/src/zlib/zlib.h
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1/* zlib.h -- interface of the 'zlib' general purpose compression library 2 version 1.2.8, April 28th, 2013 3 4 Copyright (C) 1995-2013 Jean-loup Gailly and Mark Adler 5 6 This software is provided 'as-is', without any express or implied 7 warranty. In no event will the authors be held liable for any damages 8 arising from the use of this software. 9 10 Permission is granted to anyone to use this software for any purpose, 11 including commercial applications, and to alter it and redistribute it 12 freely, subject to the following restrictions: 13 14 1. The origin of this software must not be misrepresented; you must not 15 claim that you wrote the original software. If you use this software 16 in a product, an acknowledgment in the product documentation would be 17 appreciated but is not required. 18 2. Altered source versions must be plainly marked as such, and must not be 19 misrepresented as being the original software. 20 3. This notice may not be removed or altered from any source distribution. 21 22 Jean-loup Gailly Mark Adler 23 jloup@gzip.org madler@alumni.caltech.edu 24 25 26 The data format used by the zlib library is described by RFCs (Request for 27 Comments) 1950 to 1952 in the files http://tools.ietf.org/html/rfc1950 28 (zlib format), rfc1951 (deflate format) and rfc1952 (gzip format). 29*/ 30 31#ifndef ZLIB_H 32#define ZLIB_H 33 34#include "zconf.h" 35 36#ifdef __cplusplus 37extern "C" { 38#endif 39 40#define ZLIB_VERSION "1.2.8" 41#define ZLIB_VERNUM 0x1280 42#define ZLIB_VER_MAJOR 1 43#define ZLIB_VER_MINOR 2 44#define ZLIB_VER_REVISION 8 45#define ZLIB_VER_SUBREVISION 0 46 47/* 48 The 'zlib' compression library provides in-memory compression and 49 decompression functions, including integrity checks of the uncompressed data. 50 This version of the library supports only one compression method (deflation) 51 but other algorithms will be added later and will have the same stream 52 interface. 53 54 Compression can be done in a single step if the buffers are large enough, 55 or can be done by repeated calls of the compression function. In the latter 56 case, the application must provide more input and/or consume the output 57 (providing more output space) before each call. 58 59 The compressed data format used by default by the in-memory functions is 60 the zlib format, which is a zlib wrapper documented in RFC 1950, wrapped 61 around a deflate stream, which is itself documented in RFC 1951. 62 63 The library also supports reading and writing files in gzip (.gz) format 64 with an interface similar to that of stdio using the functions that start 65 with "gz". The gzip format is different from the zlib format. gzip is a 66 gzip wrapper, documented in RFC 1952, wrapped around a deflate stream. 67 68 This library can optionally read and write gzip streams in memory as well. 69 70 The zlib format was designed to be compact and fast for use in memory 71 and on communications channels. The gzip format was designed for single- 72 file compression on file systems, has a larger header than zlib to maintain 73 directory information, and uses a different, slower check method than zlib. 74 75 The library does not install any signal handler. The decoder checks 76 the consistency of the compressed data, so the library should never crash 77 even in case of corrupted input. 78*/ 79 80typedef voidpf (*alloc_func) OF((voidpf opaque, uInt items, uInt size)); 81typedef void (*free_func) OF((voidpf opaque, voidpf address)); 82 83struct internal_state; 84 85typedef struct z_stream_s { 86 z_const Bytef *next_in; /* next input byte */ 87 uInt avail_in; /* number of bytes available at next_in */ 88 uLong total_in; /* total number of input bytes read so far */ 89 90 Bytef *next_out; /* next output byte should be put there */ 91 uInt avail_out; /* remaining free space at next_out */ 92 uLong total_out; /* total number of bytes output so far */ 93 94 z_const char *msg; /* last error message, NULL if no error */ 95 struct internal_state FAR *state; /* not visible by applications */ 96 97 alloc_func zalloc; /* used to allocate the internal state */ 98 free_func zfree; /* used to free the internal state */ 99 voidpf opaque; /* private data object passed to zalloc and zfree */ 100 101 int data_type; /* best guess about the data type: binary or text */ 102 uLong adler; /* adler32 value of the uncompressed data */ 103 uLong reserved; /* reserved for future use */ 104} z_stream; 105 106typedef z_stream FAR *z_streamp; 107 108/* 109 gzip header information passed to and from zlib routines. See RFC 1952 110 for more details on the meanings of these fields. 111*/ 112typedef struct gz_header_s { 113 int text; /* true if compressed data believed to be text */ 114 uLong time; /* modification time */ 115 int xflags; /* extra flags (not used when writing a gzip file) */ 116 int os; /* operating system */ 117 Bytef *extra; /* pointer to extra field or Z_NULL if none */ 118 uInt extra_len; /* extra field length (valid if extra != Z_NULL) */ 119 uInt extra_max; /* space at extra (only when reading header) */ 120 Bytef *name; /* pointer to zero-terminated file name or Z_NULL */ 121 uInt name_max; /* space at name (only when reading header) */ 122 Bytef *comment; /* pointer to zero-terminated comment or Z_NULL */ 123 uInt comm_max; /* space at comment (only when reading header) */ 124 int hcrc; /* true if there was or will be a header crc */ 125 int done; /* true when done reading gzip header (not used 126 when writing a gzip file) */ 127} gz_header; 128 129typedef gz_header FAR *gz_headerp; 130 131/* 132 The application must update next_in and avail_in when avail_in has dropped 133 to zero. It must update next_out and avail_out when avail_out has dropped 134 to zero. The application must initialize zalloc, zfree and opaque before 135 calling the init function. All other fields are set by the compression 136 library and must not be updated by the application. 137 138 The opaque value provided by the application will be passed as the first 139 parameter for calls of zalloc and zfree. This can be useful for custom 140 memory management. The compression library attaches no meaning to the 141 opaque value. 