1 /* zlib.h -- interface of the 'zlib' general purpose compression library
2 version 0.95, Aug 16th, 1995.
4 Copyright (C) 1995 Jean-loup Gailly and Mark Adler
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.
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:
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.
22 Jean-loup Gailly Mark Adler
23 gzip@prep.ai.mit.edu madler@alumni.caltech.edu
31 #define ZLIB_VERSION "0.95P"
34 The 'zlib' compression library provides in-memory compression and
35 decompression functions, including integrity checks of the uncompressed
36 data. This version of the library supports only one compression method
37 (deflation) but other algorithms may be added later and will have the same
40 For compression the application must provide the output buffer and
41 may optionally provide the input buffer for optimization. For decompression,
42 the application must provide the input buffer and may optionally provide
43 the output buffer for optimization.
45 Compression can be done in a single step if the buffers are large
46 enough (for example if an input file is mmap'ed), or can be done by
47 repeated calls of the compression function. In the latter case, the
48 application must provide more input and/or consume the output
49 (providing more output space) before each call.
52 typedef voidpf (*alloc_func) OF((voidpf opaque, uInt items, uInt size));
53 typedef void (*free_func) OF((voidpf opaque, voidpf address, uInt nbytes));
55 struct internal_state;
57 typedef struct z_stream_s {
58 Bytef *next_in; /* next input byte */
59 uInt avail_in; /* number of bytes available at next_in */
60 uLong total_in; /* total nb of input bytes read so far */
62 Bytef *next_out; /* next output byte should be put there */
63 uInt avail_out; /* remaining free space at next_out */
64 uLong total_out; /* total nb of bytes output so far */
66 char *msg; /* last error message, NULL if no error */
67 struct internal_state FAR *state; /* not visible by applications */
69 alloc_func zalloc; /* used to allocate the internal state */
70 free_func zfree; /* used to free the internal state */
71 voidp opaque; /* private data object passed to zalloc and zfree */
73 Byte data_type; /* best guess about the data type: ascii or binary */
78 The application must update next_in and avail_in when avail_in has
79 dropped to zero. It must update next_out and avail_out when avail_out
80 has dropped to zero. The application must initialize zalloc, zfree and
81 opaque before calling the init function. All other fields are set by the
82 compression library and must not be updated by the application.
84 The opaque value provided by the application will be passed as the first
85 parameter for calls of zalloc and zfree. This can be useful for custom
86 memory management. The compression library attaches no meaning to the
89 zalloc must return Z_NULL if there is not enough memory for the object.
90 On 16-bit systems, the functions zalloc and zfree must be able to allocate
91 exactly 65536 bytes, but will not be required to allocate more than this
92 if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS,
93 pointers returned by zalloc for objects of exactly 65536 bytes *must*
94 have their offset normalized to zero. The default allocation function
95 provided by this library ensures this (see zutil.c). To reduce memory
96 requirements and avoid any allocation of 64K objects, at the expense of
97 compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h).
99 The fields total_in and total_out can be used for statistics or
100 progress reports. After compression, total_in holds the total size of
101 the uncompressed data and may be saved for use in the decompressor
102 (particularly if the decompressor wants to decompress everything in
109 #define Z_PARTIAL_FLUSH 1
110 #define Z_FULL_FLUSH 2
111 #define Z_SYNC_FLUSH 3 /* experimental: partial_flush + byte align */
113 #define Z_PACKET_FLUSH 5
114 /* See deflate() below for the usage of these constants */
117 #define Z_STREAM_END 1
119 #define Z_STREAM_ERROR (-2)
120 #define Z_DATA_ERROR (-3)
121 #define Z_MEM_ERROR (-4)
122 #define Z_BUF_ERROR (-5)
123 /* error codes for the compression/decompression functions */
125 #define Z_BEST_SPEED 1
126 #define Z_BEST_COMPRESSION 9
127 #define Z_DEFAULT_COMPRESSION (-1)
128 /* compression levels */
131 #define Z_HUFFMAN_ONLY 2
132 #define Z_DEFAULT_STRATEGY 0
137 /* Used to set the data_type field */
139 #define Z_NULL 0 /* for initializing zalloc, zfree, opaque */
141 extern char *zlib_version;
142 /* The application can compare zlib_version and ZLIB_VERSION for consistency.
