_fstream.c

stl的源码

/*
 * Copyright (c) 1996,1997
 * 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.
 *
 */
#ifndef _STLP_FSTREAM_C
#define _STLP_FSTREAM_C

#ifndef _STLP_INTERNAL_FSTREAM_H
#  include <stl/_fstream.h>
#endif

#ifndef _STLP_INTERNAL_LIMITS
#  include <stl/_limits.h>
#endif

_STLP_BEGIN_NAMESPACE

# if defined ( _STLP_NESTED_TYPE_PARAM_BUG )
// no wchar_t is supported for this mode
# define __BF_int_type__ int
# define __BF_pos_type__ streampos
# define __BF_off_type__ streamoff
# else
# define __BF_int_type__ _STLP_TYPENAME_ON_RETURN_TYPE basic_filebuf<_CharT, _Traits>::int_type
# define __BF_pos_type__ _STLP_TYPENAME_ON_RETURN_TYPE basic_filebuf<_CharT, _Traits>::pos_type
# define __BF_off_type__ _STLP_TYPENAME_ON_RETURN_TYPE basic_filebuf<_CharT, _Traits>::off_type
# endif


//----------------------------------------------------------------------
// Public basic_filebuf<> member functions

template <class _CharT, class _Traits>
basic_filebuf<_CharT, _Traits>::basic_filebuf()
     :  basic_streambuf<_CharT, _Traits>(), _M_base(),
    _M_constant_width(false), _M_always_noconv(false),
    _M_int_buf_dynamic(false),
    _M_in_input_mode(false), _M_in_output_mode(false),
    _M_in_error_mode(false), _M_in_putback_mode(false),
    _M_int_buf(0), _M_int_buf_EOS(0),
    _M_ext_buf(0), _M_ext_buf_EOS(0),
    _M_ext_buf_converted(0), _M_ext_buf_end(0),
    _M_state(_STLP_DEFAULT_CONSTRUCTED(_State_type)),
    _M_end_state(_STLP_DEFAULT_CONSTRUCTED(_State_type)),
    _M_mmap_base(0), _M_mmap_len(0),
    _M_saved_eback(0), _M_saved_gptr(0), _M_saved_egptr(0),
    _M_codecvt(0),
    _M_width(1), _M_max_width(1)
{
  this->_M_setup_codecvt(locale(), false);
}

template <class _CharT, class _Traits>
basic_filebuf<_CharT, _Traits>::~basic_filebuf() {
  this->close();
  _M_deallocate_buffers();
}


template <class _CharT, class _Traits>
_STLP_TYPENAME_ON_RETURN_TYPE basic_filebuf<_CharT, _Traits>::int_type
basic_filebuf<_CharT, _Traits>::underflow() {
  return _Underflow<_CharT, _Traits>::_M_doit(this);
}

template <class _CharT, class _Traits>
basic_filebuf<_CharT, _Traits>*
basic_filebuf<_CharT, _Traits>::close() {
  bool __ok = this->is_open();

  if (_M_in_output_mode) {
    __ok = __ok && !_Traits::eq_int_type(this->overflow(traits_type::eof()),
                                         traits_type::eof());
    __ok == __ok && this->_M_unshift();
  }
  else if (_M_in_input_mode)
      this->_M_exit_input_mode();

  // Note order of arguments.  We close the file even if __ok is false.
  __ok = _M_base._M_close() && __ok;

  // Restore the initial state, except that we don't deallocate the buffer
  // or mess with the cached codecvt information.
  _M_state = _M_end_state = _State_type();
  _M_ext_buf_converted = _M_ext_buf_end = 0;

  _M_mmap_base = 0;
  _M_mmap_len = 0;

  this->setg(0, 0, 0);
  this->setp(0, 0);

  _M_saved_eback = _M_saved_gptr = _M_saved_egptr = 0;

  _M_in_input_mode = _M_in_output_mode = _M_in_error_mode = _M_in_putback_mode
    = false;

  return __ok ? this : 0;
}

// This member function is called whenever we exit input mode.
// It unmaps the memory-mapped file, if any, and sets
// _M_in_input_mode to false.
template <class _CharT, class _Traits>
void basic_filebuf<_CharT, _Traits>::_M_exit_input_mode() {
  if (_M_mmap_base != 0) {
    _M_base._M_unmap(_M_mmap_base, _M_mmap_len);
    _M_mmap_base = 0;
    _M_mmap_len = 0;
  }
  _M_in_input_mode = false;
}


//----------------------------------------------------------------------
// basic_filebuf<> overridden protected virtual member functions

template <class _CharT, class _Traits>
streamsize basic_filebuf<_CharT, _Traits>::showmanyc() {
  // Is there any possibility that reads can succeed?
  if (!this->is_open() || _M_in_output_mode || _M_in_error_mode)
    return -1;
  else if (_M_in_putback_mode)
    return this->egptr() - this->gptr();
  else if (_M_constant_width) {
    streamoff __pos  = _M_base._M_seek(0, ios_base::cur);
    streamoff __size = _M_base._M_file_size();
    return __pos >= 0 && __size > __pos ? __size - __pos : 0;
  }
  else
    return 0;
}


