1 /* zlib.h -- interface of the 'zlib' general purpose compression library
2 version 1.2.2, October 3rd, 2004
4 Copyright (C) 1995-2004 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 jloup@gzip.org madler@alumni.caltech.edu
26 The data format used by the zlib library is described by RFCs (Request for
27 Comments) 1950 to 1952 in the files http://www.ietf.org/rfc/rfc1950.txt
28 (zlib format), rfc1951.txt (deflate format) and rfc1952.txt (gzip format).
40 #define ZLIB_VERSION "1.2.2"
41 #define ZLIB_VERNUM 0x1220
44 The 'zlib' compression library provides in-memory compression and
45 decompression functions, including integrity checks of the uncompressed
46 data. This version of the library supports only one compression method
47 (deflation) but other algorithms will be added later and will have the same
50 Compression can be done in a single step if the buffers are large
51 enough (for example if an input file is mmap'ed), or can be done by
52 repeated calls of the compression function. In the latter case, the
53 application must provide more input and/or consume the output
54 (providing more output space) before each call.
56 The compressed data format used by default by the in-memory functions is
57 the zlib format, which is a zlib wrapper documented in RFC 1950, wrapped
58 around a deflate stream, which is itself documented in RFC 1951.
60 The library also supports reading and writing files in gzip (.gz) format
61 with an interface similar to that of stdio using the functions that start
62 with "gz". The gzip format is different from the zlib format. gzip is a
63 gzip wrapper, documented in RFC 1952, wrapped around a deflate stream.
65 This library can optionally read and write gzip streams in memory as well.
67 The zlib format was designed to be compact and fast for use in memory
68 and on communications channels. The gzip format was designed for single-
69 file compression on file systems, has a larger header than zlib to maintain
70 directory information, and uses a different, slower check method than zlib.
72 The library does not install any signal handler. The decoder checks
73 the consistency of the compressed data, so the library should never
74 crash even in case of corrupted input.
77 typedef voidpf (*alloc_func) OF((voidpf opaque, uInt items, uInt size));
78 typedef void (*free_func) OF((voidpf opaque, voidpf address));
80 struct internal_state;
82 typedef struct z_stream_s {
83 Bytef *next_in; /* next input byte */
84 uInt avail_in; /* number of bytes available at next_in */
85 uLong total_in; /* total nb of input bytes read so far */
87 Bytef *next_out; /* next output byte should be put there */
88 uInt avail_out; /* remaining free space at next_out */
89 uLong total_out; /* total nb of bytes output so far */
91 char *msg; /* last error message, NULL if no error */
92 struct internal_state FAR *state; /* not visible by applications */
94 alloc_func zalloc; /* used to allocate the internal state */
95 free_func zfree; /* used to free the internal state */
96 voidpf opaque; /* private data object passed to zalloc and zfree */
98 int data_type; /* best guess about the data type: ascii or binary */
99 uLong adler; /* adler32 value of the uncompressed data */
100 uLong reserved; /* reserved for future use */
103 typedef z_stream FAR *z_streamp;
106 The application must update next_in and avail_in when avail_in has
107 dropped to zero. It must update next_out and avail_out when avail_out
108 has dropped to zero. The application must initialize zalloc, zfree and
109 opaque before calling the init function. All other fields are set by the
110 compression library and must not be updated by the application.
112 The opaque value provided by the application will be passed as the first
113 parameter for calls of zalloc and zfree. This can be useful for custom
114 memory management. The compression library attaches no meaning to the
117 zalloc must return Z_NULL if there is not enough memory for the object.
118 If zlib is used in a multi-threaded application, zalloc and zfree must be
121 On 16-bit systems, the functions zalloc and zfree must be able to allocate
122 exactly 65536 bytes, but will not be required to allocate more than this
123 if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS,
124 pointers returned by zalloc for objects of exactly 65536 bytes *must*
125 have their offset normalized to zero. The default allocation function
126 provided by this library ensures this (see zutil.c). To reduce memory
127 requirements and avoid any allocation of 64K objects, at the expense of
128 compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h).
130 The fields total_in and total_out can be used for statistics or
131 progress reports. After compression, total_in holds the total size of
132 the uncompressed data and may be saved for use in the decompressor
133 (particularly if the decompressor wants to decompress everything in
140 #define Z_PARTIAL_FLUSH 1 /* will be removed, use Z_SYNC_FLUSH instead */
141 #define Z_SYNC_FLUSH 2
142 #define Z_FULL_FLUSH 3
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
169 #define Z_DEFAULT_STRATEGY 0
170 /* compression strategy; see deflateInit2() below for details */
175 /* Possible values of the data_type field (though see inflate()) */
178 /* The deflate compression method (the only one supported in this version) */
180 #define Z_NULL 0 /* for initializing zalloc, zfree, opaque */
182 #define zlib_version zlibVersion()
183 /* for compatibility with versions < 1.0.2 */
185 /* basic functions */
187 ZEXTERN const char * ZEXPORT zlibVersion OF((void));
188 /* The application can compare zlibVersion and ZLIB_VERSION for consistency.
189 If the first character differs, the library code actually used is
190 not compatible with the zlib.h header file used by the application.
191 This check is automatically made by deflateInit and inflateInit.
195 ZEXTERN int ZEXPORT deflateInit OF((z_streamp strm, int level));
197 Initializes the internal stream state for compression. The fields
198 zalloc, zfree and opaque must be initialized before by the caller.
199 If zalloc and zfree are set to Z_NULL, deflateInit updates them to
200 use default allocation functions.
202 The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:
203 1 gives best speed, 9 gives best compression, 0 gives no compression at
204 all (the input data is simply copied a block at a time).
205 Z_DEFAULT_COMPRESSION requests a default compromise between speed and
206 compression (currently equivalent to level 6).
208 deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not
209 enough memory, Z_STREAM_ERROR if level is not a valid compression level,
210 Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible
211 with the version assumed by the caller (ZLIB_VERSION).
