9 Copyright (C) 1995-2002 Jean-loup Gailly and Mark Adler
C This software is provided 'as-is', without any express or implied H warranty. In no event will the authors be held liable for any damages( arising from the use of this software.
G Permission is granted to anyone to use this software for any purpose, H including commercial applications, and to alter it and redistribute it0 freely, subject to the following restrictions:
* This manual is converted from zlib.h by 4 piaip
9 Visit - http://ftp.cdrom.com/pub/infozip/zlib/ ! for the official zlib web page.
F Compression can be done in a single step if the buffers are largeE enough (for example if an input file is mmap'ed), or can be done by F repeated calls of the compression function. In the latter case, the? application must provide more input and/or consume the output 1 (providing more output space) before each call.
M The library also supports reading and writing files in gzip (.gz) format - with an interface similar to that of stdio.
H The library does not install any signal handler. The decoder checksE the consistency of the compressed data, so the library should never ( crash even in case of corrupted input.
^ This function can be used to compress a whole file at once if the input file is mmap'ed.
compress returns Z_OK if success, Z_MEM_ERROR if there was notc enough memory, Z_BUF_ERROR if there was not enough room in the output buffer.
compress2 returns Z_OK if success, Z_MEM_ERROR if there was not enough d memory, Z_BUF_ERROR if there was not enough room in the output buffer,R Z_STREAM_ERROR if the level parameter is invalid.
H This function can be used to decompress a whole file at once if the input file is mmap'ed.l
uncompress returns Z_OK if success, Z_MEM_ERROR if there was notc enough memory, Z_BUF_ERROR if there was not enough room in the outputuW buffer, or Z_DATA_ERROR if the input data was corrupted.m
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b gzopen can be used to read a file which is not in gzip format ; in this\ case gzread will directly read from the file without decompression.
^ gzopen returns NULL if the file could not be opened or if there wasY insufficient memory to allocate the (de)compression state ; errnoeE can be checked to distinguish the two cases (if errno is zero, the 9 zlib error is Z_MEM_ERROR).l
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_ The next call of gzclose on the returned gzFile will also close thexI file descriptor fd, just like fclose(fdopen(fd), mode) closes the file.a descriptor fd. If you want to keep fd open, use gzdopen(dup(fd), mode).e
] gzdopen returns NULL if there was insufficient memory to allocatet2 the (de)compression state.
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gzsetparams returns Z_OK if success, or Z_STREAM_ERROR if the file was not opened for writing.
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_ gzread returns the number of uncompressed bytes actually read (0 fort end of file, -1 for error).
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d gzputs returns the number of characters written, or -1 in case of error.
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a gzgets returns buf, or Z_NULL in case of error.#
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` gzflush should be called only when strictly necessary because it can degrade compression.
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L If the file is opened for reading, this function is emulated but can beL extremely slow. If the file is opened for writing, only forward seeks are^ supported ; gzseek then compresses a sequence of zeroes up to the new starting position.
b gzseek returns the resulting offset location as measured in bytes fromG the beginning of the uncompressed stream, or -1 in case of error, intM particular if the file is opened for writing and the new starting positiona( would be before the current position.
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p gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET)
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g gztell(file) is equivalent to gzseek(file, 0L, SEEK_CUR)L
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r The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9:J 1 gives best speed, 9 gives best compression, 0 gives no compression at; all (the input data is simply copied a block at a time).n
m Z_DEFAULT_COMPRESSION requests a default compromise between speed and 1 compression (currently equivalent to level 6).
deflateInit returns Z_OK if success, Z_MEM_ERROR if there was noti enough memory, Z_STREAM_ERROR if level is not a valid compression level, Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible9 with the version assumed by the caller (ZLIB_VERSION).tw msg is set to null if there is no error message. deflateInit does not R perform any compression: this will be done by deflate().
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y e The detailed semantics are as follows. deflate performs one or both of thes following actions:
b Before the call of deflate(), the application should ensure that at leastJ one of the actions is possible, by providing more input and/or consuming more output, and updating avail_in or avail_out accordingly ; avail_out G should never be zero before the call. The application can consume thegM compressed output when it wants, for example when the output buffer is fullc (avail_out == 0), or after each call of deflate(). If deflate returns Z_OKzd and with zero avail_out, it must be called again after making room in the; output buffer because there might be more output pending.o
o d If the parameter flush is set to Z_SYNC_FLUSH, all pending output isO flushed to the output buffer and the output is aligned on a byte boundary, so_O that the decompressor can get all input data available so far. (In particular/b avail_in is zero after the call if enough output space has been providedJ before the call.) Flushing may degrade compression for some compression: algorithms and so it should be used only when necessary.
