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+COMPRESS(3) BSD Library Functions Manual COMPRESS(3)
+
+NAME
+ compress, zlibVersion, deflateInit, deflate, deflateEnd, inflateInit,
+ inflate, inflateEnd, deflateInit2, deflateSetDictionary, deflateCopy,
+ deflateReset, deflateParams, deflateTune, deflateBound, deflatePrime,
+ deflateSetHeader, inflateInit2, inflateSetDictionary, inflateSync,
+ inflateCopy, inflateReset, inflatePrime, inflateGetHeader,
+ inflateBackInit, inflateBack, inflateBackEnd, zlibCompileFlags,
+ compress2, compressBound, uncompress, gzopen, gzdopen, gzsetparams,
+ gzread, gzwrite, gzprintf, gzputs, gzgets, gzputc, gzgetc, gzungetc,
+ gzflush, gzseek, gzrewind, gztell, gzeof, gzdirect, gzclose, gzerror,
+ gzclearerr, adler32, adler32_combine, crc32, crc32_combine -- zlib gen-
+ eral purpose compression library
+
+SYNOPSIS
+ #include <zlib.h>
+
+ Basic functions
+
+ const char *
+ zlibVersion(void);
+
+ int
+ deflateInit(z_streamp strm, int level);
+
+ int
+ deflate(z_streamp strm, int flush);
+
+ int
+ deflateEnd(z_streamp strm);
+
+ int
+ inflateInit(z_streamp strm);
+
+ int
+ inflate(z_streamp strm, int flush);
+
+ int
+ inflateEnd(z_streamp strm);
+
+ Advanced functions
+
+ int
+ deflateInit2(z_streamp strm, int level, int method, int windowBits,
+ int memLevel, int strategy);
+
+ int
+ deflateSetDictionary(z_streamp strm, const Bytef *dictionary,
+ uInt dictLength);
+
+ int
+ deflateCopy(z_streamp dest, z_streamp source);
+
+ int
+ deflateReset(z_streamp strm);
+
+ int
+ deflateParams(z_streamp strm, int level, int strategy);
+
+ int
+ deflateTune(z_streamp strm, int good_length, int max_lazy,
+ int nice_length, int max_chain);
+
+ uLong
+ deflateBound(z_streamp strm, uLong sourceLen);
+
+ int
+ deflatePrime(z_streamp strm, int bits, int value);
+
+ int
+ deflateSetHeader(z_streamp strm, gz_headerp head);
+
+ int
+ inflateInit2(z_streamp strm, int windowBits);
+
+ int
+ inflateSetDictionary(z_streamp strm, const Bytef *dictionary,
+ uInt dictLength);
+
+ int
+ inflateSync(z_streamp strm);
+
+ int
+ inflateCopy(z_streamp dst, z_streamp source);
+
+ int
+ inflateReset(z_streamp strm);
+
+ int
+ inflatePrime(z_streamp strm, int bits, int value);
+
+ int
+ inflateGetHeader(z_streamp strm, gz_headerp head);
+
+ int
+ inflateBackInit(z_stream *strm, int windowBits,
+ unsigned char FAR *window);
+
+ int
+ inflateBack(z_stream *strm, in_func in, void FAR *in_desc, out_func out,
+ void FAR *out_desc);
+
+ int
+ inflateBackEnd(z_stream *strm);
+
+ uLong
+ zlibCompileFlags(void);
+
+ Utility functions
+
+ typedef voidp gzFile;
+
+ int
+ compress(Bytef *dest, uLongf *destLen, const Bytef *source,
+ uLong sourceLen);
+
+ int
+ compress2(Bytef *dest, uLongf *destLen, const Bytef *source,
+ uLong sourceLen, int level);
+
+ uLong
+ compressBound(uLong sourceLen);
+
+ int
+ uncompress(Bytef *dest, uLongf *destLen, const Bytef *source,
+ uLong sourceLen);
+
+ gzFile
+ gzopen(const char *path, const char *mode);
+
+ gzFile
+ gzdopen(int fd, const char *mode);
+
+ int
+ gzsetparams(gzFile file, int level, int strategy);
+
+ int
+ gzread(gzFile file, voidp buf, unsigned len);
+
+ int
+ gzwrite(gzFile file, voidpc buf, unsigned len);
+
+ int
+ gzprintf(gzFile file, const char *format, ...);
+
+ int
+ gzputs(gzFile file, const char *s);
+
+ char *
+ gzgets(gzFile file, char *buf, int len);
+
+ int
+ gzputc(gzFile file, int c);
+
+ int
+ gzgetc(gzFile file);
+
+ int
+ gzungetc(int c, gzFile file);
+
+ int
+ gzflush(gzFile file, int flush);
+
+ z_off_t
+ gzseek(gzFile file, z_off_t offset, int whence);
+
+ int
+ gzrewind(gzFile file);
+
+ z_off_t
+ gztell(gzFile file);
+
+ int
+ gzeof(gzFile file);
+
+ int
+ gzdirect(gzFile file);
+
+ int
+ gzclose(gzFile file);
+
+ const char *
+ gzerror(gzFile file, int *errnum);
+
+ void
+ gzclearerr(gzFile file);
+
+ Checksum functions
+
+ uLong
+ adler32(uLong adler, const Bytef *buf, uInt len);
+
+ uLong
+ adler32_combine(uLong adler1, uLong adler2, z_off_t len2);
+
+ uLong
+ crc32(uLong crc, const Bytef *buf, uInt len);
+
+ uLong
+ crc32_combine(uLong crc1, uLong crc2, z_off_t len2);
+
+DESCRIPTION
+ This manual page describes the zlib general purpose compression library,
+ version 1.2.3.