212 msg is set to null if there is no error message. deflateInit does not
213 perform any compression: this will be done by deflate().
217 ZEXTERN int ZEXPORT deflate OF((z_streamp strm, int flush));
219 deflate compresses as much data as possible, and stops when the input
220 buffer becomes empty or the output buffer becomes full. It may introduce some
221 output latency (reading input without producing any output) except when
224 The detailed semantics are as follows. deflate performs one or both of the
227 - Compress more input starting at next_in and update next_in and avail_in
228 accordingly. If not all input can be processed (because there is not
229 enough room in the output buffer), next_in and avail_in are updated and
230 processing will resume at this point for the next call of deflate().
232 - Provide more output starting at next_out and update next_out and avail_out
233 accordingly. This action is forced if the parameter flush is non zero.
234 Forcing flush frequently degrades the compression ratio, so this parameter
235 should be set only when necessary (in interactive applications).
236 Some output may be provided even if flush is not set.
238 Before the call of deflate(), the application should ensure that at least
239 one of the actions is possible, by providing more input and/or consuming
240 more output, and updating avail_in or avail_out accordingly; avail_out
241 should never be zero before the call. The application can consume the
242 compressed output when it wants, for example when the output buffer is full
243 (avail_out == 0), or after each call of deflate(). If deflate returns Z_OK
244 and with zero avail_out, it must be called again after making room in the
245 output buffer because there might be more output pending.
247 If the parameter flush is set to Z_SYNC_FLUSH, all pending output is
248 flushed to the output buffer and the output is aligned on a byte boundary, so
249 that the decompressor can get all input data available so far. (In particular
250 avail_in is zero after the call if enough output space has been provided
251 before the call.) Flushing may degrade compression for some compression
252 algorithms and so it should be used only when necessary.
254 If flush is set to Z_FULL_FLUSH, all output is flushed as with
255 Z_SYNC_FLUSH, and the compression state is reset so that decompression can
256 restart from this point if previous compressed data has been damaged or if
257 random access is desired. Using Z_FULL_FLUSH too often can seriously degrade
260 If deflate returns with avail_out == 0, this function must be called again
261 with the same value of the flush parameter and more output space (updated
262 avail_out), until the flush is complete (deflate returns with non-zero
263 avail_out). In the case of a Z_FULL_FLUSH or Z_SYNC_FLUSH, make sure that
264 avail_out is greater than six to avoid repeated flush markers due to
265 avail_out == 0 on return.
267 If the parameter flush is set to Z_FINISH, pending input is processed,
268 pending output is flushed and deflate returns with Z_STREAM_END if there
269 was enough output space; if deflate returns with Z_OK, this function must be
270 called again with Z_FINISH and more output space (updated avail_out) but no
271 more input data, until it returns with Z_STREAM_END or an error. After
272 deflate has returned Z_STREAM_END, the only possible operations on the
273 stream are deflateReset or deflateEnd.
275 Z_FINISH can be used immediately after deflateInit if all the compression
276 is to be done in a single step. In this case, avail_out must be at least
277 the value returned by deflateBound (see below). If deflate does not return
278 Z_STREAM_END, then it must be called again as described above.
280 deflate() sets strm->adler to the adler32 checksum of all input read
281 so far (that is, total_in bytes).
283 deflate() may update data_type if it can make a good guess about
284 the input data type (Z_ASCII or Z_BINARY). In doubt, the data is considered
285 binary. This field is only for information purposes and does not affect
286 the compression algorithm in any manner.
288 deflate() returns Z_OK if some progress has been made (more input
289 processed or more output produced), Z_STREAM_END if all input has been
290 consumed and all output has been produced (only when flush is set to
291 Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
292 if next_in or next_out was NULL), Z_BUF_ERROR if no progress is possible
293 (for example avail_in or avail_out was zero). Note that Z_BUF_ERROR is not
294 fatal, and deflate() can be called again with more input and more output
295 space to continue compressing.
299 ZEXTERN int ZEXPORT deflateEnd OF((z_streamp strm));
301 All dynamically allocated data structures for this stream are freed.
302 This function discards any unprocessed input and does not flush any
305 deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the
306 stream state was inconsistent, Z_DATA_ERROR if the stream was freed
307 prematurely (some input or output was discarded). In the error case,
308 msg may be set but then points to a static string (which must not be
314 ZEXTERN int ZEXPORT inflateInit OF((z_streamp strm));
316 Initializes the internal stream state for decompression. The fields
317 next_in, avail_in, zalloc, zfree and opaque must be initialized before by
318 the caller. If next_in is not Z_NULL and avail_in is large enough (the exact
319 value depends on the compression method), inflateInit determines the
320 compression method from the zlib header and allocates all data structures
321 accordingly; otherwise the allocation will be deferred to the first call of
322 inflate. If zalloc and zfree are set to Z_NULL, inflateInit updates them to
323 use default allocation functions.
325 inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
326 memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
327 version assumed by the caller. msg is set to null if there is no error
328 message. inflateInit does not perform any decompression apart from reading
329 the zlib header if present: this will be done by inflate(). (So next_in and
330 avail_in may be modified, but next_out and avail_out are unchanged.)
334 ZEXTERN int ZEXPORT inflate OF((z_streamp strm, int flush));
336 inflate decompresses as much data as possible, and stops when the input
337 buffer becomes empty or the output buffer becomes full. It may introduce
338 some output latency (reading input without producing any output) except when
341 The detailed semantics are as follows. inflate performs one or both of the
344 - Decompress more input starting at next_in and update next_in and avail_in
345 accordingly. If not all input can be processed (because there is not
346 enough room in the output buffer), next_in is updated and processing
347 will resume at this point for the next call of inflate().
349 - Provide more output starting at next_out and update next_out and avail_out
350 accordingly. inflate() provides as much output as possible, until there
351 is no more input data or no more space in the output buffer (see below
352 about the flush parameter).
354 Before the call of inflate(), the application should ensure that at least
355 one of the actions is possible, by providing more input and/or consuming
356 more output, and updating the next_* and avail_* values accordingly.