c ^ If flush is set to Z_FULL_FLUSH, all output is flushed as with} Z_SYNC_FLUSH, and the compression state is reset so that decompression canyL restart from this point if previous compressed data has been damaged or ifj random access is desired. Using Z_FULL_FLUSH too often can seriously degrade the compression.
o ~ If deflate returns with avail_out == 0, this function must be called againK with the same value of the flush parameter and more output space (updatedtx avail_out), until the flush is complete (deflate returns with non-zero& avail_out).
i b If the parameter flush is set to Z_FINISH, pending input is processed,} pending output is flushed and deflate returns with Z_STREAM_END if there z was enough output space ; if deflate returns with Z_OK, this function must be~ called again with Z_FINISH and more output space (updated avail_out) but nod more input data, until it returns with Z_STREAM_END or an error. After{ deflate has returned Z_STREAM_END, the only possible operations on thes^ stream are deflateReset or deflateEnd.
Z_FINISH can be used immediately after deflateInit if all the compressionc is to be done in a single step. In this case, avail_out must be at least.u 0.1% larger than avail_in plus 12 bytes. If deflate does not returno\ Z_STREAM_END, then it must be called again as described above.
deflate() sets strm-> adler to the adler32 checksum of all input read; so far (that is, total_in bytes).
, t deflate() may update data_type if it can make a good guess about| the input data type (Z_ASCII or Z_BINARY). In doubt, the data is consideredI binary. This field is only for information purposes and does not affect"* the compression algorithm in any manner.
> p deflate() returns Z_OK if some progress has been made (more inputd processed or more output produced), Z_STREAM_END if all input has beenF consumed and all output has been produced (only when flush is set to Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example if next_in or next_out was NULL), Z_BUF_ERROR if no progress is possible` (for example avail_in or avail_out was zero).
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deflateEnd returns Z_OK if success, Z_STREAM_ERROR if thew stream state was inconsistent, Z_DATA_ERROR if the stream was freed G prematurely (some input or output was discarded). In the error case,#Z msg may be set but then points to a static string (which must not be deallocated).
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inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enoughfn memory, Z_VERSION_ERROR if the zlib library version is incompatible with the] version assumed by the caller. msg is set to null if there is no errorsh message. inflateInit does not perform any decompression apart from reading} the zlib header if present: this will be done by inflate(). (So next_in andp avail_in may be modified, but next_out and avail_out are unchanged.)
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f c The detailed semantics are as follows. inflate performs one or both of thet following actions:
e b Before the call of inflate(), the application should ensure that at leastJ one of the actions is possible, by providing more input and/or consumingF more output, and updating the next_* and avail_* values accordingly.H The application can consume the uncompressed output when it wants, fora example when the output buffer is full (avail_out == 0), or after eachS call of inflate(). If inflate returns Z_OK and with zero avail_out, it K must be called again after making room in the output buffer because there_ might be more output pending.e
u } If the parameter flush is set to Z_SYNC_FLUSH, inflate flushes as muchse output as possible to the output buffer. The flushing behavior of inflate isSe not specified for values of the flush parameter other than Z_SYNC_FLUSHaf and Z_FINISH, but the current implementation actually flushes as much output as possible anyway.m
~ inflate() should normally be called until it returns Z_STREAM_END or anI error. However if all decompression is to be performed in a single stepaY (a single call of inflate), the parameter flush should be set toe_ Z_FINISH. In this case all pending input is processed and all pendinge] output is flushed ; avail_out must be large enough to hold all the"K uncompressed data. (The size of the uncompressed data may have been savedFM by the compressor for this purpose.) The next operation on this stream mustn be inflateEnd to deallocate the decompression state. The use of Z_FINISH>c is never required, but can be used to inform inflate that a faster routine=C may be used for the single inflate() call.i
a q If a preset dictionary is needed at this point (see inflateSetDictionaryA below), inflate sets strm-adler to the adler32 checksum of the e dictionary chosen by the compressor and returns Z_NEED_DICT ; otherwise s it sets strm-> adler to the adler32 checksum of all output producede so far (that is, total_out bytes) and returns Z_OK, Z_STREAM_END or^ an error code as described below. At the end of the stream, inflate()` checks that its computed adler32 checksum is equal to that saved by theb compressor and returns Z_STREAM_END only if the checksum is correct.
d z inflate() returns Z_OK if some progress has been made (more input processedj or more output produced), Z_STREAM_END if the end of the compressed data hasi been reached and all uncompressed output has been produced, Z_NEED_DICT if a k preset dictionary is needed at this point, Z_DATA_ERROR if the input data wasoH corrupted (input stream not conforming to the zlib format or incorrect adler32 checksum), Z_STREAM_ERROR if the stream structure was inconsistentD (for example if next_in or next_out was NULL), Z_MEM_ERROR if there was not f enough memory, Z_BUF_ERROR if no progress is possible or if there was not enough room in the output buffer when Z_FINISH is used. In the Z_DATA_ERROR _ case, the application may then call inflateSync to look for a goodt compression block.
