1 /* zlib.h -- interface of the 'zlib' general purpose compression library
3 Copyright (C) 1995-2005 Jean-loup Gailly and Mark Adler
5 This software is provided 'as-is', without any express or implied
6 warranty. In no event will the authors be held liable for any damages
7 arising from the use of this software.
9 Permission is granted to anyone to use this software for any purpose,
10 including commercial applications, and to alter it and redistribute it
11 freely, subject to the following restrictions:
13 1. The origin of this software must not be misrepresented; you must not
14 claim that you wrote the original software. If you use this software
15 in a product, an acknowledgment in the product documentation would be
16 appreciated but is not required.
17 2. Altered source versions must be plainly marked as such, and must not be
18 misrepresented as being the original software.
19 3. This notice may not be removed or altered from any source distribution.
21 Jean-loup Gailly Mark Adler
22 jloup@gzip.org madler@alumni.caltech.edu
25 The data format used by the zlib library is described by RFCs (Request for
26 Comments) 1950 to 1952 in the files http://www.ietf.org/rfc/rfc1950.txt
27 (zlib format), rfc1951.txt (deflate format) and rfc1952.txt (gzip format).
34 /* zlib deflate based on ZLIB_VERSION "1.1.3" */
35 /* zlib inflate based on ZLIB_VERSION "1.2.3" */
38 This is a modified version of zlib for use inside the Linux kernel.
39 The main changes are to perform all memory allocation in advance.
42 * Z_PACKET_FLUSH is added and used by ppp_deflate. Before returning
43 this checks there is no more input data available and the next data
44 is a STORED block. It also resets the mode to be read for the next
45 data, all as per PPP requirements.
46 * Addition of zlib_inflateIncomp which copies incompressible data into
47 the history window and adjusts the accoutning without calling
48 zlib_inflate itself to inflate the data.
52 The 'zlib' compression library provides in-memory compression and
53 decompression functions, including integrity checks of the uncompressed
54 data. This version of the library supports only one compression method
55 (deflation) but other algorithms will be added later and will have the same
58 Compression can be done in a single step if the buffers are large
59 enough (for example if an input file is mmap'ed), or can be done by
60 repeated calls of the compression function. In the latter case, the
61 application must provide more input and/or consume the output
62 (providing more output space) before each call.
64 The compressed data format used by default by the in-memory functions is
65 the zlib format, which is a zlib wrapper documented in RFC 1950, wrapped
66 around a deflate stream, which is itself documented in RFC 1951.
68 The library also supports reading and writing files in gzip (.gz) format
69 with an interface similar to that of stdio.
71 The zlib format was designed to be compact and fast for use in memory
72 and on communications channels. The gzip format was designed for single-
73 file compression on file systems, has a larger header than zlib to maintain
74 directory information, and uses a different, slower check method than zlib.
76 The library does not install any signal handler. The decoder checks
77 the consistency of the compressed data, so the library should never
78 crash even in case of corrupted input.
81 struct internal_state;
83 typedef struct z_stream_s {
84 const Byte *next_in; /* next input byte */
85 uLong avail_in; /* number of bytes available at next_in */
86 uLong total_in; /* total nb of input bytes read so far */
88 Byte *next_out; /* next output byte should be put there */
89 uLong avail_out; /* remaining free space at next_out */
90 uLong total_out; /* total nb of bytes output so far */
92 char *msg; /* last error message, NULL if no error */
93 struct internal_state *state; /* not visible by applications */
95 void *workspace; /* memory allocated for this stream */
97 int data_type; /* best guess about the data type: ascii or binary */
98 uLong adler; /* adler32 value of the uncompressed data */
99 uLong reserved; /* reserved for future use */
102 typedef z_stream *z_streamp;
105 The application must update next_in and avail_in when avail_in has
106 dropped to zero. It must update next_out and avail_out when avail_out
107 has dropped to zero. The application must initialize zalloc, zfree and
108 opaque before calling the init function. All other fields are set by the
109 compression library and must not be updated by the application.