357 The application can consume the uncompressed output when it wants, for
358 example when the output buffer is full (avail_out == 0), or after each
359 call of inflate(). If inflate returns Z_OK and with zero avail_out, it
360 must be called again after making room in the output buffer because there
361 might be more output pending.
363 The flush parameter of inflate() can be Z_NO_FLUSH, Z_SYNC_FLUSH,
364 Z_FINISH, or Z_BLOCK. Z_SYNC_FLUSH requests that inflate() flush as much
365 output as possible to the output buffer. Z_BLOCK requests that inflate() stop
366 if and when it get to the next deflate block boundary. When decoding the zlib
367 or gzip format, this will cause inflate() to return immediately after the
368 header and before the first block. When doing a raw inflate, inflate() will
369 go ahead and process the first block, and will return when it gets to the end
370 of that block, or when it runs out of data.
372 The Z_BLOCK option assists in appending to or combining deflate streams.
373 Also to assist in this, on return inflate() will set strm->data_type to the
374 number of unused bits in the last byte taken from strm->next_in, plus 64
375 if inflate() is currently decoding the last block in the deflate stream,
376 plus 128 if inflate() returned immediately after decoding an end-of-block
377 code or decoding the complete header up to just before the first byte of the
378 deflate stream. The end-of-block will not be indicated until all of the
379 uncompressed data from that block has been written to strm->next_out. The
380 number of unused bits may in general be greater than seven, except when
381 bit 7 of data_type is set, in which case the number of unused bits will be
384 inflate() should normally be called until it returns Z_STREAM_END or an
385 error. However if all decompression is to be performed in a single step
386 (a single call of inflate), the parameter flush should be set to
387 Z_FINISH. In this case all pending input is processed and all pending
388 output is flushed; avail_out must be large enough to hold all the
389 uncompressed data. (The size of the uncompressed data may have been saved
390 by the compressor for this purpose.) The next operation on this stream must
391 be inflateEnd to deallocate the decompression state. The use of Z_FINISH
392 is never required, but can be used to inform inflate that a faster approach
393 may be used for the single inflate() call.
395 In this implementation, inflate() always flushes as much output as
396 possible to the output buffer, and always uses the faster approach on the
397 first call. So the only effect of the flush parameter in this implementation
398 is on the return value of inflate(), as noted below, or when it returns early
399 because Z_BLOCK is used.
401 If a preset dictionary is needed after this call (see inflateSetDictionary
402 below), inflate sets strm->adler to the adler32 checksum of the dictionary
403 chosen by the compressor and returns Z_NEED_DICT; otherwise it sets
404 strm->adler to the adler32 checksum of all output produced so far (that is,
405 total_out bytes) and returns Z_OK, Z_STREAM_END or an error code as described
406 below. At the end of the stream, inflate() checks that its computed adler32
407 checksum is equal to that saved by the compressor and returns Z_STREAM_END
408 only if the checksum is correct.
410 inflate() will decompress and check either zlib-wrapped or gzip-wrapped
411 deflate data. The header type is detected automatically. Any information
412 contained in the gzip header is not retained, so applications that need that
413 information should instead use raw inflate, see inflateInit2() below, or
414 inflateBack() and perform their own processing of the gzip header and
417 inflate() returns Z_OK if some progress has been made (more input processed
418 or more output produced), Z_STREAM_END if the end of the compressed data has
419 been reached and all uncompressed output has been produced, Z_NEED_DICT if a
420 preset dictionary is needed at this point, Z_DATA_ERROR if the input data was
421 corrupted (input stream not conforming to the zlib format or incorrect check
422 value), Z_STREAM_ERROR if the stream structure was inconsistent (for example
423 if next_in or next_out was NULL), Z_MEM_ERROR if there was not enough memory,
424 Z_BUF_ERROR if no progress is possible or if there was not enough room in the
425 output buffer when Z_FINISH is used. Note that Z_BUF_ERROR is not fatal, and
426 inflate() can be called again with more input and more output space to
427 continue decompressing. If Z_DATA_ERROR is returned, the application may then
428 call inflateSync() to look for a good compression block if a partial recovery
429 of the data is desired.
433 ZEXTERN int ZEXPORT inflateEnd OF((z_streamp strm));
435 All dynamically allocated data structures for this stream are freed.
436 This function discards any unprocessed input and does not flush any
439 inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
440 was inconsistent. In the error case, msg may be set but then points to a
441 static string (which must not be deallocated).
444 /* Advanced functions */
447 The following functions are needed only in some special applications.
451 ZEXTERN int ZEXPORT deflateInit2 OF((z_streamp strm,
458 This is another version of deflateInit with more compression options. The
459 fields next_in, zalloc, zfree and opaque must be initialized before by
462 The method parameter is the compression method. It must be Z_DEFLATED in
463 this version of the library.
465 The windowBits parameter is the base two logarithm of the window size
466 (the size of the history buffer). It should be in the range 8..15 for this
467 version of the library. Larger values of this parameter result in better
468 compression at the expense of memory usage. The default value is 15 if
469 deflateInit is used instead.
471 windowBits can also be -8..-15 for raw deflate. In this case, -windowBits
472 determines the window size. deflate() will then generate raw deflate data
473 with no zlib header or trailer, and will not compute an adler32 check value.
475 windowBits can also be greater than 15 for optional gzip encoding. Add
476 16 to windowBits to write a simple gzip header and trailer around the
477 compressed data instead of a zlib wrapper. The gzip header will have no
478 file name, no extra data, no comment, no modification time (set to zero),
479 no header crc, and the operating system will be set to 255 (unknown). If a
480 gzip stream is being written, strm->adler is a crc32 instead of an adler32.
482 The memLevel parameter specifies how much memory should be allocated
483 for the internal compression state. memLevel=1 uses minimum memory but
484 is slow and reduces compression ratio; memLevel=9 uses maximum memory
485 for optimal speed. The default value is 8. See zconf.h for total memory
486 usage as a function of windowBits and memLevel.
