postypes.h

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// Position types -*- C++ -*-

// Copyright (C) 1997, 1998, 1999, 2000, 2001, 2003, 2004
// Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 2, or (at your option)
// any later version.

// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.

// You should have received a copy of the GNU General Public License along
// with this library; see the file COPYING.  If not, write to the Free
// Software Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307,
// USA.

// As a special exception, you may use this file as part of a free software
// library without restriction.  Specifically, if other files instantiate
// templates or use macros or inline functions from this file, or you compile
// this file and link it with other files to produce an executable, this
// file does not by itself cause the resulting executable to be covered by
// the GNU General Public License.  This exception does not however
// invalidate any other reasons why the executable file might be covered by
// the GNU General Public License.

//
// ISO C++ 14882: 27.4.1 - Types
// ISO C++ 14882: 27.4.3 - Template class fpos
//

#ifndef _GLIBCXX_POSTYPES_H
#define _GLIBCXX_POSTYPES_H 1

#pragma GCC system_header

#include <cwchar> // For mbstate_t

#ifdef _GLIBCXX_HAVE_STDINT_H
#include <stdint.h> // For int64_t
#endif

namespace std
{
  // The types streamoff, streampos and wstreampos and the class
  // template fpos<> are described in clauses 21.1.2, 21.1.3, 27.1.2,
  // 27.2, 27.4.1, 27.4.3 and D.6. Despite all this verbage, the
  // behaviour of these types is mostly implementation defined or
  // unspecified. The behaviour in this implementation is as noted
  // below.

#ifdef _GLIBCXX_HAVE_INT64_T
  typedef int64_t       streamoff;
#else
  typedef long long     streamoff;
#endif

  typedef ptrdiff_t streamsize; // Signed integral type

  template<typename _StateT>
    class fpos;

  template<typename _StateT>
    class fpos
    {
    private:
      streamoff                 _M_off;
      _StateT           _M_state;

    public:
      // The standard doesn't require that fpos objects can be default
      // constructed. This implementation provides a default
      // constructor that initializes the offset to 0 and default
      // constructs the state.
      fpos()
      : _M_off(0), _M_state() { }

      // The standard requires that fpos objects can be constructed
      // from streamoff objects using the constructor syntax, and
      // fails to give any meaningful semantics. In this
      // implementation implicit conversion is also allowed, and this
      // constructor stores the streamoff as the offset and default
      // constructs the state.
      fpos(streamoff __off)
      : _M_off(__off), _M_state() { }

      operator streamoff() const { return _M_off; }

      void
      state(_StateT __st)
      { _M_state = __st; }

      _StateT
      state() const
      { return _M_state; }

      // The standard only requires that operator== must be an
      // equivalence relation. In this implementation two fpos<StateT>
      // objects belong to the same equivalence class if the contained
      // offsets compare equal.
      bool
      operator==(const fpos& __other) const
      { return _M_off == __other._M_off; }

      bool
      operator!=(const fpos& __other) const
      { return _M_off != __other._M_off; }

      // The standard requires that this operator must be defined, but
      // gives no semantics. In this implemenation it just adds it's
      // argument to the stored offset and returns *this.
      fpos&
      operator+=(streamoff __off)
      {
    _M_off += __off;
    return *this;
      }

      // The standard requires that this operator must be defined, but
      // gives no semantics. In this implemenation it just subtracts
      // it's argument from the stored offset and returns *this.
      fpos&
      operator-=(streamoff __off)
      {
    _M_off -= __off;
    return *this;
      }

      // The standard requires that this operator must be defined, but
      // defines it's semantics only in terms of operator-. In this
      // implementation it constructs a copy of *this, adds the
      // argument to that copy using operator+= and then returns the
      // copy.
      fpos
      operator+(streamoff __off) const
      {
    fpos __pos(*this);
    __pos += __off;
    return __pos;
      }

      // The standard requires that this operator must be defined, but
      // defines it's semantics only in terms of operator+. In this
      // implementation it constructs a copy of *this, subtracts the
      // argument from that copy using operator-= and then returns the
      // copy.
      fpos
      operator-(streamoff __off) const
      {
    fpos __pos(*this);
    __pos -= __off;
    return __pos;
      }

      // The standard requires that this operator must be defined, but
      // defines it's semantics only in terms of operator+. In this
      // implementation it returns the difference between the offset
      // stored in *this and in the argument.
      streamoff
      operator-(const fpos& __other) const
      { return _M_off - __other._M_off; }
    };

  // Clauses 21.1.3.1 and 21.1.3.2 describe streampos and wstreampos
  // as implementation defined types, but clause 27.2 requires that
  // they must both be typedefs for fpos<mbstate_t>
  typedef fpos<mbstate_t> streampos;
  typedef fpos<mbstate_t> wstreampos;
} // namespace std

#endif

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