143 If the first character differs, the library code actually used is
144 not compatible with the zlib.h header file used by the application.
147 /* basic functions */
149 extern int deflateInit OF((z_stream *strm, int level));
151 Initializes the internal stream state for compression. The fields
152 zalloc, zfree and opaque must be initialized before by the caller.
153 If zalloc and zfree are set to Z_NULL, deflateInit updates them to
154 use default allocation functions.
156 The compression level must be Z_DEFAULT_COMPRESSION, or between 1 and 9:
157 1 gives best speed, 9 gives best compression. Z_DEFAULT_COMPRESSION requests
158 a default compromise between speed and compression (currently equivalent
161 deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
162 enough memory, Z_STREAM_ERROR if level is not a valid compression level.
163 msg is set to null if there is no error message. deflateInit does not
164 perform any compression: this will be done by deflate().
168 extern int deflate OF((z_stream *strm, int flush));
170 Performs one or both of the following actions:
172 - Compress more input starting at next_in and update next_in and avail_in
173 accordingly. If not all input can be processed (because there is not
174 enough room in the output buffer), next_in and avail_in are updated and
175 processing will resume at this point for the next call of deflate().
177 - Provide more output starting at next_out and update next_out and avail_out
178 accordingly. This action is forced if the parameter flush is non zero.
179 Forcing flush frequently degrades the compression ratio, so this parameter
180 should be set only when necessary (in interactive applications).
181 Some output may be provided even if flush is not set.
183 Before the call of deflate(), the application should ensure that at least
184 one of the actions is possible, by providing more input and/or consuming
185 more output, and updating avail_in or avail_out accordingly; avail_out
186 should never be zero before the call. The application can consume the
187 compressed output when it wants, for example when the output buffer is full
188 (avail_out == 0), or after each call of deflate().
190 If the parameter flush is set to Z_PARTIAL_FLUSH, the current compression
191 block is terminated and flushed to the output buffer so that the
192 decompressor can get all input data available so far. For method 9, a future
193 variant on method 8, the current block will be flushed but not terminated.
194 If flush is set to Z_FULL_FLUSH, the compression block is terminated, a
195 special marker is output and the compression dictionary is discarded; this
196 is useful to allow the decompressor to synchronize if one compressed block
197 has been damaged (see inflateSync below). Flushing degrades compression and
198 so should be used only when necessary. Using Z_FULL_FLUSH too often can
199 seriously degrade the compression. If deflate returns with avail_out == 0,
200 this function must be called again with the same value of the flush
201 parameter and more output space (updated avail_out), until the flush is
202 complete (deflate returns with non-zero avail_out).
204 If the parameter flush is set to Z_PACKET_FLUSH, the compression
205 block is terminated, and a zero-length stored block is output,
206 omitting the length bytes (the effect of this is that the 3-bit type
207 code 000 for a stored block is output, and the output is then
208 byte-aligned). This is designed for use at the end of a PPP packet.
209 In addition, if the current compression block contains all the data
210 since the last Z_PACKET_FLUSH, it is never output as a stored block.
211 If the current compression block output as a static or dynamic block
212 would not be at least `minCompression' bytes smaller than the
213 original data, then nothing is output for that block. (The type
214 code for the zero-length stored block is still output, resulting in
215 a single zero byte being output for the whole packet.)
216 `MinCompression' is a parameter to deflateInit2, or 0 if deflateInit
219 If the parameter flush is set to Z_FINISH, all pending input is processed,
220 all pending output is flushed and deflate returns with Z_STREAM_END if there
221 was enough output space; if deflate returns with Z_OK, this function must be
222 called again with Z_FINISH and more output space (updated avail_out) but no
223 more input data, until it returns with Z_STREAM_END or an error. After
224 deflate has returned Z_STREAM_END, the only possible operations on the
225 stream are deflateReset or deflateEnd.