142 143 zalloc must return Z_NULL if there is not enough memory for the object. 144 If zlib is used in a multi-threaded application, zalloc and zfree must be 145 thread safe. 146 147 On 16-bit systems, the functions zalloc and zfree must be able to allocate 148 exactly 65536 bytes, but will not be required to allocate more than this if 149 the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS, pointers 150 returned by zalloc for objects of exactly 65536 bytes *must* have their 151 offset normalized to zero. The default allocation function provided by this 152 library ensures this (see zutil.c). To reduce memory requirements and avoid 153 any allocation of 64K objects, at the expense of compression ratio, compile 154 the library with -DMAX_WBITS=14 (see zconf.h). 155 156 The fields total_in and total_out can be used for statistics or progress 157 reports. After compression, total_in holds the total size of the 158 uncompressed data and may be saved for use in the decompressor (particularly 159 if the decompressor wants to decompress everything in a single step). 160*/ 161 162 /* constants */ 163 164#define Z_NO_FLUSH 0 165#define Z_PARTIAL_FLUSH 1 166#define Z_SYNC_FLUSH 2 167#define Z_FULL_FLUSH 3 168#define Z_FINISH 4 169#define Z_BLOCK 5 170#define Z_TREES 6 171/* Allowed flush values; see deflate() and inflate() below for details */ 172 173#define Z_OK 0 174#define Z_STREAM_END 1 175#define Z_NEED_DICT 2 176#define Z_ERRNO (-1) 177#define Z_STREAM_ERROR (-2) 178#define Z_DATA_ERROR (-3) 179#define Z_MEM_ERROR (-4) 180#define Z_BUF_ERROR (-5) 181#define Z_VERSION_ERROR (-6) 182/* Return codes for the compression/decompression functions. Negative values 183 * are errors, positive values are used for special but normal events. 184 */ 185 186#define Z_NO_COMPRESSION 0 187#define Z_BEST_SPEED 1 188#define Z_BEST_COMPRESSION 9 189#define Z_DEFAULT_COMPRESSION (-1) 190/* compression levels */ 191 192#define Z_FILTERED 1 193#define Z_HUFFMAN_ONLY 2 194#define Z_RLE 3 195#define Z_FIXED 4 196#define Z_DEFAULT_STRATEGY 0 197/* compression strategy; see deflateInit2() below for details */ 198 199#define Z_BINARY 0 200#define Z_TEXT 1 201#define Z_ASCII Z_TEXT /* for compatibility with 1.2.2 and earlier */ 202#define Z_UNKNOWN 2 203/* Possible values of the data_type field (though see inflate()) */ 204 205#define Z_DEFLATED 8 206/* The deflate compression method (the only one supported in this version) */ 207 208#define Z_NULL 0 /* for initializing zalloc, zfree, opaque */ 209 210#define zlib_version zlibVersion() 211/* for compatibility with versions < 1.0.2 */ 212 213 214 /* basic functions */ 215 216ZEXTERN const char * ZEXPORT zlibVersion OF((void)); 217/* The application can compare zlibVersion and ZLIB_VERSION for consistency. 218 If the first character differs, the library code actually used is not 219 compatible with the zlib.h header file used by the application. This check 220 is automatically made by deflateInit and inflateInit. 221 */ 222 223/* 224ZEXTERN int ZEXPORT deflateInit OF((z_streamp strm, int level)); 225 226 Initializes the internal stream state for compression. The fields 227 zalloc, zfree and opaque must be initialized before by the caller. If 228 zalloc and zfree are set to Z_NULL, deflateInit updates them to use default 229 allocation functions. 230 231 The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9: 232 1 gives best speed, 9 gives best compression, 0 gives no compression at all 233 (the input data is simply copied a block at a time). Z_DEFAULT_COMPRESSION 234 requests a default compromise between speed and compression (currently 235 equivalent to level 6). 236 237 deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough 238 memory, Z_STREAM_ERROR if level is not a valid compression level, or 239 Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible 240 with the version assumed by the caller (ZLIB_VERSION). msg is set to null 241 if there is no error message. deflateInit does not perform any compression: 242 this will be done by deflate(). 243*/ 244 245 246ZEXTERN int ZEXPORT deflate OF((z_streamp strm, int flush)); 247/* 248 deflate compresses as much data as possible, and stops when the input 249 buffer becomes empty or the output buffer becomes full. It may introduce 250 some output latency (reading input without producing any output) except when 251 forced to flush. 252 253 The detailed semantics are as follows. deflate performs one or both of the 254 following actions: 255 256 - Compress more input starting at next_in and update next_in and avail_in 257 accordingly. If not all input can be processed (because there is not 258 enough room in the output buffer), next_in and avail_in are updated and 259 processing will resume at this point for the next call of deflate(). 260 261 - Provide more output starting at next_out and update next_out and avail_out 262 accordingly. This action is forced if the parameter flush is non zero. 263 Forcing flush frequently degrades the compression ratio, so this parameter 264 should be set only when necessary (in interactive applications). Some 265 output may be provided even if flush is not set. 266 267 Before the call of deflate(), the application should ensure that at least 268 one of the actions is possible, by providing more input and/or consuming more 269 output, and updating avail_in or avail_out accordingly; avail_out should 270 never be zero before the call. The application can consume the compressed 271 output when it wants, for example when the output buffer is full (avail_out 272 == 0), or after each call of deflate(). If deflate returns Z_OK and with 273 zero avail_out, it must be called again after making room in the output 274 buffer because there might be more output pending. 275 276 Normally the parameter flush is set to Z_NO_FLUSH, which allows deflate to 277 decide how much data to accumulate before producing output, in order to 278 maximize compression. 