From 0bfd18043880737648067428e40aa8ee25dbd78f Mon Sep 17 00:00:00 2001 From: tromey Date: Mon, 11 Mar 2002 21:53:27 +0000 Subject: [PATCH] Initial revision git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@50606 138bc75d-0d04-0410-961f-82ee72b054a4 --- zlib/zlib.html | 971 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 971 insertions(+) create mode 100644 zlib/zlib.html diff --git a/zlib/zlib.html b/zlib/zlib.html new file mode 100644 index 00000000000..c3437038693 --- /dev/null +++ b/zlib/zlib.html @@ -0,0 +1,971 @@ + + + + zlib general purpose compression library version 1.1.4 + + + + + +

zlib 1.1.4 Manual

+
+

Contents

+
    +
  1. Prologue +
  2. Introduction +
  3. Utility functions +
  4. Basic functions +
  5. Advanced functions +
  6. Constants +
  7. struct z_stream_s +
  8. Checksum functions +
  9. Misc +
+
+

Prologue

+ 'zlib' general purpose compression library version 1.1.4, March 11th, 2002 +

+ Copyright (C) 1995-2002 Jean-loup Gailly and Mark Adler +

+ This software is provided 'as-is', without any express or implied + warranty. In no event will the authors be held liable for any damages + arising from the use of this software. +

+ Permission is granted to anyone to use this software for any purpose, + including commercial applications, and to alter it and redistribute it + freely, subject to the following restrictions: +

    +
  1. The origin of this software must not be misrepresented ; you must not + claim that you wrote the original software. If you use this software + in a product, an acknowledgment in the product documentation would be + appreciated but is not required. +
  2. Altered source versions must be plainly marked as such, and must not be + misrepresented as being the original software. +
  3. This notice may not be removed or altered from any source distribution. +
+ +
+
Jean-loup Gailly +
jloup@gzip.org +
Mark Adler +
madler@alumni.caltech.edu +
+ + The data format used by the zlib library is described by RFCs (Request for + Comments) 1950 to 1952 in the files + + ftp://ds.internic.net/rfc/rfc1950.txt + (zlib format), + + rfc1951.txt + (deflate format) and + + rfc1952.txt + (gzip format). +

+ This manual is converted from zlib.h by + piaip +

+ Visit + http://ftp.cdrom.com/pub/infozip/zlib/ + for the official zlib web page. +

+ +

+

Introduction

+ The 'zlib' compression library provides in-memory compression and + decompression functions, including integrity checks of the uncompressed + data. This version of the library supports only one compression method + (deflation) but other algorithms will be added later and will have the same + stream interface. +

+ + Compression can be done in a single step if the buffers are large + enough (for example if an input file is mmap'ed), or can be done by + repeated calls of the compression function. In the latter case, the + application must provide more input and/or consume the output + (providing more output space) before each call. +

+ + The library also supports reading and writing files in gzip (.gz) format + with an interface similar to that of stdio. +

+ + The library does not install any signal handler. The decoder checks + the consistency of the compressed data, so the library should never + crash even in case of corrupted input. +

+ +

+

Utility functions

+ The following utility functions are implemented on top of the + basic stream-oriented functions. + To simplify the interface, some + default options are assumed (compression level and memory usage, + standard memory allocation functions). The source code of these + utility functions can easily be modified if you need special options. +

Function list

+ +

Function description

+
+
int compress (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen); +
+ Compresses the source buffer into the destination buffer. sourceLen is + the byte length of the source buffer. Upon entry, destLen is the total + size of the destination buffer, which must be at least 0.1% larger than + sourceLen plus 12 bytes. Upon exit, destLen is the actual size of the + compressed buffer.

+ 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 not + enough memory, Z_BUF_ERROR if there was not enough room in the output + buffer.