111 The opaque value provided by the application will be passed as the first
112 parameter for calls of zalloc and zfree. This can be useful for custom
113 memory management. The compression library attaches no meaning to the
116 zalloc must return NULL if there is not enough memory for the object.
117 If zlib is used in a multi-threaded application, zalloc and zfree must be
120 On 16-bit systems, the functions zalloc and zfree must be able to allocate
121 exactly 65536 bytes, but will not be required to allocate more than this
122 if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS,
123 pointers returned by zalloc for objects of exactly 65536 bytes *must*
124 have their offset normalized to zero. The default allocation function
125 provided by this library ensures this (see zutil.c). To reduce memory
126 requirements and avoid any allocation of 64K objects, at the expense of
127 compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h).
129 The fields total_in and total_out can be used for statistics or
130 progress reports. After compression, total_in holds the total size of
131 the uncompressed data and may be saved for use in the decompressor
132 (particularly if the decompressor wants to decompress everything in
139 #define Z_PARTIAL_FLUSH 1 /* will be removed, use Z_SYNC_FLUSH instead */
140 #define Z_PACKET_FLUSH 2
141 #define Z_SYNC_FLUSH 3
142 #define Z_FULL_FLUSH 4
144 #define Z_BLOCK 6 /* Only for inflate at present */
145 /* Allowed flush values; see deflate() and inflate() below for details */
148 #define Z_STREAM_END 1
149 #define Z_NEED_DICT 2
151 #define Z_STREAM_ERROR (-2)
152 #define Z_DATA_ERROR (-3)
153 #define Z_MEM_ERROR (-4)
154 #define Z_BUF_ERROR (-5)
155 #define Z_VERSION_ERROR (-6)
156 /* Return codes for the compression/decompression functions. Negative
157 * values are errors, positive values are used for special but normal events.
160 #define Z_NO_COMPRESSION 0
161 #define Z_BEST_SPEED 1
162 #define Z_BEST_COMPRESSION 9
163 #define Z_DEFAULT_COMPRESSION (-1)
164 /* compression levels */
167 #define Z_HUFFMAN_ONLY 2
168 #define Z_DEFAULT_STRATEGY 0
169 /* compression strategy; see deflateInit2() below for details */
174 /* Possible values of the data_type field */
177 /* The deflate compression method (the only one supported in this version) */
179 /* basic functions */
181 extern int zlib_deflate_workspacesize (int windowBits, int memLevel);
183 Returns the number of bytes that needs to be allocated for a per-
184 stream workspace with the specified parameters. A pointer to this
185 number of bytes should be returned in stream->workspace before
186 you call zlib_deflateInit() or zlib_deflateInit2(). If you call
187 zlib_deflateInit(), specify windowBits = MAX_WBITS and memLevel =
188 MAX_MEM_LEVEL here. If you call zlib_deflateInit2(), the windowBits
189 and memLevel parameters passed to zlib_deflateInit2() must not
190 exceed those passed here.
194 extern int deflateInit (z_streamp strm, int level);
196 Initializes the internal stream state for compression. The fields
197 zalloc, zfree and opaque must be initialized before by the caller.
198 If zalloc and zfree are set to NULL, deflateInit updates them to
199 use default allocation functions.
201 The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
202 1 gives best speed, 9 gives best compression, 0 gives no compression at
203 all (the input data is simply copied a block at a time).
204 Z_DEFAULT_COMPRESSION requests a default compromise between speed and
205 compression (currently equivalent to level 6).
207 deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
208 enough memory, Z_STREAM_ERROR if level is not a valid compression level,
209 Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible
210 with the version assumed by the caller (ZLIB_VERSION).
211 msg is set to null if there is no error message. deflateInit does not
212 perform any compression: this will be done by deflate().