279 280 If the parameter flush is set to Z_SYNC_FLUSH, all pending output is 281 flushed to the output buffer and the output is aligned on a byte boundary, so 282 that the decompressor can get all input data available so far. (In 283 particular avail_in is zero after the call if enough output space has been 284 provided before the call.) Flushing may degrade compression for some 285 compression algorithms and so it should be used only when necessary. This 286 completes the current deflate block and follows it with an empty stored block 287 that is three bits plus filler bits to the next byte, followed by four bytes 288 (00 00 ff ff). 289 290 If flush is set to Z_PARTIAL_FLUSH, all pending output is flushed to the 291 output buffer, but the output is not aligned to a byte boundary. All of the 292 input data so far will be available to the decompressor, as for Z_SYNC_FLUSH. 293 This completes the current deflate block and follows it with an empty fixed 294 codes block that is 10 bits long. This assures that enough bytes are output 295 in order for the decompressor to finish the block before the empty fixed code 296 block. 297 298 If flush is set to Z_BLOCK, a deflate block is completed and emitted, as 299 for Z_SYNC_FLUSH, but the output is not aligned on a byte boundary, and up to 300 seven bits of the current block are held to be written as the next byte after 301 the next deflate block is completed. In this case, the decompressor may not 302 be provided enough bits at this point in order to complete decompression of 303 the data provided so far to the compressor. It may need to wait for the next 304 block to be emitted. This is for advanced applications that need to control 305 the emission of deflate blocks. 306 307 If flush is set to Z_FULL_FLUSH, all output is flushed as with 308 Z_SYNC_FLUSH, and the compression state is reset so that decompression can 309 restart from this point if previous compressed data has been damaged or if 310 random access is desired. Using Z_FULL_FLUSH too often can seriously degrade 311 compression. 312 313 If deflate returns with avail_out == 0, this function must be called again 314 with the same value of the flush parameter and more output space (updated 315 avail_out), until the flush is complete (deflate returns with non-zero 316 avail_out). In the case of a Z_FULL_FLUSH or Z_SYNC_FLUSH, make sure that 317 avail_out is greater than six to avoid repeated flush markers due to 318 avail_out == 0 on return. 319 320 If the parameter flush is set to Z_FINISH, pending input is processed, 321 pending output is flushed and deflate returns with Z_STREAM_END if there was 322 enough output space; if deflate returns with Z_OK, this function must be 323 called again with Z_FINISH and more output space (updated avail_out) but no 324 more input data, until it returns with Z_STREAM_END or an error. After 325 deflate has returned Z_STREAM_END, the only possible operations on the stream 326 are deflateReset or deflateEnd. 327 328 Z_FINISH can be used immediately after deflateInit if all the compression 329 is to be done in a single step. In this case, avail_out must be at least the 330 value returned by deflateBound (see below). Then deflate is guaranteed to 331 return Z_STREAM_END. If not enough output space is provided, deflate will 332 not return Z_STREAM_END, and it must be called again as described above. 333 334 deflate() sets strm->adler to the adler32 checksum of all input read 335 so far (that is, total_in bytes). 336 337 deflate() may update strm->data_type if it can make a good guess about 338 the input data type (Z_BINARY or Z_TEXT). In doubt, the data is considered 339 binary. This field is only for information purposes and does not affect the 340 compression algorithm in any manner. 341 342 deflate() returns Z_OK if some progress has been made (more input 343 processed or more output produced), Z_STREAM_END if all input has been 344 consumed and all output has been produced (only when flush is set to 345 Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example 346 if next_in or next_out was Z_NULL), Z_BUF_ERROR if no progress is possible 347 (for example avail_in or avail_out was zero). Note that Z_BUF_ERROR is not 348 fatal, and deflate() can be called again with more input and more output 349 space to continue compressing. 350*/ 351 352 353ZEXTERN int ZEXPORT deflateEnd OF((z_streamp strm)); 354/* 355 All dynamically allocated data structures for this stream are freed. 356 This function discards any unprocessed input and does not flush any pending 357 output. 358 359 deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the 360 stream state was inconsistent, Z_DATA_ERROR if the stream was freed 361 prematurely (some input or output was discarded). In the error case, msg 362 may be set but then points to a static string (which must not be 363 deallocated). 364*/ 365 366 367/* 368ZEXTERN int ZEXPORT inflateInit OF((z_streamp strm)); 369 370 Initializes the internal stream state for decompression. The fields 371 next_in, avail_in, zalloc, zfree and opaque must be initialized before by 372 the caller. If next_in is not Z_NULL and avail_in is large enough (the 373 exact value depends on the compression method), inflateInit determines the 374 compression method from the zlib header and allocates all data structures 375 accordingly; otherwise the allocation will be deferred to the first call of 376 inflate. If zalloc and zfree are set to Z_NULL, inflateInit updates them to 377 use default allocation functions. 378 379 inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough 380 memory, Z_VERSION_ERROR if the zlib library version is incompatible with the 381 version assumed by the caller, or Z_STREAM_ERROR if the parameters are 382 invalid, such as a null pointer to the structure. msg is set to null if 383 there is no error message. inflateInit does not perform any decompression 384 apart from possibly reading the zlib header if present: actual decompression 385 will be done by inflate(). (So next_in and avail_in may be modified, but 386 next_out and avail_out are unused and unchanged.) The current implementation 387 of inflateInit() does not process any header information -- that is deferred 388 until inflate() is called. 