488 The strategy parameter is used to tune the compression algorithm. Use the
489 value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by a
490 filter (or predictor), Z_HUFFMAN_ONLY to force Huffman encoding only (no
491 string match), or Z_RLE to limit match distances to one (run-length
492 encoding). Filtered data consists mostly of small values with a somewhat
493 random distribution. In this case, the compression algorithm is tuned to
494 compress them better. The effect of Z_FILTERED is to force more Huffman
495 coding and less string matching; it is somewhat intermediate between
496 Z_DEFAULT and Z_HUFFMAN_ONLY. Z_RLE is designed to be almost as fast as
497 Z_HUFFMAN_ONLY, but give better compression for PNG image data. The strategy
498 parameter only affects the compression ratio but not the correctness of the
499 compressed output even if it is not set appropriately.
501 deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
502 memory, Z_STREAM_ERROR if a parameter is invalid (such as an invalid
503 method). msg is set to null if there is no error message. deflateInit2 does
504 not perform any compression: this will be done by deflate().
507 ZEXTERN int ZEXPORT deflateSetDictionary OF((z_streamp strm,
508 const Bytef *dictionary,
511 Initializes the compression dictionary from the given byte sequence
512 without producing any compressed output. This function must be called
513 immediately after deflateInit, deflateInit2 or deflateReset, before any
514 call of deflate. The compressor and decompressor must use exactly the same
515 dictionary (see inflateSetDictionary).
517 The dictionary should consist of strings (byte sequences) that are likely
518 to be encountered later in the data to be compressed, with the most commonly
519 used strings preferably put towards the end of the dictionary. Using a
520 dictionary is most useful when the data to be compressed is short and can be
521 predicted with good accuracy; the data can then be compressed better than
522 with the default empty dictionary.
524 Depending on the size of the compression data structures selected by
525 deflateInit or deflateInit2, a part of the dictionary may in effect be
526 discarded, for example if the dictionary is larger than the window size in
527 deflate or deflate2. Thus the strings most likely to be useful should be
528 put at the end of the dictionary, not at the front.
530 Upon return of this function, strm->adler is set to the adler32 value
531 of the dictionary; the decompressor may later use this value to determine
532 which dictionary has been used by the compressor. (The adler32 value
533 applies to the whole dictionary even if only a subset of the dictionary is
534 actually used by the compressor.) If a raw deflate was requested, then the
535 adler32 value is not computed and strm->adler is not set.
537 deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a
538 parameter is invalid (such as NULL dictionary) or the stream state is
539 inconsistent (for example if deflate has already been called for this stream
540 or if the compression method is bsort). deflateSetDictionary does not
541 perform any compression: this will be done by deflate().
544 ZEXTERN int ZEXPORT deflateCopy OF((z_streamp dest,
547 Sets the destination stream as a complete copy of the source stream.
549 This function can be useful when several compression strategies will be
550 tried, for example when there are several ways of pre-processing the input
551 data with a filter. The streams that will be discarded should then be freed
552 by calling deflateEnd. Note that deflateCopy duplicates the internal
553 compression state which can be quite large, so this strategy is slow and
554 can consume lots of memory.
556 deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
557 enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
558 (such as zalloc being NULL). msg is left unchanged in both source and
562 ZEXTERN int ZEXPORT deflateReset OF((z_streamp strm));
564 This function is equivalent to deflateEnd followed by deflateInit,
565 but does not free and reallocate all the internal compression state.
566 The stream will keep the same compression level and any other attributes
567 that may have been set by deflateInit2.
569 deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
570 stream state was inconsistent (such as zalloc or state being NULL).
573 ZEXTERN int ZEXPORT deflateParams OF((z_streamp strm,
577 Dynamically update the compression level and compression strategy. The
578 interpretation of level and strategy is as in deflateInit2. This can be
579 used to switch between compression and straight copy of the input data, or
580 to switch to a different kind of input data requiring a different
581 strategy. If the compression level is changed, the input available so far
582 is compressed with the old level (and may be flushed); the new level will
583 take effect only at the next call of deflate().
585 Before the call of deflateParams, the stream state must be set as for
586 a call of deflate(), since the currently available input may have to
587 be compressed and flushed. In particular, strm->avail_out must be non-zero.
589 deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source
590 stream state was inconsistent or if a parameter was invalid, Z_BUF_ERROR
591 if strm->avail_out was zero.
594 ZEXTERN uLong ZEXPORT deflateBound OF((z_streamp strm,
597 deflateBound() returns an upper bound on the compressed size after
598 deflation of sourceLen bytes. It must be called after deflateInit()
599 or deflateInit2(). This would be used to allocate an output buffer
600 for deflation in a single pass, and so would be called before deflate().
603 ZEXTERN int ZEXPORT deflatePrime OF((z_streamp strm,
607 deflatePrime() inserts bits in the deflate output stream. The intent
608 is that this function is used to start off the deflate output with the
609 bits leftover from a previous deflate stream when appending to it. As such,
610 this function can only be used for raw deflate, and must be used before the
611 first deflate() call after a deflateInit2() or deflateReset(). bits must be
612 less than or equal to 16, and that many of the least significant bits of
613 value will be inserted in the output.
615 deflatePrime returns Z_OK if success, or Z_STREAM_ERROR if the source
616 stream state was inconsistent.
620 ZEXTERN int ZEXPORT inflateInit2 OF((z_streamp strm,
623 This is another version of inflateInit with an extra parameter. The
624 fields next_in, avail_in, zalloc, zfree and opaque must be initialized
625 before by the caller.
