xapian-core/common/compression_stream.h

   1 /** @file
   2  * @brief class wrapper around zlib
   3  */
   4 /* Copyright (C) 2012 Dan Colish
   5  * Copyright (C) 2012,2013,2014,2016 Olly Betts
   6  *
   7  * This program is free software; you can redistribute it and/or modify
   8  * it under the terms of the GNU General Public License as published by
   9  * the Free Software Foundation; either version 2 of the License, or
  10  * (at your option) any later version.
  11  *
  12  * This program is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15  * GNU General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301 USA
  20  */
  21
  22 #ifndef XAPIAN_INCLUDED_COMPRESSION_STREAM_H
  23 #define XAPIAN_INCLUDED_COMPRESSION_STREAM_H
  24
  25 #include "internaltypes.h"
  26 #include <string>
  27 #include <zlib.h>
  28
  29 class CompressionStream {
  30     int compress_strategy;
  31
  32     size_t out_len;
  33
  34     char* out;
  35
  36     /// Zlib state object for deflating
  37     z_stream* deflate_zstream;
  38
  39     /// Zlib state object for inflating
  40     z_stream* inflate_zstream;
  41
  42     /// Allocate the zstream for deflating, if not already allocated.
  43     void lazy_alloc_deflate_zstream();
  44
  45     /// Allocate the zstream for inflating, if not already allocated.
  46     void lazy_alloc_inflate_zstream();
  47
  48   public:
  49     /* Create a new CompressionStream object.
  50      *
  51      *  @param compress_strategy_       Z_DEFAULT_STRATEGY,
  52      *                                  Z_FILTERED, Z_HUFFMAN_ONLY, or Z_RLE.
  53      */
  54     explicit CompressionStream(int compress_strategy_ = Z_DEFAULT_STRATEGY)
  55         : compress_strategy(compress_strategy_),
  56           out_len(0),
  57           out(NULL),
  58           deflate_zstream(NULL),
  59           inflate_zstream(NULL)
  60     { }
  61
  62     ~CompressionStream();
  63
  64     const char* compress(const char* buf, size_t* p_size);
  65
  66     void decompress_start() { lazy_alloc_inflate_zstream(); }
  67
  68     /** Returns true if this was the final chunk. */
  69     bool decompress_chunk(const char* p, int len, std::string& buf);
  70 };
  71
  72 #endif // XAPIAN_INCLUDED_COMPRESSION_STREAM_H