389*/ 390 391 392ZEXTERN int ZEXPORT inflate OF((z_streamp strm, int flush)); 393/* 394 inflate decompresses as much data as possible, and stops when the input 395 buffer becomes empty or the output buffer becomes full. It may introduce 396 some output latency (reading input without producing any output) except when 397 forced to flush. 398 399 The detailed semantics are as follows. inflate performs one or both of the 400 following actions: 401 402 - Decompress more input starting at next_in and update next_in and avail_in 403 accordingly. If not all input can be processed (because there is not 404 enough room in the output buffer), next_in is updated and processing will 405 resume at this point for the next call of inflate(). 406 407 - Provide more output starting at next_out and update next_out and avail_out 408 accordingly. inflate() provides as much output as possible, until there is 409 no more input data or no more space in the output buffer (see below about 410 the flush parameter). 411 412 Before the call of inflate(), the application should ensure that at least 413 one of the actions is possible, by providing more input and/or consuming more 414 output, and updating the next_* and avail_* values accordingly. The 415 application can consume the uncompressed output when it wants, for example 416 when the output buffer is full (avail_out == 0), or after each call of 417 inflate(). If inflate returns Z_OK and with zero avail_out, it must be 418 called again after making room in the output buffer because there might be 419 more output pending. 420 421 The flush parameter of inflate() can be Z_NO_FLUSH, Z_SYNC_FLUSH, Z_FINISH, 422 Z_BLOCK, or Z_TREES. Z_SYNC_FLUSH requests that inflate() flush as much 423 output as possible to the output buffer. Z_BLOCK requests that inflate() 424 stop if and when it gets to the next deflate block boundary. When decoding 425 the zlib or gzip format, this will cause inflate() to return immediately 426 after the header and before the first block. When doing a raw inflate, 427 inflate() will go ahead and process the first block, and will return when it 428 gets to the end of that block, or when it runs out of data. 429 430 The Z_BLOCK option assists in appending to or combining deflate streams. 431 Also to assist in this, on return inflate() will set strm->data_type to the 432 number of unused bits in the last byte taken from strm->next_in, plus 64 if 433 inflate() is currently decoding the last block in the deflate stream, plus 434 128 if inflate() returned immediately after decoding an end-of-block code or 435 decoding the complete header up to just before the first byte of the deflate 436 stream. The end-of-block will not be indicated until all of the uncompressed 437 data from that block has been written to strm->next_out. The number of 438 unused bits may in general be greater than seven, except when bit 7 of 439 data_type is set, in which case the number of unused bits will be less than 440 eight. data_type is set as noted here every time inflate() returns for all 441 flush options, and so can be used to determine the amount of currently 442 consumed input in bits. 443 444 The Z_TREES option behaves as Z_BLOCK does, but it also returns when the 445 end of each deflate block header is reached, before any actual data in that 446 block is decoded. This allows the caller to determine the length of the 447 deflate block header for later use in random access within a deflate block. 448 256 is added to the value of strm->data_type when inflate() returns 449 immediately after reaching the end of the deflate block header. 450 451 inflate() should normally be called until it returns Z_STREAM_END or an 452 error. However if all decompression is to be performed in a single step (a 453 single call of inflate), the parameter flush should be set to Z_FINISH. In 454 this case all pending input is processed and all pending output is flushed; 455 avail_out must be large enough to hold all of the uncompressed data for the 456 operation to complete. (The size of the uncompressed data may have been 457 saved by the compressor for this purpose.) The use of Z_FINISH is not 458 required to perform an inflation in one step. However it may be used to 459 inform inflate that a faster approach can be used for the single inflate() 460 call. Z_FINISH also informs inflate to not maintain a sliding window if the 461 stream completes, which reduces inflate's memory footprint. If the stream 462 does not complete, either because not all of the stream is provided or not 463 enough output space is provided, then a sliding window will be allocated and 464 inflate() can be called again to continue the operation as if Z_NO_FLUSH had 465 been used. 466 467 In this implementation, inflate() always flushes as much output as 468 possible to the output buffer, and always uses the faster approach on the 469 first call. So the effects of the flush parameter in this implementation are 470 on the return value of inflate() as noted below, when inflate() returns early 471 when Z_BLOCK or Z_TREES is used, and when inflate() avoids the allocation of 472 memory for a sliding window when Z_FINISH is used. 473 474 If a preset dictionary is needed after this call (see inflateSetDictionary 475 below), inflate sets strm->adler to the Adler-32 checksum of the dictionary 476 chosen by the compressor and returns Z_NEED_DICT; otherwise it sets 477 strm->adler to the Adler-32 checksum of all output produced so far (that is, 478 total_out bytes) and returns Z_OK, Z_STREAM_END or an error code as described 479 below. At the end of the stream, inflate() checks that its computed adler32 480 checksum is equal to that saved by the compressor and returns Z_STREAM_END 481 only if the checksum is correct. 482 483 inflate() can decompress and check either zlib-wrapped or gzip-wrapped 484 deflate data. The header type is detected automatically, if requested when 485 initializing with inflateInit2(). Any information contained in the gzip 486 header is not retained, so applications that need that information should 487 instead use raw inflate, see inflateInit2() below, or inflateBack() and 488 perform their own processing of the gzip header and trailer. When processing 489 gzip-wrapped deflate data, strm->adler32 is set to the CRC-32 of the output 490 producted so far. The CRC-32 is checked against the gzip trailer. 