gzip.hpp

C++的一个好库。。。现在很流行

// (C) Copyright Jonathan Turkanis 2003.
// 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.)

// See http://www.boost.org/libs/iostreams for documentation.

// Contains the definitions of the class templates gzip_compressor and
// gzip_decompressor for reading and writing files in the gzip file format
// (RFC 1952). Based in part on work of Jonathan de Halleux; see [...]

#ifndef BOOST_IOSTREAMS_GZIP_HPP_INCLUDED
#define BOOST_IOSTREAMS_GZIP_HPP_INCLUDED

#if defined(_MSC_VER) && (_MSC_VER >= 1020)
# pragma once
#endif

#include <boost/config.hpp> // STATIC_CONSTANT, STDC_NAMESPACE, 
                            // DINKUMWARE_STDLIB, __STL_CONFIG_H.
#include <algorithm>                      // min.
#include <cstdio>                         // EOF.
#include <cstddef>                        // size_t.
#include <ctime>                          // std::time_t.
#include <memory>                         // allocator.
#include <boost/config.hpp>               // Put size_t in std.
#include <boost/detail/workaround.hpp>
#include <boost/cstdint.hpp>              // uint8_t, uint32_t.
#include <boost/iostreams/constants.hpp>  // buffer size.
#include <boost/iostreams/detail/adapter/non_blocking_adapter.hpp>
#include <boost/iostreams/detail/adapter/range_adapter.hpp>
#include <boost/iostreams/detail/char_traits.hpp>
#include <boost/iostreams/detail/ios.hpp> // failure.
#include <boost/iostreams/operations.hpp>
#include <boost/iostreams/device/back_inserter.hpp>
#include <boost/iostreams/filter/zlib.hpp>
#include <boost/iostreams/pipeline.hpp>         

// Must come last.
#if defined(BOOST_MSVC)
# pragma warning(push)
# pragma warning(disable: 4309)    // Truncation of constant value.
#endif

#ifdef BOOST_NO_STDC_NAMESPACE
namespace std { using ::time_t; }
#endif

namespace boost { namespace iostreams {

namespace gzip {

using namespace boost::iostreams::zlib;

    // Error codes used by gzip_error.

const int zlib_error        = 1;
const int bad_crc           = 2; // Recorded crc doesn't match data.
const int bad_length        = 3; // Recorded length doesn't match data.
const int bad_header        = 4; // Malformed header.
const int bad_footer        = 5; // Malformed footer.

namespace magic {

    // Magic numbers used by gzip header.

const int id1               = 0x1f;
const int id2               = 0x8b;

} // End namespace magic.

namespace method {

    // Codes used for the 'CM' byte of the gzip header.

const int deflate           = 8;

} // End namespace method.

namespace flags {

    // Codes used for the 'FLG' byte of the gzip header.

const int text              = 1;
const int header_crc        = 2;
const int extra             = 4;
const int name              = 8;
const int comment           = 16;

} // End namespace flags.

namespace extra_flags {

    // Codes used for the 'XFL' byte of the gzip header.

const int best_compression  = 2;
const int best_speed        = 4;

} // End namespace extra_flags.

    // Codes used for the 'OS' byte of the gzip header.

const int os_fat            = 0;
const int os_amiga          = 1;
const int os_vms            = 2;
const int os_unix           = 3;
const int os_vm_cms         = 4;
const int os_atari          = 5;
const int os_hpfs           = 6;
const int os_macintosh      = 7;
const int os_z_system       = 8;
const int os_cp_m           = 9;
const int os_tops_20        = 10;
const int os_ntfs           = 11;
const int os_qdos           = 12;
const int os_acorn          = 13;
const int os_unknown        = 255;

} // End namespace gzip.

//
// Class name: gzip_params.
// Description: Subclass of zlib_params with an additional field
//      representing a file name.
//
struct gzip_params : zlib_params {

    // Non-explicit constructor.
    gzip_params( int level              = gzip::default_compression,
                 int method             = gzip::deflated,
                 int window_bits        = gzip::default_window_bits,
                 int mem_level          = gzip::default_mem_level,
                 int strategy           = gzip::default_strategy,
                 std::string file_name  = "",
                 std::string comment    = "",
                 std::time_t mtime      = 0 )
        : zlib_params(level, method, window_bits, mem_level, strategy),
          file_name(file_name), mtime(mtime)
        { }
    std::string  file_name;
    std::string  comment;
    std::time_t  mtime;
};