+
+ The zlib compression library provides in-memory compression and decom-
+ pression 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 compressed data format used by default by the in-memory functions is
+ the zlib format, which is a zlib wrapper documented in RFC 1950, wrapped
+ around a deflate stream, which is itself documented in RFC 1951.
+
+ The library also supports reading and writing files in gzip(1) (.gz) for-
+ mat with an interface similar to that of stdio(3) using the functions
+ that start with "gz". The gzip format is different from the zlib format.
+ gzip is a gzip wrapper, documented in RFC 1952, wrapped around a deflate
+ stream. This library can optionally read and write gzip streams in mem-
+ ory as well.
+
+ The zlib format was designed to be compact and fast for use in memory and
+ on communications channels. The gzip format was designed for single-file
+ compression on file systems, has a larger header than zlib to maintain
+ directory information, and uses a different, slower, check method than
+ zlib.
+
+ 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.
+
+ The functions within the library are divided into the following sections:
+
+ - Basic functions
+ - Advanced functions
+ - Utility functions
+ - Checksum functions
+
+BASIC FUNCTIONS
+ 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);
+
+ The deflateInit() function 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 successful, 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 to 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 com-
+ pression ratio, so this parameter should be set only when neces-
+ sary (in interactive applications). Some output may be provided
+ even if flush is not set.
+
+ Before the call to 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 to deflate(). If deflate() returns Z_OK and with zero
+ avail_out, it must be called again after making room in the out-
+ put buffer because there might be more output pending.
+
+ Normally the parameter flush is set to Z_NO_FLUSH, which allows
+ deflate() to decide how much data to accumulate before producing
+ output, in order to maximise compression.
+
+ 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 decom-
+ pression 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 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). In the case of a
+ Z_FULL_FLUSH or a Z_SYNC_FLUSH, make sure that avail_out is
+ greater than six to avoid repeated flush markers due to avail_out
+ == 0 on return.
+
+ If the parameter flush is set to Z_FINISH, pending input is pro-
+ cessed, pending output is flushed and deflate() returns with
+ Z_STREAM_END if there was enough output space; if deflate() re-
+ turns 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 the value returned by deflateBound()
+ (see below). If deflate() does not return Z_STREAM_END, then it
+ must be called again as described above.
+
+ deflate() sets strm->adler to the Adler-32 checksum of all input
+ read so far (that is, total_in bytes).
+
+ deflate() may update strm->data_type if it can make a good guess
+ about the input data type (Z_BINARY or Z_TEXT). If 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 in-
+ consistent (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). Note that Z_BUF_ERROR is not fatal, and
+ deflate() can be called again with more input and more output
+ space to continue processing.
+
+ 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 successful, 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);
+ The inflateInit() function 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 to inflate(). If zalloc and zfree are set to
+ Z_NULL, inflateInit() updates them to use default allocation
+ functions.
+
+ inflateInit() returns Z_OK if successful, Z_MEM_ERROR if there
+ was not enough memory, Z_VERSION_ERROR if the zlib library ver-
+ sion 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 un-
+ changed.)
+
+ 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 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 up-
+ dated and processing will resume at this point for the next call
+ to inflate().
+
+ Provide more output starting at next_out and update next_out and
+ avail_out accordingly. inflate() provides as much output as pos-
+ sible, until there is no more input data or no more space in the
+ output buffer (see below about the flush parameter).
+
+ Before the call to 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 to inflate(). If inflate()
+ returns Z_OK and with zero avail_out, it must be called again af-
+ ter making room in the output buffer because there might be more
+ output pending.
+
+ The flush parameter of inflate() can be Z_NO_FLUSH, Z_SYNC_FLUSH,
+ Z_FINISH, or Z_BLOCK. Z_SYNC_FLUSH requests that inflate() flush
+ as much output as possible to the output buffer. Z_BLOCK re-
+ quests that inflate() stop if and when it gets to the next de-
+ flate block boundary. When decoding the zlib or gzip format,
+ this will cause inflate() to return immediately after the header
+ and before the first block. When doing a raw inflate, inflate()
+ will go ahead and process the first block, and will return when
+ it gets to the end of that block, or when it runs out of data.
+
+ The Z_BLOCK option assists in appending to or combining deflate
+ streams. Also to assist in this, on return inflate() will set
+ strm->data_type to the number of unused bits in the last byte
+ taken from strm->next_in, plus 64 if inflate() is currently de-
+ coding the last block in the deflate stream, plus 128 if
+ inflate() returned immediately after decoding an end-of-block
+ code or decoding the complete header up to just before the first
+ byte of the deflate stream. The end-of-block will not be indi-
+ cated until all of the uncompressed data from that block has been
+ written to strm->next_out. The number of unused bits may in gen-
+ eral be greater than seven, except when bit 7 of data_type is
+ set, in which case the number of unused bits will be less than
+ eight.
+
+ 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 to 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
+ approach may be used for the single inflate() call.