491 492 inflate() returns Z_OK if some progress has been made (more input processed 493 or more output produced), Z_STREAM_END if the end of the compressed data has 494 been reached and all uncompressed output has been produced, Z_NEED_DICT if a 495 preset dictionary is needed at this point, Z_DATA_ERROR if the input data was 496 corrupted (input stream not conforming to the zlib format or incorrect check 497 value), Z_STREAM_ERROR if the stream structure was inconsistent (for example 498 next_in or next_out was Z_NULL), Z_MEM_ERROR if there was not enough memory, 499 Z_BUF_ERROR if no progress is possible or if there was not enough room in the 500 output buffer when Z_FINISH is used. Note that Z_BUF_ERROR is not fatal, and 501 inflate() can be called again with more input and more output space to 502 continue decompressing. If Z_DATA_ERROR is returned, the application may 503 then call inflateSync() to look for a good compression block if a partial 504 recovery of the data is desired. 505*/ 506 507 508ZEXTERN int ZEXPORT inflateEnd OF((z_streamp strm)); 509/* 510 All dynamically allocated data structures for this stream are freed. 511 This function discards any unprocessed input and does not flush any pending 512 output. 513 514 inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state 515 was inconsistent. In the error case, msg may be set but then points to a 516 static string (which must not be deallocated). 517*/ 518 519 520 /* Advanced functions */ 521 522/* 523 The following functions are needed only in some special applications. 524*/ 525 526/* 527ZEXTERN int ZEXPORT deflateInit2 OF((z_streamp strm, 528 int level, 529 int method, 530 int windowBits, 531 int memLevel, 532 int strategy)); 533 534 This is another version of deflateInit with more compression options. The 535 fields next_in, zalloc, zfree and opaque must be initialized before by the 536 caller. 537 538 The method parameter is the compression method. It must be Z_DEFLATED in 539 this version of the library. 540 541 The windowBits parameter is the base two logarithm of the window size 542 (the size of the history buffer). It should be in the range 8..15 for this 543 version of the library. Larger values of this parameter result in better 544 compression at the expense of memory usage. The default value is 15 if 545 deflateInit is used instead. 546 547 windowBits can also be -8..-15 for raw deflate. In this case, -windowBits 548 determines the window size. deflate() will then generate raw deflate data 549 with no zlib header or trailer, and will not compute an adler32 check value. 550 551 windowBits can also be greater than 15 for optional gzip encoding. Add 552 16 to windowBits to write a simple gzip header and trailer around the 553 compressed data instead of a zlib wrapper. The gzip header will have no 554 file name, no extra data, no comment, no modification time (set to zero), no 555 header crc, and the operating system will be set to 255 (unknown). If a 556 gzip stream is being written, strm->adler is a crc32 instead of an adler32. 557 558 The memLevel parameter specifies how much memory should be allocated 559 for the internal compression state. memLevel=1 uses minimum memory but is 560 slow and reduces compression ratio; memLevel=9 uses maximum memory for 561 optimal speed. The default value is 8. See zconf.h for total memory usage 562 as a function of windowBits and memLevel. 563 564 The strategy parameter is used to tune the compression algorithm. Use the 565 value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a 566 filter (or predictor), Z_HUFFMAN_ONLY to force Huffman encoding only (no 567 string match), or Z_RLE to limit match distances to one (run-length 568 encoding). Filtered data consists mostly of small values with a somewhat 569 random distribution. In this case, the compression algorithm is tuned to 570 compress them better. The effect of Z_FILTERED is to force more Huffman 571 coding and less string matching; it is somewhat intermediate between 572 Z_DEFAULT_STRATEGY and Z_HUFFMAN_ONLY. Z_RLE is designed to be almost as 573 fast as Z_HUFFMAN_ONLY, but give better compression for PNG image data. The 574 strategy parameter only affects the compression ratio but not the 575 correctness of the compressed output even if it is not set appropriately. 576 Z_FIXED prevents the use of dynamic Huffman codes, allowing for a simpler 577 decoder for special applications. 578 579 deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough 580 memory, Z_STREAM_ERROR if any parameter is invalid (such as an invalid 581 method), or Z_VERSION_ERROR if the zlib library version (zlib_version) is 582 incompatible with the version assumed by the caller (ZLIB_VERSION). msg is 583 set to null if there is no error message. deflateInit2 does not perform any 584 compression: this will be done by deflate(). 585*/ 586 587ZEXTERN int ZEXPORT deflateSetDictionary OF((z_streamp strm, 588 const Bytef *dictionary, 589 uInt dictLength)); 590/* 591 Initializes the compression dictionary from the given byte sequence 592 without producing any compressed output. When using the zlib format, this 593 function must be called immediately after deflateInit, deflateInit2 or 594 deflateReset, and before any call of deflate. When doing raw deflate, this 595 function must be called either before any call of deflate, or immediately 596 after the completion of a deflate block, i.e. after all input has been 597 consumed and all output has been delivered when using any of the flush 598 options Z_BLOCK, Z_PARTIAL_FLUSH, Z_SYNC_FLUSH, or Z_FULL_FLUSH. The 599 compressor and decompressor must use exactly the same dictionary (see 600 inflateSetDictionary). 601 602 The dictionary should consist of strings (byte sequences) that are likely 603 to be encountered later in the data to be compressed, with the most commonly 604 used strings preferably put towards the end of the dictionary. Using a 605 dictionary is most useful when the data to be compressed is short and can be 606 predicted with good accuracy; the data can then be compressed better than 607 with the default empty dictionary. 