1 /* $Id: zlib.h,v 1.1 1999/03/23 03:21:58 paulus Exp $ */ 2 3 /* 4 * This file is derived from zlib.h and zconf.h from the zlib-0.95 5 * distribution by Jean-loup Gailly and Mark Adler, with some additions 6 * by Paul Mackerras to aid in implementing Deflate compression and 7 * decompression for PPP packets. 8 */ 9 10 /* zlib.h -- interface of the 'zlib' general purpose compression library 11 version 0.95, Aug 16th, 1995. 12 13 Copyright (C) 1995 Jean-loup Gailly and Mark Adler 14 15 This software is provided 'as-is', without any express or implied 16 warranty. In no event will the authors be held liable for any damages 17 arising from the use of this software. 18 19 Permission is granted to anyone to use this software for any purpose, 20 including commercial applications, and to alter it and redistribute it 21 freely, subject to the following restrictions: 22 23 1. The origin of this software must not be misrepresented; you must not 24 claim that you wrote the original software. If you use this software 25 in a product, an acknowledgment in the product documentation would be 26 appreciated but is not required. 27 2. Altered source versions must be plainly marked as such, and must not be 28 misrepresented as being the original software. 29 3. This notice may not be removed or altered from any source distribution. 30 31 Jean-loup Gailly Mark Adler 32 gzip@prep.ai.mit.edu madler@alumni.caltech.edu 33 */ 34 35 #ifndef _ZLIB_H 36 #define _ZLIB_H 37 38 /* #include "zconf.h" */ /* included directly here */ 39 40 /* zconf.h -- configuration of the zlib compression library 41 * Copyright (C) 1995 Jean-loup Gailly. 42 * For conditions of distribution and use, see copyright notice in zlib.h 43 */ 44 45 /* From: zconf.h,v 1.12 1995/05/03 17:27:12 jloup Exp */ 46 47 /* 48 The library does not install any signal handler. It is recommended to 49 add at least a handler for SIGSEGV when decompressing; the library checks 50 the consistency of the input data whenever possible but may go nuts 51 for some forms of corrupted input. 52 */ 53 54 /* 55 * Compile with -DMAXSEG_64K if the alloc function cannot allocate more 56 * than 64k bytes at a time (needed on systems with 16-bit int). 57 * Compile with -DUNALIGNED_OK if it is OK to access shorts or ints 58 * at addresses which are not a multiple of their size. 59 * Under DOS, -DFAR=far or -DFAR=__far may be needed. 60 */ 61 62 #ifndef STDC 63 # if defined(MSDOS) || defined(__STDC__) || defined(__cplusplus) 64 # define STDC 65 # endif 66 #endif 67 68 #ifdef __MWERKS__ /* Metrowerks CodeWarrior declares fileno() in unix.h */ 69 # include <unix.h> 70 #endif 71 72 /* Maximum value for memLevel in deflateInit2 */ 73 #ifndef MAX_MEM_LEVEL 74 # ifdef MAXSEG_64K 75 # define MAX_MEM_LEVEL 8 76 # else 77 # define MAX_MEM_LEVEL 9 78 # endif 79 #endif 80 81 #ifndef FAR 82 # define FAR 83 #endif 84 85 /* Maximum value for windowBits in deflateInit2 and inflateInit2 */ 86 #ifndef MAX_WBITS 87 # define MAX_WBITS 15 /* 32K LZ77 window */ 88 #endif 89 90 /* The memory requirements for deflate are (in bytes): 91 1 << (windowBits+2) + 1 << (memLevel+9) 92 that is: 128K for windowBits=15 + 128K for memLevel = 8 (default values) 93 plus a few kilobytes for small objects. For example, if you want to reduce 94 the default memory requirements from 256K to 128K, compile with 95 make CFLAGS="-O -DMAX_WBITS=14 -DMAX_MEM_LEVEL=7" 96 Of course this will generally degrade compression (there's no free lunch). 97 98 The memory requirements for inflate are (in bytes) 1 << windowBits 99 that is, 32K for windowBits=15 (default value) plus a few kilobytes 100 for small objects. 101 */ 102 103 /* Type declarations */ 104 105 #ifndef OF /* function prototypes */ 106 # ifdef STDC 107 # define OF(args) args 108 # else 109 # define OF(args) () 110 # endif 111 #endif 112 113 typedef unsigned char Byte; /* 8 bits */ 114 typedef unsigned int uInt; /* 16 bits or more */ 115 typedef unsigned long uLong; /* 32 bits or more */ 116 117 typedef Byte FAR Bytef; 118 typedef char FAR charf; 119 typedef int FAR intf; 120 typedef uInt FAR uIntf; 121 typedef uLong FAR uLongf; 122 123 #ifdef STDC 124 typedef void FAR *voidpf; 125 typedef void *voidp; 126 #else 127 typedef Byte FAR *voidpf; 128 typedef Byte *voidp; 129 #endif 130 131 /* end of original zconf.h */ 132 133 #define ZLIB_VERSION "0.95P" 134 135 /* 136 The 'zlib' compression library provides in-memory compression and 137 decompression functions, including integrity checks of the uncompressed 138 data. This version of the library supports only one compression method 139 (deflation) but other algorithms may be added later and will have the same 140 stream interface. 