boost/iostreams/copy.hpp

// (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com)
// (C) Copyright 2003-2007 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.)

// 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)
# pragma once
#endif

#include <boost/config.hpp>                 // Make sure ptrdiff_t is in std.
#include <algorithm>                        // copy, min.
#include <cstddef>                          // ptrdiff_t.
#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/enable_if_stream.hpp>
#include <boost/iostreams/detail/execute.hpp>
#include <boost/iostreams/detail/functional.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 {

    // The following four overloads of copy_impl() optimize
    // copying in the case that one or both of the two devices
    // models Direct (see
    // http://www.boost.org/libs/iostreams/doc/index.html?path=4.1.1.4)

// Copy from a direct source to a direct sink
template<typename Source, typename Sink>
std::streamsize copy_impl( Source& src, Sink& snk,
                           std::streamsize /* buffer_size */,
                           mpl::true_, mpl::true_ )
{
    using namespace std;
    typedef typename char_type_of<Source>::type  char_type;
    typedef std::pair<char_type*, char_type*>    pair_type;
    pair_type p1 = iostreams::input_sequence(src);
    pair_type p2 = iostreams::output_sequence(snk);
    std::streamsize total =
        static_cast<std::streamsize>(
            (std::min)(p1.second - p1.first, p2.second - p2.first)
        );
    std::copy(p1.first, p1.first + total, p2.first);
    return total;
}

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

// Copy from an indirect source to a direct sink
template<typename Source, typename Sink>
std::streamsize copy_impl( Source& src, Sink& snk,
                           std::streamsize buffer_size,
                           mpl::false_, mpl::true_ )
{
    typedef typename char_type_of<Source>::type  char_type;
    typedef std::pair<char_type*, char_type*>    pair_type;
    detail::basic_buffer<char_type>  buf(buffer_size);
    pair_type                        p = snk.output_sequence();
    std::streamsize                  total = 0;
    std::ptrdiff_t                   capacity = p.second - p.first;
    while (true) {
        std::streamsize amt =
            iostreams::read(
                src,
                buf.data(),
                buffer_size < capacity - total ?
                    buffer_size :
                    static_cast<std::streamsize>(capacity - total)
            );
        if (amt == -1)
            break;
        std::copy(buf.data(), buf.data() + amt, p.first + total);
        total += amt;
    }
    return total;
}

// Copy from an indirect source to an indirect sink
template<typename Source, typename Sink>
std::streamsize copy_impl( Source& src, Sink& snk,
                           std::streamsize buffer_size,
                           mpl::false_, mpl::false_ )
{
    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;
}

    // The following function object is used with
    // boost::iostreams::detail::execute() in the primary
    // overload of copy_impl(), below

// Function object that delegates to one of the above four
// overloads of compl_impl()
template<typename Source, typename Sink>
class copy_operation {
public:
    typedef std::streamsize result_type;
    copy_operation(Source& src, Sink& snk, std::streamsize buffer_size)
        : src_(src), snk_(snk), buffer_size_(buffer_size)
        { }
    std::streamsize operator()()
    {
        return copy_impl( src_, snk_, buffer_size_,
                          is_direct<Source>(), is_direct<Sink>() );
    }
private:
    copy_operation& operator=(const copy_operation&);
    Source&          src_;
    Sink&            snk_;
    std::streamsize  buffer_size_;
};

// Primary overload of copy_impl. Delegates to one of the above four
// overloads of compl_impl(), depending on which of the two given
// devices, if any, models Direct (see
// http://www.boost.org/libs/iostreams/doc/index.html?path=4.1.1.4)
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));
    return detail::execute_all(
               copy_operation<Source, Sink>(src, snk, buffer_size),
               detail::call_close_all(src),
               detail::call_close_all(snk)
           );
}

} // End namespace detail.

//------------------Definition of copy----------------------------------------//

// Overload of copy() for the case where neither the source nor the sink is
// a standard stream or stream buffer
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 );
}

// Overload of copy() for the case where the source, but not the sink, is
// a standard stream or stream buffer
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 );
}

// Overload of copy() for the case where the sink, but not the source, is
// a standard stream or stream buffer
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 );
}

// Overload of copy() for the case where neither the source nor the sink is
// a standard stream or stream buffer
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);
}

} } // End namespaces iostreams, boost.

#endif // #ifndef BOOST_IOSTREAMS_COPY_HPP_INCLUDED