+ +

int compress2 (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen, int level); +
+ Compresses the source buffer into the destination buffer. The level + parameter has the same meaning as in deflateInit. sourceLen is the byte + length of the source buffer. Upon entry, destLen is the total size of the + destination buffer, which must be at least 0.1% larger than sourceLen plus + 12 bytes. Upon exit, destLen is the actual size of the compressed buffer. +

+ + compress2 returns Z_OK if success, Z_MEM_ERROR if there was not enough + memory, Z_BUF_ERROR if there was not enough room in the output buffer, + Z_STREAM_ERROR if the level parameter is invalid. +

+ +

int uncompress (Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen); +
+ Decompresses the source buffer into the destination buffer. sourceLen is + the byte length of the source buffer. Upon entry, destLen is the total + size of the destination buffer, which must be large enough to hold the + entire uncompressed data. (The size of the uncompressed data must have + been saved previously by the compressor and transmitted to the decompressor + by some mechanism outside the scope of this compression library.) + Upon exit, destLen is the actual size of the compressed buffer.

+ This function can be used to decompress a whole file at once if the + input file is mmap'ed. +

+ + uncompress returns Z_OK if success, Z_MEM_ERROR if there was not + enough memory, Z_BUF_ERROR if there was not enough room in the output + buffer, or Z_DATA_ERROR if the input data was corrupted. +

+ +

typedef voidp gzFile; +

+ +

gzFile gzopen (const char *path, const char *mode); +
+ Opens a gzip (.gz) file for reading or writing. The mode parameter + is as in fopen ("rb" or "wb") but can also include a compression level + ("wb9") or a strategy: 'f' for filtered data as in "wb6f", 'h' for + Huffman only compression as in "wb1h". (See the description + of deflateInit2 for more information about the strategy parameter.) +

+ + 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 was + insufficient memory to allocate the (de)compression state ; errno + can be checked to distinguish the two cases (if errno is zero, the + zlib error is Z_MEM_ERROR). +

+ +

gzFile gzdopen (int fd, const char *mode); +
+ gzdopen() associates a gzFile with the file descriptor fd. File + descriptors are obtained from calls like open, dup, creat, pipe or + fileno (in the file has been previously opened with fopen). + The mode parameter is as in gzopen. +

+ The next call of gzclose on the returned gzFile will also close the + file descriptor fd, just like fclose(fdopen(fd), mode) closes the file + descriptor fd. If you want to keep fd open, use gzdopen(dup(fd), mode). +

+ gzdopen returns NULL if there was insufficient memory to allocate + the (de)compression state. +

+ +

int gzsetparams (gzFile file, int level, int strategy); +
+ Dynamically update the compression level or strategy. See the description + of deflateInit2 for the meaning of these parameters. +

+ gzsetparams returns Z_OK if success, or Z_STREAM_ERROR if the file was not + opened for writing. +

+ +

int gzread (gzFile file, voidp buf, unsigned len); +
+ Reads the given number of uncompressed bytes from the compressed file. + If the input file was not in gzip format, gzread copies the given number + of bytes into the buffer. +

+ gzread returns the number of uncompressed bytes actually read (0 for + end of file, -1 for error). +

+ +

int gzwrite (gzFile file, const voidp buf, unsigned len); +
+ Writes the given number of uncompressed bytes into the compressed file. + gzwrite returns the number of uncompressed bytes actually written + (0 in case of error). +

+ +

int VA gzprintf (gzFile file, const char *format, ...); +
+ Converts, formats, and writes the args to the compressed file under + control of the format string, as in fprintf. gzprintf returns the number of + uncompressed bytes actually written (0 in case of error). +

+ +

int gzputs (gzFile file, const char *s); +
+ Writes the given null-terminated string to the compressed file, excluding + the terminating null character. +

+ gzputs returns the number of characters written, or -1 in case of error. +

+ +

char * gzgets (gzFile file, char *buf, int len); +
+ Reads bytes from the compressed file until len-1 characters are read, or + a newline character is read and transferred to buf, or an end-of-file + condition is encountered. The string is then terminated with a null + character. +

