1 /* zlib.h -- interface of the 'zlib' general purpose compression library
2 version 1.0, Jan 14th, 1996.
4 Copyright (C) 1995-1996 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
35 #define ZLIB_VERSION "1.0"
38 The 'zlib' compression library provides in-memory compression and
39 decompression functions, including integrity checks of the uncompressed
40 data. This version of the library supports only one compression method
41 (deflation) but other algorithms may be added later and will have the same
44 For compression the application must provide the output buffer and
45 may optionally provide the input buffer for optimization. For decompression,
46 the application must provide the input buffer and may optionally provide
47 the output buffer for optimization.
49 Compression can be done in a single step if the buffers are large
50 enough (for example if an input file is mmap'ed), or can be done by
51 repeated calls of the compression function. In the latter case, the
52 application must provide more input and/or consume the output
53 (providing more output space) before each call.
56 typedef voidpf (*alloc_func) OF((voidpf opaque, uInt items, uInt size));
57 typedef void (*free_func) OF((voidpf opaque, voidpf address));
59 struct internal_state;
61 typedef struct z_stream_s {
62 Bytef *next_in; /* next input byte */
63 uInt avail_in; /* number of bytes available at next_in */
64 uLong total_in; /* total nb of input bytes read so far */
66 Bytef *next_out; /* next output byte should be put there */
67 uInt avail_out; /* remaining free space at next_out */
68 uLong total_out; /* total nb of bytes output so far */
70 char *msg; /* last error message, NULL if no error */
71 struct internal_state FAR *state; /* not visible by applications */
73 alloc_func zalloc; /* used to allocate the internal state */
74 free_func zfree; /* used to free the internal state */
75 voidpf opaque; /* private data object passed to zalloc and zfree */
77 Byte data_type; /* best guess about the data type: ascii or binary */
82 The application must update next_in and avail_in when avail_in has
83 dropped to zero. It must update next_out and avail_out when avail_out
84 has dropped to zero. The application must initialize zalloc, zfree and
85 opaque before calling the init function. All other fields are set by the
86 compression library and must not be updated by the application.
88 The opaque value provided by the application will be passed as the first
89 parameter for calls of zalloc and zfree. This can be useful for custom
90 memory management. The compression library attaches no meaning to the
93 zalloc must return Z_NULL if there is not enough memory for the object.
94 On 16-bit systems, the functions zalloc and zfree must be able to allocate
95 exactly 65536 bytes, but will not be required to allocate more than this
96 if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS,
97 pointers returned by zalloc for objects of exactly 65536 bytes *must*
98 have their offset normalized to zero. The default allocation function
99 provided by this library ensures this (see zutil.c). To reduce memory
100 requirements and avoid any allocation of 64K objects, at the expense of
101 compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h).
103 The fields total_in and total_out can be used for statistics or
104 progress reports. After compression, total_in holds the total size of
105 the uncompressed data and may be saved for use in the decompressor
106 (particularly if the decompressor wants to decompress everything in
113 #define Z_PARTIAL_FLUSH 1
114 #define Z_SYNC_FLUSH 2
115 #define Z_FULL_FLUSH 3
117 /* Allowed flush values; see deflate() below for details */
120 #define Z_STREAM_END 1
122 #define Z_STREAM_ERROR (-2)
123 #define Z_DATA_ERROR (-3)
124 #define Z_MEM_ERROR (-4)
125 #define Z_BUF_ERROR (-5)
126 /* error codes for the compression/decompression functions */
128 #define Z_NO_COMPRESSION 0
129 #define Z_BEST_SPEED 1
130 #define Z_BEST_COMPRESSION 9
131 #define Z_DEFAULT_COMPRESSION (-1)
132 /* compression levels */
135 #define Z_HUFFMAN_ONLY 2
136 #define Z_DEFAULT_STRATEGY 0
141 /* Used to set the data_type field */
144 /* The deflate compression method (the only one supported in this version) */
146 #define Z_NULL 0 /* for initializing zalloc, zfree, opaque */
148 extern char *zlib_version;
149 /* The application can compare zlib_version and ZLIB_VERSION for consistency.
150 If the first character differs, the library code actually used is
151 not compatible with the zlib.h header file used by the application.
154 /* basic functions */
156 extern int deflateInit OF((z_stream *strm, int level));
158 Initializes the internal stream state for compression. The fields
159 zalloc, zfree and opaque must be initialized before by the caller.
160 If zalloc and zfree are set to Z_NULL, deflateInit updates them to
161 use default allocation functions.
163 The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
164 1 gives best speed, 9 gives best compression, 0 gives no compression at
165 all (the input data is simply copied a block at a time).
