compress.cc

   1 /*
   2  * Copyright (c) 2001, Robert Collins.
   3  *
   4  *     This program is free software; you can redistribute it and/or modify
   5  *     it under the terms of the GNU General Public License as published by
   6  *     the Free Software Foundation; either version 2 of the License, or
   7  *     (at your option) any later version.
   8  *
   9  *     A copy of the GNU General Public License can be found at
  10  *     http://www.gnu.org/
  11  *
  12  * Written by Robert Collins  <rbtcollins@hotmail.com>
  13  *
  14  */
  15
  16 #include "compress.h"
  17 #include "compress_gz.h"
  18 #include "compress_bz.h"
  19 #include "compress_xz.h"
  20 #include <string.h>
  21
  22 /* In case you are wondering why the file magic is not in one place:
  23  * It could be. But there is little (any?) benefit.
  24  * What is important is that the file magic required for any _task_ is centralised.
  25  * One such task is identifying compresss
  26  *
  27  * to federate into each class one might add a magic parameter to the constructor, which
  28  * the class could test itself.
  29  */
  30
  31 #define longest_magic 14 /* lzma_alone */
  32
  33 io_stream *
  34 compress::decompress (io_stream * original)
  35 {
  36   if (!original)
  37     return NULL;
  38   char magic[longest_magic];
  39   if (original->peek (magic, longest_magic) > 0)
  40     {
  41       if (memcmp (magic, "\037\213", 2) == 0)
  42         {
  43           /* tar */
  44           compress_gz *rv = new compress_gz (original);
  45           if (!rv->error ())
  46             return rv;
  47           /* else */
  48           rv->release_original();
  49           delete rv;
  50           return NULL;
  51         }
  52       else if (memcmp (magic, "BZh", 3) == 0)
  53         {
  54           compress_bz *rv = new compress_bz (original);
  55           if (!rv->error ())
  56             return rv;
  57           /* else */
  58           rv->release_original();
  59           delete rv;
  60           return NULL;
  61         }
  62       else if (compress_xz::is_xz_or_lzma (magic, 14))
  63         {
  64           compress_xz *rv = new compress_xz (original);
  65           if (!rv->error ())
  66             return rv;
  67           /* else */
  68           rv->release_original();
  69           delete rv;
  70           return NULL;
  71         }
  72     }
  73   return NULL;
  74 }
  75
  76 compress::~compress () {}