boost::iostreams::bzip2bzip2_paramsbzip2_compressorbzip2_decompressorbzip2_error
The class templates basic_bzip2_compressor and basic_bzip2_decompressor perform compression and decompression using Julian Seward's libbzip2 compression library ([Seward]).
The bzip2 Filters are DualUseFilters so that they may be used for either input or output. Most commonly, however, the compression Filters will be used for output and the decompression Filters for input.
The bzip2 Filters were influences by the work of Jeff Garland ([Garland]) and Jonathan de Halleux ([de Halleux]).
Thanks to Julian Seward for making his excellent library available to the public with a Boost-compatible license.<boost/iostreams/filter/bzip2.hpp>namespace boost { namespace iostreams { namespace bzip2 { // Error codes extern const int data_error; extern const int data_error_magic; extern const int config_error; } // End namespace boost::iostreams::bzip2 struct bzip2_params; template<typename Alloc = std::allocator<char> > struct basic_bzip2_compressor; template<typename Alloc = std::allocator<char> > struct basic_bzip2_decompressor; typedef basic_bzip2_compressor<> bzip2_compressor; typedef basic_bzip2_decompressor<> bzip2_decompressor; class bzip2_error; } } // End namespace boost::io
boost::iostreams::bzip2The namespace boost::iostreams::bzip2 contains integral error codes. The constants have the following interpretations. See [Seward] for additional details.
bzip2_paramsEncapsulates the parameters used to configure basic_bzip2_compressor and basic_bzip2_decompressor.
struct bzip2_params { // Non-explicit constructor for compression bzip2_params( int block_size = default value, int work_factor = default value ); // Constructor for decompression. bzip2_params( bool small ); union { int block_size; // For compression bool small; // For decompression }; int work_factor; // For compression };
bzip2_params::bzip2_paramsbzip2_params( int block_size = default value, int work_factor = default value ); bzip2_params( bool small );
The first member constructs a bzip2_params object for configuring basic_bzip2_compressor.
The second constructs a bzip2_params object for configuring basic_bzip2_decompressor.
| small | - | Indicates whether a slower decompression algorithm, using less memory, should be used. |
See [Seward] for additional details.
basic_bzip2_compressortemplate<typename Alloc = std::allocator<char> > struct basic_bzip2_compressor { typedef char char_type; typedef implementation-defined category; basic_bzip2_compressor( const bzip2_params& = bzip2::default_block_size, std::streamsize buffer_size = default value ); ... }; typedef basic_bzip2_compressor<> bzip2_compressor;
| Alloc | - | A C++ standard library allocator type ([ISO], 20.1.5), used to allocate a character buffer and to configure libbzip2. |
basic_bzip2_compressor::basic_bzip2_compressor basic_bzip2_compressor(const bzip2_params&, std::streamsize buffer_size);
Constructs an instance of basic_bzip2_compressor with the given parameters and buffer size. Since a bzip2_params object is implicitly constructible from an int representing a block size, an int may be passed as the first constructor argument.
basic_bzip2_decompressortemplate<typename Alloc = std::allocator<char> > struct basic_bzip2_decompressor { typedef char char_type; typedef implementation-defined category; basic_bzip2_decompressor( bool small = false, std::streamsize buffer_size = default value ); ... }; typedef basic_bzip2_decompressor<> bzip2_decompressor;
| Alloc | - | A C++ standard library allocator type ([ISO], 20.1.5), used to allocate a character buffer and to configure libbzip2. |
basic_bzip2_decompressor::basic_bzip2_decompressor basic_bzip2_decompressor(bool small, std::streamsize buffer_size);
Constructs an instance of basic_bzip2_decompressor with the given value for small and the given buffer size.
bzip2_errorclass bzip2_error : public std::ios_base::failure { public: bzip2_error(int error); int error() const; };
bzip2_error::bzip2_error bzip2_error(int error);
Constructs an instance of bzip2_error with the given error code from the namespace boost::iostreams::bzip2.
bzip2_error::errorvoid error() const;
Returns an error code from the namespace boost::iostreams::bzip2.
#include <fstream> #include <iostream> #include <boost/iostreams/filtering_streambuf.hpp> #include <boost/iostreams/copy.hpp> #include <boost/iostreams/filter/bzip2.hpp> int main() { using namespace std; using namespace boost::iostreams; ifstream file("hello.bz2", ios_base::in | ios_base::binary); filtering_streambuf<input> in; in.push(bzip2_decompressor()); in.push(file); boost::iostreams::copy(in, cout); }
The bzip2 Filters depend on the third-party libbz2 library, which is not included in the Boost distribution. Prebuilt libbz2 binaries are available on most UNIX and UNIX-like systems, and will be found automatically by the Boost build system. Users can also configure the Boost Iostream library to build libbz2 from the source code, which is available at the libbz2 homepage. For details on configuring the build system to find your libbz2 installation, please see Installation.
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© Copyright 2004-2007 Jonathan Turkanis
Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)