216 extern int zlib_deflate (z_streamp strm, int flush);
218 deflate compresses as much data as possible, and stops when the input
219 buffer becomes empty or the output buffer becomes full. It may introduce some
220 output latency (reading input without producing any output) except when
223 The detailed semantics are as follows. deflate performs one or both of the
226 - Compress more input starting at next_in and update next_in and avail_in
227 accordingly. If not all input can be processed (because there is not
228 enough room in the output buffer), next_in and avail_in are updated and
229 processing will resume at this point for the next call of deflate().
231 - Provide more output starting at next_out and update next_out and avail_out
232 accordingly. This action is forced if the parameter flush is non zero.
233 Forcing flush frequently degrades the compression ratio, so this parameter
234 should be set only when necessary (in interactive applications).
235 Some output may be provided even if flush is not set.
237 Before the call of deflate(), the application should ensure that at least
238 one of the actions is possible, by providing more input and/or consuming
239 more output, and updating avail_in or avail_out accordingly; avail_out
240 should never be zero before the call. The application can consume the
241 compressed output when it wants, for example when the output buffer is full
242 (avail_out == 0), or after each call of deflate(). If deflate returns Z_OK
243 and with zero avail_out, it must be called again after making room in the
244 output buffer because there might be more output pending.
246 If the parameter flush is set to Z_SYNC_FLUSH, all pending output is
247 flushed to the output buffer and the output is aligned on a byte boundary, so
248 that the decompressor can get all input data available so far. (In particular
249 avail_in is zero after the call if enough output space has been provided
250 before the call.) Flushing may degrade compression for some compression
251 algorithms and so it should be used only when necessary.
253 If flush is set to Z_FULL_FLUSH, all output is flushed as with
254 Z_SYNC_FLUSH, and the compression state is reset so that decompression can
255 restart from this point if previous compressed data has been damaged or if
256 random access is desired. Using Z_FULL_FLUSH too often can seriously degrade
259 If deflate returns with avail_out == 0, this function must be called again
260 with the same value of the flush parameter and more output space (updated
261 avail_out), until the flush is complete (deflate returns with non-zero
264 If the parameter flush is set to Z_FINISH, pending input is processed,
265 pending output is flushed and deflate returns with Z_STREAM_END if there
266 was enough output space; if deflate returns with Z_OK, this function must be
267 called again with Z_FINISH and more output space (updated avail_out) but no
268 more input data, until it returns with Z_STREAM_END or an error. After
269 deflate has returned Z_STREAM_END, the only possible operations on the
270 stream are deflateReset or deflateEnd.
272 Z_FINISH can be used immediately after deflateInit if all the compression
273 is to be done in a single step. In this case, avail_out must be at least
274 0.1% larger than avail_in plus 12 bytes. If deflate does not return
275 Z_STREAM_END, then it must be called again as described above.
277 deflate() sets strm->adler to the adler32 checksum of all input read
278 so far (that is, total_in bytes).
280 deflate() may update data_type if it can make a good guess about
281 the input data type (Z_ASCII or Z_BINARY). In doubt, the data is considered
282 binary. This field is only for information purposes and does not affect
283 the compression algorithm in any manner.
285 deflate() returns Z_OK if some progress has been made (more input
286 processed or more output produced), Z_STREAM_END if all input has been
287 consumed and all output has been produced (only when flush is set to
288 Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
289 if next_in or next_out was NULL), Z_BUF_ERROR if no progress is possible
290 (for example avail_in or avail_out was zero).
294 extern int zlib_deflateEnd (z_streamp strm);
296 All dynamically allocated data structures for this stream are freed.
297 This function discards any unprocessed input and does not flush any
300 deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
301 stream state was inconsistent, Z_DATA_ERROR if the stream was freed
302 prematurely (some input or output was discarded). In the error case,
303 msg may be set but then points to a static string (which must not be
308 extern int zlib_inflate_workspacesize (void);
310 Returns the number of bytes that needs to be allocated for a per-
311 stream workspace. A pointer to this number of bytes should be
312 returned in stream->workspace before calling zlib_inflateInit().