+
+ In this implementation, inflate() always flushes as much output
+ as possible to the output buffer, and always uses the faster ap-
+ proach on the first call. So the only effect of the flush param-
+ eter in this implementation is on the return value of inflate(),
+ as noted below, or when it returns early because Z_BLOCK is used.
+
+ If a preset dictionary is needed after this call (see
+ inflateSetDictionary() below), inflate() sets strm->adler to the
+ Adler-32 checksum of the dictionary chosen by the compressor and
+ returns Z_NEED_DICT; otherwise it sets strm->adler to the
+ Adler-32 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 Adler-32 checksum is equal to that saved by the
+ compressor and returns Z_STREAM_END only if the checksum is cor-
+ rect.
+
+ inflate() will decompress and check either zlib-wrapped or gzip-
+ wrapped deflate data. The header type is detected automatically.
+ Any information contained in the gzip header is not retained, so
+ applications that need that information should instead use raw
+ inflate; see inflateInit2() below, or inflateBack() and perform
+ their own processing of the gzip header and trailer.
+
+ 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 (in-
+ put stream not conforming to the zlib format or incorrect check
+ value), 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 possi-
+ ble or if there was not enough room in the output buffer when
+ Z_FINISH is used. Note that Z_BUF_ERROR is not fatal, and
+ inflate() can be called again with more input and more output
+ space to continue compressing. If Z_DATA_ERROR is returned, the
+ application may then call inflateSync() to look for a good com-
+ pression block if a partial recovery of the data is desired.
+
+ 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 successful, or 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.
+
+ 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 pa-
+ rameter result in better compression at the expense of memory us-
+ age. The default value is 15 if deflateInit() is used instead.
+
+ windowBits can also be -8..-15 for raw deflate. In this case,
+ -windowBits determines the window size. deflate() will then gen-
+ erate raw deflate data with no zlib header or trailer, and will
+ not compute an Adler-32 check value.
+
+ windowBits can also be greater than 15 for optional gzip encod-
+ ing. Add 16 to windowBits to write a simple gzip header and
+ trailer around the compressed data instead of a zlib wrapper.
+ The gzip header will have no file name, no extra data, no com-
+ ment, no modification time (set to zero), no header crc, and the
+ operating system will be set to 255 (unknown). If a gzip stream
+ is being written, strm->adler is a crc32 instead of an adler32.
+
+ The memLevel parameter specifies how much memory should be allo-
+ cated for the internal compression state. memLevel=1 uses mini-
+ mum 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); Z_HUFFMAN_ONLY to force
+ Huffman encoding only (no string match), or Z_RLE to limit match
+ distances to one (run-length encoding). 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. Z_RLE is designed to be almost as
+ fast as Z_HUFFMAN_ONLY, but gives better compression for PNG im-
+ age data. The strategy parameter only affects the compression
+ ratio but not the correctness of the compressed output, even if
+ it is not set appropriately. Z_FIXED prevents the use of dynamic
+ Huffman codes, allowing for a simpler decoder for special appli-
+ cations.
+
+ deflateInit2() returns Z_OK if successful, 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 se-
+ quence without producing any compressed output. This function
+ must be called immediately after deflateInit(), deflateInit2(),
+ or deflateReset(), before any call to 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. In addition, the current implemen-
+ tation of deflate() will use at most the window size minus 262
+ bytes of the provided dictionary.
+
+ Upon return of this function, strm->adler is set to the Adler-32
+ value of the dictionary; the decompressor may later use this
+ value to determine which dictionary has been used by the compres-
+ sor. (The Adler-32 value applies to the whole dictionary even if
+ only a subset of the dictionary is actually used by the compres-
+ sor.) If a raw deflate was requested, then the Adler-32 value is
+ not computed and strm->adler is not set.
+
+ deflateSetDictionary() returns Z_OK if successful, 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 com-
+ pression method is bsort). deflateSetDictionary() does not per-
+ form any compression: this will be done by deflate().
+
+ int deflateCopy(z_streamp dest, z_streamp source);
+
+ The deflateCopy() function sets the destination stream as a com-
+ plete 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 con-
+ sume lots of memory.
+
+ deflateCopy() returns Z_OK if successful, 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 un-
+ changed 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 successful, 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);
+
+ The deflateParams() function dynamically updates the compression
+ level and compression strategy. The interpretation of level and
+ strategy is as in deflateInit2(). This can be used to switch be-
+ tween 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 avail-
+ able so far is compressed with the old level (and may be
+ flushed); the new level will take effect only at the next call to
+ deflate().
+
+ Before the call to deflateParams(), the stream state must be set
+ as for a call to 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 successful, Z_STREAM_ERROR if the
+ source stream state was inconsistent or if a parameter was in-
+ valid, or Z_BUF_ERROR if strm->avail_out was zero.
+
+ int deflateTune(z_streamp strm, int good_length, int max_lazy, int
+ nice_length, int max_chain)
+
+ Fine tune deflate()'s internal compression parameters. This
+ should only be used by someone who understands the algorithm used
+ by zlib's deflate for searching for the best matching string, and
+ even then only by the most fanatic optimizer trying to squeeze
+ out the last compressed bit for their specific input data. Read
+ the deflate.c source code for the meaning of the max_lazy,
+ good_length, nice_length, and max_chain parameters.
