1 /* $OpenBSD: zlib.h,v 1.4 2001/06/09 06:16:39 angelos Exp $ */
2 /* $NetBSD: zlib.h,v 1.1 1996/03/15 02:28:17 paulus Exp $ */
3
4 /*
5 * This file is derived from zlib.h and zconf.h from the zlib-0.95
6 * distribution by Jean-loup Gailly and Mark Adler, with some additions
7 * by Paul Mackerras to aid in implementing Deflate compression and
8 * decompression for PPP packets.
9 */
10
11 /* zlib.h -- interface of the 'zlib' general purpose compression library
12 version 0.95, Aug 16th, 1995.
13
14 Copyright (C) 1995 Jean-loup Gailly and Mark Adler
15
16 This software is provided 'as-is', without any express or implied
17 warranty. In no event will the authors be held liable for any damages
18 arising from the use of this software.
19
20 Permission is granted to anyone to use this software for any purpose,
21 including commercial applications, and to alter it and redistribute it
22 freely, subject to the following restrictions:
23
24 1. The origin of this software must not be misrepresented; you must not
25 claim that you wrote the original software. If you use this software
26 in a product, an acknowledgment in the product documentation would be
27 appreciated but is not required.
28 2. Altered source versions must be plainly marked as such, and must not be
29 misrepresented as being the original software.
30 3. This notice may not be removed or altered from any source distribution.
31
32 Jean-loup Gailly Mark Adler
33 gzip@prep.ai.mit.edu madler@alumni.caltech.edu
34 */
35
36 #ifndef _NET_ZLIB_H_
37 #define _NET_ZLIB_H_
38
39 /* #include "zconf.h" */ /* included directly here */
40
41 /* zconf.h -- configuration of the zlib compression library
42 * Copyright (C) 1995 Jean-loup Gailly.
43 * For conditions of distribution and use, see copyright notice in zlib.h
44 */
45
46 /* From: zconf.h,v 1.12 1995/05/03 17:27:12 jloup Exp */
47
48 /*
49 The library does not install any signal handler. It is recommended to
50 add at least a handler for SIGSEGV when decompressing; the library checks
51 the consistency of the input data whenever possible but may go nuts
52 for some forms of corrupted input.
53 */
54
55 /*
56 * Compile with -DMAXSEG_64K if the alloc function cannot allocate more
57 * than 64k bytes at a time (needed on systems with 16-bit int).
58 * Compile with -DUNALIGNED_OK if it is OK to access shorts or ints
59 * at addresses which are not a multiple of their size.
60 * Under DOS, -DFAR=far or -DFAR=__far may be needed.
61 */
62
63 #ifndef STDC
64 # if defined(MSDOS) || defined(__STDC__) || defined(__cplusplus)
65 # define STDC
66 # endif
67 #endif
68
69 #ifdef __MWERKS__ /* Metrowerks CodeWarrior declares fileno() in unix.h */
70 # include <unix.h>
71 #endif
72
73 /* Maximum value for memLevel in deflateInit2 */
74 #ifndef MAX_MEM_LEVEL
75 # ifdef MAXSEG_64K
76 # define MAX_MEM_LEVEL 8
77 # else
78 # define MAX_MEM_LEVEL 9
79 # endif
80 #endif
81
82 #ifndef FAR
83 # define FAR
84 #endif
85
86 /* Maximum value for windowBits in deflateInit2 and inflateInit2 */
87 #ifndef MAX_WBITS
88 # define MAX_WBITS 15 /* 32K LZ77 window */
89 #endif
90
91 /* The memory requirements for deflate are (in bytes):
92 1 << (windowBits+2) + 1 << (memLevel+9)
93 that is: 128K for windowBits=15 + 128K for memLevel = 8 (default values)
94 plus a few kilobytes for small objects. For example, if you want to reduce
95 the default memory requirements from 256K to 128K, compile with
96 make CFLAGS="-O -DMAX_WBITS=14 -DMAX_MEM_LEVEL=7"
97 Of course this will generally degrade compression (there's no free lunch).
98
99 The memory requirements for inflate are (in bytes) 1 << windowBits
100 that is, 32K for windowBits=15 (default value) plus a few kilobytes
101 for small objects.