316 extern int zlib_inflateInit (z_streamp strm);
318 Initializes the internal stream state for decompression. The fields
319 next_in, avail_in, and workspace must be initialized before by
320 the caller. If next_in is not NULL and avail_in is large enough (the exact
321 value depends on the compression method), inflateInit determines the
322 compression method from the zlib header and allocates all data structures
323 accordingly; otherwise the allocation will be deferred to the first call of
324 inflate. If zalloc and zfree are set to NULL, inflateInit updates them to
325 use default allocation functions.
327 inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
328 memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
329 version assumed by the caller. msg is set to null if there is no error
330 message. inflateInit does not perform any decompression apart from reading
331 the zlib header if present: this will be done by inflate(). (So next_in and
332 avail_in may be modified, but next_out and avail_out are unchanged.)
336 extern int zlib_inflate (z_streamp strm, int flush);
338 inflate decompresses as much data as possible, and stops when the input
339 buffer becomes empty or the output buffer becomes full. It may introduce
340 some output latency (reading input without producing any output) except when
343 The detailed semantics are as follows. inflate performs one or both of the
346 - Decompress more input starting at next_in and update next_in and avail_in
347 accordingly. If not all input can be processed (because there is not
348 enough room in the output buffer), next_in is updated and processing
349 will resume at this point for the next call of inflate().
351 - Provide more output starting at next_out and update next_out and avail_out
352 accordingly. inflate() provides as much output as possible, until there
353 is no more input data or no more space in the output buffer (see below
354 about the flush parameter).
356 Before the call of inflate(), the application should ensure that at least
357 one of the actions is possible, by providing more input and/or consuming
358 more output, and updating the next_* and avail_* values accordingly.
359 The application can consume the uncompressed output when it wants, for
360 example when the output buffer is full (avail_out == 0), or after each
361 call of inflate(). If inflate returns Z_OK and with zero avail_out, it
362 must be called again after making room in the output buffer because there
363 might be more output pending.
365 The flush parameter of inflate() can be Z_NO_FLUSH, Z_SYNC_FLUSH,
366 Z_FINISH, or Z_BLOCK. Z_SYNC_FLUSH requests that inflate() flush as much
367 output as possible to the output buffer. Z_BLOCK requests that inflate() stop
368 if and when it gets to the next deflate block boundary. When decoding the
369 zlib or gzip format, this will cause inflate() to return immediately after
370 the header and before the first block. When doing a raw inflate, inflate()
371 will go ahead and process the first block, and will return when it gets to
372 the end of that block, or when it runs out of data.
374 The Z_BLOCK option assists in appending to or combining deflate streams.
375 Also to assist in this, on return inflate() will set strm->data_type to the
376 number of unused bits in the last byte taken from strm->next_in, plus 64
377 if inflate() is currently decoding the last block in the deflate stream,
378 plus 128 if inflate() returned immediately after decoding an end-of-block
379 code or decoding the complete header up to just before the first byte of the
380 deflate stream. The end-of-block will not be indicated until all of the
381 uncompressed data from that block has been written to strm->next_out. The
382 number of unused bits may in general be greater than seven, except when
383 bit 7 of data_type is set, in which case the number of unused bits will be
386 inflate() should normally be called until it returns Z_STREAM_END or an
387 error. However if all decompression is to be performed in a single step
388 (a single call of inflate), the parameter flush should be set to
389 Z_FINISH. In this case all pending input is processed and all pending
390 output is flushed; avail_out must be large enough to hold all the
391 uncompressed data. (The size of the uncompressed data may have been saved
392 by the compressor for this purpose.) The next operation on this stream must
393 be inflateEnd to deallocate the decompression state. The use of Z_FINISH
394 is never required, but can be used to inform inflate that a faster approach
395 may be used for the single inflate() call.
397 In this implementation, inflate() always flushes as much output as
398 possible to the output buffer, and always uses the faster approach on the
399 first call. So the only effect of the flush parameter in this implementation
400 is on the return value of inflate(), as noted below, or when it returns early
401 because Z_BLOCK is used.