+ gzgets returns buf, or Z_NULL in case of error. +

+ +

int gzputc (gzFile file, int c); +
+ Writes c, converted to an unsigned char, into the compressed file. + gzputc returns the value that was written, or -1 in case of error. +

+ +

int gzgetc (gzFile file); +
+ Reads one byte from the compressed file. gzgetc returns this byte + or -1 in case of end of file or error. +

+ +

int gzflush (gzFile file, int flush); +
+ Flushes all pending output into the compressed file. The parameter + flush is as in the deflate() function. The return value is the zlib + error number (see function gzerror below). gzflush returns Z_OK if + the flush parameter is Z_FINISH and all output could be flushed. +

+ gzflush should be called only when strictly necessary because it can + degrade compression. +

+ +

z_off_t gzseek (gzFile file, z_off_t offset, int whence); +
+ Sets the starting position for the next gzread or gzwrite on the + given compressed file. The offset represents a number of bytes in the + uncompressed data stream. The whence parameter is defined as in lseek(2); + the value SEEK_END is not supported. +

+ If the file is opened for reading, this function is emulated but can be + 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. +

+ gzseek returns the resulting offset location as measured in bytes from + the beginning of the uncompressed stream, or -1 in case of error, in + particular if the file is opened for writing and the new starting position + would be before the current position. +

+ +

int gzrewind (gzFile file); +
+ Rewinds the given file. This function is supported only for reading. +

+ gzrewind(file) is equivalent to (int)gzseek(file, 0L, SEEK_SET) +

+ +

z_off_t gztell (gzFile file); +
+ Returns the starting position for the next gzread or gzwrite on the + given compressed file. This position represents a number of bytes in the + uncompressed data stream. +

+ + gztell(file) is equivalent to gzseek(file, 0L, SEEK_CUR) +

+ +

int gzeof (gzFile file); +
+ Returns 1 when EOF has previously been detected reading the given + input stream, otherwise zero. +

+ +

int gzclose (gzFile file); +
+ Flushes all pending output if necessary, closes the compressed file + and deallocates all the (de)compression state. The return value is the zlib + error number (see function gzerror below). +

+ +

const char * gzerror (gzFile file, int *errnum); +
+ Returns the error message for the last error which occurred on the + given compressed file. errnum is set to zlib error number. If an + error occurred in the file system and not in the compression library, + errnum is set to Z_ERRNO and the application may consult errno + to get the exact error code. +

+

+
+

Basic functions

+

Function list

+ + +

Function description

+
+
const char * zlibVersion (void); +
The application can compare zlibVersion and ZLIB_VERSION for consistency. + If the first character differs, the library code actually used is + not compatible with the zlib.h header file used by the application. + This check is automatically made by deflateInit and inflateInit. +

+ +

int deflateInit (z_streamp strm, int level); +
+ Initializes the internal stream state for compression. The fields + zalloc, zfree and opaque must be initialized before by the caller. + If zalloc and zfree are set to Z_NULL, deflateInit updates them to + use default allocation functions. +

+ + The compression level must be Z_DEFAULT_COMPRESSION, or between 0 and 9: + 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). +

+ + Z_DEFAULT_COMPRESSION requests a default compromise between speed and + compression (currently equivalent to level 6). +

+ + deflateInit returns Z_OK if success, Z_MEM_ERROR if there was not + enough memory, Z_STREAM_ERROR if level is not a valid compression level, + Z_VERSION_ERROR if the zlib library version (zlib_version) is incompatible + with the version assumed by the caller (ZLIB_VERSION). + msg is set to null if there is no error message. deflateInit does not + perform any compression: this will be done by deflate(). +

+ +

int deflate (z_streamp strm, int flush); +
+ deflate compresses as much data as possible, and stops when the input + buffer becomes empty or the output buffer becomes full. It may introduce some + output latency (reading input without producing any output) except when + forced to flush.