102 */
103
104 /* Type declarations */
105
106 #ifndef OF /* function prototypes */
107 # ifdef STDC
108 # define OF(args) args
109 # else
110 # define OF(args) ()
111 # endif
112 #endif
113
114 typedef unsigned char Byte; /* 8 bits */
115 typedef unsigned int uInt; /* 16 bits or more */
116 typedef unsigned long uLong; /* 32 bits or more */
117
118 typedef Byte FAR Bytef;
119 typedef char FAR charf;
120 typedef int FAR intf;
121 typedef uInt FAR uIntf;
122 typedef uLong FAR uLongf;
123
124 #ifdef STDC
125 typedef void FAR *voidpf;
126 typedef void *voidp;
127 #else
128 typedef Byte FAR *voidpf;
129 typedef Byte *voidp;
130 #endif
131
132 /* end of original zconf.h */
133
134 #define ZLIB_VERSION "0.95P"
135
136 /*
137 The 'zlib' compression library provides in-memory compression and
138 decompression functions, including integrity checks of the uncompressed
139 data. This version of the library supports only one compression method
140 (deflation) but other algorithms may be added later and will have the same
141 stream interface.
142
143 For compression the application must provide the output buffer and
144 may optionally provide the input buffer for optimization. For decompression,
145 the application must provide the input buffer and may optionally provide
146 the output buffer for optimization.
147
148 Compression can be done in a single step if the buffers are large
149 enough (for example if an input file is mmap'ed), or can be done by
150 repeated calls of the compression function. In the latter case, the
151 application must provide more input and/or consume the output
152 (providing more output space) before each call.
153 */
154
155 typedef voidpf (*alloc_func) OF((voidpf opaque, uInt items, uInt size));
156 typedef void (*free_func) OF((voidpf opaque, voidpf address, uInt nbytes));
157
158 struct internal_state;
159
160 typedef struct z_stream_s {
161 Bytef *next_in; /* next input byte */
162 uInt avail_in; /* number of bytes available at next_in */
163 uLong total_in; /* total nb of input bytes read so far */
164
165 Bytef *next_out; /* next output byte should be put there */
166 uInt avail_out; /* remaining free space at next_out */
167 uLong total_out; /* total nb of bytes output so far */
168
169 char *msg; /* last error message, NULL if no error */
170 struct internal_state FAR *state; /* not visible by applications */
171
172 alloc_func zalloc; /* used to allocate the internal state */
173 free_func zfree; /* used to free the internal state */
174 voidp opaque; /* private data object passed to zalloc and zfree */
175
176 Byte data_type; /* best guess about the data type: ascii or binary */
177
178 } z_stream;
179
180 /*
181 The application must update next_in and avail_in when avail_in has
182 dropped to zero. It must update next_out and avail_out when avail_out
183 has dropped to zero. The application must initialize zalloc, zfree and
184 opaque before calling the init function. All other fields are set by the
185 compression library and must not be updated by the application.
186
187 The opaque value provided by the application will be passed as the first
188 parameter for calls of zalloc and zfree. This can be useful for custom
189 memory management. The compression library attaches no meaning to the
190 opaque value.
191
192 zalloc must return Z_NULL if there is not enough memory for the object.
193 On 16-bit systems, the functions zalloc and zfree must be able to allocate
194 exactly 65536 bytes, but will not be required to allocate more than this
195 if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS,
196 pointers returned by zalloc for objects of exactly 65536 bytes *must*
197 have their offset normalized to zero. The default allocation function
198 provided by this library ensures this (see zutil.c). To reduce memory
199 requirements and avoid any allocation of 64K objects, at the expense of
200 compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h).
201
202 The fields total_in and total_out can be used for statistics or
203 progress reports. After compression, total_in holds the total size of
204 the uncompressed data and may be saved for use in the decompressor
205 (particularly if the decompressor wants to decompress everything in
206 a single step).