403 If a preset dictionary is needed after this call (see inflateSetDictionary
404 below), inflate sets strm->adler to the adler32 checksum of the dictionary
405 chosen by the compressor and returns Z_NEED_DICT; otherwise it sets
406 strm->adler to the adler32 checksum of all output produced so far (that is,
407 total_out bytes) and returns Z_OK, Z_STREAM_END or an error code as described
408 below. At the end of the stream, inflate() checks that its computed adler32
409 checksum is equal to that saved by the compressor and returns Z_STREAM_END
410 only if the checksum is correct.
412 inflate() will decompress and check either zlib-wrapped or gzip-wrapped
413 deflate data. The header type is detected automatically. Any information
414 contained in the gzip header is not retained, so applications that need that
415 information should instead use raw inflate, see inflateInit2() below, or
416 inflateBack() and perform their own processing of the gzip header and
419 inflate() returns Z_OK if some progress has been made (more input processed
420 or more output produced), Z_STREAM_END if the end of the compressed data has
421 been reached and all uncompressed output has been produced, Z_NEED_DICT if a
422 preset dictionary is needed at this point, Z_DATA_ERROR if the input data was
423 corrupted (input stream not conforming to the zlib format or incorrect check
424 value), Z_STREAM_ERROR if the stream structure was inconsistent (for example
425 if next_in or next_out was NULL), Z_MEM_ERROR if there was not enough memory,
426 Z_BUF_ERROR if no progress is possible or if there was not enough room in the
427 output buffer when Z_FINISH is used. Note that Z_BUF_ERROR is not fatal, and
428 inflate() can be called again with more input and more output space to
429 continue decompressing. If Z_DATA_ERROR is returned, the application may then
430 call inflateSync() to look for a good compression block if a partial recovery
431 of the data is desired.
435 extern int zlib_inflateEnd (z_streamp strm);
437 All dynamically allocated data structures for this stream are freed.
438 This function discards any unprocessed input and does not flush any
441 inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
442 was inconsistent. In the error case, msg may be set but then points to a
443 static string (which must not be deallocated).
446 /* Advanced functions */
449 The following functions are needed only in some special applications.
453 extern int deflateInit2 (z_streamp strm,
460 This is another version of deflateInit with more compression options. The
461 fields next_in, zalloc, zfree and opaque must be initialized before by
464 The method parameter is the compression method. It must be Z_DEFLATED in
465 this version of the library.
467 The windowBits parameter is the base two logarithm of the window size
468 (the size of the history buffer). It should be in the range 8..15 for this
469 version of the library. Larger values of this parameter result in better
470 compression at the expense of memory usage. The default value is 15 if
471 deflateInit is used instead.
473 The memLevel parameter specifies how much memory should be allocated
474 for the internal compression state. memLevel=1 uses minimum memory but
475 is slow and reduces compression ratio; memLevel=9 uses maximum memory
476 for optimal speed. The default value is 8. See zconf.h for total memory
477 usage as a function of windowBits and memLevel.
479 The strategy parameter is used to tune the compression algorithm. Use the
480 value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a
481 filter (or predictor), or Z_HUFFMAN_ONLY to force Huffman encoding only (no
482 string match). Filtered data consists mostly of small values with a
483 somewhat random distribution. In this case, the compression algorithm is
484 tuned to compress them better. The effect of Z_FILTERED is to force more
485 Huffman coding and less string matching; it is somewhat intermediate
486 between Z_DEFAULT and Z_HUFFMAN_ONLY. The strategy parameter only affects
487 the compression ratio but not the correctness of the compressed output even
488 if it is not set appropriately.
490 deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
491 memory, Z_STREAM_ERROR if a parameter is invalid (such as an invalid
492 method). msg is set to null if there is no error message. deflateInit2 does
493 not perform any compression: this will be done by deflate().
496 extern int zlib_deflateReset (z_streamp strm);
498 This function is equivalent to deflateEnd followed by deflateInit,
499 but does not free and reallocate all the internal compression state.
500 The stream will keep the same compression level and any other attributes
501 that may have been set by deflateInit2.