+
+ deflateTune() can be called after deflateInit() or
+ deflateInit2(), and returns Z_OK on success, or Z_STREAM_ERROR
+ for an invalid deflate stream.
+
+ uLong deflateBound(z_streamp strm, uLong sourceLen)
+
+ deflateBound() returns an upper bound on the compressed size af-
+ ter deflation of sourceLen bytes. It must be called after
+ deflateInit() or deflateInit2(). This would be used to allocate
+ an output buffer for deflation in a single pass, and so would be
+ called before deflate().
+
+ int deflatePrime(z_streamp strm, int bits, int value)
+
+ deflatePrime() inserts bits in the deflate output stream. The
+ intent is that this function is used to start off the deflate
+ output with the bits leftover from a previous deflate stream when
+ appending to it. As such, this function can only be used for raw
+ deflate, and must be used before the first deflate() call after a
+ deflateInit2() or deflateReset(). bits must be less than or
+ equal to 16, and that many of the least significant bits of value
+ will be inserted in the output.
+
+ deflatePrime() returns Z_OK if successful, or Z_STREAM_ERROR if
+ the source stream state was inconsistent.
+
+ int deflateSetHeader(z_streamp strm, gz_headerp head)
+
+ deflateSetHeader() provides gzip header information for when a
+ gzip stream is requested by deflateInit2(). deflateSetHeader()
+ may be called after deflateInit2() or deflateReset() and before
+ the first call of deflate(). The text, time, os, extra field,
+ name, and comment information in the provided gz_header structure
+ are written to the gzip header (xflag is ignored - the extra
+ flags are set according to the compression level). The caller
+ must assure that, if not Z_NULL, name and comment are terminated
+ with a zero byte, and that if extra is not Z_NULL, that extra_len
+ bytes are available there. If hcrc is true, a gzip header CRC is
+ included. Note that the current versions of the command-line
+ version of gzip(1) do not support header CRCs, and will report
+ that it is a "multi-part gzip file" and give up.
+
+ If deflateSetHeader() is not used, the default gzip header has
+ text false, the time set to zero, and os set to 255, with no ex-
+ tra, name, or comment fields. The gzip header is returned to the
+ default state by deflateReset().
+
+ deflateSetHeader() returns Z_OK if successful, or Z_STREAM_ERROR
+ if the source stream state was inconsistent.
+
+ 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. windowBits must be
+ greater than or equal to the windowBits value provided to
+ deflateInit2() while compressing, or it must be equal to 15 if
+ deflateInit2() was not used. 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.
+
+ windowBits can also be -8..-15 for raw inflate. In this case,
+ -windowBits determines the window size. inflate() will then
+ process raw deflate data, not looking for a zlib or gzip header,
+ not generating a check value, and not looking for any check val-
+ ues for comparison at the end of the stream. This is for use
+ with other formats that use the deflate compressed data format
+ such as zip. Those formats provide their own check values. If a
+ custom format is developed using the raw deflate format for com-
+ pressed data, it is recommended that a check value such as an
+ Adler-32 or a crc32 be applied to the uncompressed data as is
+ done in the zlib, gzip, and zip formats. For most applications,
+ the zlib format should be used as is. Note that comments above
+ on the use in deflateInit2() applies to the magnitude of
+ windowBits.
+
+ windowBits can also be greater than 15 for optional gzip decod-
+ ing. Add 32 to windowBits to enable zlib and gzip decoding with
+ automatic header detection, or add 16 to decode only the gzip
+ format (the zlib format will return a Z_DATA_ERROR). If a gzip
+ stream is being decoded, strm->adler is a crc32 instead of an
+ adler32.
+
+ inflateInit2() returns Z_OK if successful, Z_MEM_ERROR if there
+ was not enough memory, Z_STREAM_ERROR if a parameter is invalid
+ (such as a null strm). 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 uncom-
+ pressed byte sequence. This function must be called immediately
+ after a call to inflate() if that call returned Z_NEED_DICT. The
+ dictionary chosen by the compressor can be determined from the
+ Adler-32 value returned by that call to inflate(). The compres-
+ sor and decompressor must use exactly the same dictionary (see
+ deflateSetDictionary()). For raw inflate, this function can be
+ called immediately after inflateInit2() or inflateReset() and be-
+ fore any call to inflate() to set the dictionary. The applica-
+ tion must ensure that the dictionary that was used for compres-
+ sion is provided.
+
+ inflateSetDictionary() returns Z_OK if successful, 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 Adler-32 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 value of total_in which indicates where
+ valid compressed data was found. In the error case, the applica-
+ tion may repeatedly call inflateSync(), providing more input each
+ time, until success or end of the input data.
+
+ int inflateCopy(z_streamp dest, z_streamp source)
+
+ Sets the destination stream as a complete copy of the source
+ stream.
+
+ This function can be useful when randomly accessing a large
+ stream. The first pass through the stream can periodically
+ record the inflate state, allowing restarting inflate at those
+ points when randomly accessing the stream.
+
+ inflateCopy() 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 dest.
+
+ 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 successful, or Z_STREAM_ERROR if
+ the source stream state was inconsistent (such as zalloc or state
+ being NULL).