207 */
208
209 /* constants */
210
211 #define Z_NO_FLUSH 0
212 #define Z_PARTIAL_FLUSH 1
213 #define Z_FULL_FLUSH 2
214 #define Z_SYNC_FLUSH 3 /* experimental: partial_flush + byte align */
215 #define Z_FINISH 4
216 #define Z_PACKET_FLUSH 5
217 /* See deflate() below for the usage of these constants */
218
219 #define Z_OK 0
220 #define Z_STREAM_END 1
221 #define Z_ERRNO (-1)
222 #define Z_STREAM_ERROR (-2)
223 #define Z_DATA_ERROR (-3)
224 #define Z_MEM_ERROR (-4)
225 #define Z_BUF_ERROR (-5)
226 /* error codes for the compression/decompression functions */
227
228 #define Z_BEST_SPEED 1
229 #define Z_BEST_COMPRESSION 9
230 #define Z_DEFAULT_COMPRESSION (-1)
231 /* compression levels */
232
233 #define Z_FILTERED 1
234 #define Z_HUFFMAN_ONLY 2
235 #define Z_DEFAULT_STRATEGY 0
236
237 #define Z_BINARY 0
238 #define Z_ASCII 1
239 #define Z_UNKNOWN 2
240 /* Used to set the data_type field */
241
242 #define Z_NULL 0 /* for initializing zalloc, zfree, opaque */
243
244 extern char *zlib_version;
245 /* The application can compare zlib_version and ZLIB_VERSION for consistency.
246 If the first character differs, the library code actually used is
247 not compatible with the zlib.h header file used by the application.
248 */
249
250 /* basic functions */
251
252 extern int deflateInit OF((z_stream *strm, int level));
253 /*
254 Initializes the internal stream state for compression. The fields
255 zalloc, zfree and opaque must be initialized before by the caller.
256 If zalloc and zfree are set to Z_NULL, deflateInit updates them to
257 use default allocation functions.
258
259 The compression level must be Z_DEFAULT_COMPRESSION, or between 1 and 9:
260 1 gives best speed, 9 gives best compression. Z_DEFAULT_COMPRESSION requests
261 a default compromise between speed and compression (currently equivalent
262 to level 6).
263
264 deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
265 enough memory, Z_STREAM_ERROR if level is not a valid compression level.
266 msg is set to null if there is no error message. deflateInit does not
267 perform any compression: this will be done by deflate().
268 */
269
270
271 extern int deflate OF((z_stream *strm, int flush));
272 /*
273 Performs one or both of the following actions:
274
275 - Compress more input starting at next_in and update next_in and avail_in
276 accordingly. If not all input can be processed (because there is not
277 enough room in the output buffer), next_in and avail_in are updated and
278 processing will resume at this point for the next call of deflate().
279
280 - Provide more output starting at next_out and update next_out and avail_out
281 accordingly. This action is forced if the parameter flush is non zero.
282 Forcing flush frequently degrades the compression ratio, so this parameter
283 should be set only when necessary (in interactive applications).
284 Some output may be provided even if flush is not set.
285
286 Before the call of deflate(), the application should ensure that at least
287 one of the actions is possible, by providing more input and/or consuming
288 more output, and updating avail_in or avail_out accordingly; avail_out
289 should never be zero before the call. The application can consume the
290 compressed output when it wants, for example when the output buffer is full
291 (avail_out == 0), or after each call of deflate().
292
293 If the parameter flush is set to Z_PARTIAL_FLUSH, the current compression
294 block is terminated and flushed to the output buffer so that the
295 decompressor can get all input data available so far. For method 9, a future
296 variant on method 8, the current block will be flushed but not terminated.
297 If flush is set to Z_FULL_FLUSH, the compression block is terminated, a
298 special marker is output and the compression dictionary is discarded; this
299 is useful to allow the decompressor to synchronize if one compressed block
300 has been damaged (see inflateSync below). Flushing degrades compression and
301 so should be used only when necessary. Using Z_FULL_FLUSH too often can
302 seriously degrade the compression. If deflate returns with avail_out == 0,
303 this function must be called again with the same value of the flush
304 parameter and more output space (updated avail_out), until the flush is
305 complete (deflate returns with non-zero avail_out).
306
307 If the parameter flush is set to Z_PACKET_FLUSH, the compression
308 block is terminated, and a zero-length stored block is output,
309 omitting the length bytes (the effect of this is that the 3-bit type
310 code 000 for a stored block is output, and the output is then
311 byte-aligned). This is designed for use at the end of a PPP packet.
312 In addition, if the current compression block contains all the data
313 since the last Z_PACKET_FLUSH, it is never output as a stored block.