141 142 For compression the application must provide the output buffer and 143 may optionally provide the input buffer for optimization. For decompression, 144 the application must provide the input buffer and may optionally provide 145 the output buffer for optimization. 146 147 Compression can be done in a single step if the buffers are large 148 enough (for example if an input file is mmap'ed), or can be done by 149 repeated calls of the compression function. In the latter case, the 150 application must provide more input and/or consume the output 151 (providing more output space) before each call. 152 */ 153 154 typedef voidpf (*alloc_func) OF((voidpf opaque, uInt items, uInt size)); 155 typedef void (*free_func) OF((voidpf opaque, voidpf address, uInt nbytes)); 156 157 struct internal_state; 158 159 typedef struct z_stream_s { 160 Bytef *next_in; /* next input byte */ 161 uInt avail_in; /* number of bytes available at next_in */ 162 uLong total_in; /* total nb of input bytes read so far */ 163 164 Bytef *next_out; /* next output byte should be put there */ 165 uInt avail_out; /* remaining free space at next_out */ 166 uLong total_out; /* total nb of bytes output so far */ 167 168 char *msg; /* last error message, NULL if no error */ 169 struct internal_state FAR *state; /* not visible by applications */ 170 171 alloc_func zalloc; /* used to allocate the internal state */ 172 free_func zfree; /* used to free the internal state */ 173 voidp opaque; /* private data object passed to zalloc and zfree */ 174 175 Byte data_type; /* best guess about the data type: ascii or binary */ 176 177 } z_stream; 178 179 /* 180 The application must update next_in and avail_in when avail_in has 181 dropped to zero. It must update next_out and avail_out when avail_out 182 has dropped to zero. The application must initialize zalloc, zfree and 183 opaque before calling the init function. All other fields are set by the 184 compression library and must not be updated by the application. 185 186 The opaque value provided by the application will be passed as the first 187 parameter for calls of zalloc and zfree. This can be useful for custom 188 memory management. The compression library attaches no meaning to the 189 opaque value. 190 191 zalloc must return Z_NULL if there is not enough memory for the object. 192 On 16-bit systems, the functions zalloc and zfree must be able to allocate 193 exactly 65536 bytes, but will not be required to allocate more than this 194 if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS, 195 pointers returned by zalloc for objects of exactly 65536 bytes *must* 196 have their offset normalized to zero. The default allocation function 197 provided by this library ensures this (see zutil.c). To reduce memory 198 requirements and avoid any allocation of 64K objects, at the expense of 199 compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h). 200 201 The fields total_in and total_out can be used for statistics or 202 progress reports. After compression, total_in holds the total size of 203 the uncompressed data and may be saved for use in the decompressor 204 (particularly if the decompressor wants to decompress everything in 205 a single step). 206 */ 207 208 /* constants */ 209 210 #define Z_NO_FLUSH 0 211 #define Z_PARTIAL_FLUSH 1 212 #define Z_FULL_FLUSH 2 213 #define Z_SYNC_FLUSH 3 /* experimental: partial_flush + byte align */ 214 #define Z_FINISH 4 215 #define Z_PACKET_FLUSH 5 216 /* See deflate() below for the usage of these constants */ 217 218 #define Z_OK 0 219 #define Z_STREAM_END 1 220 #define Z_ERRNO (-1) 221 #define Z_STREAM_ERROR (-2) 222 #define Z_DATA_ERROR (-3) 223 #define Z_MEM_ERROR (-4) 224 #define Z_BUF_ERROR (-5) 225 /* error codes for the compression/decompression functions */ 226 227 #define Z_BEST_SPEED 1 228 #define Z_BEST_COMPRESSION 9 229 #define Z_DEFAULT_COMPRESSION (-1) 230 /* compression levels */ 231 232 #define Z_FILTERED 1 233 #define Z_HUFFMAN_ONLY 2 234 #define Z_DEFAULT_STRATEGY 0 235 236 #define Z_BINARY 0 237 #define Z_ASCII 1 238 #define Z_UNKNOWN 2 239 /* Used to set the data_type field */ 240 241 #define Z_NULL 0 /* for initializing zalloc, zfree, opaque */ 242 243 extern char *zlib_version; 244 /* The application can compare zlib_version and ZLIB_VERSION for consistency. 245 If the first character differs, the library code actually used is 246 not compatible with the zlib.h header file used by the application. 247 */ 248 249 /* basic functions */ 250 251 extern int deflateInit OF((z_stream *strm, int level)); 252 /* 253 Initializes the internal stream state for compression. The fields 254 zalloc, zfree and opaque must be initialized before by the caller. 