Back to...

   1  --  BZip2.Decoding - a standalone, generic BZip2 decoding package.
   2  ------------------
   3  --
   4  --  Legal licensing note:
   5  --
   6  --  Copyright (c) 2009 .. 2024 Gautier de Montmollin (maintainer of the Ada version)
   7  --  SWITZERLAND
   8  --
   9  --  Permission is hereby granted, free of charge, to any person obtaining a copy
  10  --  of this software and associated documentation files (the "Software"), to deal
  11  --  in the Software without restriction, including without limitation the rights
  12  --  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  13  --  copies of the Software, and to permit persons to whom the Software is
  14  --  furnished to do so, subject to the following conditions:
  15  --
  16  --  The above copyright notice and this permission notice shall be included in
  17  --  all copies or substantial portions of the Software.
  18  --
  19  --  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  20  --  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  21  --  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  22  --  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  23  --  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  24  --  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  25  --  THE SOFTWARE.
  26  --
  27  --  NB: this is the MIT License, as found 21-Aug-2016 on the site
  28  --  http://www.opensource.org/licenses/mit-license.php
  29  
  30  --------------------------------------------------------------
  31  --  | This Ada code is a reworked 2009 translation of a Pascal version,
  32  --  | bzip2.pas, by Daniel Mantione, of the decompression code of libbzip2
  33  --  | by Julian Seward. bzip2.pas is part of the FreePascal sources.
  34  --
  35  --  Translated on 20-Oct-2009 by (New) P2Ada v. 15-Nov-2006
  36  --  Rework by G. de Montmollin
  37  --
  38  --  Main differences over the FreePascal version:
  39  --
  40  --  * There is no more pointer arithmetics.
  41  --    The only pointer is tt, for dynamically allocating the biggest
  42  --    decoding array.
  43  --
  44  --  * In 2024 the overcomplicated and buggy RLE_1 part was rewritten.
  45  --
  46  --  With the appropriate options, the performance is very close to
  47  --  the bzip2 tool in C: it takes around 7%-11% more time depending on data
  48  --  to be decompressed (tested in 2009). Add some 5% when CRC checking is enabled.
  49  --  These timings are obtained with bunzip.adb compiled on GNAT 2008, Win32,
  50  --  with the -O2 -gnatpn -fpeel-loops -funroll-loops -fweb -frename-registers
  51  --  options, average on several runs (see bz_test.cmd).
  52  
  53  generic
  54    --  Input:
  55    with function Read_Byte return Byte;
  56    --  Output:
  57    with procedure Write_Byte (b : Byte);
  58  
  59    --  CRC checking is useless if the whole bzip stream is enclosed
  60    --  in another CRC-checked stream, like a in Zip archive.
  61    check_crc : Boolean;
  62  
  63  package BZip2.Decoding is
  64  
  65    bad_header_magic,
  66    bad_block_magic,
  67    data_error,
  68    block_crc_check_failed,
  69    randomized_not_yet_implemented : exception;
  70  
  71    --  Decompress: decompression of bzip2 data streams.
  72    procedure Decompress;
  73  
  74  end BZip2.Decoding;