227 Z_FINISH can be used immediately after deflateInit if all the compression
228 is to be done in a single step. In this case, avail_out must be at least
229 0.1% larger than avail_in plus 12 bytes. If deflate does not return
230 Z_STREAM_END, then it must be called again as described above.
232 deflate() may update data_type if it can make a good guess about
233 the input data type (Z_ASCII or Z_BINARY). In doubt, the data is considered
234 binary. This field is only for information purposes and does not affect
235 the compression algorithm in any manner.
237 deflate() returns Z_OK if some progress has been made (more input
238 processed or more output produced), Z_STREAM_END if all input has been
239 consumed and all output has been produced (only when flush is set to
240 Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
241 if next_in or next_out was NULL), Z_BUF_ERROR if no progress is possible.
245 extern int deflateEnd OF((z_stream *strm));
247 All dynamically allocated data structures for this stream are freed.
248 This function discards any unprocessed input and does not flush any
251 deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
252 stream state was inconsistent. In the error case, msg may be set
253 but then points to a static string (which must not be deallocated).
257 extern int inflateInit OF((z_stream *strm));
259 Initializes the internal stream state for decompression. The fields
260 zalloc and zfree must be initialized before by the caller. If zalloc and
261 zfree are set to Z_NULL, inflateInit updates them to use default allocation
264 inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
265 enough memory. msg is set to null if there is no error message.
266 inflateInit does not perform any decompression: this will be done by
271 extern int inflate OF((z_stream *strm, int flush));
273 Performs one or both of the following actions:
275 - Decompress 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 is updated and processing
278 will resume at this point for the next call of inflate().
280 - Provide more output starting at next_out and update next_out and avail_out
281 accordingly. inflate() always provides as much output as possible
282 (until there is no more input data or no more space in the output buffer).
284 Before the call of inflate(), the application should ensure that at least
285 one of the actions is possible, by providing more input and/or consuming
286 more output, and updating the next_* and avail_* values accordingly.
287 The application can consume the uncompressed output when it wants, for
288 example when the output buffer is full (avail_out == 0), or after each
291 If the parameter flush is set to Z_PARTIAL_FLUSH or Z_PACKET_FLUSH,
292 inflate flushes as much output as possible to the output buffer. The
293 flushing behavior of inflate is not specified for values of the flush
294 parameter other than Z_PARTIAL_FLUSH, Z_PACKET_FLUSH or Z_FINISH, but the
295 current implementation actually flushes as much output as possible
296 anyway. For Z_PACKET_FLUSH, inflate checks that once all the input data
297 has been consumed, it is expecting to see the length field of a stored
298 block; if not, it returns Z_DATA_ERROR.
300 inflate() should normally be called until it returns Z_STREAM_END or an
301 error. However if all decompression is to be performed in a single step
302 (a single call of inflate), the parameter flush should be set to
303 Z_FINISH. In this case all pending input is processed and all pending
304 output is flushed; avail_out must be large enough to hold all the
305 uncompressed data. (The size of the uncompressed data may have been saved
306 by the compressor for this purpose.) The next operation on this stream must
307 be inflateEnd to deallocate the decompression state. The use of Z_FINISH
308 is never required, but can be used to inform inflate that a faster routine
309 may be used for the single inflate() call.