166 Z_DEFAULT_COMPRESSION requests a default compromise between speed and
167 compression (currently equivalent to level 6).
169 deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
170 enough memory, Z_STREAM_ERROR if level is not a valid compression level.
171 msg is set to null if there is no error message. deflateInit does not
172 perform any compression: this will be done by deflate().
176 extern int deflate OF((z_stream *strm, int flush));
178 Performs one or both of the following actions:
180 - Compress more input starting at next_in and update next_in and avail_in
181 accordingly. If not all input can be processed (because there is not
182 enough room in the output buffer), next_in and avail_in are updated and
183 processing will resume at this point for the next call of deflate().
185 - Provide more output starting at next_out and update next_out and avail_out
186 accordingly. This action is forced if the parameter flush is non zero.
187 Forcing flush frequently degrades the compression ratio, so this parameter
188 should be set only when necessary (in interactive applications).
189 Some output may be provided even if flush is not set.
191 Before the call of deflate(), the application should ensure that at least
192 one of the actions is possible, by providing more input and/or consuming
193 more output, and updating avail_in or avail_out accordingly; avail_out
194 should never be zero before the call. The application can consume the
195 compressed output when it wants, for example when the output buffer is full
196 (avail_out == 0), or after each call of deflate().
198 If the parameter flush is set to Z_PARTIAL_FLUSH, the current compression
199 block is terminated and flushed to the output buffer so that the
200 decompressor can get all input data available so far. For method 9, a future
201 variant on method 8, the current block will be flushed but not terminated.
202 Z_SYNC_FLUSH has the same effect as partial flush except that the compressed
203 output is byte aligned (the compressor can clear its internal bit buffer)
204 and the current block is always terminated; this can be useful if the
205 compressor has to be restarted from scratch after an interruption (in which
206 case the internal state of the compressor may be lost).
207 If flush is set to Z_FULL_FLUSH, the compression block is terminated, a
208 special marker is output and the compression dictionary is discarded; this
209 is useful to allow the decompressor to synchronize if one compressed block
210 has been damaged (see inflateSync below). Flushing degrades compression and
211 so should be used only when necessary. Using Z_FULL_FLUSH too often can
212 seriously degrade the compression. If deflate returns with avail_out == 0,
213 this function must be called again with the same value of the flush
214 parameter and more output space (updated avail_out), until the flush is
215 complete (deflate returns with non-zero avail_out).
217 If the parameter flush is set to Z_FINISH, all pending input is processed,
218 all pending output is flushed and deflate returns with Z_STREAM_END if there
219 was enough output space; if deflate returns with Z_OK, this function must be
220 called again with Z_FINISH and more output space (updated avail_out) but no
221 more input data, until it returns with Z_STREAM_END or an error. After
222 deflate has returned Z_STREAM_END, the only possible operations on the
223 stream are deflateReset or deflateEnd.
225 Z_FINISH can be used immediately after deflateInit if all the compression
226 is to be done in a single step. In this case, avail_out must be at least
227 0.1% larger than avail_in plus 12 bytes. If deflate does not return
228 Z_STREAM_END, then it must be called again as described above.
230 deflate() may update data_type if it can make a good guess about
231 the input data type (Z_ASCII or Z_BINARY). In doubt, the data is considered
232 binary. This field is only for information purposes and does not affect
233 the compression algorithm in any manner.
235 deflate() returns Z_OK if some progress has been made (more input
236 processed or more output produced), Z_STREAM_END if all input has been
237 consumed and all output has been produced (only when flush is set to
238 Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
239 if next_in or next_out was NULL), Z_BUF_ERROR if no progress is possible.
243 extern int deflateEnd OF((z_stream *strm));
245 All dynamically allocated data structures for this stream are freed.
246 This function discards any unprocessed input and does not flush any
249 deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
250 stream state was inconsistent. In the error case, msg may be set
251 but then points to a static string (which must not be deallocated).
255 extern int inflateInit OF((z_stream *strm));
257 Initializes the internal stream state for decompression. The fields
258 zalloc, zfree and opaque must be initialized before by the caller. If
259 zalloc and zfree are set to Z_NULL, inflateInit updates them to use default
260 allocation functions.
262 inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
263 enough memory. msg is set to null if there is no error message.
264 inflateInit does not perform any decompression: this will be done by
269 extern int inflate OF((z_stream *strm, int flush));
271 Performs one or both of the following actions:
273 - Decompress more input starting at next_in and update next_in and avail_in
274 accordingly. If not all input can be processed (because there is not
275 enough room in the output buffer), next_in is updated and processing
276 will resume at this point for the next call of inflate().
