restrict_impl.hpp

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/*
 * 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.

 * File:        boost/iostreams/detail/restrict_impl.hpp
 * Date:        Sun Jan 06 12:57:30 MST 2008
 * Copyright:   2007-2008 CodeRage, LLC
 * Author:      Jonathan Turkanis
 * Contact:     turkanis at coderage dot com
 *
 * If included with the macro BOOST_IOSTREAMS_RESTRICT undefined, defines the 
 * class template boost::iostreams::restriction. If included with the macro
 * BOOST_IOSTREAMS_RESTRICT defined as an identifier, defines the overloaded
 * function template boost::iostreams::BOOST_IOSTREAMS_RESTRICT, and object 
 * generator for boost::iostreams::restriction.
 *
 * This design allows <boost/iostreams/restrict.hpp> and 
 * <boost/iostreams/slice.hpp> to share an implementation.
 */

#if !defined(BOOST_IOSTREAMS_RESTRICT_IMPL_HPP_INCLUDED) && \
    !defined(BOOST_IOSTREAMS_RESTRICT)
# define BOOST_IOSTREAMS_RESTRICT_IMPL_HPP_INCLUDED
                    
//------------------Implementation of restriction-----------------------------//

# include <algorithm>          // min.
# include <utility>            // pair.
# include <boost/cstdint.hpp>  // intmax_t.
# include <boost/config.hpp>   // DEDUCED_TYPENAME.
# include <boost/iostreams/categories.hpp>
# include <boost/iostreams/char_traits.hpp>
# include <boost/iostreams/detail/adapter/device_adapter.hpp>
# include <boost/iostreams/detail/adapter/filter_adapter.hpp>
# include <boost/iostreams/detail/call_traits.hpp>
# include <boost/iostreams/detail/enable_if_stream.hpp>
# include <boost/iostreams/detail/error.hpp>
# include <boost/iostreams/detail/ios.hpp>     // failure.
# include <boost/iostreams/detail/select.hpp>
# include <boost/iostreams/operations.hpp>
# include <boost/iostreams/skip.hpp>
# include <boost/iostreams/traits.hpp>         // mode_of, is_direct.
# include <boost/mpl/bool.hpp>
# include <boost/static_assert.hpp>
# include <boost/type_traits/is_convertible.hpp>

# include <boost/iostreams/detail/config/disable_warnings.hpp>

namespace boost { namespace iostreams {

namespace detail {

//
// Template name: restricted_indirect_device.
// Description: Provides an restricted view of an indirect Device.
// Template paramters:
//      Device - An indirect model of Device that models either Source or
//          SeekableDevice.
//
template<typename Device>
class restricted_indirect_device : public device_adapter<Device> {
private:
    typedef typename detail::param_type<Device>::type  param_type;
public:
    typedef typename char_type_of<Device>::type  char_type;
    typedef typename mode_of<Device>::type       mode;
    BOOST_STATIC_ASSERT(!(is_convertible<mode, detail::two_sequence>::value));
    struct category
        : mode,
          device_tag,
          closable_tag,
          flushable_tag,
          localizable_tag,
          optimally_buffered_tag
        { };
    restricted_indirect_device( param_type dev, stream_offset off,
                                stream_offset len = -1 );
    std::streamsize read(char_type* s, std::streamsize n);
    std::streamsize write(const char_type* s, std::streamsize n);
    std::streampos seek(stream_offset off, BOOST_IOS::seekdir way);
private:
    stream_offset beg_, pos_, end_;
};

//
// Template name: restricted_direct_device.
// Description: Provides an restricted view of a Direct Device.
// Template paramters:
//      Device - A model of Direct and Device.
//
template<typename Device>
class restricted_direct_device : public device_adapter<Device> {
public:
    typedef typename char_type_of<Device>::type  char_type;
    typedef std::pair<char_type*, char_type*>    pair_type;
    typedef typename mode_of<Device>::type       mode;
    BOOST_STATIC_ASSERT(!(is_convertible<mode, detail::two_sequence>::value));
    struct category
        : mode_of<Device>::type,
          device_tag,
          direct_tag,
          closable_tag,
          localizable_tag
        { };
    restricted_direct_device( const Device& dev, stream_offset off,
                              stream_offset len = -1 );
    pair_type input_sequence();
    pair_type output_sequence();
private:
    pair_type sequence(mpl::true_);
    pair_type sequence(mpl::false_);
    char_type *beg_, *end_;
};

