source: downloads/boost_1_33_1/boost/iostreams/copy.hpp @ 20

// (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 function template copy, which reads data from a Source 
// and writes it to a Sink until the end of the sequence is reached, returning 
// the number of characters transfered.

// The implementation is complicated by the need to handle smart adapters
// and direct devices.

#ifndef BOOST_IOSTREAMS_COPY_HPP_INCLUDED
#define BOOST_IOSTREAMS_COPY_HPP_INCLUDED

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

#include <algorithm>                        // copy.
#include <utility>                          // pair.
#include <boost/detail/workaround.hpp>
#include <boost/iostreams/chain.hpp>
#include <boost/iostreams/constants.hpp>
#include <boost/iostreams/detail/adapter/non_blocking_adapter.hpp>        
#include <boost/iostreams/detail/buffer.hpp>       
#include <boost/iostreams/detail/closer.hpp>    
#include <boost/iostreams/detail/enable_if_stream.hpp>  
#include <boost/iostreams/detail/ios.hpp>   // failure, streamsize.                   
#include <boost/iostreams/detail/resolve.hpp>                   
#include <boost/iostreams/detail/wrap_unwrap.hpp>
#include <boost/iostreams/operations.hpp>  // read, write, close.
#include <boost/iostreams/pipeline.hpp>
#include <boost/static_assert.hpp>  
#include <boost/type_traits/is_same.hpp> 

namespace boost { namespace iostreams {

namespace detail {

template<typename Source, typename Sink>
std::streamsize copy_impl( Source& src, Sink& snk, 
                           std::streamsize /* buffer_size */,
                           mpl::true_, mpl::true_ )
{   // Copy from a direct Source to a direct Sink.
    using namespace std;
    typedef typename char_type_of<Source>::type  char_type;
    typedef pair<char_type*, char_type*>         pair_type;
    pair_type p1 = iostreams::input_sequence(src);
    pair_type p2 = iostreams::output_sequence(snk);
    if (p1.second - p1.first < p2.second - p2.first) {
        std::copy(p1.first, p1.second, p2.first);
        return static_cast<streamsize>(p1.second - p1.first);
    } else {
        throw BOOST_IOSTREAMS_FAILURE("destination too small");
    }
}

template<typename Source, typename Sink>
std::streamsize copy_impl( Source& src, Sink& snk, 
                           std::streamsize /* buffer_size */,
                           mpl::true_, mpl::false_ )
{   // Copy from a direct Source to an indirect Sink.
    using namespace std;
    typedef typename char_type_of<Source>::type  char_type;
    typedef pair<char_type*, char_type*>         pair_type;
    pair_type p = iostreams::input_sequence(src);
    std::streamsize size, total;
    for ( total = 0, size = static_cast<streamsize>(p.second - p.first);
          total < size; )
    {
        std::streamsize amt = 
            iostreams::write(snk, p.first + total, size - total); 
        total += amt;
    }
    return size;
}

template<typename Source, typename Sink>
std::streamsize copy_impl( Source& src, Sink& snk, 
                           std::streamsize buffer_size,
                           mpl::false_, mpl::true_ )
{   // Copy from an indirect Source to a direct Sink.
    using namespace std;
    typedef typename char_type_of<Source>::type  char_type;
    typedef pair<char_type*, char_type*>         pair_type;
    detail::basic_buffer<char_type>  buf(buffer_size);
    pair_type                        p = snk.output_sequence();
    streamsize                       total = 0;
    bool                             done  = false;
    while (!done) {
        streamsize amt;
        done = (amt = iostreams::read(src, buf.data(), buffer_size)) == -1;
        std::copy(buf.data(), buf.data() + amt, p.first + total);
        if (amt != -1)
            total += amt;
    }
    return total;
}