278 - Provide more output starting at next_out and update next_out and avail_out
279 accordingly. inflate() always provides as much output as possible
280 (until there is no more input data or no more space in the output buffer).
282 Before the call of inflate(), the application should ensure that at least
283 one of the actions is possible, by providing more input and/or consuming
284 more output, and updating the next_* and avail_* values accordingly.
285 The application can consume the uncompressed output when it wants, for
286 example when the output buffer is full (avail_out == 0), or after each
289 If the parameter flush is set to Z_PARTIAL_FLUSH, inflate flushes as much
290 output as possible to the output buffer. The flushing behavior of inflate is
291 not specified for values of the flush parameter other than Z_PARTIAL_FLUSH
292 and Z_FINISH, but the current implementation actually flushes as much output
295 inflate() should normally be called until it returns Z_STREAM_END or an
296 error. However if all decompression is to be performed in a single step
297 (a single call of inflate), the parameter flush should be set to
298 Z_FINISH. In this case all pending input is processed and all pending
299 output is flushed; avail_out must be large enough to hold all the
300 uncompressed data. (The size of the uncompressed data may have been saved
301 by the compressor for this purpose.) The next operation on this stream must
302 be inflateEnd to deallocate the decompression state. The use of Z_FINISH
303 is never required, but can be used to inform inflate that a faster routine
304 may be used for the single inflate() call.
306 inflate() returns Z_OK if some progress has been made (more input
307 processed or more output produced), Z_STREAM_END if the end of the
308 compressed data has been reached and all uncompressed output has been
309 produced, Z_DATA_ERROR if the input data was corrupted, Z_STREAM_ERROR if
310 the stream structure was inconsistent (for example if next_in or next_out
311 was NULL), Z_MEM_ERROR if there was not enough memory, Z_BUF_ERROR if no
312 progress is possible or if there was not enough room in the output buffer
313 when Z_FINISH is used. In the Z_DATA_ERROR case, the application may then
314 call inflateSync to look for a good compression block.
318 extern int inflateEnd OF((z_stream *strm));
320 All dynamically allocated data structures for this stream are freed.
321 This function discards any unprocessed input and does not flush any
324 inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
325 was inconsistent. In the error case, msg may be set but then points to a
326 static string (which must not be deallocated).
329 /* advanced functions */
332 The following functions are needed only in some special applications.
335 extern int deflateInit2 OF((z_stream *strm,
342 This is another version of deflateInit with more compression options. The
343 fields next_in, zalloc, zfree and opaque must be initialized before by
346 The method parameter is the compression method. It must be Z_DEFLATED in
347 this version of the library. (Method 9 will allow a 64K history buffer and
348 partial block flushes.)
350 The windowBits parameter is the base two logarithm of the window size
351 (the size of the history buffer). It should be in the range 8..15 for this
352 version of the library (the value 16 will be allowed for method 9). Larger
353 values of this parameter result in better compression at the expense of
354 memory usage. The default value is 15 if deflateInit is used instead.
356 The memLevel parameter specifies how much memory should be allocated
357 for the internal compression state. memLevel=1 uses minimum memory but
358 is slow and reduces compression ratio; memLevel=9 uses maximum memory
359 for optimal speed. The default value is 8. See zconf.h for total memory
360 usage as a function of windowBits and memLevel.
362 The strategy parameter is used to tune the compression algorithm. Use
363 the value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data
364 produced by a filter (or predictor), or Z_HUFFMAN_ONLY to force Huffman
365 encoding only (no string match). Filtered data consists mostly of small
366 values with a somewhat random distribution. In this case, the
367 compression algorithm is tuned to compress them better. The strategy
368 parameter only affects the compression ratio but not the correctness of
369 the compressed output even if it is not set appropriately.
371 If next_in is not null, the library will use this buffer to hold also
372 some history information; the buffer must either hold the entire input
373 data, or have at least 1<<(windowBits+1) bytes and be writable. If next_in
374 is null, the library will allocate its own history buffer (and leave next_in
375 null). next_out need not be provided here but must be provided by the
376 application for the next call of deflate().
378 If the history buffer is provided by the application, next_in must
379 must never be changed by the application since the compressor maintains
380 information inside this buffer from call to call; the application
381 must provide more input only by increasing avail_in. next_in is always
382 reset by the library in this case.
384 deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was
385 not enough memory, Z_STREAM_ERROR if a parameter is invalid (such as
386 an invalid method). msg is set to null if there is no error message.
