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ZLIB(3) 			   BSD Library Functions Manual 			  ZLIB(3)

NAME
     zlib -- general 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
     inflateInit2(z_streamp strm, int windowBits);

     int
     inflateSetDictionary(z_streamp strm, const Bytef *dictionary, uInt dictLength);

     int
     inflateSync(z_streamp strm);

     int
     inflateReset(z_streamp strm);

   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);

     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, const voidp 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
     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
     gzclose(gzFile file);

     const char *
     gzerror(gzFile file, int *errnum);

   Checksum functions
     uLong
     adler32(uLong adler, const Bytef *buf, uInt len);

     uLong
     crc32(uLong crc, const Bytef *buf, uInt len);

DESCRIPTION
     This manual page describes the zlib general purpose compression library, version 1.1.4.

     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(1) (.gz) format with an inter-
     face similar to that of stdio(3).

     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 allo-
	     cation 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 mem-
	     ory, 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 fol-
	     lowing 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 accord-
	     ingly.  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 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 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 pre-
	     vious 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 out-
	     put 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 Adler-32 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).  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 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 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 mem-
	     ory, 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 modi-
	     fied, 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 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 fol-
	     lowing actions:

	     Decompress more input starting at next_in and update next_in and avail_in accord-
	     ingly.  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 to inflate().

	     Provide more output starting at next_out and update next_out and avail_out accord-
	     ingly.  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 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 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 cur-
	     rent implementation actually flushes as much output as possible anyway.

	     inflate() should normally be called until it returns Z_STREAM_END or an error.  How-
	     ever 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 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 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 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 Adler-32 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 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 ver-
	     sion 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 inter-
	     nal compression state.  memLevel=1 uses minimum memory but is slow and reduces com-
	     pression 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 successful, Z_MEM_ERROR if there was not enough mem-
	     ory, 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 com-
	     pression: 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 produc-
	     ing 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.

	     Upon return of this function, strm->adler is set to the Adler-32 value of the dic-
	     tionary; the decompressor may later use this value to determine which dictionary has
	     been used by the compressor.  (The Adler-32 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 successful, or Z_STREAM_ERROR if a parameter
	     is invalid (such as NULL dictionary) or the stream state is inconsistent (for exam-
	     ple 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);

	     The deflateCopy() function 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 successful, Z_MEM_ERROR if there was not enough mem-
	     ory, 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 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 compres-
	     sion 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
	     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 invalid, or 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 call-
	     er.

	     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 com-
	     pressed 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 successful, Z_MEM_ERROR if there was not enough mem-
	     ory, 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 to inflate() if this call
	     returned Z_NEED_DICT.  The dictionary chosen by the compressor can be determined
	     from the Adler-32 value returned by this call to inflate().  The compressor and
	     decompressor must use exactly the same dictionary (see deflateSetDictionary()).

	     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 sub-
	     sequent 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 com-
	     pressed 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 successful, or Z_STREAM_ERROR if the source stream
	     state was inconsistent (such as zalloc or state being NULL).

UTILITY FUNCTIONS
     The following utility functions are implemented on top of the basic stream-oriented func-
     tions.  To simplify the interface, some default options are assumed (compression level and
     memory usage, standard memory allocation functions).  The source code of these utility func-
     tions 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 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 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 destina-
	     tion 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 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 uncompress(Bytef *dest, uLongf *destLen, const Bytef *source, uLong sourceLen);

	     The uncompress() function decompresses the source buffer into the destination buf-
	     fer.  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 previ-
	     ously by the compressor and transmitted to the decompressor by some mechanism out-
	     side 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 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 corrupted.

     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".  (See the description of deflateInit2() for more informa-
	     tion 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 descriptor 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 parame-
	     ter is as in gzopen().

	     The next call to gzclose() on the returned gzFile will also close the file descrip-
	     tor 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)compres-
	     sion 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 com-
	     pressed 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);

	     The gzwrite() function writes the given number of uncompressed bytes into the com-
	     pressed 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).

     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 gzflush(gzFile file, int flush);

	     The gzflush() function 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 parame-
	     ter is Z_FINISH and all output could be flushed.

	     gzflush() should be called only when strictly necessary because it can degrade com-
	     pression.

     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 com-
	     pressed 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 begin-
	     ning 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);

	     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 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);

	     The gzeof() function returns 1 when EOF has previously been detected reading the
	     given input stream, otherwise zero.

     int gzclose(gzFile file);

	     The gzclose() function flushes all pending output if necessary, closes the com-
	     pressed 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);

	     The gzerror() function returns the error message for the last error which occurred
	     on the given compressed file.  errnum is set to the 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.

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

     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 crc32(uLong crc, const Bytef *buf, uInt len);
	     The crc32() function updates a running CRC with the bytes buf[0..len-1] and returns
	     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();

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 */
	 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;      /* Adler-32 value of the uncompressed data */
	 uLong	 reserved;   /* reserved for future use */
     } z_stream;

     typedef z_stream FAR * z_streamp;

     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 ini-
     tialize 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 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 < 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);

     const char * zError(int err);

     int inflateSyncPoint(z_streamp z);

     const uLongf * get_crc_table(void);

SEE ALSO
     RFC 1950	   ZLIB Compressed Data Format Specification.
     RFC 1951	   DEFLATE Compressed Data Format Specification.
     RFC 1952	   GZIP File Format Specification.

     http://www.gzip.org/zlib/

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					   May 1, 2004					      BSD
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