include/wvgzip.h

   1 /* -*- Mode: C++ -*-
   2  * Worldvisions Weaver Software:
   3  *   Copyright (C) 1997-2002 Net Integration Technologies, Inc.
   4  *
   5  * Gzip encoder/decoder based on zlib.
   6  */
   7 #ifndef __WVGZIP_H
   8 #define __WVGZIP_H
   9
  10 #include "wvencoder.h"
  11 #include "wvencoderstream.h"
  12
  13 struct z_stream_s;
  14
  15 /**
  16  * An encoder implementing Gzip encryption and decryption.
  17  *
  18  * When compressing:
  19  *
  20  *  - On flush(), the encoded data stream is synchronized such that
  21  *     all data compressed up to this point can be fully decompressed.
  22  *
  23  *  - On finish(), the encoded data stream is finalized an a Gzip
  24  *     end of data marker is emitted.
  25  *
  26  *
  27  * When decompressing:
  28  *
  29  *  - The encoder will transition to isfinished() == true on its own
  30  *     if a Gzip end of data marker is detected in the input.  After
  31  *     this point, no additional data can be decompressed.
  32  *
  33  *
  34  */
  35 class WvGzipEncoder : public WvEncoder
  36 {
  37 public:
  38     enum Mode {
  39         Deflate, /*!< Compress using deflate */
  40         Inflate  /*!< Decompress using inflate */
  41     };
  42
  43     /**
  44      * Creates a Gzip encoder.
  45      *
  46      * "mode" is the compression mode
  47      */
  48     WvGzipEncoder(Mode mode, size_t _out_limit = 0);
  49     virtual ~WvGzipEncoder();
  50
  51     /**
  52      * Limit the amount of output produced in one call to encode().
  53      * Defaults to 0, meaning no limit (empty the input buffer).
  54      */
  55     size_t out_limit;
  56
  57     /**
  58      * Continue decompression if errors are found.
  59      * If true, upon running into a decompression error, the encoder will
  60      * seek to the next unbroken block.  Most useful if at least some blocks
  61      * are fully flushed (see 'full_flush' below).  Defaults to false.
  62      * Note that it may be impossible to ignore really bad decompression
  63      * errors, in which case the encoder will go !isok(), as it would
  64      * if this boolean is false.
  65      */
  66     bool ignore_decompression_errors;
  67
  68     /**
  69      * Do full flushes.
  70      * Makes the encoder use Z_FULL_FLUSH instead of Z_SYNC_FLUSH, which
  71      * resets the compression state to improve chances of recovering
  72      * corrupted compressed data.  Degrades compression, so don't use it too
  73      * often.  Defaults to false.
  74      */
  75     bool full_flush;
  76
  77 protected:
  78     virtual bool _encode(WvBuf &inbuf, WvBuf &outbuf, bool flush);
  79     virtual bool _finish(WvBuf &outbuf);
  80     virtual bool _reset();
  81
  82 private:
  83     struct z_stream_s *zstr;
  84     WvInPlaceBuf tmpbuf;
  85     Mode mode;
  86     size_t output;
  87
  88     void init();
  89     void close();
  90     void prepare(WvBuf *inbuf);
  91     bool process(WvBuf &outbuf, bool flush, bool finish);
  92 };
  93
  94
  95 #endif // __WVGZIP_H