311 inflate() returns Z_OK if some progress has been made (more input
312 processed or more output produced), Z_STREAM_END if the end of the
313 compressed data has been reached and all uncompressed output has been
314 produced, Z_DATA_ERROR if the input data was corrupted, Z_STREAM_ERROR if
315 the stream structure was inconsistent (for example if next_in or next_out
316 was NULL), Z_MEM_ERROR if there was not enough memory, Z_BUF_ERROR if no
317 progress is possible or if there was not enough room in the output buffer
318 when Z_FINISH is used. In the Z_DATA_ERROR case, the application may then
319 call inflateSync to look for a good compression block. */
322 extern int inflateEnd OF((z_stream *strm));
324 All dynamically allocated data structures for this stream are freed.
325 This function discards any unprocessed input and does not flush any
328 inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
329 was inconsistent. In the error case, msg may be set but then points to a
330 static string (which must not be deallocated).
333 /* advanced functions */
336 The following functions are needed only in some special applications.
339 extern int deflateInit2 OF((z_stream *strm,
345 int minCompression));
347 This is another version of deflateInit with more compression options. The
348 fields next_in, zalloc and zfree must be initialized before by the caller.
350 The method parameter is the compression method. It must be 8 in this
351 version of the library. (Method 9 will allow a 64K history buffer and
352 partial block flushes.)
354 The windowBits parameter is the base two logarithm of the window size
355 (the size of the history buffer). It should be in the range 8..15 for this
356 version of the library (the value 16 will be allowed for method 9). Larger
357 values of this parameter result in better compression at the expense of
358 memory usage. The default value is 15 if deflateInit is used instead.
360 The memLevel parameter specifies how much memory should be allocated
361 for the internal compression state. memLevel=1 uses minimum memory but
362 is slow and reduces compression ratio; memLevel=9 uses maximum memory
363 for optimal speed. The default value is 8. See zconf.h for total memory
364 usage as a function of windowBits and memLevel.
366 The strategy parameter is used to tune the compression algorithm. Use
367 the value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data
368 produced by a filter (or predictor), or Z_HUFFMAN_ONLY to force Huffman
369 encoding only (no string match). Filtered data consists mostly of small
370 values with a somewhat random distribution. In this case, the
371 compression algorithm is tuned to compress them better. The strategy
372 parameter only affects the compression ratio but not the correctness of
373 the compressed output even if it is not set appropriately.
375 The minCompression parameter specifies the minimum reduction in size
376 required for a compressed block to be output when Z_PACKET_FLUSH is
377 used (see the description of deflate above).
379 If next_in is not null, the library will use this buffer to hold also
380 some history information; the buffer must either hold the entire input
381 data, or have at least 1<<(windowBits+1) bytes and be writable. If next_in
382 is null, the library will allocate its own history buffer (and leave next_in
383 null). next_out need not be provided here but must be provided by the
384 application for the next call of deflate().
386 If the history buffer is provided by the application, next_in must
387 must never be changed by the application since the compressor maintains
388 information inside this buffer from call to call; the application
389 must provide more input only by increasing avail_in. next_in is always
390 reset by the library in this case.
392 deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was
393 not enough memory, Z_STREAM_ERROR if a parameter is invalid (such as
394 an invalid method). msg is set to null if there is no error message.
395 deflateInit2 does not perform any compression: this will be done by
399 extern int deflateCopy OF((z_stream *dest,
402 Sets the destination stream as a complete copy of the source stream. If
403 the source stream is using an application-supplied history buffer, a new
404 buffer is allocated for the destination stream. The compressed output
405 buffer is always application-supplied. It's the responsibility of the
406 application to provide the correct values of next_out and avail_out for the
407 next call of deflate.
409 This function is useful when several compression strategies will be
410 tried, for example when there are several ways of pre-processing the input
411 data with a filter. The streams that will be discarded should then be freed
412 by calling deflateEnd. Note that deflateCopy duplicates the internal
413 compression state which can be quite large, so this strategy is slow and
414 can consume lots of memory.
416 deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
417 enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
418 (such as zalloc being NULL). msg is left unchanged in both source and
422 extern int deflateReset OF((z_stream *strm));
424 This function is equivalent to deflateEnd followed by deflateInit,
425 but does not free and reallocate all the internal compression state.
426 The stream will keep the same compression level and any other attributes
427 that may have been set by deflateInit2.