608 609 Depending on the size of the compression data structures selected by 610 deflateInit or deflateInit2, a part of the dictionary may in effect be 611 discarded, for example if the dictionary is larger than the window size 612 provided in deflateInit or deflateInit2. Thus the strings most likely to be 613 useful should be put at the end of the dictionary, not at the front. In 614 addition, the current implementation of deflate will use at most the window 615 size minus 262 bytes of the provided dictionary. 616 617 Upon return of this function, strm->adler is set to the adler32 value 618 of the dictionary; the decompressor may later use this value to determine 619 which dictionary has been used by the compressor. (The adler32 value 620 applies to the whole dictionary even if only a subset of the dictionary is 621 actually used by the compressor.) If a raw deflate was requested, then the 622 adler32 value is not computed and strm->adler is not set. 623 624 deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a 625 parameter is invalid (e.g. dictionary being Z_NULL) or the stream state is 626 inconsistent (for example if deflate has already been called for this stream 627 or if not at a block boundary for raw deflate). deflateSetDictionary does 628 not perform any compression: this will be done by deflate(). 629*/ 630 631ZEXTERN int ZEXPORT deflateCopy OF((z_streamp dest, 632 z_streamp source)); 633/* 634 Sets the destination stream as a complete copy of the source stream. 635 636 This function can be useful when several compression strategies will be 637 tried, for example when there are several ways of pre-processing the input 638 data with a filter. The streams that will be discarded should then be freed 639 by calling deflateEnd. Note that deflateCopy duplicates the internal 640 compression state which can be quite large, so this strategy is slow and can 641 consume lots of memory. 642 643 deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not 644 enough memory, Z_STREAM_ERROR if the source stream state was inconsistent 645 (such as zalloc being Z_NULL). msg is left unchanged in both source and 646 destination. 647*/ 648 649ZEXTERN int ZEXPORT deflateReset OF((z_streamp strm)); 650/* 651 This function is equivalent to deflateEnd followed by deflateInit, 652 but does not free and reallocate all the internal compression state. The 653 stream will keep the same compression level and any other attributes that 654 may have been set by deflateInit2. 655 656 deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source 657 stream state was inconsistent (such as zalloc or state being Z_NULL). 658*/ 659 660ZEXTERN int ZEXPORT deflateParams OF((z_streamp strm, 661 int level, 662 int strategy)); 663/* 664 Dynamically update the compression level and compression strategy. The 665 interpretation of level and strategy is as in deflateInit2. This can be 666 used to switch between compression and straight copy of the input data, or 667 to switch to a different kind of input data requiring a different strategy. 668 If the compression level is changed, the input available so far is 669 compressed with the old level (and may be flushed); the new level will take 670 effect only at the next call of deflate(). 671 672 Before the call of deflateParams, the stream state must be set as for 673 a call of deflate(), since the currently available input may have to be 674 compressed and flushed. In particular, strm->avail_out must be non-zero. 675 676 deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source 677 stream state was inconsistent or if a parameter was invalid, Z_BUF_ERROR if 678 strm->avail_out was zero. 679*/ 680 681ZEXTERN int ZEXPORT deflateTune OF((z_streamp strm, 682 int good_length, 683 int max_lazy, 684 int nice_length, 685 int max_chain)); 686/* 687 Fine tune deflate's internal compression parameters. This should only be 688 used by someone who understands the algorithm used by zlib's deflate for 689 searching for the best matching string, and even then only by the most 690 fanatic optimizer trying to squeeze out the last compressed bit for their 691 specific input data. Read the deflate.c source code for the meaning of the 692 max_lazy, good_length, nice_length, and max_chain parameters. 693 694 deflateTune() can be called after deflateInit() or deflateInit2(), and 695 returns Z_OK on success, or Z_STREAM_ERROR for an invalid deflate stream. 696 */ 697 698ZEXTERN uLong ZEXPORT deflateBound OF((z_streamp strm, 699 uLong sourceLen)); 700/* 701 deflateBound() returns an upper bound on the compressed size after 702 deflation of sourceLen bytes. It must be called after deflateInit() or 703 deflateInit2(), and after deflateSetHeader(), if used. This would be used 704 to allocate an output buffer for deflation in a single pass, and so would be 705 called before deflate(). If that first deflate() call is provided the 706 sourceLen input bytes, an output buffer allocated to the size returned by 707 deflateBound(), and the flush value Z_FINISH, then deflate() is guaranteed 708 to return Z_STREAM_END. Note that it is possible for the compressed size to 709 be larger than the value returned by deflateBound() if flush options other 710 than Z_FINISH or Z_NO_FLUSH are used. 711*/ 712 713ZEXTERN int ZEXPORT deflatePending OF((z_streamp strm, 714 unsigned *pending, 715 int *bits)); 716/* 717 deflatePending() returns the number of bytes and bits of output that have 718 been generated, but not yet provided in the available output. The bytes not 719 provided would be due to the available output space having being consumed. 720 The number of bits of output not provided are between 0 and 7, where they 721 await more bits to join them in order to fill out a full byte. If pending 722 or bits are Z_NULL, then those values are not set. 723 724 deflatePending returns Z_OK if success, or Z_STREAM_ERROR if the source 725 stream state was inconsistent. 