template<typename Source, typename Sink>
std::streamsize copy_impl( Source& src, Sink& snk, 
                           std::streamsize buffer_size,
                           mpl::false_, mpl::false_ )
{   // Copy from an indirect Source to a indirect Sink. This algorithm
    // can be improved by eliminating the non_blocking_adapter.
    typedef typename char_type_of<Source>::type char_type;
    detail::basic_buffer<char_type>  buf(buffer_size);
    non_blocking_adapter<Sink>       nb(snk);
    std::streamsize                  total = 0;
    bool                             done = false;
    while (!done) {
        std::streamsize amt;
        done = (amt = iostreams::read(src, buf.data(), buffer_size)) == -1;
        if (amt != -1) {
            iostreams::write(nb, buf.data(), amt);
            total += amt;
        }
    }
    return total;
}

template<typename Source, typename Sink>
std::streamsize copy_impl(Source src, Sink snk, std::streamsize buffer_size)
{
    using namespace std;
    typedef typename char_type_of<Source>::type  src_char;
    typedef typename char_type_of<Sink>::type    snk_char;
    BOOST_STATIC_ASSERT((is_same<src_char, snk_char>::value));
    bool                     nothrow = false;
    external_closer<Source>  close_source(src, BOOST_IOS::in, nothrow);
    external_closer<Sink>    close_sink(snk, BOOST_IOS::out, nothrow);
    streamsize result =
        copy_impl( src, snk, buffer_size, 
                   is_direct<Source>(), is_direct<Sink>() );
    return result; 
}

} // End namespace detail.
                    
//------------------Definition of copy----------------------------------------//

template<typename Source, typename Sink>
std::streamsize
copy( const Source& src, const Sink& snk,
      std::streamsize buffer_size = default_device_buffer_size
      BOOST_IOSTREAMS_DISABLE_IF_STREAM(Source)
      BOOST_IOSTREAMS_DISABLE_IF_STREAM(Sink) )
{ 
    typedef typename char_type_of<Source>::type char_type;
    return detail::copy_impl( detail::resolve<input, char_type>(src), 
                              detail::resolve<output, char_type>(snk), 
                              buffer_size ); 
}

#if !BOOST_WORKAROUND(BOOST_MSVC, <= 1300) //---------------------------------//

template<typename Source, typename Sink>
std::streamsize
copy( Source& src, const Sink& snk,
      std::streamsize buffer_size = default_device_buffer_size
      BOOST_IOSTREAMS_ENABLE_IF_STREAM(Source)
      BOOST_IOSTREAMS_DISABLE_IF_STREAM(Sink) ) 
{ 
    typedef typename char_type_of<Source>::type char_type;
    return detail::copy_impl( detail::wrap(src), 
                              detail::resolve<output, char_type>(snk), 
                              buffer_size );
}

template<typename Source, typename Sink>
std::streamsize
copy( const Source& src, Sink& snk,
      std::streamsize buffer_size = default_device_buffer_size
      BOOST_IOSTREAMS_DISABLE_IF_STREAM(Source)
      BOOST_IOSTREAMS_ENABLE_IF_STREAM(Sink) ) 
{ 
    typedef typename char_type_of<Source>::type char_type;
    return detail::copy_impl( detail::resolve<input, char_type>(src), 
                              detail::wrap(snk), buffer_size);
}

template<typename Source, typename Sink>
std::streamsize
copy( Source& src, Sink& snk,
      std::streamsize buffer_size = default_device_buffer_size
      BOOST_IOSTREAMS_ENABLE_IF_STREAM(Source)
      BOOST_IOSTREAMS_ENABLE_IF_STREAM(Sink) ) 
{ 
    return detail::copy_impl(detail::wrap(src), detail::wrap(snk), buffer_size);
}

#endif // #if !BOOST_WORKAROUND(BOOST_MSVC, <= 1300) //-----------------------//

} } // End namespaces iostreams, boost.

#endif // #ifndef BOOST_IOSTREAMS_COPY_HPP_INCLUDED