255 If zalloc and zfree are set to Z_NULL, deflateInit updates them to 256 use default allocation functions. 257 258 The compression level must be Z_DEFAULT_COMPRESSION, or between 1 and 9: 259 1 gives best speed, 9 gives best compression. Z_DEFAULT_COMPRESSION requests 260 a default compromise between speed and compression (currently equivalent 261 to level 6). 262 263 deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not 264 enough memory, Z_STREAM_ERROR if level is not a valid compression level. 265 msg is set to null if there is no error message. deflateInit does not 266 perform any compression: this will be done by deflate(). 267 */ 268 269 270 extern int deflate OF((z_stream *strm, int flush)); 271 /* 272 Performs one or both of the following actions: 273 274 - Compress more input starting at next_in and update next_in and avail_in 275 accordingly. If not all input can be processed (because there is not 276 enough room in the output buffer), next_in and avail_in are updated and 277 processing will resume at this point for the next call of deflate(). 278 279 - Provide more output starting at next_out and update next_out and avail_out 280 accordingly. This action is forced if the parameter flush is non zero. 281 Forcing flush frequently degrades the compression ratio, so this parameter 282 should be set only when necessary (in interactive applications). 283 Some output may be provided even if flush is not set. 284 285 Before the call of deflate(), the application should ensure that at least 286 one of the actions is possible, by providing more input and/or consuming 287 more output, and updating avail_in or avail_out accordingly; avail_out 288 should never be zero before the call. The application can consume the 289 compressed output when it wants, for example when the output buffer is full 290 (avail_out == 0), or after each call of deflate(). 291 292 If the parameter flush is set to Z_PARTIAL_FLUSH, the current compression 293 block is terminated and flushed to the output buffer so that the 294 decompressor can get all input data available so far. For method 9, a future 295 variant on method 8, the current block will be flushed but not terminated. 296 If flush is set to Z_FULL_FLUSH, the compression block is terminated, a 297 special marker is output and the compression dictionary is discarded; this 298 is useful to allow the decompressor to synchronize if one compressed block 299 has been damaged (see inflateSync below). Flushing degrades compression and 300 so should be used only when necessary. Using Z_FULL_FLUSH too often can 301 seriously degrade the compression. If deflate returns with avail_out == 0, 302 this function must be called again with the same value of the flush 303 parameter and more output space (updated avail_out), until the flush is 304 complete (deflate returns with non-zero avail_out). 305 306 If the parameter flush is set to Z_PACKET_FLUSH, the compression 307 block is terminated, and a zero-length stored block is output, 308 omitting the length bytes (the effect of this is that the 3-bit type 309 code 000 for a stored block is output, and the output is then 310 byte-aligned). This is designed for use at the end of a PPP packet. 311 In addition, if the current compression block contains all the data 312 since the last Z_PACKET_FLUSH, it is never output as a stored block. 313 If the current compression block output as a static or dynamic block 314 would not be at least `minCompression' bytes smaller than the 315 original data, then nothing is output for that block. (The type 316 code for the zero-length stored block is still output, resulting in 317 a single zero byte being output for the whole packet.) 318 `MinCompression' is a parameter to deflateInit2, or 0 if deflateInit 319 is used. 320 321 If the parameter flush is set to Z_FINISH, all pending input is processed, 322 all pending output is flushed and deflate returns with Z_STREAM_END if there 323 was enough output space; if deflate returns with Z_OK, this function must be 324 called again with Z_FINISH and more output space (updated avail_out) but no 325 more input data, until it returns with Z_STREAM_END or an error. After 326 deflate has returned Z_STREAM_END, the only possible operations on the 327 stream are deflateReset or deflateEnd. 328 329 Z_FINISH can be used immediately after deflateInit if all the compression 330 is to be done in a single step. In this case, avail_out must be at least 331 0.1% larger than avail_in plus 12 bytes. If deflate does not return 332 Z_STREAM_END, then it must be called again as described above. 