Index

Package: BZip2 (generic)

Description

generic

  input_buffer_size : Integer:= 1024;
  output_buffer_size: Integer:= 4096;

  type Buffer is array(Natural range <>) of Interfaces.Unsigned_8;

  check_CRC: Boolean;
  -- ^ useless if the whole bzip stream is in
  -- another CRC-checked stream, like a Zip archive

  -- Input:
  with procedure Read(buf: out Buffer);
  -- Output:
  with procedure Write(buf: in Buffer);

package BZip2 is
BZip2.Decompress - decompression of bzip2 data streams. bzip2 compresses files using the Burrows-Wheeler block-sorting text compression algorithm, and Huffman coding. Compression is generally considerably better than that achieved by more conventional LZ77/LZ78-based compressors, and approaches the performance of the PPM family of statistical compressors. This Ada code (a) is a reworked translation of a Pascal version (b) by Daniel Mantione of the decompression code of libbzip2 (c) by Julian Seward. Both (a) and (b) refer to (c)'s license which follows here, as in bzip version 1.0.5, from http://www.bzip.org : *************************************************************************** bzip2 and libbzip2, version 1.0.5: A program and library for data compression by Julian Seward Copyright (c) 1996-2007 Julian Seward This program, bzip2, the associated library libbzip2, and all documentation, are copyright (c) 1996-2007 Julian Seward. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: * Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. * The origin of this software must not be misrepresented; you must not claim that you wrote the original software. If you use this software in a product, an acknowledgment in the product documentation would be appreciated but is not required. * Altered source versions must be plainly marked as such, and must not be misrepresented as being the original software. * The name of the author may not be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE AUTHOR "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. PATENTS: To the best of my knowledge, bzip2 and libbzip2 do not use any patented algorithms. However, I do not have the resources to carry out a patent search. Therefore I cannot give any guarantee of the above statement. *************************************************************************** Translated on 20-Oct-2009 by (New) P2Ada v. 15-Nov-2006 Rework by G. de Montmollin Main difference over the FreePascal version: there is no more pointer arithmetics. The only pointer is tt, for dynamically allocating the biggest decoding array. With the appropriate options, the performance is very close to the bzip2 tool in C: it takes around 7%-11% more time according to data to be decompressed. Add 5% when CRC checking is enabled. These timings are obtained with bunzip.adb compiled on GNAT 2008, Win32, with the -O2 -gnatpn -fpeel-loops -funroll-loops -fweb -frename-registers options, average on several runs (see bz_test.cmd).

Types

Buffer

type Buffer is array(Natural range <>) of Interfaces.Unsigned_8;

Constants & Global variables

input_buffer_size (Integer)

input_buffer_size : Integer:= 1024;

output_buffer_size (Integer)

output_buffer_size: Integer:= 4096;

check_CRC (Boolean)

check_CRC: Boolean;
^ useless if the whole bzip stream is in another CRC-checked stream, like a Zip archive

bad_header_magic

bad_header_magic,
  bad_block_magic,
  data_error,
  block_crc_check_failed,
  randomized_not_yet_implemented: exception;

bad_block_magic

bad_block_magic,
  data_error,
  block_crc_check_failed,
  randomized_not_yet_implemented: exception;

data_error

data_error,
  block_crc_check_failed,
  randomized_not_yet_implemented: exception;

block_crc_check_failed

block_crc_check_failed,
  randomized_not_yet_implemented: exception;

randomized_not_yet_implemented

randomized_not_yet_implemented: exception;

Subprograms & Entries

Read

procedure Read
(buf: out Buffer);
Input:

Write

procedure Write
(buf: in Buffer);
Output:

Decompress

procedure Decompress;