627 The windowBits parameter is the base two logarithm of the maximum window
628 size (the size of the history buffer). It should be in the range 8..15 for
629 this version of the library. The default value is 15 if inflateInit is used
630 instead. windowBits must be greater than or equal to the windowBits value
631 provided to deflateInit2() while compressing, or it must be equal to 15 if
632 deflateInit2() was not used. If a compressed stream with a larger window
633 size is given as input, inflate() will return with the error code
634 Z_DATA_ERROR instead of trying to allocate a larger window.
636 windowBits can also be -8..-15 for raw inflate. In this case, -windowBits
637 determines the window size. inflate() will then process raw deflate data,
638 not looking for a zlib or gzip header, not generating a check value, and not
639 looking for any check values for comparison at the end of the stream. This
640 is for use with other formats that use the deflate compressed data format
641 such as zip. Those formats provide their own check values. If a custom
642 format is developed using the raw deflate format for compressed data, it is
643 recommended that a check value such as an adler32 or a crc32 be applied to
644 the uncompressed data as is done in the zlib, gzip, and zip formats. For
645 most applications, the zlib format should be used as is. Note that comments
646 above on the use in deflateInit2() applies to the magnitude of windowBits.
648 windowBits can also be greater than 15 for optional gzip decoding. Add
649 32 to windowBits to enable zlib and gzip decoding with automatic header
650 detection, or add 16 to decode only the gzip format (the zlib format will
651 return a Z_DATA_ERROR. If a gzip stream is being decoded, strm->adler is
652 a crc32 instead of an adler32.
654 inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
655 memory, Z_STREAM_ERROR if a parameter is invalid (such as a negative
656 memLevel). msg is set to null if there is no error message. inflateInit2
657 does not perform any decompression apart from reading the zlib header if
658 present: this will be done by inflate(). (So next_in and avail_in may be
659 modified, but next_out and avail_out are unchanged.)
662 ZEXTERN int ZEXPORT inflateSetDictionary OF((z_streamp strm,
663 const Bytef *dictionary,
666 Initializes the decompression dictionary from the given uncompressed byte
667 sequence. This function must be called immediately after a call of inflate
668 if this call returned Z_NEED_DICT. The dictionary chosen by the compressor
669 can be determined from the adler32 value returned by this call of
670 inflate. The compressor and decompressor must use exactly the same
671 dictionary (see deflateSetDictionary).
673 inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a
674 parameter is invalid (such as NULL dictionary) or the stream state is
675 inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the
676 expected one (incorrect adler32 value). inflateSetDictionary does not
677 perform any decompression: this will be done by subsequent calls of
681 ZEXTERN int ZEXPORT inflateSync OF((z_streamp strm));
683 Skips invalid compressed data until a full flush point (see above the
684 description of deflate with Z_FULL_FLUSH) can be found, or until all
685 available input is skipped. No output is provided.
687 inflateSync returns Z_OK if a full flush point has been found, Z_BUF_ERROR
688 if no more input was provided, Z_DATA_ERROR if no flush point has been found,
689 or Z_STREAM_ERROR if the stream structure was inconsistent. In the success
690 case, the application may save the current current value of total_in which
691 indicates where valid compressed data was found. In the error case, the
692 application may repeatedly call inflateSync, providing more input each time,
693 until success or end of the input data.
696 ZEXTERN int ZEXPORT inflateCopy OF((z_streamp dest,
699 Sets the destination stream as a complete copy of the source stream.
701 This function can be useful when randomly accessing a large stream. The
702 first pass through the stream can periodically record the inflate state,
703 allowing restarting inflate at those points when randomly accessing the
706 inflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not
707 enough memory, Z_STREAM_ERROR if the source stream state was inconsistent
708 (such as zalloc being NULL). msg is left unchanged in both source and
712 ZEXTERN int ZEXPORT inflateReset OF((z_streamp strm));
714 This function is equivalent to inflateEnd followed by inflateInit,
715 but does not free and reallocate all the internal decompression state.
716 The stream will keep attributes that may have been set by inflateInit2.
718 inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source
719 stream state was inconsistent (such as zalloc or state being NULL).
723 ZEXTERN int ZEXPORT inflateBackInit OF((z_stream FAR *strm, int windowBits,
724 unsigned char FAR *window));
726 Initialize the internal stream state for decompression using inflateBack()
727 calls. The fields zalloc, zfree and opaque in strm must be initialized
728 before the call. If zalloc and zfree are Z_NULL, then the default library-
729 derived memory allocation routines are used. windowBits is the base two
730 logarithm of the window size, in the range 8..15. window is a caller
731 supplied buffer of that size. Except for special applications where it is
732 assured that deflate was used with small window sizes, windowBits must be 15
733 and a 32K byte window must be supplied to be able to decompress general
736 See inflateBack() for the usage of these routines.
738 inflateBackInit will return Z_OK on success, Z_STREAM_ERROR if any of
739 the paramaters are invalid, Z_MEM_ERROR if the internal state could not
740 be allocated, or Z_VERSION_ERROR if the version of the library does not
741 match the version of the header file.
744 typedef unsigned (*in_func) OF((void FAR *, unsigned char FAR * FAR *));
745 typedef int (*out_func) OF((void FAR *, unsigned char FAR *, unsigned));
747 ZEXTERN int ZEXPORT inflateBack OF((z_stream FAR *strm,
748 in_func in, void FAR *in_desc,
749 out_func out, void FAR *out_desc));
751 inflateBack() does a raw inflate with a single call using a call-back
752 interface for input and output. This is more efficient than inflate() for
753 file i/o applications in that it avoids copying between the output and the
754 sliding window by simply making the window itself the output buffer. This
755 function trusts the application to not change the output buffer passed by
756 the output function, at least until inflateBack() returns.
758 inflateBackInit() must be called first to allocate the internal state
759 and to initialize the state with the user-provided window buffer.
760 inflateBack() may then be used multiple times to inflate a complete, raw
761 deflate stream with each call. inflateBackEnd() is then called to free
764 A raw deflate stream is one with no zlib or gzip header or trailer.
765 This routine would normally be used in a utility that reads zip or gzip
766 files and writes out uncompressed files. The utility would decode the
767 header and process the trailer on its own, hence this routine expects
768 only the raw deflate stream to decompress. This is different from the
769 normal behavior of inflate(), which expects either a zlib or gzip header and
770 trailer around the deflate stream.
