// (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com)

// (C) Copyright 2005-2007 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.



namespace boost { namespace iostreams {



namespace detail {



template<typename T> 

struct read_device_impl;



template<typename T> 

struct read_filter_impl;



} // End namespace detail.



template<typename T>

typename int_type_of<T>::type get(T& t)

{

    typedef typename detail::unwrapped_type<T>::type unwrapped;

    return detail::read_device_impl<T>::inner<unwrapped>::get(detail::unwrap(t));

}



template<typename T>

inline std::streamsize

read(T& t, typename char_type_of<T>::type* s, std::streamsize n)

{

    typedef typename detail::unwrapped_type<T>::type unwrapped;

    return detail::read_device_impl<T>::inner<unwrapped>::read(detail::unwrap(t), s, n);

}



template<typename T, typename Source>

std::streamsize

read(T& t, Source& src, typename char_type_of<T>::type* s, std::streamsize n)

{

    typedef typename detail::unwrapped_type<T>::type unwrapped;

    return detail::read_filter_impl<T>::inner<unwrapped>::read(detail::unwrap(t), src, s, n);

}



template<typename T>

bool putback(T& t, typename char_type_of<T>::type c)

{

    typedef typename detail::unwrapped_type<T>::type unwrapped;

    return detail::read_device_impl<T>::inner<unwrapped>::putback(detail::unwrap(t), c);

}



//----------------------------------------------------------------------------//



namespace detail {



// Helper function for adding -1 as EOF indicator.

inline std::streamsize check_eof(std::streamsize n) { return n != 0 ? n : -1; }



// Helper templates for reading from streambufs.

template<bool IsLinked>

struct true_eof_impl;



template<>

struct true_eof_impl<true> {

    template<typename T>

    static bool true_eof(T& t) { return t.true_eof(); }

};



template<>

struct true_eof_impl<false> {

    template<typename T>

    static bool true_eof(T& t) { return true; }

};



template<typename T>

inline bool true_eof(T& t)

{

    const bool linked = is_linked<T>::value;

    return true_eof_impl<linked>::true_eof(t);

}

                    

//------------------Definition of read_device_impl----------------------------//



template<typename T>

struct read_device_impl

    : mpl::if_<

          detail::is_custom<T>,

          operations<T>,

          read_device_impl<

              BOOST_DEDUCED_TYPENAME

              detail::dispatch<

                  T, istream_tag, streambuf_tag, input

              >::type

          >

      >::type

    { };



template<>

struct read_device_impl<istream_tag> {

    template<typename T>

    struct inner {

        static typename int_type_of<T>::type get(T& t)

        { return t.get(); }



        static std::streamsize

        read(T& t, typename char_type_of<T>::type* s, std::streamsize n)

        { return check_eof(t.rdbuf()->sgetn(s, n)); }



        static bool putback(T& t, typename char_type_of<T>::type c)

        {

            typedef typename char_type_of<T>::type          char_type;

            typedef BOOST_IOSTREAMS_CHAR_TRAITS(char_type)  traits_type;

            return !traits_type::eq_int_type( t.rdbuf()->sputbackc(c),

                                              traits_type::eof() );

        }

    };

};



template<>

struct read_device_impl<streambuf_tag> {

    template<typename T>

    struct inner {

        static typename int_type_of<T>::type

        get(T& t)

        {

            typedef typename char_type_of<T>::type  char_type;

            typedef char_traits<char_type>          traits_type;

            typename int_type_of<T>::type c;

            return !traits_type::is_eof(c = t.sbumpc()) ||

                    detail::true_eof(t)

                        ?

                    c : traits_type::would_block();

        }



        static std::streamsize

        read(T& t, typename char_type_of<T>::type* s, std::streamsize n)

        {

            std::streamsize amt;

            return (amt = t.sgetn(s, n)) != 0 ?

                amt :

                detail::true_eof(t) ?

                    -1 :

                    0;

        }



        static bool putback(T& t, typename char_type_of<T>::type c)

        {

            typedef typename char_type_of<T>::type  char_type;

            typedef char_traits<char_type>          traits_type;

            return !traits_type::is_eof(t.sputbackc(c));

        }

    };

};



template<>

struct read_device_impl<input> {

    template<typename T>

    struct inner {

        static typename int_type_of<T>::type

        get(T& t)

        {

            typedef typename char_type_of<T>::type  char_type;

            typedef char_traits<char_type>          traits_type;

            char_type c;

            std::streamsize amt;

            return (amt = t.read(&c, 1)) == 1 ?

                traits_type::to_int_type(c) :

                amt == -1 ?

                    traits_type::eof() :

                    traits_type::would_block();

        }



        template<typename T>

        static std::streamsize

        read(T& t, typename char_type_of<T>::type* s, std::streamsize n)

        { return t.read(s, n); }



        template<typename T>

        static bool putback(T& t, typename char_type_of<T>::type c)

        {   // T must be Peekable.

            return t.putback(c);

        }

    };

};



//------------------Definition of read_filter_impl----------------------------//



template<typename T>

struct read_filter_impl

    : mpl::if_<

          detail::is_custom<T>,

          operations<T>,

          read_filter_impl<

              BOOST_DEDUCED_TYPENAME

              detail::dispatch<

                  T, multichar_tag, any_tag

              >::type

          >

      >::type

    { };



template<>

struct read_filter_impl<multichar_tag> {

    template<typename T>

    struct inner {

        template<typename Source>

        static std::streamsize read

            ( T& t, Source& src, typename char_type_of<T>::type* s,   

              std::streamsize n )

        { return t.read(src, s, n); }

    };

};



template<>

struct read_filter_impl<any_tag> {

    template<typename T>

    struct inner {

        template<typename Source>

        static std::streamsize read

            ( T& t, Source& src, typename char_type_of<T>::type* s, 

              std::streamsize n )

        {

            typedef typename char_type_of<T>::type  char_type;

            typedef char_traits<char_type>          traits_type;

            for (std::streamsize off = 0; off < n; ++off) {

                typename traits_type::int_type c = t.get(src);

                if (traits_type::is_eof(c))

                    return check_eof(off);

                if (traits_type::would_block(c))

                    return off;

                s[off] = traits_type::to_char_type(c);

            }

            return n;

        }

    };

};



} // End namespace detail.



} } // End namespaces iostreams, boost.

