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Filename : buffer.hpp
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//  Copyright (c) 2001-2011 Hartmut Kaiser
//
//  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)

#ifndef BOOST_SPIRIT_KARMA_DIRECTIVE_BUFFER_HPP
#define BOOST_SPIRIT_KARMA_DIRECTIVE_BUFFER_HPP

#if defined(_MSC_VER)
#pragma once
#endif

#include <boost/spirit/home/karma/meta_compiler.hpp>
#include <boost/spirit/home/karma/generator.hpp>
#include <boost/spirit/home/karma/domain.hpp>
#include <boost/spirit/home/karma/detail/output_iterator.hpp>
#include <boost/spirit/home/support/unused.hpp>
#include <boost/spirit/home/support/info.hpp>
#include <boost/spirit/home/support/common_terminals.hpp>
#include <boost/spirit/home/support/has_semantic_action.hpp>
#include <boost/spirit/home/support/handles_container.hpp>
#include <boost/spirit/home/karma/detail/attributes.hpp>

namespace boost { namespace spirit
{
    ///////////////////////////////////////////////////////////////////////////
    // Enablers
    ///////////////////////////////////////////////////////////////////////////
    template <>
    struct use_directive<karma::domain, tag::buffer> // enables buffer
      : mpl::true_ {};

}}

namespace boost { namespace spirit { namespace karma
{
#ifndef BOOST_SPIRIT_NO_PREDEFINED_TERMINALS
    using spirit::buffer;
#endif
    using spirit::buffer_type;

    ///////////////////////////////////////////////////////////////////////////
    // buffer_directive buffers all generated output of the embedded generator
    // and flushes it only if the whole embedded generator succeeds
    ///////////////////////////////////////////////////////////////////////////
    template <typename Subject>
    struct buffer_directive : unary_generator<buffer_directive<Subject> >
    {
        typedef Subject subject_type;
        typedef mpl::int_<
            subject_type::properties::value | 
            generator_properties::countingbuffer
        > properties;

        buffer_directive(Subject const& subject)
          : subject(subject) {}

        template <typename Context, typename Iterator>
        struct attribute
          : traits::attribute_of<subject_type, Context, Iterator>
        {};

        template <typename OutputIterator, typename Context, typename Delimiter
          , typename Attribute>
        bool generate(OutputIterator& sink, Context& ctx, Delimiter const& d
          , Attribute const& attr) const
        {
            // wrap the given output iterator to avoid output as long as the
            // embedded generator (subject) fails
            detail::enable_buffering<OutputIterator> buffering(sink);
            bool r = false;
            {
                detail::disable_counting<OutputIterator> nocounting(sink);
                r = subject.generate(sink, ctx, d, attr);
            }
            if (r) 
                buffering.buffer_copy();
            return r;
        }

        template <typename Context>
        info what(Context& context) const
        {
            return info("buffer", subject.what(context));
        }

        Subject subject;
    };

    ///////////////////////////////////////////////////////////////////////////
    // Generator generators: make_xxx function (objects)
    ///////////////////////////////////////////////////////////////////////////
    template <typename Subject, typename Modifiers>
    struct make_directive<tag::buffer, Subject, Modifiers>
    {
        typedef buffer_directive<Subject> result_type;
        result_type operator()(unused_type, Subject const& subject
          , unused_type) const
        {
            return result_type(subject);
        }
    };

    // make sure buffer[buffer[...]] does not result in double buffering
    template <typename Subject, typename Modifiers>
    struct make_directive<tag::buffer, buffer_directive<Subject>, Modifiers>
    {
        typedef buffer_directive<Subject> result_type;
        result_type operator()(unused_type
          , buffer_directive<Subject> const& subject, unused_type) const
        {
            return subject;
        }
    };
}}}

namespace boost { namespace spirit { namespace traits
{
    ///////////////////////////////////////////////////////////////////////////
    template <typename Subject>
    struct has_semantic_action<karma::buffer_directive<Subject> >
      : unary_has_semantic_action<Subject> {};

    ///////////////////////////////////////////////////////////////////////////
    template <typename Subject, typename Attribute, typename Context
        , typename Iterator>
    struct handles_container<karma::buffer_directive<Subject>, Attribute
        , Context, Iterator>
      : unary_handles_container<Subject, Attribute, Context, Iterator> {};
}}}

#endif