772 inflateBack() uses two subroutines supplied by the caller that are then
773 called by inflateBack() for input and output. inflateBack() calls those
774 routines until it reads a complete deflate stream and writes out all of the
775 uncompressed data, or until it encounters an error. The function's
776 parameters and return types are defined above in the in_func and out_func
777 typedefs. inflateBack() will call in(in_desc, &buf) which should return the
778 number of bytes of provided input, and a pointer to that input in buf. If
779 there is no input available, in() must return zero--buf is ignored in that
780 case--and inflateBack() will return a buffer error. inflateBack() will call
781 out(out_desc, buf, len) to write the uncompressed data buf[0..len-1]. out()
782 should return zero on success, or non-zero on failure. If out() returns
783 non-zero, inflateBack() will return with an error. Neither in() nor out()
784 are permitted to change the contents of the window provided to
785 inflateBackInit(), which is also the buffer that out() uses to write from.
786 The length written by out() will be at most the window size. Any non-zero
787 amount of input may be provided by in().
789 For convenience, inflateBack() can be provided input on the first call by
790 setting strm->next_in and strm->avail_in. If that input is exhausted, then
791 in() will be called. Therefore strm->next_in must be initialized before
792 calling inflateBack(). If strm->next_in is Z_NULL, then in() will be called
793 immediately for input. If strm->next_in is not Z_NULL, then strm->avail_in
794 must also be initialized, and then if strm->avail_in is not zero, input will
795 initially be taken from strm->next_in[0 .. strm->avail_in - 1].
797 The in_desc and out_desc parameters of inflateBack() is passed as the
798 first parameter of in() and out() respectively when they are called. These
799 descriptors can be optionally used to pass any information that the caller-
800 supplied in() and out() functions need to do their job.
802 On return, inflateBack() will set strm->next_in and strm->avail_in to
803 pass back any unused input that was provided by the last in() call. The
804 return values of inflateBack() can be Z_STREAM_END on success, Z_BUF_ERROR
805 if in() or out() returned an error, Z_DATA_ERROR if there was a format
806 error in the deflate stream (in which case strm->msg is set to indicate the
807 nature of the error), or Z_STREAM_ERROR if the stream was not properly
808 initialized. In the case of Z_BUF_ERROR, an input or output error can be
809 distinguished using strm->next_in which will be Z_NULL only if in() returned
810 an error. If strm->next is not Z_NULL, then the Z_BUF_ERROR was due to
811 out() returning non-zero. (in() will always be called before out(), so
812 strm->next_in is assured to be defined if out() returns non-zero.) Note
813 that inflateBack() cannot return Z_OK.
816 ZEXTERN int ZEXPORT inflateBackEnd OF((z_stream FAR *strm));
818 All memory allocated by inflateBackInit() is freed.
820 inflateBackEnd() returns Z_OK on success, or Z_STREAM_ERROR if the stream
821 state was inconsistent.
824 ZEXTERN uLong ZEXPORT zlibCompileFlags OF((void));
825 /* Return flags indicating compile-time options.
827 Type sizes, two bits each, 00 = 16 bits, 01 = 32, 10 = 64, 11 = other:
830 5.4: size of voidpf (pointer)
833 Compiler, assembler, and debug options:
835 9: ASMV or ASMINF -- use ASM code
836 10: ZLIB_WINAPI -- exported functions use the WINAPI calling convention
839 One-time table building (smaller code, but not thread-safe if true):
840 12: BUILDFIXED -- build static block decoding tables when needed
841 13: DYNAMIC_CRC_TABLE -- build CRC calculation tables when needed
844 Library content (indicates missing functionality):
845 16: NO_GZCOMPRESS -- gz* functions cannot compress (to avoid linking
846 deflate code when not needed)
847 17: NO_GZIP -- deflate can't write gzip streams, and inflate can't detect
848 and decode gzip streams (to avoid linking crc code)
851 Operation variations (changes in library functionality):
852 20: PKZIP_BUG_WORKAROUND -- slightly more permissive inflate
853 21: FASTEST -- deflate algorithm with only one, lowest compression level
856 The sprintf variant used by gzprintf (zero is best):
857 24: 0 = vs*, 1 = s* -- 1 means limited to 20 arguments after the format
858 25: 0 = *nprintf, 1 = *printf -- 1 means gzprintf() not secure!
859 26: 0 = returns value, 1 = void -- 1 means inferred string length returned
866 /* utility functions */
869 The following utility functions are implemented on top of the
870 basic stream-oriented functions. To simplify the interface, some
871 default options are assumed (compression level and memory usage,
872 standard memory allocation functions). The source code of these
873 utility functions can easily be modified if you need special options.
876 ZEXTERN int ZEXPORT compress OF((Bytef *dest, uLongf *destLen,
877 const Bytef *source, uLong sourceLen));
879 Compresses the source buffer into the destination buffer. sourceLen is
880 the byte length of the source buffer. Upon entry, destLen is the total
881 size of the destination buffer, which must be at least the value returned
882 by compressBound(sourceLen). Upon exit, destLen is the actual size of the
884 This function can be used to compress a whole file at once if the
885 input file is mmap'ed.
886 compress returns Z_OK if success, Z_MEM_ERROR if there was not
887 enough memory, Z_BUF_ERROR if there was not enough room in the output
891 ZEXTERN int ZEXPORT compress2 OF((Bytef *dest, uLongf *destLen,
892 const Bytef *source, uLong sourceLen,
895 Compresses the source buffer into the destination buffer. The level
896 parameter has the same meaning as in deflateInit. sourceLen is the byte
897 length of the source buffer. Upon entry, destLen is the total size of the
898 destination buffer, which must be at least the value returned by
899 compressBound(sourceLen). Upon exit, destLen is the actual size of the
902 compress2 returns Z_OK if success, Z_MEM_ERROR if there was not enough
903 memory, Z_BUF_ERROR if there was not enough room in the output buffer,
904 Z_STREAM_ERROR if the level parameter is invalid.
907 ZEXTERN uLong ZEXPORT compressBound OF((uLong sourceLen));
909 compressBound() returns an upper bound on the compressed size after
910 compress() or compress2() on sourceLen bytes. It would be used before
911 a compress() or compress2() call to allocate the destination buffer.