503 deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
504 stream state was inconsistent (such as zalloc or state being NULL).
507 static inline unsigned long deflateBound(unsigned long s)
509 return s + ((s + 7) >> 3) + ((s + 63) >> 6) + 11;
513 extern int inflateInit2 (z_streamp strm, int windowBits);
515 This is another version of inflateInit with an extra parameter. The
516 fields next_in, avail_in, zalloc, zfree and opaque must be initialized
517 before by the caller.
519 The windowBits parameter is the base two logarithm of the maximum window
520 size (the size of the history buffer). It should be in the range 8..15 for
521 this version of the library. The default value is 15 if inflateInit is used
522 instead. windowBits must be greater than or equal to the windowBits value
523 provided to deflateInit2() while compressing, or it must be equal to 15 if
524 deflateInit2() was not used. If a compressed stream with a larger window
525 size is given as input, inflate() will return with the error code
526 Z_DATA_ERROR instead of trying to allocate a larger window.
528 windowBits can also be -8..-15 for raw inflate. In this case, -windowBits
529 determines the window size. inflate() will then process raw deflate data,
530 not looking for a zlib or gzip header, not generating a check value, and not
531 looking for any check values for comparison at the end of the stream. This
532 is for use with other formats that use the deflate compressed data format
533 such as zip. Those formats provide their own check values. If a custom
534 format is developed using the raw deflate format for compressed data, it is
535 recommended that a check value such as an adler32 or a crc32 be applied to
536 the uncompressed data as is done in the zlib, gzip, and zip formats. For
537 most applications, the zlib format should be used as is. Note that comments
538 above on the use in deflateInit2() applies to the magnitude of windowBits.
540 windowBits can also be greater than 15 for optional gzip decoding. Add
541 32 to windowBits to enable zlib and gzip decoding with automatic header
542 detection, or add 16 to decode only the gzip format (the zlib format will
543 return a Z_DATA_ERROR). If a gzip stream is being decoded, strm->adler is
544 a crc32 instead of an adler32.
546 inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
547 memory, Z_STREAM_ERROR if a parameter is invalid (such as a null strm). msg
548 is set to null if there is no error message. inflateInit2 does not perform
549 any decompression apart from reading the zlib header if present: this will
550 be done by inflate(). (So next_in and avail_in may be modified, but next_out
551 and avail_out are unchanged.)
554 extern int zlib_inflateReset (z_streamp strm);
556 This function is equivalent to inflateEnd followed by inflateInit,
557 but does not free and reallocate all the internal decompression state.
558 The stream will keep attributes that may have been set by inflateInit2.
560 inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
561 stream state was inconsistent (such as zalloc or state being NULL).
564 extern int zlib_inflateIncomp (z_stream *strm);
566 This function adds the data at next_in (avail_in bytes) to the output
567 history without performing any output. There must be no pending output,
568 and the decompressor must be expecting to see the start of a block.
569 Calling this function is equivalent to decompressing a stored block
570 containing the data at next_in (except that the data is not output).
573 #define zlib_deflateInit(strm, level) \
574 zlib_deflateInit2((strm), (level), Z_DEFLATED, MAX_WBITS, \
575 DEF_MEM_LEVEL, Z_DEFAULT_STRATEGY)
576 #define zlib_inflateInit(strm) \
577 zlib_inflateInit2((strm), DEF_WBITS)
579 extern int zlib_deflateInit2(z_streamp strm, int level, int method,
580 int windowBits, int memLevel,
582 extern int zlib_inflateInit2(z_streamp strm, int windowBits);
584 #if !defined(_Z_UTIL_H) && !defined(NO_DUMMY_DECL)
585 struct internal_state {int dummy;}; /* hack for buggy compilers */
588 /* Utility function: initialize zlib, unpack binary blob, clean up zlib,
589 * return len or negative error code. */
590 extern int zlib_inflate_blob(void *dst, unsigned dst_sz, const void *src, unsigned src_sz);
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