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inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state^ was inconsistent. In the error case, msg may be set but then points to a1 static string (which must not be deallocated).I
_ g The method parameter is the compression method. It must be Z_DEFLATED in<" this version of the library.
J The windowBits parameter is the base two logarithm of the window sizeN (the size of the history buffer). It should be in the range 8..15 for thisK version of the library. Larger values of this parameter result in better I compression at the expense of memory usage. The default value is 15 ife= deflateInit is used instead.
i I The memLevel parameter specifies how much memory should be allocated ^ for the internal compression state. memLevel=1 uses minimum memory butI is slow and reduces compression ratio ; memLevel=9 uses maximum memory J for optimal speed. The default value is 8. See zconf.h for total memory5 usage as a function of windowBits and memLevel.
I N The strategy parameter is used to tune the compression algorithm. Use the value Z_DEFAULT_STRATEGY for normal data, Z_FILTERED for data produced by al filter (or predictor), or Z_HUFFMAN_ONLY to force Huffman encoding only (noG string match). Filtered data consists mostly of small values with acK somewhat random distribution. In this case, the compression algorithm isl} tuned to compress them better. The effect of Z_FILTERED is to force more H Huffman coding and less string matching ; it is somewhat intermediatej between Z_DEFAULT and Z_HUFFMAN_ONLY. The strategy parameter only affectsN the compression ratio but not the correctness of the compressed output even% if it is not set appropriately.
o deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enoughe memory, Z_STREAM_ERROR if a parameter is invalid (such as an invalid<~ method). msg is set to null if there is no error message. deflateInit2 doesY not perform any compression: this will be done by deflate().
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N The dictionary should consist of strings (byte sequences) that are likelyO to be encountered later in the data to be compressed, with the most commonly I used strings preferably put towards the end of the dictionary. Using aoO dictionary is most useful when the data to be compressed is short and can bexM predicted with good accuracy ; the data can then be compressed better thand( with the default empty dictionary.
I Depending on the size of the compression data structures selected bye deflateInit or deflateInit2, a part of the dictionary may in effect beM discarded, for example if the dictionary is larger than the window size in b deflate or deflate2. Thus the strings most likely to be useful should be9 put at the end of the dictionary, not at the front.
r b Upon return of this function, strm-> adler is set to the Adler32 valueM of the dictionary ; the decompressor may later use this value to determinerG which dictionary has been used by the compressor. (The Adler32 valuepM applies to the whole dictionary even if only a subset of the dictionary isr' actually used by the compressor.)
S deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a"] parameter is invalid (such as NULL dictionary) or the stream state is"f inconsistent (for example if deflate has already been called for this streaml or if the compression method is bsort). deflateSetDictionary does notU perform any compression: this will be done by deflate().
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L This function can be useful when several compression strategies will beM tried, for example when there are several ways of pre-processing the inputuN data with a filter. The streams that will be discarded should then be freed} by calling deflateEnd. Note that deflateCopy duplicates the internalF` compression state which can be quite large, so this strategy is slow and! can consume lots of memory.
_ deflateCopy returns Z_OK if success, Z_MEM_ERROR if there was not enough memory, Z_STREAM_ERROR if the source stream state was inconsistentzq (such as zalloc being NULL). msg is left unchanged in both source ande destination.
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n deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the sources stream state was inconsistent (such as zalloc or state being NULL).
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| Before the call of deflateParams, the stream state must be set as for^ a call of deflate(), since the currently available input may have toa be compressed and flushed. In particular, strm-> avail_out must be non-zero.
m deflateParams returns Z_OK if success, Z_STREAM_ERROR if the sourcea{ stream state was inconsistent or if a parameter was invalid, Z_BUF_ERRORb$ if strm->avail_out was zero.
M The windowBits parameter is the base two logarithm of the maximum window N size (the size of the history buffer). It should be in the range 8..15 fori this version of the library. The default value is 15 if inflateInit is usednH instead. If a compressed stream with a larger window size is given as~ input, inflate() will return with the error code Z_DATA_ERROR instead of) trying to allocate a larger window.
. inflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enoughe memory, Z_STREAM_ERROR if a parameter is invalid (such as a negative { memLevel). msg is set to null if there is no error message. inflateInit2mK does not perform any decompression apart from reading the zlib header ift present: this will be done by inflate(). (So next_in and avail_in may be k modified, but next_out and avail_out are unchanged.)
inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a] parameter is invalid (such as NULL dictionary) or the stream state isyc inconsistent, Z_DATA_ERROR if the given dictionary doesn't match thedl expected one (incorrect Adler32 value). inflateSetDictionary does notF perform any decompression: this will be done by subsequent calls of' inflate().
