boost/iostreams/positioning.hpp

   1 // (C) Copyright 2008 CodeRage, LLC (turkanis at coderage dot com)
   2 // (C) Copyright 2003-2007 Jonathan Turkanis
   3 // Distributed under the Boost Software License, Version 1.0. (See accompanying
   4 // file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt.)
   5
   6 // See http://www.boost.org/libs/iostreams for documentation.
   7
   8 // Thanks to Gareth Sylvester-Bradley for the Dinkumware versions of the
   9 // positioning functions.
  10
  11 #ifndef BOOST_IOSTREAMS_POSITIONING_HPP_INCLUDED
  12 #define BOOST_IOSTREAMS_POSITIONING_HPP_INCLUDED
  13
  14 #if defined(_MSC_VER) && (_MSC_VER >= 1020)
  15 # pragma once
  16 #endif
  17
  18 #include <boost/config.hpp>
  19 #include <boost/cstdint.hpp>
  20 #include <boost/integer_traits.hpp>
  21 #include <boost/iostreams/detail/config/codecvt.hpp> // mbstate_t.
  22 #include <boost/iostreams/detail/config/fpos.hpp>
  23 #include <boost/iostreams/detail/ios.hpp> // streamoff, streampos.
  24
  25 // Must come last.
  26 #include <boost/iostreams/detail/config/disable_warnings.hpp>
  27
  28 #ifdef BOOST_NO_STDC_NAMESPACE
  29 namespace std { using ::fpos_t; }
  30 #endif
  31
  32 namespace boost { namespace iostreams {
  33
  34 //------------------Definition of stream_offset-------------------------------//
  35
  36 typedef boost::intmax_t stream_offset;
  37
  38 //------------------Definition of stream_offset_to_streamoff------------------//
  39
  40 inline std::streamoff stream_offset_to_streamoff(stream_offset off)
  41 { return static_cast<stream_offset>(off); }
  42
  43 //------------------Definition of offset_to_position--------------------------//
  44
  45 # ifndef BOOST_IOSTREAMS_HAS_DINKUMWARE_FPOS
  46
  47 inline std::streampos offset_to_position(stream_offset off) { return off; }
  48
  49 # else // # ifndef BOOST_IOSTREAMS_HAS_DINKUMWARE_FPOS
  50
  51 inline std::streampos offset_to_position(stream_offset off)
  52 { return std::streampos(std::mbstate_t(), off); }
  53
  54 # endif // # ifndef BOOST_IOSTREAMS_HAS_DINKUMWARE_FPOS
  55
  56 //------------------Definition of position_to_offset--------------------------//
  57
  58 // Hande custom pos_type's
  59 template<typename PosType>
  60 inline stream_offset position_to_offset(PosType pos)
  61 { return std::streamoff(pos); }
  62
  63 # ifndef BOOST_IOSTREAMS_HAS_DINKUMWARE_FPOS
  64
  65 inline stream_offset position_to_offset(std::streampos pos) { return pos; }
  66
  67 # else // # ifndef BOOST_IOSTREAMS_HAS_DINKUMWARE_FPOS
  68
  69 // In the Dinkumware standard library, a std::streampos consists of two stream
  70 // offsets -- _Fpos, of type std::fpos_t, and _Myoff, of type std::streamoff --
  71 // together with a conversion state. A std::streampos is converted to a
  72 // boost::iostreams::stream_offset by extracting the two stream offsets and
  73 // summing them. The value of _Fpos can be extracted using the implementation-
  74 // defined member functions seekpos() or get_fpos_t(), depending on the
  75 // Dinkumware version. The value of _Myoff cannot be extracted directly, but can
  76 // be calculated as the difference between the result of converting the
  77 // std::fpos to a std::streamoff and the result of converting the member _Fpos
  78 // to a long. The latter operation is accomplished with the macro _FPOSOFF,
  79 // which works correctly on platforms where std::fpos_t is an integral type and
  80 // platforms where it is a struct
  81
  82 // Converts a std::fpos_t to a stream_offset
  83 inline stream_offset fpos_t_to_offset(std::fpos_t pos)
  84 {
  85 #  if defined(_POSIX_) || (_INTEGRAL_MAX_BITS >= 64) || defined(__IBMCPP__)
  86     return pos;
  87 #  else
  88     return _FPOSOFF(pos);
  89 #  endif
  90 }
  91
  92 // Extracts the member _Fpos from a std::fpos
  93 inline std::fpos_t streampos_to_fpos_t(std::streampos pos)
  94 {
  95 #  if defined (_CPPLIB_VER) || defined(__IBMCPP__)
  96     return pos.seekpos();
  97 #  else
  98     return pos.get_fpos_t();
  99 #  endif
 100 }
 101
 102 inline stream_offset position_to_offset(std::streampos pos)
 103 {
 104     return fpos_t_to_offset(streampos_to_fpos_t(pos)) +
 105            static_cast<stream_offset>(static_cast<std::streamoff>(pos)) -
 106            static_cast<stream_offset>(_FPOSOFF(streampos_to_fpos_t(pos)));
 107 }
 108
 109 # endif // # ifndef BOOST_IOSTREAMS_HAS_DINKUMWARE_FPOS
 110
 111 } } // End namespaces iostreams, boost.
 112
 113 #include <boost/iostreams/detail/config/enable_warnings.hpp>
 114
 115 #endif // #ifndef BOOST_IOSTREAMS_POSITIONING_HPP_INCLUDED