333 334 deflate() may update data_type if it can make a good guess about 335 the input data type (Z_ASCII or Z_BINARY). In doubt, the data is considered 336 binary. This field is only for information purposes and does not affect 337 the compression algorithm in any manner. 338 339 deflate() returns Z_OK if some progress has been made (more input 340 processed or more output produced), Z_STREAM_END if all input has been 341 consumed and all output has been produced (only when flush is set to 342 Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example 343 if next_in or next_out was NULL), Z_BUF_ERROR if no progress is possible. 344 */ 345 346 347 extern int deflateEnd OF((z_stream *strm)); 348 /* 349 All dynamically allocated data structures for this stream are freed. 350 This function discards any unprocessed input and does not flush any 351 pending output. 352 353 deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the 354 stream state was inconsistent. In the error case, msg may be set 355 but then points to a static string (which must not be deallocated). 356 */ 357 358 359 extern int inflateInit OF((z_stream *strm)); 360 /* 361 Initializes the internal stream state for decompression. The fields 362 zalloc and zfree must be initialized before by the caller. If zalloc and 363 zfree are set to Z_NULL, inflateInit updates them to use default allocation 364 functions. 365 366 inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not 367 enough memory. msg is set to null if there is no error message. 368 inflateInit does not perform any decompression: this will be done by 369 inflate(). 370 */ 371 372 373 extern int inflate OF((z_stream *strm, int flush)); 374 /* 375 Performs one or both of the following actions: 376 377 - Decompress more input starting at next_in and update next_in and avail_in 378 accordingly. If not all input can be processed (because there is not 379 enough room in the output buffer), next_in is updated and processing 380 will resume at this point for the next call of inflate(). 381 382 - Provide more output starting at next_out and update next_out and avail_out 383 accordingly. inflate() always provides as much output as possible 384 (until there is no more input data or no more space in the output buffer). 385 386 Before the call of inflate(), the application should ensure that at least 387 one of the actions is possible, by providing more input and/or consuming 388 more output, and updating the next_* and avail_* values accordingly. 389 The application can consume the uncompressed output when it wants, for 390 example when the output buffer is full (avail_out == 0), or after each 391 call of inflate(). 392 393 If the parameter flush is set to Z_PARTIAL_FLUSH or Z_PACKET_FLUSH, 394 inflate flushes as much output as possible to the output buffer. The 395 flushing behavior of inflate is not specified for values of the flush 396 parameter other than Z_PARTIAL_FLUSH, Z_PACKET_FLUSH or Z_FINISH, but the 397 current implementation actually flushes as much output as possible 398 anyway. For Z_PACKET_FLUSH, inflate checks that once all the input data 399 has been consumed, it is expecting to see the length field of a stored 400 block; if not, it returns Z_DATA_ERROR. 401 402 inflate() should normally be called until it returns Z_STREAM_END or an 403 error. However if all decompression is to be performed in a single step 404 (a single call of inflate), the parameter flush should be set to 405 Z_FINISH. In this case all pending input is processed and all pending 406 output is flushed; avail_out must be large enough to hold all the 407 uncompressed data. (The size of the uncompressed data may have been saved 408 by the compressor for this purpose.) The next operation on this stream must 409 be inflateEnd to deallocate the decompression state. The use of Z_FINISH 410 is never required, but can be used to inform inflate that a faster routine 411 may be used for the single inflate() call. 412 413 inflate() returns Z_OK if some progress has been made (more input 414 processed or more output produced), Z_STREAM_END if the end of the 415 compressed data has been reached and all uncompressed output has been 416 produced, Z_DATA_ERROR if the input data was corrupted, Z_STREAM_ERROR if 417 the stream structure was inconsistent (for example if next_in or next_out 418 was NULL), Z_MEM_ERROR if there was not enough memory, Z_BUF_ERROR if no 419 progress is possible or if there was not enough room in the output buffer 420 when Z_FINISH is used. In the Z_DATA_ERROR case, the application may then 421 call inflateSync to look for a good compression block. */ 422 423 424 extern int inflateEnd OF((z_stream *strm)); 425 /* 426 All dynamically allocated data structures for this stream are freed. 427 This function discards any unprocessed input and does not flush any 428 pending output. 