/*

 * Copyright (c) 1999

 * Silicon Graphics Computer Systems, Inc.

 *

 * Copyright (c) 1999

 * Boris Fomitchev

 *

 * This material is provided "as is", with absolutely no warranty expressed

 * or implied. Any use is at your own risk.

 *

 * Permission to use or copy this software for any purpose is hereby granted

 * without fee, provided the above notices are retained on all copies.

 * Permission to modify the code and to distribute modified code is granted,

 * provided the above notices are retained, and a notice that the code was

 * modified is included with the above copyright notice.

 *

 */

#include "stlport_prefix.h"

#ifdef _STLP_USE_UNIX_IO

# include "details/fstream_unistd.cpp"

#elif defined(_STLP_USE_STDIO_IO)

# include "details/fstream_stdio.cpp"

#elif defined(_STLP_USE_WIN32_IO)

# include "details/fstream_win32io.cpp"

#else

#  error "Can't recognize IO scheme to use"

#endif

_STLP_BEGIN_NAMESPACE

// fbp : let us map 1 MB maximum, just be sure not to trash VM

#define MMAP_CHUNK 0x100000L

_Underflow< char, char_traits<char> >::int_type _STLP_CALL

_Underflow< char, char_traits<char> >::_M_doit(basic_filebuf<char, char_traits<char> >* __this)

{

  typedef char_traits<char> traits_type;

  typedef traits_type::int_type int_type;

  if ( (__this->int_flags_ & basic_filebuf<char, char_traits<char> >::_in_input_mode) == 0 ) {

    if ( !__this->_M_switch_to_input_mode() ) {

      return traits_type::eof();

    }

  } else if ( __this->int_flags_ & basic_filebuf<char, char_traits<char> >::_in_putback_mode ) {

    __this->_M_exit_putback_mode();

    if (__this->gptr() != __this->egptr()) {

      int_type __c = traits_type::to_int_type(*__this->gptr());

      return __c;

    }

  }

  // If it's a disk file, and if the internal and external character

  // sequences are guaranteed to be identical, then try to use memory

  // mapped I/O.  Otherwise, revert to ordinary read.

  if (__this->_M_base.__regular_file()

      && ((__this->int_flags_ & basic_filebuf<char, char_traits<char> >::_always_noconv) != 0)

      && __this->_M_base._M_in_binary_mode()) {

    // If we've mmapped part of the file already, then unmap it.

    if (__this->_M_mmap_base)

      __this->_M_base._M_unmap(__this->_M_mmap_base, __this->_M_mmap_len);

    // Determine the position where we start mapping.  It has to be

    // a multiple of the page size.

    streamoff __cur = __this->_M_base._M_seek(0, ios_base::cur);

    streamoff __size = __this->_M_base._M_file_size();

    if (__size > 0 && __cur >= 0 && __cur < __size) {

      streamoff __offset = (__cur / __this->_M_base.__page_size()) * __this->_M_base.__page_size();

      streamoff __remainder = __cur - __offset;

      __this->_M_mmap_len = __size - __offset;

      if (__this->_M_mmap_len > MMAP_CHUNK)

        __this->_M_mmap_len = MMAP_CHUNK;

      if ((__this->_M_mmap_base = __this->_M_base._M_mmap(__offset, __this->_M_mmap_len)) != 0) {

        __this->setg(__STATIC_CAST(char*, __this->_M_mmap_base),

                     __STATIC_CAST(char*, __this->_M_mmap_base) + __STATIC_CAST(ptrdiff_t, __remainder),

                     __STATIC_CAST(char*, __this->_M_mmap_base) + __STATIC_CAST(ptrdiff_t, __this->_M_mmap_len));

        return traits_type::to_int_type(*__this->gptr());

      }

      else

        __this->_M_mmap_len = 0;

    }

    else {

      __this->_M_mmap_base = 0;

      __this->_M_mmap_len = 0;

    }

  }

  return __this->_M_underflow_aux();

}

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

// Force instantiation of filebuf and fstream classes.

#if !defined(_STLP_NO_FORCE_INSTANTIATE)

template class basic_filebuf<char, char_traits<char> >;

template class basic_ifstream<char, char_traits<char> >;

template class basic_ofstream<char, char_traits<char> >;

template class basic_fstream<char, char_traits<char> >;

#  if !defined (_STLP_NO_WCHAR_T)

template class _Underflow<wchar_t, char_traits<wchar_t> >;

template class basic_filebuf<wchar_t, char_traits<wchar_t> >;

template class basic_ifstream<wchar_t, char_traits<wchar_t> >;

template class basic_ofstream<wchar_t, char_traits<wchar_t> >;

template class basic_fstream<wchar_t, char_traits<wchar_t> >;

#  endif /* _STLP_NO_WCHAR_T */

#endif

_STLP_END_NAMESPACE