+ + The detailed semantics are as follows. deflate performs one or both of the + following actions: + +

    +
  • Compress more input starting at next_in and update next_in and avail_in + accordingly. If not all input can be processed (because there is not + enough room in the output buffer), next_in and avail_in are updated and + processing will resume at this point for the next call of deflate(). + +
  • + Provide more output starting at next_out and update next_out and avail_out + accordingly. This action is forced if the parameter flush is non zero. + Forcing flush frequently degrades the compression ratio, so this parameter + should be set only when necessary (in interactive applications). + Some output may be provided even if flush is not set. +

+ + Before the call of deflate(), the application should ensure that at least + 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 + should never be zero before the call. The application can consume the + compressed output when it wants, for example when the output buffer is full + (avail_out == 0), or after each call of deflate(). If deflate returns Z_OK + and with zero avail_out, it must be called again after making room in the + output buffer because there might be more output pending. +

+ + If the parameter flush is set to Z_SYNC_FLUSH, all pending output is + flushed to the output buffer and the output is aligned on a byte boundary, so + that the decompressor can get all input data available so far. (In particular + avail_in is zero after the call if enough output space has been provided + before the call.) Flushing may degrade compression for some compression + algorithms and so it should be used only when necessary. +

+ + 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 can + restart from this point if previous compressed data has been damaged or if + random access is desired. Using Z_FULL_FLUSH too often can seriously degrade + the compression. +

+ + If deflate returns with avail_out == 0, this function must be called again + with the same value of the flush parameter and more output space (updated + avail_out), until the flush is complete (deflate returns with non-zero + avail_out). +

+ + 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 + 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 no + 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 the + stream are deflateReset or deflateEnd. +

+ + Z_FINISH can be used immediately after deflateInit if all the compression + is to be done in a single step. In this case, avail_out must be at least + 0.1% larger than avail_in plus 12 bytes. If deflate does not return + 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). +

+ + 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 considered + binary. This field is only for information purposes and does not affect + the compression algorithm in any manner. +

+ + deflate() returns Z_OK if some progress has been made (more input + processed or more output produced), Z_STREAM_END if all input has been + 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). +

+ +

int deflateEnd (z_streamp strm); +
+ All dynamically allocated data structures for this stream are freed. + This function discards any unprocessed input and does not flush any + pending output. +

+ + deflateEnd returns Z_OK if success, Z_STREAM_ERROR if the + stream state was inconsistent, Z_DATA_ERROR if the stream was freed + prematurely (some input or output was discarded). In the error case, + msg may be set but then points to a static string (which must not be + deallocated). +

+ +

int inflateInit (z_streamp strm); +
+ Initializes the internal stream state for decompression. The fields + next_in, avail_in, zalloc, zfree and opaque must be initialized before by + the caller. If next_in is not Z_NULL and avail_in is large enough (the exact + value depends on the compression method), inflateInit determines the + compression method from the zlib header and allocates all data structures + accordingly ; otherwise the allocation will be deferred to the first call of + inflate. If zalloc and zfree are set to Z_NULL, inflateInit updates them to + use default allocation functions. +

+ + inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough + 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 error + message. inflateInit does not perform any decompression apart from reading + the zlib header if present: this will be done by inflate(). (So next_in and + avail_in may be modified, but next_out and avail_out are unchanged.) +

+ +

int inflate (z_streamp strm, int flush); +
+ inflate decompresses as much data as possible, and stops when the input + buffer becomes empty or the output buffer becomes full. It may some + introduce some output latency (reading input without producing any output) + except when forced to flush. +

+ + The detailed semantics are as follows. inflate performs one or both of the + following actions: + +

    +
  • Decompress more input starting at next_in and update next_in and avail_in + accordingly. If not all input can be processed (because there is not + enough room in the output buffer), next_in is updated and processing + will resume at this point for the next call of inflate(). + +
  • Provide more output starting at next_out and update next_out and + avail_out accordingly. inflate() provides as much output as possible, + until there is no more input data or no more space in the output buffer + (see below about the flush parameter). +