+
+ int inflatePrime(z_stream strm, int bits, int value)
+
+ This function inserts bits in the inflate input stream. The in-
+ tent is that this function is used to start inflating at a bit
+ position in the middle of a byte. The provided bits will be used
+ before any bytes are used from next_in. This function should
+ only be used with raw inflate, and should be used before the
+ first inflate() call after inflateInit2() or inflateReset().
+ bits must be less than or equal to 16, and that many of the least
+ significant bits of value will be inserted in the input.
+
+ inflatePrime() returns Z_OK if successful, or Z_STREAM_ERROR if
+ the source stream state was inconsistent.
+
+ int inflateGetHeader(z_streamp strm, gz_headerp head)
+
+ inflateGetHeader() requests that gzip header information be
+ stored in the provided gz_header structure. inflateGetHeader()
+ may be called after inflateInit2() or inflateReset(), and before
+ the first call of inflate(). As inflate() processes the gzip
+ stream, head->done is zero until the header is completed, at
+ which time head->done is set to one. If a zlib stream is being
+ decoded, then head->done is set to -1 to indicate that there will
+ be no gzip header information forthcoming. Note that Z_BLOCK can
+ be used to force inflate() to return immediately after header
+ processing is complete and before any actual data is decom-
+ pressed.
+
+ The text, time, xflags, and os fields are filled in with the gzip
+ header contents. hcrc is set to true if there is a header CRC.
+ (The header CRC was valid if done is set to one.) If extra is
+ not Z_NULL, then extra_max contains the maximum number of bytes
+ to write to extra. Once done is true, extra_len contains the ac-
+ tual extra field length, and extra contains the extra field, or
+ that field truncated if extra_max is less than extra_len. If
+ name is not Z_NULL, then up to name_max characters are written
+ there, terminated with a zero unless the length is greater than
+ name_max. If comment is not Z_NULL, then up to comm_max charac-
+ ters are written there, terminated with a zero unless the length
+ is greater than comm_max. When any of extra, name, or comment
+ are not Z_NULL and the respective field is not present in the
+ header, then that field is set to Z_NULL to signal its absence.
+ This allows the use of deflateSetHeader() with the returned
+ structure to duplicate the header. However if those fields are
+ set to allocated memory, then the application will need to save
+ those pointers elsewhere so that they can be eventually freed.
+
+ If inflateGetHeader() is not used, then the header information is
+ simply discarded. The header is always checked for validity, in-
+ cluding the header CRC if present. inflateReset() will reset the
+ process to discard the header information. The application would
+ need to call inflateGetHeader() again to retrieve the header from
+ the next gzip stream.
+
+ inflateGetHeader() returns Z_OK if successful, or Z_STREAM_ERROR
+ if the source stream state was inconsistent.
+
+ int inflateBackInit(z_stream *strm, int windowBits, unsigned char FAR
+ *window)
+
+ Initialize the internal stream state for decompression using
+ inflateBack() calls. The fields zalloc, zfree and opaque in strm
+ must be initialized before the call. If zalloc and zfree are
+ Z_NULL, then the default library-derived memory allocation rou-
+ tines are used. windowBits is the base two logarithm of the win-
+ dow size, in the range 8..15. window is a caller supplied buffer
+ of that size. Except for special applications where it is as-
+ sured that deflate() was used with small window sizes, windowBits
+ must be 15 and a 32K byte window must be supplied to be able to
+ decompress general deflate streams.
+
+ See inflateBack() for the usage of these routines.
+
+ inflateBackInit() will return Z_OK on success, Z_STREAM_ERROR if
+ any of the parameters are invalid, Z_MEM_ERROR if the internal
+ state could not be allocated, or Z_VERSION_ERROR if the version
+ of the library does not match the version of the header file.
+
+ int inflateBack(z_stream *strm, in_func in, void FAR *in_desc, out_func
+ out, void FAR *out_desc)
+
+ inflateBack() does a raw inflate with a single call using a call-
+ back interface for input and output. This is more efficient than
+ inflate() for file I/O applications in that it avoids copying be-
+ tween the output and the sliding window by simply making the win-
+ dow itself the output buffer. This function trusts the applica-
+ tion to not change the output buffer passed by the output func-
+ tion, at least until inflateBack() returns.
+
+ inflateBackInit() must be called first to allocate the internal
+ state and to initialize the state with the user-provided window
+ buffer. inflateBack() may then be used multiple times to inflate
+ a complete, raw deflate stream with each call. inflateBackEnd()
+ is then called to free the allocated state.
+
+ A raw deflate stream is one with no zlib or gzip header or
+ trailer. This routine would normally be used in a utility that
+ reads zip or gzip files and writes out uncompressed files. The
+ utility would decode the header and process the trailer on its
+ own, hence this routine expects only the raw deflate stream to
+ decompress. This is different from the normal behavior of
+ inflate(), which expects either a zlib or gzip header and trailer
+ around the deflate stream.
+
+ inflateBack() uses two subroutines supplied by the caller that
+ are then called by inflateBack() for input and output.
+ inflateBack() calls those routines until it reads a complete de-
+ flate stream and writes out all of the uncompressed data, or un-
+ til it encounters an error. The function's parameters and return
+ types are defined above in the in_func and out_func typedefs.