914 ZEXTERN int ZEXPORT uncompress OF((Bytef *dest, uLongf *destLen,
915 const Bytef *source, uLong sourceLen));
917 Decompresses the source buffer into the destination buffer. sourceLen is
918 the byte length of the source buffer. Upon entry, destLen is the total
919 size of the destination buffer, which must be large enough to hold the
920 entire uncompressed data. (The size of the uncompressed data must have
921 been saved previously by the compressor and transmitted to the decompressor
922 by some mechanism outside the scope of this compression library.)
923 Upon exit, destLen is the actual size of the compressed buffer.
924 This function can be used to decompress a whole file at once if the
925 input file is mmap'ed.
927 uncompress returns Z_OK if success, Z_MEM_ERROR if there was not
928 enough memory, Z_BUF_ERROR if there was not enough room in the output
929 buffer, or Z_DATA_ERROR if the input data was corrupted or incomplete.
933 typedef voidp gzFile;
935 ZEXTERN gzFile ZEXPORT gzopen OF((const char *path, const char *mode));
937 Opens a gzip (.gz) file for reading or writing. The mode parameter
938 is as in fopen ("rb" or "wb") but can also include a compression level
939 ("wb9") or a strategy: 'f' for filtered data as in "wb6f", 'h' for
940 Huffman only compression as in "wb1h", or 'R' for run-length encoding
941 as in "wb1R". (See the description of deflateInit2 for more information
942 about the strategy parameter.)
944 gzopen can be used to read a file which is not in gzip format; in this
945 case gzread will directly read from the file without decompression.
947 gzopen returns NULL if the file could not be opened or if there was
948 insufficient memory to allocate the (de)compression state; errno
949 can be checked to distinguish the two cases (if errno is zero, the
950 zlib error is Z_MEM_ERROR). */
952 ZEXTERN gzFile ZEXPORT gzdopen OF((int fd, const char *mode));
954 gzdopen() associates a gzFile with the file descriptor fd. File
955 descriptors are obtained from calls like open, dup, creat, pipe or
956 fileno (in the file has been previously opened with fopen).
957 The mode parameter is as in gzopen.
958 The next call of gzclose on the returned gzFile will also close the
959 file descriptor fd, just like fclose(fdopen(fd), mode) closes the file
960 descriptor fd. If you want to keep fd open, use gzdopen(dup(fd), mode).
961 gzdopen returns NULL if there was insufficient memory to allocate
962 the (de)compression state.
965 ZEXTERN int ZEXPORT gzsetparams OF((gzFile file, int level, int strategy));
967 Dynamically update the compression level or strategy. See the description
968 of deflateInit2 for the meaning of these parameters.
969 gzsetparams returns Z_OK if success, or Z_STREAM_ERROR if the file was not
973 ZEXTERN int ZEXPORT gzread OF((gzFile file, voidp buf, unsigned len));
975 Reads the given number of uncompressed bytes from the compressed file.
976 If the input file was not in gzip format, gzread copies the given number
977 of bytes into the buffer.
978 gzread returns the number of uncompressed bytes actually read (0 for
979 end of file, -1 for error). */
981 ZEXTERN int ZEXPORT gzwrite OF((gzFile file,
982 voidpc buf, unsigned len));
984 Writes the given number of uncompressed bytes into the compressed file.
985 gzwrite returns the number of uncompressed bytes actually written
986 (0 in case of error).
989 ZEXTERN int ZEXPORTVA gzprintf OF((gzFile file, const char *format, ...));
991 Converts, formats, and writes the args to the compressed file under
992 control of the format string, as in fprintf. gzprintf returns the number of
993 uncompressed bytes actually written (0 in case of error). The number of
994 uncompressed bytes written is limited to 4095. The caller should assure that
995 this limit is not exceeded. If it is exceeded, then gzprintf() will return
996 return an error (0) with nothing written. In this case, there may also be a
997 buffer overflow with unpredictable consequences, which is possible only if
998 zlib was compiled with the insecure functions sprintf() or vsprintf()
999 because the secure snprintf() or vsnprintf() functions were not available.
1002 ZEXTERN int ZEXPORT gzputs OF((gzFile file, const char *s));
1004 Writes the given null-terminated string to the compressed file, excluding
1005 the terminating null character.
1006 gzputs returns the number of characters written, or -1 in case of error.
1009 ZEXTERN char * ZEXPORT gzgets OF((gzFile file, char *buf, int len));
1011 Reads bytes from the compressed file until len-1 characters are read, or
1012 a newline character is read and transferred to buf, or an end-of-file
1013 condition is encountered. The string is then terminated with a null
1015 gzgets returns buf, or Z_NULL in case of error.
1018 ZEXTERN int ZEXPORT gzputc OF((gzFile file, int c));
1020 Writes c, converted to an unsigned char, into the compressed file.
1021 gzputc returns the value that was written, or -1 in case of error.
1024 ZEXTERN int ZEXPORT gzgetc OF((gzFile file));
1026 Reads one byte from the compressed file. gzgetc returns this byte
1027 or -1 in case of end of file or error.
1030 ZEXTERN int ZEXPORT gzungetc OF((int c, gzFile file));
1032 Push one character back onto the stream to be read again later.
1033 Only one character of push-back is allowed. gzungetc() returns the
1034 character pushed, or -1 on failure. gzungetc() will fail if a
1035 character has been pushed but not read yet, or if c is -1. The pushed
1036 character will be discarded if the stream is repositioned with gzseek()
1040 ZEXTERN int ZEXPORT gzflush OF((gzFile file, int flush));
1042 Flushes all pending output into the compressed file. The parameter
1043 flush is as in the deflate() function. The return value is the zlib
1044 error number (see function gzerror below). gzflush returns Z_OK if
1045 the flush parameter is Z_FINISH and all output could be flushed.