+ + Before the call of inflate(), the application should ensure that at least + one of the actions is possible, by providing more input and/or consuming + more output, and updating the next_* and avail_* values accordingly. + The application can consume the uncompressed output when it wants, for + example when the output buffer is full (avail_out == 0), or after each + call of inflate(). If inflate returns Z_OK and with zero avail_out, it + must be called again after making room in the output buffer because there + might be more output pending. +

+ + If the parameter flush is set to Z_SYNC_FLUSH, inflate flushes as much + output as possible to the output buffer. The flushing behavior of inflate is + not specified for values of the flush parameter other than Z_SYNC_FLUSH + and Z_FINISH, but the current implementation actually flushes as much output + as possible anyway. +

+ + inflate() should normally be called until it returns Z_STREAM_END or an + error. However if all decompression is to be performed in a single step + (a single call of inflate), the parameter flush should be set to + Z_FINISH. In this case all pending input is processed and all pending + output is flushed ; avail_out must be large enough to hold all the + uncompressed data. (The size of the uncompressed data may have been saved + by the compressor for this purpose.) The next operation on this stream must + be inflateEnd to deallocate the decompression state. The use of Z_FINISH + is never required, but can be used to inform inflate that a faster routine + may be used for the single inflate() call. +

+ + If a preset dictionary is needed at this point (see inflateSetDictionary + below), inflate sets strm-adler to the adler32 checksum of the + dictionary chosen by the compressor and returns Z_NEED_DICT ; otherwise + it sets strm-> adler to the adler32 checksum of all output produced + 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 the + compressor and returns Z_STREAM_END only if the checksum is correct. +

+ + inflate() returns Z_OK if some progress has been made (more input processed + or more output produced), Z_STREAM_END if the end of the compressed data has + been reached and all uncompressed output has been produced, Z_NEED_DICT if a + preset dictionary is needed at this point, Z_DATA_ERROR if the input data was + corrupted (input stream not conforming to the zlib format or incorrect + adler32 checksum), Z_STREAM_ERROR if the stream structure was inconsistent + (for example if next_in or next_out was NULL), Z_MEM_ERROR if there was not + 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 good + compression block. +

+ +

int inflateEnd (z_streamp strm); +
+ All dynamically allocated data structures for this stream are freed. + This function discards any unprocessed input and does not flush any + pending output. +

+ + 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 a + static string (which must not be deallocated). +

+
+

Advanced functions

+ The following functions are needed only in some special applications. +

Function list

+ +

Function description

+
+
int deflateInit2 (z_streamp strm, int level, int method, int windowBits, int memLevel, int strategy); + +
This is another version of deflateInit with more compression options. The + fields next_in, zalloc, zfree and opaque must be initialized before by + the caller.

+ + The method parameter is the compression method. It must be Z_DEFLATED in + this version of the library.

+ + The windowBits parameter is the base two logarithm of the window size + (the size of the history buffer). It should be in the range 8..15 for this + version of the library. Larger values of this parameter result in better + compression at the expense of memory usage. The default value is 15 if + deflateInit is used instead.

+ + The memLevel parameter specifies how much memory should be allocated + for the internal compression state. memLevel=1 uses minimum memory but + is slow and reduces compression ratio ; memLevel=9 uses maximum memory + for optimal speed. The default value is 8. See zconf.h for total memory + usage as a function of windowBits and memLevel.

+ + 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 a + filter (or predictor), or Z_HUFFMAN_ONLY to force Huffman encoding only (no + string match). Filtered data consists mostly of small values with a + somewhat random distribution. In this case, the compression algorithm is + tuned to compress them better. The effect of Z_FILTERED is to force more + Huffman coding and less string matching ; it is somewhat intermediate + between Z_DEFAULT and Z_HUFFMAN_ONLY. The strategy parameter only affects + the compression ratio but not the correctness of the compressed output even + if it is not set appropriately.