+ inflateBack() will call in(in_desc, &buf) which should return the
+ number of bytes of provided input, and a pointer to that input in
+ buf. If there is no input available, in() must return zero --
+ buf is ignored in that case -- and inflateBack() will return a
+ buffer error. inflateBack() will call out(out_desc, buf, len) to
+ write the uncompressed data buf[0..len-1]. out() should return
+ zero on success, or non-zero on failure. If out() returns non-
+ zero, inflateBack() will return with an error. Neither in() nor
+ out() are permitted to change the contents of the window provided
+ to inflateBackInit(), which is also the buffer that out() uses to
+ write from. The length written by out() will be at most the win-
+ dow size. Any non-zero amount of input may be provided by in().
+
+ For convenience, inflateBack() can be provided input on the first
+ call by setting strm->next_in and strm->avail_in. If that input
+ is exhausted, then in() will be called. Therefore strm->next_in
+ must be initialized before calling inflateBack(). If
+ strm->next_in is Z_NULL, then in() will be called immediately for
+ input. If strm->next_in is not Z_NULL, then strm->avail_in must
+ also be initialized, and then if strm->avail_in is not zero, in-
+ put will initially be taken from strm->next_in[0 ..
+ strm->avail_in - 1].
+
+ The in_desc and out_desc parameters of inflateBack() are passed
+ as the first parameter of in() and out() respectively when they
+ are called. These descriptors can be optionally used to pass any
+ information that the caller-supplied in() and out() functions
+ need to do their job.
+
+ On return, inflateBack() will set strm->next_in and
+ strm->avail_in to pass back any unused input that was provided by
+ the last in() call. The return values of inflateBack() can be
+ Z_STREAM_END on success, Z_BUF_ERROR if in() or out() returned an
+ error, Z_DATA_ERROR if there was a format error in the deflate
+ stream (in which case strm->msg is set to indicate the nature of
+ the error), or Z_STREAM_ERROR if the stream was not properly ini-
+ tialized. In the case of Z_BUF_ERROR, an input or output error
+ can be distinguished using strm->next_in which will be Z_NULL
+ only if in() returned an error. If strm->next is not Z_NULL,
+ then the Z_BUF_ERROR was due to out() returning non-zero. (in()
+ will always be called before out(), so strm->next_in is assured
+ to be defined if out() returns non-zero.) Note that
+ inflateBack() cannot return Z_OK.
+
+ int inflateBackEnd(z_stream *strm)
+
+ All memory allocated by inflateBackInit() is freed.
+
+ inflateBackEnd() returns Z_OK on success, or Z_STREAM_ERROR if
+ the stream state was inconsistent.
+
+ uLong zlibCompileFlags(void)
+
+ This function returns flags indicating compile-time options.
+
+ Type sizes, two bits each:
+
+ 00 16 bits
+ 01 32 bits
+ 10 64 bits
+ 11 other:
+
+ 1.0 size of uInt
+ 3.2 size of uLong
+ 5.4 size of voidpf (pointer)
+ 7.6 size of z_off_t
+
+ Compiler, assembler, and debug options:
+
+ 8 DEBUG
+ 9 ASMV or ASMINF -- use ASM code
+ 10 ZLIB_WINAPI -- exported functions use the WINAPI
+ calling convention
+ 11 0 (reserved)
+
+ One-time table building (smaller code, but not thread-safe if
+ true):
+
+ 12 BUILDFIXED -- build static block decoding tables
+ when needed
+ 13 DYNAMIC_CRC_TABLE -- build CRC calculation tables
+ when needed
+ 14,15 0 (reserved)
+
+ Library content (indicates missing functionality):
+
+ 16 NO_GZCOMPRESS -- gz* functions cannot compress (to
+ avoid linking deflate code when not needed)
+ 17 NO_GZIP -- deflate can't write gzip streams, and
+ inflate can't detect and decode gzip streams (to
+ avoid linking CRC code)
+ 18-19 0 (reserved)
+
+ Operation variations (changes in library functionality):
+
+ 20 PKZIP_BUG_WORKAROUND -- slightly more permissive
+ inflate
+ 21 FASTEST -- deflate algorithm with only one, lowest
+ compression level
+ 22,23 0 (reserved)
+
+ The sprintf variant used by gzprintf (zero is best):
+
+ 24 0 = vs*, 1 = s* -- 1 means limited to 20 arguments
+ after the format
+ 25 0 = *nprintf, 1 = *printf -- 1 means gzprintf() not
+ secure!
+ 26 0 = returns value, 1 = void -- 1 means inferred
+ string length returned
+
+ Remainder:
+
+ 27-31 0 (reserved)
+
+UTILITY FUNCTIONS
+ The following utility functions are implemented on top of the basic
+ stream-oriented functions. To simplify the interface, some default op-
+ tions 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.
+
+ int compress(Bytef *dest, uLongf *destLen, const Bytef *source, uLong
+ sourceLen);
+
+ The compress() function 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 the value returned by
+ compressBound(sourcelen). 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 successful, Z_MEM_ERROR if there was
+ not enough memory, or 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);
+
+ The compress2() function 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 the value returned by
+ compressBound(sourceLen). Upon exit, destLen is the actual size
+ of the compressed buffer.
+
+ compress2() returns Z_OK if successful, Z_MEM_ERROR if there was
+ not enough memory, Z_BUF_ERROR if there was not enough room in
+ the output buffer, or Z_STREAM_ERROR if the level parameter is
+ invalid.
