| ZLIB(3) | Library Functions Manual | ZLIB(3) | 
zlib —
#include <zlib.h>
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);
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);
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);
adler32(uLong
  adler, const Bytef
  *buf, uInt len);
uLong
  
  crc32(uLong
    crc, const Bytef
    *buf, uInt
  len);
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 interface 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:
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().
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().
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 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 previous compressed
        data has been damaged or if random access is desired. Using
        Z_FULL_FLUSH too often can seriously degrade the
        compression.
If deflate() returns with avail_out ==
        0, this function must be called again with the same value of the flush
        parameter and more output space (updated
        avail_out), until the flush is complete
        (deflate() returns with non-zero
        avail_out).
If the parameter flush is set to
        Z_FINISH, pending input is processed, pending
        output is flushed and deflate() returns with
        Z_STREAM_END if there was enough output space;
        if deflate() returns with
        Z_OK, this function must be called again with
        Z_FINISH and more output space (updated
        avail_out but no more input data, until it returns
        with Z_STREAM_END or an error. After
        deflate() has returned
        Z_STREAM_END, the only possible operations on
        the stream are deflateReset() or
        deflateEnd().
Z_FINISH can be used immediately after
        deflateInit() if all the compression is to be
        done in a single step. In this case, avail_out
        must be at least 0.1% larger than avail_in plus 12
        bytes. If deflate() does not return
        Z_STREAM_END, then it must be called again as
        described above.
deflate() sets strm->adler to the
        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).
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).
inflateInit(z_streamp
    strm);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 version is incompatible with the
        version assumed by the caller. msg is set to null
        if there is no error message. inflateInit() does
        not perform any decompression apart from reading the
        zlib header if present: this will be done by
        inflate(). (So next_in and
        avail_in may be modified, but
        next_out and avail_out are
        unchanged.)
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 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 accordingly.
        inflate() provides as much output as possible,
        until there is no more input data or no more space in the output buffer
        (see below about the flush parameter).
Before the call 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 current implementation
        actually flushes as much output as possible anyway.
inflate() should normally be called
        until it returns Z_STREAM_END or an error.
        However if all decompression is to be performed in a single step (a
        single call 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.
inflateEnd(z_streamp
    strm);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).
deflateInit2(z_streamp strm,
    int level, int method,
    int windowBits, int memLevel,
    int strategy);This is another version of
        deflateInit() with more compression options. The
        fields next_in, zalloc,
        zfree, and opaque must be
        initialized before by the caller.
The method parameter is the compression
        method. It must be Z_DEFLATED in this version of
        the library.
The windowBits parameter is the base two
        logarithm of the window size (the size of the history buffer). It should
        be in the range 8..15 for this version of the library. Larger values of
        this parameter result in better compression at the expense of memory
        usage. The default value is 15 if deflateInit()
        is used instead.
The memLevel parameter specifies how
        much memory should be allocated for the internal compression state.
        memLevel=1 uses minimum memory but is slow and reduces compression
        ratio; memLevel=9 uses maximum memory for optimal speed. The default
        value is 8. See
        <zconf.h> for total
        memory usage as a function of windowBits and
        memLevel.
The strategy parameter is used to tune
        the compression algorithm. Use the value
        Z_DEFAULT_STRATEGY for normal data;
        Z_FILTERED for data produced by a filter (or
        predictor); or Z_HUFFMAN_ONLY to force Huffman
        encoding only (no string match). Filtered data consists mostly of small
        values with a somewhat random distribution. In this case, the
        compression algorithm is tuned to compress them better. The effect of
        Z_FILTERED is to force more Huffman coding and
        less string matching; it is somewhat intermediate between
        Z_DEFAULT and
        Z_HUFFMAN_ONLY. The
        strategy parameter only affects the compression
        ratio but not the correctness of the compressed output, even if it is
        not set appropriately.
deflateInit2() returns
        Z_OK if 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().
deflateSetDictionary(z_streamp
    strm, const Bytef *dictionary,
    uInt dictLength);Initializes the compression dictionary from the given byte
        sequence without producing any compressed output. This function must be
        called immediately after deflateInit(),
        deflateInit2(), or
        deflateReset(), before any call 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 dictionary; 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 example if
        deflate() has already been called for this
        stream or if the compression method is bsort).
        deflateSetDictionary() does not perform any
        compression: this will be done by deflate().
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 memory,