+ + deflateInit2 returns Z_OK if success, Z_MEM_ERROR if there was not enough + 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 does + not perform any compression: this will be done by deflate().

+ +

int deflateSetDictionary (z_streamp strm, const Bytef *dictionary, uInt dictLength); +
+ Initializes the compression dictionary from the given byte sequence + without producing any compressed output. This function must be called + immediately after deflateInit, deflateInit2 or deflateReset, before any + call of deflate. The compressor and decompressor must use exactly the same + dictionary (see inflateSetDictionary).

+ + The dictionary should consist of strings (byte sequences) that are likely + to be encountered later in the data to be compressed, with the most commonly + used strings preferably put towards the end of the dictionary. Using a + dictionary is most useful when the data to be compressed is short and can be + predicted with good accuracy ; the data can then be compressed better than + with the default empty dictionary.

+ + Depending on the size of the compression data structures selected by + deflateInit or deflateInit2, a part of the dictionary may in effect be + discarded, for example if the dictionary is larger than the window size in + deflate or deflate2. Thus the strings most likely to be useful should be + put at the end of the dictionary, not at the front.

+ + Upon return of this function, strm-> adler is set to the Adler32 value + of the dictionary ; the decompressor may later use this value to determine + which dictionary has been used by the compressor. (The Adler32 value + applies to the whole dictionary even if only a subset of the dictionary is + actually used by the compressor.)

+ + deflateSetDictionary returns Z_OK if success, or Z_STREAM_ERROR if a + parameter is invalid (such as NULL dictionary) or the stream state is + inconsistent (for example if deflate has already been called for this stream + or if the compression method is bsort). deflateSetDictionary does not + perform any compression: this will be done by deflate().

+ +

int deflateCopy (z_streamp dest, z_streamp source); +
+ Sets the destination stream as a complete copy of the source stream.

+ + This function can be useful when several compression strategies will be + tried, for example when there are several ways of pre-processing the input + data with a filter. The streams that will be discarded should then be freed + by calling deflateEnd. Note that deflateCopy duplicates the internal + 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 inconsistent + (such as zalloc being NULL). msg is left unchanged in both source and + destination.

+ +

int deflateReset (z_streamp strm); +
This function is equivalent to deflateEnd followed by deflateInit, + but does not free and reallocate all the internal compression state. + The stream will keep the same compression level and any other attributes + that may have been set by deflateInit2.

+ + deflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source + stream state was inconsistent (such as zalloc or state being NULL).

+ +

int deflateParams (z_streamp strm, int level, int strategy); +
+ Dynamically update the compression level and compression strategy. The + interpretation of level and strategy is as in deflateInit2. This can be + used to switch between compression and straight copy of the input data, or + to switch to a different kind of input data requiring a different + strategy. If the compression level is changed, the input available so far + is compressed with the old level (and may be flushed); the new level will + take effect only at the next call of deflate().

+ + Before the call of deflateParams, the stream state must be set as for + a call of deflate(), since the currently available input may have to + be compressed and flushed. In particular, strm-> avail_out must be + non-zero.

+ + deflateParams returns Z_OK if success, Z_STREAM_ERROR if the source + stream state was inconsistent or if a parameter was invalid, Z_BUF_ERROR + if strm->avail_out was zero.

+ +

int inflateInit2 (z_streamp strm, int windowBits); + +
This is another version of inflateInit with an extra parameter. The + fields next_in, avail_in, zalloc, zfree and opaque must be initialized + before by the caller.

+ + The windowBits parameter is the base two logarithm of the maximum window + size (the size of the history buffer). It should be in the range 8..15 for + this version of the library. The default value is 15 if inflateInit is used + 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 enough + 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. inflateInit2 + does not perform any decompression apart from reading the zlib header if + present: this will be done by inflate(). (So next_in and avail_in may be + modified, but next_out and avail_out are unchanged.)