726 */ 727 728ZEXTERN int ZEXPORT deflatePrime OF((z_streamp strm, 729 int bits, 730 int value)); 731/* 732 deflatePrime() inserts bits in the deflate output stream. The intent 733 is that this function is used to start off the deflate output with the bits 734 leftover from a previous deflate stream when appending to it. As such, this 735 function can only be used for raw deflate, and must be used before the first 736 deflate() call after a deflateInit2() or deflateReset(). bits must be less 737 than or equal to 16, and that many of the least significant bits of value 738 will be inserted in the output. 739 740 deflatePrime returns Z_OK if success, Z_BUF_ERROR if there was not enough 741 room in the internal buffer to insert the bits, or Z_STREAM_ERROR if the 742 source stream state was inconsistent. 743*/ 744 745ZEXTERN int ZEXPORT deflateSetHeader OF((z_streamp strm, 746 gz_headerp head)); 747/* 748 deflateSetHeader() provides gzip header information for when a gzip 749 stream is requested by deflateInit2(). deflateSetHeader() may be called 750 after deflateInit2() or deflateReset() and before the first call of 751 deflate(). The text, time, os, extra field, name, and comment information 752 in the provided gz_header structure are written to the gzip header (xflag is 753 ignored -- the extra flags are set according to the compression level). The 754 caller must assure that, if not Z_NULL, name and comment are terminated with 755 a zero byte, and that if extra is not Z_NULL, that extra_len bytes are 756 available there. If hcrc is true, a gzip header crc is included. Note that 757 the current versions of the command-line version of gzip (up through version 758 1.3.x) do not support header crc's, and will report that it is a "multi-part 759 gzip file" and give up. 760 761 If deflateSetHeader is not used, the default gzip header has text false, 762 the time set to zero, and os set to 255, with no extra, name, or comment 763 fields. The gzip header is returned to the default state by deflateReset(). 764 765 deflateSetHeader returns Z_OK if success, or Z_STREAM_ERROR if the source 766 stream state was inconsistent. 767*/ 768 769/* 770ZEXTERN int ZEXPORT inflateInit2 OF((z_streamp strm, 771 int windowBits)); 772 773 This is another version of inflateInit with an extra parameter. The 774 fields next_in, avail_in, zalloc, zfree and opaque must be initialized 775 before by the caller. 776 777 The windowBits parameter is the base two logarithm of the maximum window 778 size (the size of the history buffer). It should be in the range 8..15 for 779 this version of the library. The default value is 15 if inflateInit is used 780 instead. windowBits must be greater than or equal to the windowBits value 781 provided to deflateInit2() while compressing, or it must be equal to 15 if 782 deflateInit2() was not used. If a compressed stream with a larger window 783 size is given as input, inflate() will return with the error code 784 Z_DATA_ERROR instead of trying to allocate a larger window. 785 786 windowBits can also be zero to request that inflate use the window size in 787 the zlib header of the compressed stream. 788 789 windowBits can also be -8..-15 for raw inflate. In this case, -windowBits 790 determines the window size. inflate() will then process raw deflate data, 791 not looking for a zlib or gzip header, not generating a check value, and not 792 looking for any check values for comparison at the end of the stream. This 793 is for use with other formats that use the deflate compressed data format 794 such as zip. Those formats provide their own check values. If a custom 795 format is developed using the raw deflate format for compressed data, it is 796 recommended that a check value such as an adler32 or a crc32 be applied to 797 the uncompressed data as is done in the zlib, gzip, and zip formats. For 798 most applications, the zlib format should be used as is. Note that comments 799 above on the use in deflateInit2() applies to the magnitude of windowBits. 800 801 windowBits can also be greater than 15 for optional gzip decoding. Add 802 32 to windowBits to enable zlib and gzip decoding with automatic header 803 detection, or add 16 to decode only the gzip format (the zlib format will 804 return a Z_DATA_ERROR). If a gzip stream is being decoded, strm->adler is a 805 crc32 instead of an adler32. 806 807 inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough 808 memory, Z_VERSION_ERROR if the zlib library version is incompatible with the 809 version assumed by the caller, or Z_STREAM_ERROR if the parameters are 810 invalid, such as a null pointer to the structure. msg is set to null if 811 there is no error message. inflateInit2 does not perform any decompression 812 apart from possibly reading the zlib header if present: actual decompression 813 will be done by inflate(). (So next_in and avail_in may be modified, but 814 next_out and avail_out are unused and unchanged.) The current implementation 815 of inflateInit2() does not process any header information -- that is 816 deferred until inflate() is called. 817*/ 818 819ZEXTERN int ZEXPORT inflateSetDictionary OF((z_streamp strm, 820 const Bytef *dictionary, 821 uInt dictLength)); 822/* 823 Initializes the decompression dictionary from the given uncompressed byte 824 sequence. This function must be called immediately after a call of inflate, 825 if that call returned Z_NEED_DICT. The dictionary chosen by the compressor 826 can be determined from the adler32 value returned by that call of inflate. 827 The compressor and decompressor must use exactly the same dictionary (see 828 deflateSetDictionary). For raw inflate, this function can be called at any 829 time to set the dictionary. If the provided dictionary is smaller than the 830 window and there is already data in the window, then the provided dictionary 831 will amend what's there. The application must insure that the dictionary 832 that was used for compression is provided. 833 834 inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a 835 parameter is invalid (e.g. dictionary being Z_NULL) or the stream state is 836 inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the 837 expected one (incorrect adler32 value). inflateSetDictionary does not 838 perform any decompression: this will be done by subsequent calls of 839 inflate(). 