zlib.h

linux得一些常用命令,以及linux环境下的c编程

    accordingly. This action is forced if the parameter flush is non zero.
    Forcing flush frequently degrades the compression ratio, so this parameter
    should be set only when necessary (in interactive applications).
    Some output may be provided even if flush is not set.

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

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

    If flush is set to Z_FULL_FLUSH, all output is flushed as with
  Z_SYNC_FLUSH, and the compression state is reset so that decompression can
  restart from this point if previous compressed data has been damaged or if
  random access is desired. Using Z_FULL_FLUSH too often can seriously degrade
  the compression.

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

    If the parameter flush is set to Z_FINISH, pending input is processed,
  pending output is flushed and deflate returns with Z_STREAM_END if there
  was enough output space; if deflate returns with Z_OK, this function must be
  called again with Z_FINISH and more output space (updated avail_out) but no
  more input data, until it returns with Z_STREAM_END or an error. After
  deflate has returned Z_STREAM_END, the only possible operations on the
  stream are deflateReset or deflateEnd.
  
    Z_FINISH can be used immediately after deflateInit if all the compression
  is to be done in a single step. In this case, avail_out must be at least
  0.1% larger than avail_in plus 12 bytes.  If deflate does not return
  Z_STREAM_END, then it must be called again as described above.

    deflate() sets strm->adler to the adler32 checksum of all input read
  so far (that is, total_in bytes).

    deflate() may update data_type if it can make a good guess about
  the input data type (Z_ASCII or Z_BINARY). In doubt, the data is considered
  binary. This field is only for information purposes and does not affect
  the compression algorithm in any manner.

    deflate() returns Z_OK if some progress has been made (more input
  processed or more output produced), Z_STREAM_END if all input has been
  consumed and all output has been produced (only when flush is set to
  Z_FINISH), Z_STREAM_ERROR if the stream state was inconsistent (for example
  if next_in or next_out was NULL), Z_BUF_ERROR if no progress is possible
  (for example avail_in or avail_out was zero).
*/


ZEXTERN int ZEXPORT zlib_deflateEnd OF((z_streamp strm));
/*
     All dynamically allocated data structures for this stream are freed.
   This function discards any unprocessed input and does not flush any
   pending output.

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


ZEXTERN int ZEXPORT zlib_inflate_workspacesize OF((void));
/*
   Returns the number of bytes that needs to be allocated for a per-
   stream workspace.  A pointer to this number of bytes should be
   returned in stream->workspace before calling zlib_inflateInit().
*/

/* 
ZEXTERN int ZEXPORT zlib_inflateInit OF((z_streamp strm));

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

     inflateInit returns Z_OK if success, Z_MEM_ERROR if there was not enough
   memory, Z_VERSION_ERROR if the zlib library version is incompatible with the
   version assumed by the caller.  msg is set to null if there is no error
   message. inflateInit does not perform any decompression apart from reading
   the zlib header if present: this will be done by inflate().  (So next_in and
   avail_in may be modified, but next_out and avail_out are unchanged.)
*/


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

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

  - Decompress more input starting at next_in and update next_in and avail_in
    accordingly. If not all input can be processed (because there is not
    enough room in the output buffer), next_in is updated and processing
    will resume at this point for the next call of inflate().

  - Provide more output starting at next_out and update next_out and avail_out
    accordingly.  inflate() provides as much output as possible, until there
    is no more input data or no more space in the output buffer (see below
    about the flush parameter).

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

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

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

     If a preset dictionary is needed at this point (see inflateSetDictionary
  below), inflate sets strm-adler to the adler32 checksum of the
  dictionary chosen by the compressor and returns Z_NEED_DICT; otherwise 
  it sets strm->adler to the adler32 checksum of all output produced
  so far (that is, total_out bytes) and returns Z_OK, Z_STREAM_END or
  an error code as described below. At the end of the stream, inflate()
  checks that its computed adler32 checksum is equal to that saved by the
  compressor and returns Z_STREAM_END only if the checksum is correct.

    inflate() returns Z_OK if some progress has been made (more input processed
  or more output produced), Z_STREAM_END if the end of the compressed data has
  been reached and all uncompressed output has been produced, Z_NEED_DICT if a
  preset dictionary is needed at this point, Z_DATA_ERROR if the input data was
  corrupted (input stream not conforming to the zlib format or incorrect
  adler32 checksum), Z_STREAM_ERROR if the stream structure was inconsistent
  (for example if next_in or next_out was NULL), Z_MEM_ERROR if there was not
  enough memory, Z_BUF_ERROR if no progress is possible or if there was not
  enough room in the output buffer when Z_FINISH is used. In the Z_DATA_ERROR
  case, the application may then call inflateSync to look for a good
  compression block.
*/


ZEXTERN int ZEXPORT zlib_inflateEnd OF((z_streamp strm));
/*
     All dynamically allocated data structures for this stream are freed.
   This function discards any unprocessed input and does not flush any
   pending output.

     inflateEnd returns Z_OK if success, Z_STREAM_ERROR if the stream state
   was inconsistent. In the error case, msg may be set but then points to a
   static string (which must not be deallocated).
*/

                        /* Advanced functions */

/*
    The following functions are needed only in some special applications.
*/

/*   
ZEXTERN int ZEXPORT deflateInit2 OF((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