314 If the current compression block output as a static or dynamic block
315 would not be at least `minCompression' bytes smaller than the
316 original data, then nothing is output for that block. (The type
317 code for the zero-length stored block is still output, resulting in
318 a single zero byte being output for the whole packet.)
319 `MinCompression' is a parameter to deflateInit2, or 0 if deflateInit
320 is used.
321
322 If the parameter flush is set to Z_FINISH, all pending input is processed,
323 all pending output is flushed and deflate returns with Z_STREAM_END if there
324 was enough output space; if deflate returns with Z_OK, this function must be
325 called again with Z_FINISH and more output space (updated avail_out) but no
326 more input data, until it returns with Z_STREAM_END or an error. After
327 deflate has returned Z_STREAM_END, the only possible operations on the
328 stream are deflateReset or deflateEnd.
329
330 Z_FINISH can be used immediately after deflateInit if all the compression
331 is to be done in a single step. In this case, avail_out must be at least
332 0.1% larger than avail_in plus 12 bytes. If deflate does not return
333 Z_STREAM_END, then it must be called again as described above.
334
335 deflate() may update data_type if it can make a good guess about
336 the input data type (Z_ASCII or Z_BINARY). In doubt, the data is considered
337 binary. This field is only for information purposes and does not affect
338 the compression algorithm in any manner.
339
340 deflate() returns Z_OK if some progress has been made (more input
341 processed or more output produced), Z_STREAM_END if all input has been
342 consumed and all output has been produced (only when flush is set to
343 Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
344 if next_in or next_out was NULL), Z_BUF_ERROR if no progress is possible.
345 */
346
347
348 extern int deflateEnd OF((z_stream *strm));
349 /*
350 All dynamically allocated data structures for this stream are freed.
351 This function discards any unprocessed input and does not flush any
352 pending output.
353
354 deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
355 stream state was inconsistent. In the error case, msg may be set
356 but then points to a static string (which must not be deallocated).
357 */
358
359
360 extern int inflateInit OF((z_stream *strm));
361 /*
362 Initializes the internal stream state for decompression. The fields
363 zalloc and zfree must be initialized before by the caller. If zalloc and
364 zfree are set to Z_NULL, inflateInit updates them to use default allocation
365 functions.
366
367 inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
368 enough memory. msg is set to null if there is no error message.
369 inflateInit does not perform any decompression: this will be done by
370 inflate().
371 */
372
373
374 extern int inflate OF((z_stream *strm, int flush));
375 /*
376 Performs one or both of the following actions:
377
378 - Decompress more input starting at next_in and update next_in and avail_in
379 accordingly. If not all input can be processed (because there is not
380 enough room in the output buffer), next_in is updated and processing
381 will resume at this point for the next call of inflate().
382
383 - Provide more output starting at next_out and update next_out and avail_out
384 accordingly. inflate() always provides as much output as possible
385 (until there is no more input data or no more space in the output buffer).
386
387 Before the call of inflate(), the application should ensure that at least
388 one of the actions is possible, by providing more input and/or consuming
389 more output, and updating the next_* and avail_* values accordingly.
390 The application can consume the uncompressed output when it wants, for
391 example when the output buffer is full (avail_out == 0), or after each
392 call of inflate().
393
394 If the parameter flush is set to Z_PARTIAL_FLUSH or Z_PACKET_FLUSH,
395 inflate flushes as much output as possible to the output buffer. The
396 flushing behavior of inflate is not specified for values of the flush
397 parameter other than Z_PARTIAL_FLUSH, Z_PACKET_FLUSH or Z_FINISH, but the
398 current implementation actually flushes as much output as possible
399 anyway. For Z_PACKET_FLUSH, inflate checks that once all the input data
400 has been consumed, it is expecting to see the length field of a stored
401 block; if not, it returns Z_DATA_ERROR.
402
403 inflate() should normally be called until it returns Z_STREAM_END or an
404 error. However if all decompression is to be performed in a single step
405 (a single call of inflate), the parameter flush should be set to
406 Z_FINISH. In this case all pending input is processed and all pending
407 output is flushed; avail_out must be large enough to hold all the
408 uncompressed data. (The size of the uncompressed data may have been saved
409 by the compressor for this purpose.) The next operation on this stream must
410 be inflateEnd to deallocate the decompression state. The use of Z_FINISH
411 is never required, but can be used to inform inflate that a faster routine
412 may be used for the single inflate() call.