//
// Template name: restricted_filter.
// Description: Provides an restricted view of a Filter.
// Template paramters:
//      Filter - An indirect model of Filter.
//
template<typename Filter>
class restricted_filter : public filter_adapter<Filter> {
public:
    typedef typename char_type_of<Filter>::type char_type;
    typedef typename mode_of<Filter>::type      mode;
    BOOST_STATIC_ASSERT(!(is_convertible<mode, detail::two_sequence>::value));
    struct category
        : mode,
          filter_tag,
          multichar_tag,
          closable_tag,
          localizable_tag,
          optimally_buffered_tag
        { };
    restricted_filter( const Filter& flt, stream_offset off, 
                       stream_offset len = -1 );

    template<typename Source>
    std::streamsize read(Source& src, char_type* s, std::streamsize n)
    {
        using namespace std;
        if (!open_)
            open(src, BOOST_IOS::in);
        std::streamsize amt =
            end_ != -1 ?
                (std::min) (n, static_cast<std::streamsize>(end_ - pos_)) :
                n;
        std::streamsize result = 
            iostreams::read(this->component(), src, s, amt);
        if (result != -1)
            pos_ += result;
        return result;
    }

    template<typename Sink>
    std::streamsize write(Sink& snk, const char_type* s, std::streamsize n)
    {
        if (!open_)
            open(snk, BOOST_IOS::out);
        if (end_ != -1 && pos_ + n >= end_)
            bad_write();
        std::streamsize result = 
            iostreams::write(this->component(), snk, s, n);
        pos_ += result;
        return result;
    }

    template<typename Device>
    std::streampos seek(Device& dev, stream_offset off, BOOST_IOS::seekdir way)
    {
        stream_offset next;
        if (way == BOOST_IOS::beg) {
            next = beg_ + off;
        } else if (way == BOOST_IOS::cur) {
            next = pos_ + off;
        } else if (end_ != -1) {
            next = end_ + off;
        } else {
            // Restriction is half-open; seek relative to the actual end.
            pos_ = this->component().seek(dev, off, BOOST_IOS::end);
            if (pos_ < beg_)
                bad_seek();
            return offset_to_position(pos_ - beg_);
        }
        if (next < beg_ || end_ != -1 && next >= end_)
            bad_seek();
        pos_ = this->component().seek(dev, next, BOOST_IOS::cur);
        return offset_to_position(pos_ - beg_);
    }

    template<typename Device>
    void close(Device& dev) 
    { 
        open_ = false;
        detail::close_all(this->component(), dev); 
    }

    template<typename Device>
    void close(Device& dev, BOOST_IOS::openmode which) 
    { 
        open_ = false;
        iostreams::close(this->component(), dev, which); 
    }
private:
    template<typename Device>
    void open(Device& dev, BOOST_IOS::openmode which)
    {
        typedef typename is_convertible<mode, dual_use>::type is_dual_use;
        open_ = true;
        which = is_dual_use() ? which : (BOOST_IOS::in | BOOST_IOS::out);
        iostreams::skip(this->component(), dev, beg_, which);
    }

    stream_offset  beg_, pos_, end_;
    bool           open_;
};

template<typename T>
struct restriction_traits
    : iostreams::select<  // Disambiguation for Tru64.
          is_filter<T>,  restricted_filter<T>,
          is_direct<T>,  restricted_direct_device<T>,
          else_,         restricted_indirect_device<T>
      >
    { };

} // End namespace detail.

template<typename T>
struct restriction : public detail::restriction_traits<T>::type {
    typedef typename detail::param_type<T>::type          param_type;
    typedef typename detail::restriction_traits<T>::type  base_type;
    restriction(param_type t, stream_offset off, stream_offset len = -1)
        : base_type(t, off, len)
        { }
};