+ +

int inflateSetDictionary (z_streamp strm, const Bytef *dictionary, uInt dictLength); +
+ Initializes the decompression dictionary from the given uncompressed byte + sequence. This function must be called immediately after a call of inflate + if this call returned Z_NEED_DICT. The dictionary chosen by the compressor + can be determined from the Adler32 value returned by this call of + inflate. The compressor and decompressor must use exactly the same + dictionary (see deflateSetDictionary).

+ + inflateSetDictionary returns Z_OK if success, Z_STREAM_ERROR if a + parameter is invalid (such as NULL dictionary) or the stream state is + inconsistent, Z_DATA_ERROR if the given dictionary doesn't match the + expected one (incorrect Adler32 value). inflateSetDictionary does not + perform any decompression: this will be done by subsequent calls of + inflate().

+ +

int inflateSync (z_streamp strm); + +
Skips invalid compressed data until a full flush point (see above the + description of deflate with Z_FULL_FLUSH) can be found, or until all + available input is skipped. No output is provided.

+ + inflateSync returns Z_OK if a full flush point has been found, Z_BUF_ERROR + if no more input was provided, Z_DATA_ERROR if no flush point has been found, + or Z_STREAM_ERROR if the stream structure was inconsistent. In the success + case, the application may save the current current value of total_in which + indicates where valid compressed data was found. In the error case, the + application may repeatedly call inflateSync, providing more input each time, + until success or end of the input data.

+ +

int inflateReset (z_streamp strm); +
+ This function is equivalent to inflateEnd followed by inflateInit, + but does not free and reallocate all the internal decompression state. + The stream will keep attributes that may have been set by inflateInit2. +

+ + inflateReset returns Z_OK if success, or Z_STREAM_ERROR if the source + stream state was inconsistent (such as zalloc or state being NULL). +

+

+ +
+

Checksum functions

+ These functions are not related to compression but are exported + anyway because they might be useful in applications using the + compression library. +

Function list

+ +

Function description

+
+
uLong adler32 (uLong adler, const Bytef *buf, uInt len); +
+ Update a running Adler-32 checksum with the bytes buf[0..len-1] and + return the updated checksum. If buf is NULL, this function returns + the required initial value for the checksum. +

+ An Adler-32 checksum is almost as reliable as a CRC32 but can be computed + much faster. Usage example: + 

+
+     uLong adler = adler32(0L, Z_NULL, 0);
+
+     while (read_buffer(buffer, length) != EOF) {
+       adler = adler32(adler, buffer, length);
+     }
+     if (adler != original_adler) error();
+
+ +
uLong crc32 (uLong crc, const Bytef *buf, uInt len); +
+ Update a running crc with the bytes buf[0..len-1] and return the updated + crc. If buf is NULL, this function returns the required initial value + for the crc. Pre- and post-conditioning (one's complement) is performed + within this function so it shouldn't be done by the application. + Usage example: + 
+
+     uLong crc = crc32(0L, Z_NULL, 0);
+
+     while (read_buffer(buffer, length) != EOF) {
+       crc = crc32(crc, buffer, length);
+     }
+     if (crc != original_crc) error();
+
+
+
+

struct z_stream_s

+ + +
+typedef struct z_stream_s {
+    Bytef    *next_in;  /* next input byte */
+    uInt     avail_in;  /* number of bytes available at next_in */
+    uLong    total_in;  /* total nb of input bytes read so far */
+
+    Bytef    *next_out; /* next output byte should be put there */
+    uInt     avail_out; /* remaining free space at next_out */
+    uLong    total_out; /* total nb of bytes output so far */
+
+    char     *msg;      /* last error message, NULL if no error */
+    struct internal_state FAR *state; /* not visible by applications */
+
+    alloc_func zalloc;  /* used to allocate the internal state */
+    free_func  zfree;   /* used to free the internal state */
+    voidpf     opaque;  /* private data object passed to zalloc and zfree */
+
+    int     data_type;  /* best guess about the data type: ascii or binary */
+    uLong   adler;      /* adler32 value of the uncompressed data */
+    uLong   reserved;   /* reserved for future use */
+} z_stream ;
+
+typedef z_stream FAR * z_streamp;  ΓΏ 
+
+ + 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_out + has dropped to zero. The application must initialize zalloc, zfree and + opaque before calling the init function. All other fields are set by the + compression library and must not be updated by the application.