1046 gzflush should be called only when strictly necessary because it can
1047 degrade compression.
1050 ZEXTERN z_off_t ZEXPORT gzseek OF((gzFile file,
1051 z_off_t offset, int whence));
1053 Sets the starting position for the next gzread or gzwrite on the
1054 given compressed file. The offset represents a number of bytes in the
1055 uncompressed data stream. The whence parameter is defined as in lseek(2);
1056 the value SEEK_END is not supported.
1057 If the file is opened for reading, this function is emulated but can be
1058 extremely slow. If the file is opened for writing, only forward seeks are
1059 supported; gzseek then compresses a sequence of zeroes up to the new
1062 gzseek returns the resulting offset location as measured in bytes from
1063 the beginning of the uncompressed stream, or -1 in case of error, in
1064 particular if the file is opened for writing and the new starting position
1065 would be before the current position.
1068 ZEXTERN int ZEXPORT gzrewind OF((gzFile file));
1070 Rewinds the given file. This function is supported only for reading.
1072 gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET)
1075 ZEXTERN z_off_t ZEXPORT gztell OF((gzFile file));
1077 Returns the starting position for the next gzread or gzwrite on the
1078 given compressed file. This position represents a number of bytes in the
1079 uncompressed data stream.
1081 gztell(file) is equivalent to gzseek(file, 0L, SEEK_CUR)
1084 ZEXTERN int ZEXPORT gzeof OF((gzFile file));
1086 Returns 1 when EOF has previously been detected reading the given
1087 input stream, otherwise zero.
1090 ZEXTERN int ZEXPORT gzclose OF((gzFile file));
1092 Flushes all pending output if necessary, closes the compressed file
1093 and deallocates all the (de)compression state. The return value is the zlib
1094 error number (see function gzerror below).
1097 ZEXTERN const char * ZEXPORT gzerror OF((gzFile file, int *errnum));
1099 Returns the error message for the last error which occurred on the
1100 given compressed file. errnum is set to zlib error number. If an
1101 error occurred in the file system and not in the compression library,
1102 errnum is set to Z_ERRNO and the application may consult errno
1103 to get the exact error code.
1106 ZEXTERN void ZEXPORT gzclearerr OF((gzFile file));
1108 Clears the error and end-of-file flags for file. This is analogous to the
1109 clearerr() function in stdio. This is useful for continuing to read a gzip
1110 file that is being written concurrently.
1113 /* checksum functions */
1116 These functions are not related to compression but are exported
1117 anyway because they might be useful in applications using the
1118 compression library.
1121 ZEXTERN uLong ZEXPORT adler32 OF((uLong adler, const Bytef *buf, uInt len));
1124 Update a running Adler-32 checksum with the bytes buf[0..len-1] and
1125 return the updated checksum. If buf is NULL, this function returns
1126 the required initial value for the checksum.
1127 An Adler-32 checksum is almost as reliable as a CRC32 but can be computed
1128 much faster. Usage example:
1130 uLong adler = adler32(0L, Z_NULL, 0);
1132 while (read_buffer(buffer, length) != EOF) {
1133 adler = adler32(adler, buffer, length);
1135 if (adler != original_adler) error();
1138 ZEXTERN uLong ZEXPORT crc32 OF((uLong crc, const Bytef *buf, uInt len));
1140 Update a running crc with the bytes buf[0..len-1] and return the updated
1141 crc. If buf is NULL, this function returns the required initial value
1142 for the crc. Pre- and post-conditioning (one's complement) is performed
1143 within this function so it shouldn't be done by the application.
1146 uLong crc = crc32(0L, Z_NULL, 0);
1148 while (read_buffer(buffer, length) != EOF) {
1149 crc = crc32(crc, buffer, length);
1151 if (crc != original_crc) error();
1155 /* various hacks, don't look :) */
1157 /* deflateInit and inflateInit are macros to allow checking the zlib version
1158 * and the compiler's view of z_stream:
1160 ZEXTERN int ZEXPORT deflateInit_ OF((z_streamp strm, int level,
1161 const char *version, int stream_size));
1162 ZEXTERN int ZEXPORT inflateInit_ OF((z_streamp strm,
1163 const char *version, int stream_size));
1164 ZEXTERN int ZEXPORT deflateInit2_ OF((z_streamp strm, int level, int method,
1165 int windowBits, int memLevel,
1166 int strategy, const char *version,
1168 ZEXTERN int ZEXPORT inflateInit2_ OF((z_streamp strm, int windowBits,
1169 const char *version, int stream_size));
1170 ZEXTERN int ZEXPORT inflateBackInit_ OF((z_stream FAR *strm, int windowBits,
1171 unsigned char FAR *window,
1172 const char *version,
1174 #define deflateInit(strm, level) \
1175 deflateInit_((strm), (level), ZLIB_VERSION, sizeof(z_stream))
1176 #define inflateInit(strm) \
1177 inflateInit_((strm), ZLIB_VERSION, sizeof(z_stream))
1178 #define deflateInit2(strm, level, method, windowBits, memLevel, strategy) \
1179 deflateInit2_((strm),(level),(method),(windowBits),(memLevel),\
1180 (strategy), ZLIB_VERSION, sizeof(z_stream))
1181 #define inflateInit2(strm, windowBits) \
1182 inflateInit2_((strm), (windowBits), ZLIB_VERSION, sizeof(z_stream))
1183 #define inflateBackInit(strm, windowBits, window) \
1184 inflateBackInit_((strm), (windowBits), (window), \
1185 ZLIB_VERSION, sizeof(z_stream))
1188 #if !defined(ZUTIL_H) && !defined(NO_DUMMY_DECL)
1189 struct internal_state {int dummy;}; /* hack for buggy compilers */
1192 ZEXTERN const char * ZEXPORT zError OF((int));
1193 ZEXTERN int ZEXPORT inflateSyncPoint OF((z_streamp z));
1194 ZEXTERN const uLongf * ZEXPORT get_crc_table OF((void));
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