        Z_STREAM_ERROR if the source stream state was
        inconsistent (such as zalloc being NULL).
        msg is left unchanged in both source and
        destination.
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).
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
        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.
inflateInit2(z_streamp strm,
    int windowBits);This is another version of
        inflateInit() with an extra parameter. The
        fields next_in, avail_in,
        zalloc, zfree, and
        opaque must be initialized before by the
      caller.
The windowBits parameter is the base two
        logarithm of the maximum window size (the size of the history buffer).
        It should be in the range 8..15 for this version of the library. The
        default value is 15 if inflateInit() is used
        instead. If a compressed stream with a larger window size is given as
        input, inflate() will return with the error code
        Z_DATA_ERROR instead of trying to allocate a
        larger window.
inflateInit2() returns
        Z_OK if successful,
        Z_MEM_ERROR if there was not enough memory,
        Z_STREAM_ERROR if a parameter is invalid (such
        as a negative memLevel). msg
        is set to null if there is no error message.
        inflateInit2() does not perform any
        decompression apart from reading the zlib header
        if present: this will be done by inflate(). (So
        next_in and avail_in may be
        modified, but next_out and
        avail_out are unchanged.)
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 subsequent calls of
        inflate().
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 application may
        repeatedly call inflateSync(), providing more
        input each time, until success or end of the input data.
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).
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.
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 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.
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
        uncompressed data. (The size of the uncompressed data must have been
        saved previously by the compressor and transmitted to the decompressor
        by some mechanism outside the scope of this compression library.) Upon
        exit, destLen is the actual size of the compressed
        buffer. This function can be used to decompress a whole file at once if
        the input file is mmap'ed.
uncompress() returns
        Z_OK if 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.
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
        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).
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 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 gzdopen(dup(fd), mode).
gzdopen() returns
        NULL if there was insufficient memory to
        allocate the (de)compression state.
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.
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).
gzwrite(gzFile file,
    const voidp 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).
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).
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.
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.
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.
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.
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 parameter is Z_FINISH and all
        output could be flushed.
gzflush() should be called only when
        strictly necessary because it can degrade compression.
gzseek(gzFile file,
    z_off_t offset, int
    whence);Sets the starting position for the next
        gzread() or gzwrite() on
        the given compressed file. The offset represents a number of bytes in
        the uncompressed data stream. The whence parameter is defined as in
        lseek(2); the value
        SEEK_END is not supported.
If the file is opened for reading, this function is emulated
        but can be extremely slow. If the file is opened for writing, only
        forward seeks are supported; gzseek() then
        compresses a sequence of zeroes up to the new starting position.
gzseek() returns the resulting offset
        location as measured in bytes from the beginning of the uncompressed
        stream, or -1 in case of error, in particular if the file is opened for
        writing and the new starting position would be before the current
        position.
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).
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).
gzeof(gzFile file);The gzeof() function returns 1 when
        EOF has previously been detected reading the
        given input stream, otherwise zero.
gzclose(gzFile file);The gzclose() function flushes all
        pending output if necessary, closes the compressed file and deallocates
        all the (de)compression state. The return value is the
        zlib error number (see function
        gzerror() below).
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.
adler32(uLong adler,
    const Bytef *buf, uInt
    len);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();
    
    crc32(uLong crc,
    const Bytef *buf, uInt
    len);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();
    
    
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 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 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).
#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 */
zlib version and the compiler's view of
  z_stream.
deflateInit_(z_stream strm,
    int level, const char *version,
    int stream_size);inflateInit_(z_stream strm,
    const char *version, int
    stream_size);deflateInit2_(z_stream strm,
    int level, int method,
    int windowBits, int memLevel,
    int strategy, const char
    *version, int stream_size);inflateInit2_(z_stream strm,
    int windowBits, const char
    *version, int stream_size);zError(int err);inflateSyncPoint(z_streamp
    z);get_crc_table(void);<zlib.h> converted by
  piaip
  <piaip@csie.ntu.edu.tw>
  and was converted to mdoc format by the OpenBSD
  project.
| May 1, 2004 | NetBSD 9.3 |