840*/ 841 842ZEXTERN int ZEXPORT inflateGetDictionary OF((z_streamp strm, 843 Bytef *dictionary, 844 uInt *dictLength)); 845/* 846 Returns the sliding dictionary being maintained by inflate. dictLength is 847 set to the number of bytes in the dictionary, and that many bytes are copied 848 to dictionary. dictionary must have enough space, where 32768 bytes is 849 always enough. If inflateGetDictionary() is called with dictionary equal to 850 Z_NULL, then only the dictionary length is returned, and nothing is copied. 851 Similary, if dictLength is Z_NULL, then it is not set. 852 853 inflateGetDictionary returns Z_OK on success, or Z_STREAM_ERROR if the 854 stream state is inconsistent. 855*/ 856 857ZEXTERN int ZEXPORT inflateSync OF((z_streamp strm)); 858/* 859 Skips invalid compressed data until a possible full flush point (see above 860 for the description of deflate with Z_FULL_FLUSH) can be found, or until all 861 available input is skipped. No output is provided. 862 863 inflateSync searches for a 00 00 FF FF pattern in the compressed data. 864 All full flush points have this pattern, but not all occurrences of this 865 pattern are full flush points. 866 867 inflateSync returns Z_OK if a possible full flush point has been found, 868 Z_BUF_ERROR if no more input was provided, Z_DATA_ERROR if no flush point 869 has been found, or Z_STREAM_ERROR if the stream structure was inconsistent. 870 In the success case, the application may save the current current value of 871 total_in which indicates where valid compressed data was found. In the 872 error case, the application may repeatedly call inflateSync, providing more 873 input each time, until success or end of the input data. 874*/ 875 876ZEXTERN int ZEXPORT inflateCopy OF((z_streamp dest, 877 z_streamp source)); 878/* 879 Sets the destination stream as a complete copy of the source stream. 880 881 This function can be useful when randomly accessing a large stream. The 882 first pass through the stream can periodically record the inflate state, 883 allowing restarting inflate at those points when randomly accessing the 884 stream. 885 886 inflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not 887 enough memory, Z_STREAM_ERROR if the source stream state was inconsistent 888 (such as zalloc being Z_NULL). msg is left unchanged in both source and 889 destination. 890*/ 891 892ZEXTERN int ZEXPORT inflateReset OF((z_streamp strm)); 893/* 894 This function is equivalent to inflateEnd followed by inflateInit, 895 but does not free and reallocate all the internal decompression state. The 896 stream will keep attributes that may have been set by inflateInit2. 897 898 inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source 899 stream state was inconsistent (such as zalloc or state being Z_NULL). 900*/ 901 902ZEXTERN int ZEXPORT inflateReset2 OF((z_streamp strm, 903 int windowBits)); 904/* 905 This function is the same as inflateReset, but it also permits changing 906 the wrap and window size requests. The windowBits parameter is interpreted 907 the same as it is for inflateInit2. 908 909 inflateReset2 returns Z_OK if success, or Z_STREAM_ERROR if the source 910 stream state was inconsistent (such as zalloc or state being Z_NULL), or if 911 the windowBits parameter is invalid. 912*/ 913 914ZEXTERN int ZEXPORT inflatePrime OF((z_streamp strm, 915 int bits, 916 int value)); 917/* 918 This function inserts bits in the inflate input stream. The intent is 919 that this function is used to start inflating at a bit position in the 920 middle of a byte. The provided bits will be used before any bytes are used 921 from next_in. This function should only be used with raw inflate, and 922 should be used before the first inflate() call after inflateInit2() or 923 inflateReset(). bits must be less than or equal to 16, and that many of the 924 least significant bits of value will be inserted in the input. 925 926 If bits is negative, then the input stream bit buffer is emptied. Then 927 inflatePrime() can be called again to put bits in the buffer. This is used 928 to clear out bits leftover after feeding inflate a block description prior 929 to feeding inflate codes. 930 931 inflatePrime returns Z_OK if success, or Z_STREAM_ERROR if the source 932 stream state was inconsistent. 933*/ 934 935ZEXTERN long ZEXPORT inflateMark OF((z_streamp strm)); 936/* 937 This function returns two values, one in the lower 16 bits of the return 938 value, and the other in the remaining upper bits, obtained by shifting the 939 return value down 16 bits. If the upper value is -1 and the lower value is 940 zero, then inflate() is currently decoding information outside of a block. 941 If the upper value is -1 and the lower value is non-zero, then inflate is in 942 the middle of a stored block, with the lower value equaling the number of 943 bytes from the input remaining to copy. If the upper value is not -1, then 944 it is the number of bits back from the current bit position in the input of 945 the code (literal or length/distance pair) currently being processed. In 946 that case the lower value is the number of bytes already emitted for that 947 code. 948 949 A code is being processed if inflate is waiting for more input to complete 950 decoding of the code, or if it has completed decoding but is waiting for 951 more output space to write the literal or match data. 952 953 inflateMark() is used to mark locations in the input data for random 954 access, which may be at bit positions, and to note those cases where the 955 output of a code may span boundaries of random access blocks. The current 956 location in the input stream can be determined from avail_in and data_type 957 as noted in the description for the Z_BLOCK flush parameter for inflate. 958 959 inflateMark returns the value noted above or -1 << 16 if the provided 960 source stream state was inconsistent. 961*/ 962 963ZEXTERN int ZEXPORT inflateGetHeader OF((z_streamp strm, 964 gz_headerp head)); 965/* 966 inflateGetHeader() requests that gzip header information be stored in the 967 provided gz_header structure. inflateGetHeader() may be called after 968 inflateInit2() or inflateReset(), and before the first call of inflate(). 969 As inflate() processes the gzip stream, head->done is zero until …
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