// Make a putback position available, if necessary, by switching to a
// special internal buffer used only for putback.  The buffer is
// [_M_pback_buf, _M_pback_buf + _S_pback_buf_size), but the base
// class only sees a piece of it at a time.  (We want to make sure
// that we don't try to read a character that hasn't been initialized.)
// The end of the putback buffer is always _M_pback_buf + _S_pback_buf_size,
// but the beginning is usually not _M_pback_buf.
template <class _CharT, class _Traits>
__BF_int_type__
basic_filebuf<_CharT, _Traits>::pbackfail(int_type __c) {
  const int_type __eof = traits_type::eof();

  // If we aren't already in input mode, pushback is impossible.
  if (!_M_in_input_mode)
    return __eof;

  // We can use the ordinary get buffer if there's enough space, and
  // if it's a buffer that we're allowed to write to.
  if (this->gptr() != this->eback() &&
      (traits_type::eq_int_type(__c, __eof) ||
       traits_type::eq(traits_type::to_char_type(__c), this->gptr()[-1]) ||
       !_M_mmap_base)) {
    this->gbump(-1);
    if (traits_type::eq_int_type(__c, __eof) ||
        traits_type::eq(traits_type::to_char_type(__c), *this->gptr()))
      return traits_type::to_int_type(*this->gptr());
  }
  else if (!traits_type::eq_int_type(__c, __eof)) {
    // Are we in the putback buffer already?
    _CharT* __pback_end = _M_pback_buf + __STATIC_CAST(int,_S_pback_buf_size);
    if (_M_in_putback_mode) {
      // Do we have more room in the putback buffer?
      if (this->eback() != _M_pback_buf)
        this->setg(this->egptr() - 1, this->egptr() - 1, __pback_end);
      else
        return __eof;           // No more room in the buffer, so fail.
    }
    else {                      // We're not yet in the putback buffer.
      _M_saved_eback = this->eback();
      _M_saved_gptr  = this->gptr();
      _M_saved_egptr = this->egptr();
      this->setg(__pback_end - 1, __pback_end - 1, __pback_end);
      _M_in_putback_mode = true;
    }
  }
  else
    return __eof;

  // We have made a putback position available.  Assign to it, and return.
  *this->gptr() = traits_type::to_char_type(__c);
  return __c;
}

// This member function flushes the put area, and also outputs the
// character __c (unless __c is eof).  Invariant: we always leave room
// in the internal buffer for one character more than the base class knows
// about.  We see the internal buffer as [_M_int_buf, _M_int_buf_EOS), but
// the base class only sees [_M_int_buf, _M_int_buf_EOS - 1).
template <class _CharT, class _Traits>
__BF_int_type__
basic_filebuf<_CharT, _Traits>::overflow(int_type __c) {
  // Switch to output mode, if necessary.
  if (!_M_in_output_mode)
    if (!_M_switch_to_output_mode())
      return traits_type::eof();

  _CharT* __ibegin = this->_M_int_buf;
  _CharT* __iend   = this->pptr();
  this->setp(_M_int_buf, _M_int_buf_EOS - 1);

  // Put __c at the end of the internal buffer.
  if (!traits_type::eq_int_type(__c, traits_type::eof()))
    *__iend++ = _Traits::to_char_type(__c);

  // For variable-width encodings, output may take more than one pass.
  while (__ibegin != __iend) {
    const _CharT* __inext = __ibegin;
    char* __enext         = _M_ext_buf;
    typename _Codecvt::result __status
      = _M_codecvt->out(_M_state, __ibegin, __iend, __inext,
                        _M_ext_buf, _M_ext_buf_EOS, __enext);
    if (__status == _Codecvt::noconv) {
      return _Noconv_output<_Traits>::_M_doit(this, __ibegin, __iend)
        ? traits_type::not_eof(__c)
        : _M_output_error();
    }

    // For a constant-width encoding we know that the external buffer
    // is large enough, so failure to consume the entire internal buffer
    // or to produce the correct number of external characters, is an error.
    // For a variable-width encoding, however, we require only that we
    // consume at least one internal character
    else if (__status != _Codecvt::error &&
             (((__inext == __iend) &&
               (__enext - _M_ext_buf == _M_width * (__iend - __ibegin))) ||
              (!_M_constant_width && __inext != __ibegin))) {
        // We successfully converted part or all of the internal buffer.
      ptrdiff_t __n = __enext - _M_ext_buf;
      if (_M_write(_M_ext_buf, __n))
        __ibegin += __inext - __ibegin;
      else
        return _M_output_error();
    }
    else
      return _M_output_error();
  }