413
414 inflate() returns Z_OK if some progress has been made (more input
415 processed or more output produced), Z_STREAM_END if the end of the
416 compressed data has been reached and all uncompressed output has been
417 produced, Z_DATA_ERROR if the input data was corrupted, Z_STREAM_ERROR if
418 the stream structure was inconsistent (for example if next_in or next_out
419 was NULL), Z_MEM_ERROR if there was not enough memory, Z_BUF_ERROR if no
420 progress is possible or if there was not enough room in the output buffer
421 when Z_FINISH is used. In the Z_DATA_ERROR case, the application may then
422 call inflateSync to look for a good compression block. */
423
424
425 extern int inflateEnd OF((z_stream *strm));
426 /*
427 All dynamically allocated data structures for this stream are freed.
428 This function discards any unprocessed input and does not flush any
429 pending output.
430
431 inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
432 was inconsistent. In the error case, msg may be set but then points to a
433 static string (which must not be deallocated).
434 */
435
436 /* advanced functions */
437
438 /*
439 The following functions are needed only in some special applications.
440 */
441
442 extern int deflateInit2 OF((z_stream *strm,
443 int level,
444 int method,
445 int windowBits,
446 int memLevel,
447 int strategy,
448 int minCompression));
449 /*
450 This is another version of deflateInit with more compression options. The
451 fields next_in, zalloc and zfree must be initialized before by the caller.
452
453 The method parameter is the compression method. It must be 8 in this
454 version of the library. (Method 9 will allow a 64K history buffer and
455 partial block flushes.)
456
457 The windowBits parameter is the base two logarithm of the window size
458 (the size of the history buffer). It should be in the range 8..15 for this
459 version of the library (the value 16 will be allowed for method 9). Larger
460 values of this parameter result in better compression at the expense of
461 memory usage. The default value is 15 if deflateInit is used instead.
462
463 The memLevel parameter specifies how much memory should be allocated
464 for the internal compression state. memLevel=1 uses minimum memory but
465 is slow and reduces compression ratio; memLevel=9 uses maximum memory
466 for optimal speed. The default value is 8. See zconf.h for total memory
467 usage as a function of windowBits and memLevel.
468
469 The strategy parameter is used to tune the compression algorithm. Use
470 the value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data
471 produced by a filter (or predictor), or Z_HUFFMAN_ONLY to force Huffman
472 encoding only (no string match). Filtered data consists mostly of small
473 values with a somewhat random distribution. In this case, the
474 compression algorithm is tuned to compress them better. The strategy
475 parameter only affects the compression ratio but not the correctness of
476 the compressed output even if it is not set appropriately.
477
478 The minCompression parameter specifies the minimum reduction in size
479 required for a compressed block to be output when Z_PACKET_FLUSH is
480 used (see the description of deflate above).
481
482 If next_in is not null, the library will use this buffer to hold also
483 some history information; the buffer must either hold the entire input
484 data, or have at least 1<<(windowBits+1) bytes and be writable. If next_in
485 is null, the library will allocate its own history buffer (and leave next_in
486 null). next_out need not be provided here but must be provided by the
487 application for the next call of deflate().
488
489 If the history buffer is provided by the application, next_in must
490 must never be changed by the application since the compressor maintains
491 information inside this buffer from call to call; the application
492 must provide more input only by increasing avail_in. next_in is always
493 reset by the library in this case.
494
495 deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was
496 not enough memory, Z_STREAM_ERROR if a parameter is invalid (such as
497 an invalid method). msg is set to null if there is no error message.
498 deflateInit2 does not perform any compression: this will be done by
499 deflate().
500 */
501
502 extern int deflateCopy OF((z_stream *dest,
503 z_stream *source));
504 /*
505 Sets the destination stream as a complete copy of the source stream. If
506 the source stream is using an application-supplied history buffer, a new
507 buffer is allocated for the destination stream. The compressed output
508 buffer is always application-supplied. It's the responsibility of the
509 application to provide the correct values of next_out and avail_out for the
510 next call of deflate.
511
512 This function is useful when several compression strategies will be
513 tried, for example when there are several ways of pre-processing the input
514 data with a filter. The streams that will be discarded should then be freed
515 by calling deflateEnd. Note that deflateCopy duplicates the internal
516 compression state which can be quite large, so this strategy is slow and
517 can consume lots of memory.