//
// Class name: gzip_error.
// Description: Subclass of std::ios_base::failure thrown to indicate
//     zlib errors other than out-of-memory conditions.
//
class gzip_error : public BOOST_IOSTREAMS_FAILURE {
public:
    explicit gzip_error(int error)
        : BOOST_IOSTREAMS_FAILURE("gzip error"),
          error_(error), zlib_error_code_(zlib::okay) { }
    explicit gzip_error(const zlib_error& e)
        : BOOST_IOSTREAMS_FAILURE("gzip error"),
          error_(gzip::zlib_error), zlib_error_code_(e.error())
        { }
    int error() const { return error_; }
    int zlib_error_code() const { return zlib_error_code_; }
private:
    int error_;
    int zlib_error_code_;
};

//
// Template name: gzip_compressor
// Description: Model of OutputFilter implementing compression in the
//      gzip format.
//
template<typename Alloc = std::allocator<char> >
class basic_gzip_compressor : basic_zlib_compressor<Alloc> {
private:
    typedef basic_zlib_compressor<Alloc>  base_type;
public:
    typedef char char_type;
    struct category
        : dual_use,
          filter_tag,
          multichar_tag,
          closable_tag
        { };
    basic_gzip_compressor( const gzip_params& = gzip::default_compression,
                           int buffer_size = default_device_buffer_size );

    template<typename Source>
    std::streamsize read(Source& src, char_type* s, std::streamsize n)
    {
        using namespace std;
        streamsize result = 0;

        // Read header.
        if (!(flags_ & f_header_done))
            result += read_string(s, n, header_);

        // Read body.
        if (!(flags_ & f_body_done)) {

            // Read from basic_zlib_filter.
            streamsize amt = base_type::read(src, s + result, n - result);
            if (amt != -1) {
                result += amt;
                if (amt < n - result) { // Double-check for EOF.
                    amt = base_type::read(src, s + result, n - result);
                    if (amt != -1)
                        result += amt;
                }
            }
            if (amt == -1)
                prepare_footer();
        }

        // Read footer.
        if ((flags_ & f_body_done) != 0 && result < n)
            result += read_string(s + result, n - result, footer_);

        return result != 0 ? result : -1;
    }

    template<typename Sink>
    std::streamsize write(Sink& snk, const char_type* s, std::streamsize n)
    {
        if (!(flags_ & f_header_done)) {
            std::streamsize amt = 
                static_cast<std::streamsize>(header_.size() - offset_);
            offset_ += boost::iostreams::write(snk, header_.data() + offset_, amt);
            if (offset_ == header_.size())
                flags_ |= f_header_done;
            else
                return 0;
        }
        return base_type::write(snk, s, n);
    }

    template<typename Sink>
    void close(Sink& snk, BOOST_IOS::openmode m)
    {
        namespace io = boost::iostreams;

        if (m & BOOST_IOS::out) {

                // Close zlib compressor.
                base_type::close(snk, BOOST_IOS::out);

            if (flags_ & f_header_done) {

                // Write final fields of gzip file format.
                write_long(this->crc(), snk);
                write_long(this->total_in(), snk);
            }

        }
        #if BOOST_WORKAROUND(__GNUC__, == 2) && defined(__STL_CONFIG_H) || \
            BOOST_WORKAROUND(BOOST_DINKUMWARE_STDLIB, == 1) \
            /**/
            footer_.erase(0, std::string::npos);
        #else
            footer_.clear();
        #endif
        offset_ = 0;
        flags_ = 0;
    }
private:
    static gzip_params normalize_params(gzip_params p);
    void prepare_footer();
    std::streamsize read_string(char* s, std::streamsize n, std::string& str);

    template<typename Sink>
    static void write_long(long n, Sink& next)
    {
        boost::iostreams::put(next, static_cast<char>(0xFF & n));
        boost::iostreams::put(next, static_cast<char>(0xFF & (n >> 8)));
        boost::iostreams::put(next, static_cast<char>(0xFF & (n >> 16)));
        boost::iostreams::put(next, static_cast<char>(0xFF & (n >> 24)));
    }

    enum flag_type {
        f_header_done = 1,
        f_body_done = f_header_done << 1,
        f_footer_done = f_body_done << 1
    };
    std::string  header_;
    std::string  footer_;
    std::size_t  offset_;
    int          flags_;
};
BOOST_IOSTREAMS_PIPABLE(basic_gzip_compressor, 1)

typedef basic_gzip_compressor<> gzip_compressor;

//
// Template name: basic_gzip_decompressor
// Description: Model of InputFilter implementing compression in the
//      gzip format.
//
template<typename Alloc = std::allocator<char> >
class basic_gzip_decompressor : basic_zlib_decompressor<Alloc> {
public:
    typedef char char_type;