+ + The opaque value provided by the application will be passed as the first + parameter for calls of zalloc and zfree. This can be useful for custom + memory management. The compression library attaches no meaning to the + opaque value.

+ + zalloc must return Z_NULL if there is not enough memory for the object. + If zlib is used in a multi-threaded application, zalloc and zfree must be + thread safe.

+ + On 16-bit systems, the functions zalloc and zfree must be able to allocate + exactly 65536 bytes, but will not be required to allocate more than this + if the symbol MAXSEG_64K is defined (see zconf.h). WARNING: On MSDOS, + pointers returned by zalloc for objects of exactly 65536 bytes *must* + have their offset normalized to zero. The default allocation function + provided by this library ensures this (see zutil.c). To reduce memory + requirements and avoid any allocation of 64K objects, at the expense of + compression ratio, compile the library with -DMAX_WBITS=14 (see zconf.h). +

+ + The fields total_in and total_out can be used for statistics or + progress reports. After compression, total_in holds the total size of + the uncompressed data and may be saved for use in the decompressor + (particularly if the decompressor wants to decompress everything in + a single step).

+ +

+

Constants

+ +
+#define Z_NO_FLUSH      0
+#define Z_PARTIAL_FLUSH 1 
+	/* will be removed, use Z_SYNC_FLUSH instead */
+#define Z_SYNC_FLUSH    2
+#define Z_FULL_FLUSH    3
+#define Z_FINISH        4
+/* Allowed flush values ; see deflate() below for details */
+
+#define Z_OK            0
+#define Z_STREAM_END    1
+#define Z_NEED_DICT     2
+#define Z_ERRNO        (-1)
+#define Z_STREAM_ERROR (-2)
+#define Z_DATA_ERROR   (-3)
+#define Z_MEM_ERROR    (-4)
+#define Z_BUF_ERROR    (-5)
+#define Z_VERSION_ERROR (-6)
+/* Return codes for the compression/decompression functions. Negative
+ * values are errors, positive values are used for special but normal events.
+ */
+
+#define Z_NO_COMPRESSION         0
+#define Z_BEST_SPEED             1
+#define Z_BEST_COMPRESSION       9
+#define Z_DEFAULT_COMPRESSION  (-1)
+/* compression levels */
+
+#define Z_FILTERED            1
+#define Z_HUFFMAN_ONLY        2
+#define Z_DEFAULT_STRATEGY    0
+/* compression strategy ; see deflateInit2() below for details */
+
+#define Z_BINARY   0
+#define Z_ASCII    1
+#define Z_UNKNOWN  2
+/* Possible values of the data_type field */
+
+#define Z_DEFLATED   8
+/* The deflate compression method (the only one supported in this version) */
+
+#define Z_NULL  0  /* for initializing zalloc, zfree, opaque */
+
+#define zlib_version zlibVersion()
+/* for compatibility with versions less than 1.0.2 */
+
+ + +
+

Misc

+ deflateInit and inflateInit are macros to allow checking the zlib version + and the compiler's view of z_stream. +

+ Other functions: +

+
const char * zError (int err); +
int inflateSyncPoint (z_streamp z); +
const uLongf * get_crc_table (void); +
+
+ + Last update: Wed Oct 13 20:42:34 1999
+ piapi@csie.ntu.edu.tw + + + + -- 2.11.0