+
+ int compressBound(uLong sourceLen)
+
+ compressBound() returns an upper bound on the compressed size af-
+ ter compress() or compress2() on sourceLen bytes. It would be
+ used before a compress() or compress2() call to allocate the des-
+ tination buffer.
+
+ int uncompress(Bytef *dest, uLongf *destLen, const Bytef *source, uLong
+ sourceLen);
+
+ The uncompress() function 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 uncom-
+ pressed data. (The size of the uncompressed data must have been
+ saved previously by the compressor and transmitted to the decom-
+ pressor by some mechanism outside the scope of this compression
+ library.) Upon exit, destLen is the actual size of the com-
+ pressed 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 successful, 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 cor-
+ rupted or incomplete.
+
+ gzFile gzopen(const char *path, const char *mode);
+
+ The gzopen() function opens a gzip (.gz) file for reading or
+ writing. The mode parameter is as in fopen(3) ("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", or `R' for run-length encoding as in "wb1R". (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);
+
+ The gzdopen() function associates a gzFile with the file descrip-
+ tor fd. File descriptors are obtained from calls like open(2),
+ dup(2), creat(3), pipe(2), or fileno(3) (if the file has been
+ previously opened with fopen(3)). The mode parameter is as in
+ gzopen().
+
+ The next call to 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 gz-
+ dopen(dup(fd), mode).
+
+ gzdopen() returns NULL if there was insufficient memory to allo-
+ cate the (de)compression state.
+
+ int gzsetparams(gzFile file, int level, int strategy);
+
+ The gzsetparams() function dynamically updates the compression
+ level or strategy. See the description of deflateInit2() for the
+ meaning of these parameters.
+
+ gzsetparams() returns Z_OK if successful, or Z_STREAM_ERROR if
+ the file was not opened for writing.
+
+ int gzread(gzFile file, voidp buf, unsigned len);
+
+ The gzread() function 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, voidpc buf, unsigned len);
+
+ The gzwrite() function 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 gzprintf(gzFile file, const char *format, ...);
+
+ The gzprintf() function converts, formats, and writes the args to
+ the compressed file under control of the format string, as in
+ fprintf(3). gzprintf() returns the number of uncompressed bytes
+ actually written (0 in case of error). The number of uncom-
+ pressed bytes written is limited to 4095. The caller should make
+ sure that this limit is not exceeded. If it is exceeded, then
+ gzprintf() will return an error (0) with nothing written. In
+ this case, there may also be a buffer overflow with unpredictable
+ consequences, which is possible only if zlib was compiled with
+ the insecure functions sprintf() or vsprintf() because the secure
+ snprintf() or vsnprintf() functions were not available.
+
+ int gzputs(gzFile file, const char *s);
+
+ The gzputs() function 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);
+
+ The gzgets() function 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);
+
+ The gzputc() function 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);
+
+ The gzgetc() function reads one byte from the compressed file.
+ gzgetc() returns this byte or -1 in case of end of file or error.
+
+ int gzungetc(int c, gzFile file)
+
+ Push one character back onto the stream to be read again later.
+ Only one character of push-back is allowed. gzungetc() returns
+ the character pushed, or -1 on failure. gzungetc() will fail if
+ a character has been pushed but not read yet, or if c is -1. The
+ pushed character will be discarded if the stream is repositioned
+ with gzseek() or gzrewind().
+
+ int gzflush(gzFile file, int flush);
+
+ The gzflush() function flushes all pending output into the com-
+ pressed file. The parameter flush is as in the deflate() func-
+ tion. 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 posi-
+ tion.
+
+ int gzrewind(gzFile file);
+
+ The gzrewind() function 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);
+
+ The gztell() function returns the starting position for the next
+ gzread() or gzwrite() on the given compressed file. This posi-
+ tion represents a number of bytes in the uncompressed data
+ stream.
+
+ gztell(file) is equivalent to gzseek(file, 0L, SEEK_CUR).
+
+ int gzeof(gzFile file);
+
+ The gzeof() function returns 1 when EOF has previously been de-
+ tected reading the given input stream, otherwise zero.
+
+ int gzdirect(gzFile file);
+
+ The gzdirect() function returns 1 if the file is being read di-
+ rectly without compression; otherwise it returns 0.
+
+ int gzclose(gzFile file);
+
+ The gzclose() function flushes all pending output if necessary,
+ closes the compressed file and deallocates all the (de)compres-
+ sion state. The return value is the zlib error number (see func-
+ tion gzerror() below).
+
+ const char * gzerror(gzFile file, int *errnum);
+
+ The gzerror() function returns the error message for the last er-
+ ror which occurred on the given compressed file. errnum is set
+ to the zlib error number. If an error occurred in the file sys-
+ tem and not in the compression library, errnum is set to Z_ERRNO
+ and the application may consult errno to get the exact error
+ code.
+
+ void gzclearerr(gzFile file)
+ Clears the error and end-of-file flags for file. This is analo-
+ gous to the clearerr() function in stdio. This is useful for
+ continuing to read a gzip file that is being written concur-
+ rently.
+
+CHECKSUM FUNCTIONS
+ These functions are not related to compression but are exported anyway
+ because they might be useful in applications using the compression li-
+ brary.