387 deflateInit2 does not perform any compression: this will be done by
391 extern int deflateCopy OF((z_stream *dest,
394 Sets the destination stream as a complete copy of the source stream. If
395 the source stream is using an application-supplied history buffer, a new
396 buffer is allocated for the destination stream. The compressed output
397 buffer is always application-supplied. It's the responsibility of the
398 application to provide the correct values of next_out and avail_out for the
399 next call of deflate.
401 This function is useful when several compression strategies will be
402 tried, for example when there are several ways of pre-processing the input
403 data with a filter. The streams that will be discarded should then be freed
404 by calling deflateEnd. Note that deflateCopy duplicates the internal
405 compression state which can be quite large, so this strategy is slow and
406 can consume lots of memory.
408 deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
409 enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
410 (such as zalloc being NULL). msg is left unchanged in both source and
414 extern int deflateReset OF((z_stream *strm));
416 This function is equivalent to deflateEnd followed by deflateInit,
417 but does not free and reallocate all the internal compression state.
418 The stream will keep the same compression level and any other attributes
419 that may have been set by deflateInit2.
421 deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
422 stream state was inconsistent (such as zalloc or state being NULL).
425 extern int deflateParams OF((z_stream *strm, int level, int strategy));
427 Dynamically update the compression level and compression strategy.
428 This can be used to switch between compression and straight copy of
429 the input data, or to switch to a different kind of input data requiring
430 a different strategy. If the compression level is changed, the input
431 available so far is compressed with the old level (and may be flushed);
432 the new level will take effect only at the next call of deflate().
434 deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source
435 stream state was inconsistent or if a parameter was invalid.
438 extern int inflateInit2 OF((z_stream *strm,
441 This is another version of inflateInit with more compression options. The
442 fields next_out, zalloc, zfree and opaque must be initialized before by
445 The windowBits parameter is the base two logarithm of the maximum window
446 size (the size of the history buffer). It should be in the range 8..15 for
447 this version of the library (the value 16 will be allowed soon). The
448 default value is 15 if inflateInit is used instead. If a compressed stream
449 with a larger window size is given as input, inflate() will return with
450 the error code Z_DATA_ERROR instead of trying to allocate a larger window.
452 If next_out is not null, the library will use this buffer for the history
453 buffer; the buffer must either be large enough to hold the entire output
454 data, or have at least 1<<windowBits bytes. If next_out is null, the
455 library will allocate its own buffer (and leave next_out null). next_in
456 need not be provided here but must be provided by the application for the
457 next call of inflate().
459 If the history buffer is provided by the application, next_out must
460 never be changed by the application since the decompressor maintains
461 history information inside this buffer from call to call; the application
462 can only reset next_out to the beginning of the history buffer when
463 avail_out is zero and all output has been consumed.
465 inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was
466 not enough memory, Z_STREAM_ERROR if a parameter is invalid (such as
467 windowBits < 8). msg is set to null if there is no error message.
468 inflateInit2 does not perform any decompression: this will be done by
472 extern int inflateSync OF((z_stream *strm));
474 Skips invalid compressed data until the special marker (see deflate()
475 above) can be found, or until all available input is skipped. No output
478 inflateSync returns Z_OK if the special marker has been found, Z_BUF_ERROR
479 if no more input was provided, Z_DATA_ERROR if no marker has been found,
480 or Z_STREAM_ERROR if the stream structure was inconsistent. In the success
481 case, the application may save the current current value of total_in which
482 indicates where valid compressed data was found. In the error case, the
483 application may repeatedly call inflateSync, providing more input each time,
484 until success or end of the input data.
487 extern int inflateReset OF((z_stream *strm));
489 This function is equivalent to inflateEnd followed by inflateInit,
490 but does not free and reallocate all the internal decompression state.
491 The stream will keep attributes that may have been set by inflateInit2.
493 inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
494 stream state was inconsistent (such as zalloc or state being NULL).
498 /* utility functions */
501 The following utility functions are implemented on top of the
502 basic stream-oriented functions. To simplify the interface, some
503 default options are assumed (compression level, window size,
504 standard memory allocation functions). The source code of these
505 utility functions can easily be modified if you need special options.
508 extern int compress OF((Bytef *dest, uLongf *destLen,
509 Bytef *source, uLong sourceLen));
511 Compresses the source buffer into the destination buffer. sourceLen is
512 the byte length of the source buffer. Upon entry, destLen is the total
513 size of the destination buffer, which must be at least 0.1% larger than
514 sourceLen plus 12 bytes. Upon exit, destLen is the actual size of the
516 This function can be used to compress a whole file at once if the
517 input file is mmap'ed.