429 430 inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state 431 was inconsistent. In the error case, msg may be set but then points to a 432 static string (which must not be deallocated). 433 */ 434 435 /* advanced functions */ 436 437 /* 438 The following functions are needed only in some special applications. 439 */ 440 441 extern int deflateInit2 OF((z_stream *strm, 442 int level, 443 int method, 444 int windowBits, 445 int memLevel, 446 int strategy, 447 int minCompression)); 448 /* 449 This is another version of deflateInit with more compression options. The 450 fields next_in, zalloc and zfree must be initialized before by the caller. 451 452 The method parameter is the compression method. It must be 8 in this 453 version of the library. (Method 9 will allow a 64K history buffer and 454 partial block flushes.) 455 456 The windowBits parameter is the base two logarithm of the window size 457 (the size of the history buffer). It should be in the range 8..15 for this 458 version of the library (the value 16 will be allowed for method 9). Larger 459 values of this parameter result in better compression at the expense of 460 memory usage. The default value is 15 if deflateInit is used instead. 461 462 The memLevel parameter specifies how much memory should be allocated 463 for the internal compression state. memLevel=1 uses minimum memory but 464 is slow and reduces compression ratio; memLevel=9 uses maximum memory 465 for optimal speed. The default value is 8. See zconf.h for total memory 466 usage as a function of windowBits and memLevel. 467 468 The strategy parameter is used to tune the compression algorithm. Use 469 the value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data 470 produced by a filter (or predictor), or Z_HUFFMAN_ONLY to force Huffman 471 encoding only (no string match). Filtered data consists mostly of small 472 values with a somewhat random distribution. In this case, the 473 compression algorithm is tuned to compress them better. The strategy 474 parameter only affects the compression ratio but not the correctness of 475 the compressed output even if it is not set appropriately. 476 477 The minCompression parameter specifies the minimum reduction in size 478 required for a compressed block to be output when Z_PACKET_FLUSH is 479 used (see the description of deflate above). 480 481 If next_in is not null, the library will use this buffer to hold also 482 some history information; the buffer must either hold the entire input 483 data, or have at least 1<<(windowBits+1) bytes and be writable. If next_in 484 is null, the library will allocate its own history buffer (and leave next_in 485 null). next_out need not be provided here but must be provided by the 486 application for the next call of deflate(). 487 488 If the history buffer is provided by the application, next_in must 489 must never be changed by the application since the compressor maintains 490 information inside this buffer from call to call; the application 491 must provide more input only by increasing avail_in. next_in is always 492 reset by the library in this case. 493 494 deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was 495 not enough memory, Z_STREAM_ERROR if a parameter is invalid (such as 496 an invalid method). msg is set to null if there is no error message. 497 deflateInit2 does not perform any compression: this will be done by 498 deflate(). 499 */ 500 501 extern int deflateCopy OF((z_stream *dest, 502 z_stream *source)); 503 /* 504 Sets the destination stream as a complete copy of the source stream. If 505 the source stream is using an application-supplied history buffer, a new 506 buffer is allocated for the destination stream. The compressed output 507 buffer is always application-supplied. It's the responsibility of the 508 application to provide the correct values of next_out and avail_out for the 509 next call of deflate. 510 511 This function is useful when several compression strategies will be 512 tried, for example when there are several ways of pre-processing the input 513 data with a filter. The streams that will be discarded should then be freed 514 by calling deflateEnd. Note that deflateCopy duplicates the internal 515 compression state which can be quite large, so this strategy is slow and 516 can consume lots of memory. 517 518 deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not 519 enough memory, Z_STREAM_ERROR if the source stream state was inconsistent 520 (such as zalloc being NULL). msg is left unchanged in both source and 521 destination. 