518
519 deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
520 enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
521 (such as zalloc being NULL). msg is left unchanged in both source and
522 destination.
523 */
524
525 extern int deflateReset OF((z_stream *strm));
526 /*
527 This function is equivalent to deflateEnd followed by deflateInit,
528 but does not free and reallocate all the internal compression state.
529 The stream will keep the same compression level and any other attributes
530 that may have been set by deflateInit2.
531
532 deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
533 stream state was inconsistent (such as zalloc or state being NULL).
534 */
535
536 extern int inflateInit2 OF((z_stream *strm,
537 int windowBits));
538 /*
539 This is another version of inflateInit with more compression options. The
540 fields next_out, zalloc and zfree must be initialized before by the caller.
541
542 The windowBits parameter is the base two logarithm of the maximum window
543 size (the size of the history buffer). It should be in the range 8..15 for
544 this version of the library (the value 16 will be allowed soon). The
545 default value is 15 if inflateInit is used instead. If a compressed stream
546 with a larger window size is given as input, inflate() will return with
547 the error code Z_DATA_ERROR instead of trying to allocate a larger window.
548
549 If next_out is not null, the library will use this buffer for the history
550 buffer; the buffer must either be large enough to hold the entire output
551 data, or have at least 1<<windowBits bytes. If next_out is null, the
552 library will allocate its own buffer (and leave next_out null). next_in
553 need not be provided here but must be provided by the application for the
554 next call of inflate().
555
556 If the history buffer is provided by the application, next_out must
557 never be changed by the application since the decompressor maintains
558 history information inside this buffer from call to call; the application
559 can only reset next_out to the beginning of the history buffer when
560 avail_out is zero and all output has been consumed.
561
562 inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was
563 not enough memory, Z_STREAM_ERROR if a parameter is invalid (such as
564 windowBits < 8). msg is set to null if there is no error message.
565 inflateInit2 does not perform any decompression: this will be done by
566 inflate().
567 */
568
569 extern int inflateSync OF((z_stream *strm));
570 /*
571 Skips invalid compressed data until the special marker (see deflate()
572 above) can be found, or until all available input is skipped. No output
573 is provided.
574
575 inflateSync returns Z_OK if the special marker has been found, Z_BUF_ERROR
576 if no more input was provided, Z_DATA_ERROR if no marker has been found,
577 or Z_STREAM_ERROR if the stream structure was inconsistent. In the success
578 case, the application may save the current current value of total_in which
579 indicates where valid compressed data was found. In the error case, the
580 application may repeatedly call inflateSync, providing more input each time,
581 until success or end of the input data.
582 */
583
584 extern int inflateReset OF((z_stream *strm));
585 /*
586 This function is equivalent to inflateEnd followed by inflateInit,
587 but does not free and reallocate all the internal decompression state.
588 The stream will keep attributes that may have been set by inflateInit2.
589
590 inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
591 stream state was inconsistent (such as zalloc or state being NULL).
592 */
593
594 extern int inflateIncomp OF((z_stream *strm));
595 /*
596 This function adds the data at next_in (avail_in bytes) to the output
597 history without performing any output. There must be no pending output,
598 and the decompressor must be expecting to see the start of a block.
599 Calling this function is equivalent to decompressing a stored block
600 containing the data at next_in (except that the data is not output).
601 */
602
603 /* checksum functions */
604
605 /*
606 This function is not related to compression but is exported
607 anyway because it might be useful in applications using the
608 compression library.
609 */
610
611 extern uLong adler32 OF((uLong adler, Bytef *buf, uInt len));
612
613 /*
614 Update a running Adler-32 checksum with the bytes buf[0..len-1] and
615 return the updated checksum. If buf is NULL, this function returns
616 the required initial value for the checksum.
617 An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
618 much faster. Usage example:
619
620 uLong adler = adler32(0L, Z_NULL, 0);
621
622 while (read_buffer(buffer, length) != EOF) {
623 adler = adler32(adler, buffer, length);
624 }
625 if (adler != original_adler) error();
626 */
627
628 #ifndef _Z_UTIL_H
629 struct internal_state {int dummy;}; /* hack for buggy compilers */
630 #endif
631 #endif /* _NET_ZLIB_H_ */