518 compress returns Z_OK if success, Z_MEM_ERROR if there was not
519 enough memory, Z_BUF_ERROR if there was not enough room in the output
523 extern int uncompress OF((Bytef *dest, uLongf *destLen,
524 Bytef *source, uLong sourceLen));
526 Decompresses the source buffer into the destination buffer. sourceLen is
527 the byte length of the source buffer. Upon entry, destLen is the total
528 size of the destination buffer, which must be large enough to hold the
529 entire uncompressed data. (The size of the uncompressed data must have
530 been saved previously by the compressor and transmitted to the decompressor
531 by some mechanism outside the scope of this compression library.)
532 Upon exit, destLen is the actual size of the compressed buffer.
533 This function can be used to decompress a whole file at once if the
534 input file is mmap'ed.
536 uncompress returns Z_OK if success, Z_MEM_ERROR if there was not
537 enough memory, Z_BUF_ERROR if there was not enough room in the output
538 buffer, or Z_DATA_ERROR if the input data was corrupted.
542 typedef voidp gzFile;
544 extern gzFile gzopen OF((char *path, char *mode));
546 Opens a gzip (.gz) file for reading or writing. The mode parameter
547 is as in fopen ("rb" or "wb") but can also include a compression level
548 ("wb9"). gzopen can be used to read a file which is not in gzip format;
549 in this case gzread will directly read from the file without decompression.
550 gzopen returns NULL if the file could not be opened or if there was
551 insufficient memory to allocate the (de)compression state; errno
552 can be checked to distinguish the two cases (if errno is zero, the
553 zlib error is Z_MEM_ERROR).
556 extern gzFile gzdopen OF((int fd, char *mode));
558 gzdopen() associates a gzFile with the file descriptor fd. File
559 descriptors are obtained from calls like open, dup, creat, pipe or
560 fileno (in the file has been previously opened with fopen).
561 The mode parameter is as in fopen ("rb" or "wb").
562 gzdopen returns NULL if there was insufficient memory to allocate
563 the (de)compression state.
566 extern int gzread OF((gzFile file, voidp buf, unsigned len));
568 Reads the given number of uncompressed bytes from the compressed file.
569 If the input file was not in gzip format, gzread copies the given number
570 of bytes into the buffer.
571 gzread returns the number of uncompressed bytes actually read (0 for
572 end of file, -1 for error). */
574 extern int gzwrite OF((gzFile file, voidp buf, unsigned len));
576 Writes the given number of uncompressed bytes into the compressed file.
577 gzwrite returns the number of uncompressed bytes actually written
578 (0 in case of error).
581 extern int gzflush OF((gzFile file, int flush));
583 Flushes all pending output into the compressed file. The parameter
584 flush is as in the deflate() function. The return value is the zlib
585 error number (see function gzerror below). gzflush returns Z_OK if
586 the flush parameter is Z_FINISH and all output could be flushed.
587 gzflush should be called only when strictly necessary because it can
591 extern int gzclose OF((gzFile file));
593 Flushes all pending output if necessary, closes the compressed file
594 and deallocates all the (de)compression state. The return value is the zlib
595 error number (see function gzerror below).
598 extern char* gzerror OF((gzFile file, int *errnum));
600 Returns the error message for the last error which occurred on the
601 given compressed file. errnum is set to zlib error number. If an
602 error occurred in the file system and not in the compression library,
603 errnum is set to Z_ERRNO and the application may consult errno
604 to get the exact error code.
607 /* checksum functions */
610 These functions are not related to compression but are exported
611 anyway because they might be useful in applications using the
615 extern uLong adler32 OF((uLong adler, Bytef *buf, uInt len));
618 Update a running Adler-32 checksum with the bytes buf[0..len-1] and
619 return the updated checksum. If buf is NULL, this function returns
620 the required initial value for the checksum.
621 An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
622 much faster. Usage example:
624 uLong adler = adler32(0L, Z_NULL, 0);
626 while (read_buffer(buffer, length) != EOF) {
627 adler = adler32(adler, buffer, length);
629 if (adler != original_adler) error();
632 extern uLong crc32 OF((uLong crc, Bytef *buf, uInt len));
634 Update a running crc with the bytes buf[0..len-1] and return the updated
635 crc. If buf is NULL, this function returns the required initial value
636 for the crc. Pre- and post-conditioning (one's complement) is performed
637 within this function so it shouldn't be done by the application.
640 uLong crc = crc32(0L, Z_NULL, 0);
642 while (read_buffer(buffer, length) != EOF) {
643 crc = crc32(crc, buffer, length);
645 if (crc != original_crc) error();
649 struct internal_state {int dummy;}; /* hack for buggy compilers */