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m inflateSync returns Z_OK if a full flush point has been found, Z_BUF_ERRORk if no more input was provided, Z_DATA_ERROR if no flush point has been found,cj or Z_STREAM_ERROR if the stream structure was inconsistent. In the successd case, the application may save the current current value of total_in whichI indicates where valid compressed data was found. In the error case, theri application may repeatedly call inflateSync, providing more input each time,a, until success or end of the input data.
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inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the sourcer stream state was inconsistent (such as zalloc or state being NULL).
L An Adler-32 checksum is almost as reliable as a CRC32 but can be computed much faster. Usage example:
l uLong adler = adler32(0L, Z_NULL, 0); 1 while (read_buffer(buffer, length) != EOF) {no adler = adler32(adler, buffer, length);s }? if (adler != original_adler) error();d d j Q uLong crc = crc32(0L, Z_NULL, 0);r 1 while (read_buffer(buffer, length) != EOF) { = crc = crc32(crc, buffer, length);t }& if (crc != original_crc) error(); / e typedef struct z_stream_s {aC Bytef *next_in; /* next input byte */cp uInt avail_in; /* number of bytes available at next_in */X uLong total_in; /* total nb of input bytes read so far */ Y Bytef *next_out; /* next output byte should be put there */ n uInt avail_out; /* remaining free space at next_out */U uLong total_out; /* total nb of bytes output so far */a T char *msg; /* last error message, NULL if no error */[ struct internal_state FAR *state; /* not visible by applications */# k alloc_func zalloc; /* used to allocate the internal state */ f free_func zfree; /* used to free the internal state */ voidpf opaque; /* private data object passed to zalloc and zfree */ e int data_type; /* best guess about the data type: ascii or binary */mo uLong adler; /* adler32 value of the uncompressed data */fd uLong reserved; /* reserved for future use */& } z_stream ; W typedef z_stream FAR * z_streamp; l The application must update next_in and avail_in when avail_in has dropped to zero. It must update next_out and avail_out when avail_outt has dropped to zero. The application must initialize zalloc, zfree anda opaque before calling the init function. All other fields are set by theaF compression library and must not be updated by the application. a The opaque value provided by the application will be passed as the firstht parameter for calls of zalloc and zfree. This can be useful for customH memory management. The compression library attaches no meaning to the* opaque value.
v zalloc must return Z_NULL if there is not enough memory for the object.w If zlib is used in a multi-threaded application, zalloc and zfree must ber thread safe.
u x On 16-bit systems, the functions zalloc and zfree must be able to allocateK exactly 65536 bytes, but will not be required to allocate more than this H if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS,^ pointers returned by zalloc for objects of exactly 65536 bytes *must*H have their offset normalized to zero. The default allocation functionH provided by this library ensures this (see zutil.c). To reduce memoryJ requirements and avoid any allocation of 64K objects, at the expense ofL compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h).
s The fields total_in and total_out can be used for statistics orf` progress reports. After compression, total_in holds the total size ofE the uncompressed data and may be saved for use in the decompressor F (particularly if the decompressor wants to decompress everything in a single step).
2 #define Z_NO_FLUSH 08 #define Z_PARTIAL_FLUSH 1 L /* will be removed, use Z_SYNC_FLUSH instead */4 #define Z_SYNC_FLUSH 24 #define Z_FULL_FLUSH 30 #define Z_FINISH 4S /* Allowed flush values ; see deflate() below for details */i , #define Z_OK 04 #define Z_STREAM_END 13 #define Z_NEED_DICT 2 1 #define Z_ERRNO (-1)a8 #define Z_STREAM_ERROR (-2)6 #define Z_DATA_ERROR (-3)5 #define Z_MEM_ERROR (-4)T5 #define Z_BUF_ERROR (-5)u: #define Z_VERSION_ERROR (-6)E /* Return codes for the compression/decompression functions. NegativecM * values are errors, positive values are used for special but normal events.i */ A #define Z_NO_COMPRESSION 0h= #define Z_BEST_SPEED 1fC #define Z_BEST_COMPRESSION 9dG #define Z_DEFAULT_COMPRESSION (-1)s /* compression levels */ 8 #define Z_FILTERED 1< #define Z_HUFFMAN_ONLY 2@ #define Z_DEFAULT_STRATEGY 0] /* compression strategy ; see deflateInit2() below for details */r + #define Z_BINARY 0 * #define Z_ASCII 1, #define Z_UNKNOWN 2E /* Possible values of the data_type field */Z / #define Z_DEFLATED 8 d /* The deflate compression method (the only one supported in this version) */ #define Z_NULL 0 /* for initializing zalloc, zfree, opaque */t X #define zlib_version zlibVersion()5 /* for compatibility with versions less than 1.0.2 */>g
Other functions:<