+
+ uLong adler32(uLong adler, const Bytef *buf, uInt len);
+ The adler32() function updates a running Adler-32 checksum with
+ the bytes buf[0..len-1] and returns 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 adler32_combine(uLong adler1, uLong adler2, z_off_t len2)
+
+ The adler32_combine() function combines two Adler-32 checksums
+ into one. For two sequences of bytes, seq1 and seq2 with lengths
+ len1 and len2, Adler-32 checksums are calculated for each, adler1
+ and adler2. adler32_combine() returns the Adler-32 checksum of
+ seq1 and seq2 concatenated, requiring only adler1, adler2, and
+ len2.
+
+ uLong crc32(uLong crc, const Bytef *buf, uInt len);
+
+ The crc32() function updates a running CRC-32 with the bytes
+ buf[0..len-1] and returns the updated CRC-32. 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();
+
+ uLong crc32_combine(uLong crc1, uLong crc2, z_off_t len2)
+
+ The crc32_combine() function combines two CRC-32 check values
+ into one. For two sequences of bytes, seq1 and seq2 with lengths
+ len1 and len2, CRC-32 check values are calculated for each, crc1
+ and crc2. crc32_combine() returns the CRC-32 check value of seq1
+ and seq2 concatenated, requiring only crc1, crc2, and len2.
+
+STRUCTURES
+ struct internal_state;
+
+ typedef struct z_stream_s {
+ Bytef *next_in; /* next input byte */
+ uInt avail_in; /* number of bytes available at next_in */
+ off_t 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 */
+ off_t 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: binary or text*/
+ uLong adler; /* adler32 value of the uncompressed data */
+ uLong reserved; /* reserved for future use */
+ } z_stream;
+
+ typedef z_stream FAR * z_streamp;
+
+ /*
+ gzip header information passed to and from zlib routines.
+ See RFC 1952 for more details on the meanings of these fields.
+ */
+ typedef struct gz_header_s {
+ int text; /* true if compressed data believed to be text */
+ uLong time; /* modification time */
+ int xflags; /*extra flags (not used when writing a gzip file)*/
+ int os; /* operating system */
+ Bytef *extra; /* pointer to extra field or Z_NULL if none */
+ uInt extra_len; /* extra field length (valid if extra != Z_NULL) */
+ uInt extra_max; /* space at extra (only when reading header) */
+ Bytef *name; /* pointer to zero-terminated file name or Z_NULL*/
+ uInt name_max; /* space at name (only when reading header) */
+ Bytef *comment; /* pointer to zero-terminated comment or Z_NULL */
+ uInt comm_max; /* space at comment (only when reading header) */
+ int hcrc; /* true if there was or will be a header crc */
+ int done; /* true when done reading gzip header (not used
+ when writing a gzip file) */
+ } gz_header;
+
+ typedef gz_header FAR *gz_headerp;
+
+ 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 to zalloc() and zfree(). This can be useful for cus-
+ tom 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 allo-
+ cate 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 al-
+ location 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 uncom-
+ pressed 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
+ #define Z_BLOCK 5
+ /* Allowed flush values; see deflate() and inflate() 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_RLE 3
+ #define Z_FIXED 4
+ #define Z_DEFAULT_STRATEGY 0
+ /* compression strategy; see deflateInit2() below for details */
+
+ #define Z_BINARY 0
+ #define Z_TEXT 1
+ #define Z_ASCII Z_TEXT /* for compatibility with 1.2.2 and earlier */
+ #define Z_UNKNOWN 2
+ /* Possible values of the data_type field (though see inflate()) */
+
+ #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 < 1.0.2 */
+
+VARIOUS HACKS
+ deflateInit and inflateInit are macros to allow checking the zlib version
+ and the compiler's view of z_stream.
+
+ int deflateInit_(z_stream strm, int level, const char *version, int
+ stream_size);
+
+ int inflateInit_(z_stream strm, const char *version, int stream_size);
+
+ int deflateInit2_(z_stream strm, int level, int method, int windowBits,
+ int memLevel, int strategy, const char *version, int stream_size)
+
+ int inflateInit2_(z_stream strm, int windowBits, const char *version, int
+ stream_size);
+
+ int inflateBackInit_(z_stream *strm, int windowBits, unsigned char FAR
+ *window, const char *version, int stream_size)
+
+ const char * zError(int err);
+
+ int inflateSyncPoint(z_streamp z);
+
+ const uLongf * get_crc_table(void);
+
+SEE ALSO
+ compress(1), gzip(1)
+
+STANDARDS
+ P. Deutsch and J-L. Gailly, ZLIB Compressed Data Format Specification
+ version 3.3, RFC 1950, May 1996.
+
+ P. Deutsch, DEFLATE Compressed Data Format Specification version 1.3, RFC
+ 1951, May 1996.
+
+ P. Deutsch, GZIP file format specification version 4.3, RFC 1952, May
+ 1996.
+
+HISTORY
+ This manual page is based on an HTML version of <zlib.h> converted by
+ piaip <piaip@csie.ntu.edu.tw> and was converted to mdoc format by the
+ OpenBSD project.
+
+AUTHORS
+ Jean-loup Gailly <jloup@gzip.org>
+ Mark Adler <madler@alumni.caltech.edu>
+
+BSD March 16, 2018 BSD
generated by cgit v1.2.3 (git 2.39.1) at 2025-02-16 14:21:11 +0000