429 deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
430 stream state was inconsistent (such as zalloc or state being NULL).
433 extern int inflateInit2 OF((z_stream *strm,
436 This is another version of inflateInit with more compression options. The
437 fields next_out, zalloc and zfree must be initialized before by the caller.
439 The windowBits parameter is the base two logarithm of the maximum window
440 size (the size of the history buffer). It should be in the range 8..15 for
441 this version of the library (the value 16 will be allowed soon). The
442 default value is 15 if inflateInit is used instead. If a compressed stream
443 with a larger window size is given as input, inflate() will return with
444 the error code Z_DATA_ERROR instead of trying to allocate a larger window.
446 If next_out is not null, the library will use this buffer for the history
447 buffer; the buffer must either be large enough to hold the entire output
448 data, or have at least 1<<windowBits bytes. If next_out is null, the
449 library will allocate its own buffer (and leave next_out null). next_in
450 need not be provided here but must be provided by the application for the
451 next call of inflate().
453 If the history buffer is provided by the application, next_out must
454 never be changed by the application since the decompressor maintains
455 history information inside this buffer from call to call; the application
456 can only reset next_out to the beginning of the history buffer when
457 avail_out is zero and all output has been consumed.
459 inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was
460 not enough memory, Z_STREAM_ERROR if a parameter is invalid (such as
461 windowBits < 8). msg is set to null if there is no error message.
462 inflateInit2 does not perform any decompression: this will be done by
466 extern int inflateSync OF((z_stream *strm));
468 Skips invalid compressed data until the special marker (see deflate()
469 above) can be found, or until all available input is skipped. No output
472 inflateSync returns Z_OK if the special marker has been found, Z_BUF_ERROR
473 if no more input was provided, Z_DATA_ERROR if no marker has been found,
474 or Z_STREAM_ERROR if the stream structure was inconsistent. In the success
475 case, the application may save the current current value of total_in which
476 indicates where valid compressed data was found. In the error case, the
477 application may repeatedly call inflateSync, providing more input each time,
478 until success or end of the input data.
481 extern int inflateReset OF((z_stream *strm));
483 This function is equivalent to inflateEnd followed by inflateInit,
484 but does not free and reallocate all the internal decompression state.
485 The stream will keep attributes that may have been set by inflateInit2.
487 inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
488 stream state was inconsistent (such as zalloc or state being NULL).
491 extern int inflateIncomp OF((z_stream *strm));
493 This function adds the data at next_in (avail_in bytes) to the output
494 history without performing any output. There must be no pending output,
495 and the decompressor must be expecting to see the start of a block.
496 Calling this function is equivalent to decompressing a stored block
497 containing the data at next_in (except that the data is not output).
500 /* checksum functions */
503 These functions are not related to compression but are exported
504 anyway because they might be useful in applications using the
508 extern uLong adler32 OF((uLong adler, Bytef *buf, uInt len));
511 Update a running Adler-32 checksum with the bytes buf[0..len-1] and
512 return the updated checksum. If buf is NULL, this function returns
513 the required initial value for the checksum.
514 An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
515 much faster. Usage example:
517 uLong adler = adler32(0L, Z_NULL, 0);
519 while (read_buffer(buffer, length) != EOF) {
520 adler = adler32(adler, buffer, length);
522 if (adler != original_adler) error();
525 extern uLong crc32 OF((uLong crc, Bytef *buf, uInt len));
527 Update a running crc with the bytes buf[0..len-1] and return the updated
528 crc. If buf is NULL, this function returns the required initial value
529 for the crc. Pre- and post-conditioning (one's complement) is performed
530 within this function so it shouldn't be done by the application.
533 uLong crc = crc32(0L, Z_NULL, 0);
535 while (read_buffer(buffer, length) != EOF) {
536 crc = crc32(crc, buffer, length);
538 if (crc != original_crc) error();
542 struct internal_state {int dummy;}; /* hack for buggy compilers */