see the start of a block.
 688   Calling this function is equivalent to decompressing a stored block
 689   containing the data at next_in (except that the data is not output).
 690*/
 691
 692#define zlib_deflateInit(strm, level) \
 693        zlib_deflateInit2((strm), (level), Z_DEFLATED, MAX_WBITS, \
 694                              DEF_MEM_LEVEL, Z_DEFAULT_STRATEGY)
 695#define zlib_inflateInit(strm) \
 696        zlib_inflateInit2((strm), DEF_WBITS)
 697
 698extern int zlib_deflateInit2(z_streamp strm, int  level, int  method,
 699                                      int windowBits, int memLevel,
 700                                      int strategy);
 701extern int zlib_inflateInit2(z_streamp strm, int  windowBits);
 702
 703#if !defined(_Z_UTIL_H) && !defined(NO_DUMMY_DECL)
 704    struct internal_state {int dummy;}; /* hack for buggy compilers */
 705#endif
 706
 707/* Utility function: initialize zlib, unpack binary blob, clean up zlib,
 708 * return len or negative error code. */
 709extern int zlib_inflate_blob(void *dst, unsigned dst_sz, const void *src, unsigned src_sz);
 710
 711#endif /* _ZLIB_H */
 712
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