522 */ 523 524 extern int deflateReset OF((z_stream *strm)); 525 /* 526 This function is equivalent to deflateEnd followed by deflateInit, 527 but does not free and reallocate all the internal compression state. 528 The stream will keep the same compression level and any other attributes 529 that may have been set by deflateInit2. 530 531 deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source 532 stream state was inconsistent (such as zalloc or state being NULL). 533 */ 534 535 extern int inflateInit2 OF((z_stream *strm, 536 int windowBits)); 537 /* 538 This is another version of inflateInit with more compression options. The 539 fields next_out, zalloc and zfree must be initialized before by the caller. 540 541 The windowBits parameter is the base two logarithm of the maximum window 542 size (the size of the history buffer). It should be in the range 8..15 for 543 this version of the library (the value 16 will be allowed soon). The 544 default value is 15 if inflateInit is used instead. If a compressed stream 545 with a larger window size is given as input, inflate() will return with 546 the error code Z_DATA_ERROR instead of trying to allocate a larger window. 547 548 If next_out is not null, the library will use this buffer for the history 549 buffer; the buffer must either be large enough to hold the entire output 550 data, or have at least 1<<windowBits bytes. If next_out is null, the 551 library will allocate its own buffer (and leave next_out null). next_in 552 need not be provided here but must be provided by the application for the 553 next call of inflate(). 554 555 If the history buffer is provided by the application, next_out must 556 never be changed by the application since the decompressor maintains 557 history information inside this buffer from call to call; the application 558 can only reset next_out to the beginning of the history buffer when 559 avail_out is zero and all output has been consumed. 560 561 inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was 562 not enough memory, Z_STREAM_ERROR if a parameter is invalid (such as 563 windowBits < 8). msg is set to null if there is no error message. 564 inflateInit2 does not perform any decompression: this will be done by 565 inflate(). 566 */ 567 568 extern int inflateSync OF((z_stream *strm)); 569 /* 570 Skips invalid compressed data until the special marker (see deflate() 571 above) can be found, or until all available input is skipped. No output 572 is provided. 573 574 inflateSync returns Z_OK if the special marker has been found, Z_BUF_ERROR 575 if no more input was provided, Z_DATA_ERROR if no marker has been found, 576 or Z_STREAM_ERROR if the stream structure was inconsistent. In the success 577 case, the application may save the current current value of total_in which 578 indicates where valid compressed data was found. In the error case, the 579 application may repeatedly call inflateSync, providing more input each time, 580 until success or end of the input data. 581 */ 582 583 extern int inflateReset OF((z_stream *strm)); 584 /* 585 This function is equivalent to inflateEnd followed by inflateInit, 586 but does not free and reallocate all the internal decompression state. 587 The stream will keep attributes that may have been set by inflateInit2. 588 589 inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source 590 stream state was inconsistent (such as zalloc or state being NULL). 591 */ 592 593 extern int inflateIncomp OF((z_stream *strm)); 594 /* 595 This function adds the data at next_in (avail_in bytes) to the output 596 history without performing any output. There must be no pending output, 597 and the decompressor must be expecting to see the start of a block. 598 Calling this function is equivalent to decompressing a stored block 599 containing the data at next_in (except that the data is not output). 600 */ 601 602 /* checksum functions */ 603 604 /* 605 This function is not related to compression but is exported 606 anyway because it might be useful in applications using the 607 compression library. 608 */ 609 610 extern uLong adler32 OF((uLong adler, Bytef *buf, uInt len)); 611 612 /* 613 Update a running Adler-32 checksum with the bytes buf[0..len-1] and 614 return the updated checksum. If buf is NULL, this function returns 615 the required initial value for the checksum. 616 An Adler-32 checksum is almost as reliable as a CRC32 but can be computed 617 much faster. Usage example: 618 619 uLong adler = adler32(0L, Z_NULL, 0); 620 621 while (read_buffer(buffer, length) != EOF) { 622 adler = adler32(adler, buffer, length); 623 } 624 if (adler != original_adler) error(); 625 */ 626 627 #ifndef _Z_UTIL_H 628 struct internal_state {int dummy;}; /* hack for buggy compilers */ 629 #endif 630 631 #endif /* _ZLIB_H */ 632