  return traits_type::not_eof(__c);
}

// This member function must be called before any I/O has been
// performed on the stream, otherwise it has no effect.
//
// __buf == 0 && __n == 0 means to make this stream unbuffered.
// __buf != 0 && __n > 0 means to use __buf as the stream's internal
// buffer, rather than the buffer that would otherwise be allocated
// automatically.  __buf must be a pointer to an array of _CharT whose
// size is at least __n.
template <class _CharT, class _Traits>
basic_streambuf<_CharT, _Traits>*
basic_filebuf<_CharT, _Traits>::setbuf(_CharT* __buf, streamsize __n) {
  if (!_M_in_input_mode &&! _M_in_output_mode && !_M_in_error_mode &&
      _M_int_buf == 0) {
    if (__buf == 0 && __n == 0)
      _M_allocate_buffers(0, 1);
    else if (__buf != 0 && __n > 0)
      _M_allocate_buffers(__buf, __n);
  }
  return this;
}

#if defined (_STLP_ASSERTIONS)
// helper class.
template <class _CharT>
struct _Filebuf_Tmp_Buf {
  _CharT* _M_ptr;
  _Filebuf_Tmp_Buf(ptrdiff_t __n) : _M_ptr(0) { _M_ptr = new _CharT[__n]; }
  ~_Filebuf_Tmp_Buf() { delete[] _M_ptr; }
};
#endif

template <class _CharT, class _Traits>
__BF_pos_type__
basic_filebuf<_CharT, _Traits>::seekoff(off_type __off,
                                        ios_base::seekdir __whence,
                                        ios_base::openmode /* dummy */) {
  if (!this->is_open())
    return pos_type(-1);

  if (!_M_constant_width && __off != 0)
    return pos_type(-1);

  if (!_M_seek_init(__off != 0 || __whence != ios_base::cur))
    return pos_type(-1);

  // Seek to beginning or end, regardless of whether we're in input mode.
  if (__whence == ios_base::beg || __whence == ios_base::end)
    return _M_seek_return(_M_base._M_seek(_M_width * __off, __whence),
                          _State_type());

  // Seek relative to current position.  Complicated if we're in input mode.
  _STLP_ASSERT(__whence == ios_base::cur)
  if (!_M_in_input_mode)
    return _M_seek_return(_M_base._M_seek(_M_width * __off, __whence),
                          _State_type());

  if (_M_mmap_base != 0) {
    // __off is relative to gptr().  We need to do a bit of arithmetic
    // to get an offset relative to the external file pointer.
    streamoff __adjust = _M_mmap_len - (this->gptr() - (_CharT*) _M_mmap_base);

    // if __off == 0, we do not need to exit input mode and to shift file pointer
    return __off == 0 ? pos_type(_M_base._M_seek(0, ios_base::cur) - __adjust)
                      : _M_seek_return(_M_base._M_seek(__off - __adjust, ios_base::cur), _State_type());
  }

  if (_M_constant_width) { // Get or set the position.
    streamoff __iadj = _M_width * (this->gptr() - this->eback());

    // Compensate for offset relative to gptr versus offset relative
    // to external pointer.  For a text-oriented stream, where the
    // compensation is more than just pointer arithmetic, we may get
    // but not set the current position.

    if (__iadj <= _M_ext_buf_end - _M_ext_buf) {
      streamoff __eadj =  _M_base._M_get_offset(_M_ext_buf + __STATIC_CAST(ptrdiff_t, __iadj), _M_ext_buf_end);

      return __off == 0 ? pos_type(_M_base._M_seek(0, ios_base::cur) - __eadj)
                        : _M_seek_return(_M_base._M_seek(__off - __eadj, ios_base::cur), _State_type());
    }
  }
  else {                    // Get the position.  Encoding is var width.
    // Get position in internal buffer.
    ptrdiff_t __ipos = this->gptr() - this->eback();

    // Get corresponding position in external buffer.
    _State_type __state = _M_state;
    int __epos = _M_codecvt->length(__state, _M_ext_buf, _M_ext_buf_converted,
                                    __ipos);
#if defined (_STLP_ASSERTIONS)
    // Sanity check (expensive): make sure __epos is the right answer.
    _STLP_ASSERT(__epos >= 0)
    _State_type __tmp_state = _M_state;
    _Filebuf_Tmp_Buf<_CharT> __buf(__ipos);
    _CharT* __ibegin = __buf._M_ptr;
    _CharT* __inext  = __ibegin;
    const char* __dummy;
    typename _Codecvt::result __status
      = _M_codecvt->in(__tmp_state,
                       _M_ext_buf, _M_ext_buf + __epos, __dummy,
                       __ibegin, __ibegin + __ipos, __inext);
    // The result code is necessarily ok because:
    // - noconv: impossible for a variable encoding
    // - error: length method is supposed to count until it reach max value or find an error so we cannot have
    //          an error again when decoding an external buffer up to length return value.
    // - partial: idem error, it is also a reason for length to stop counting.
    _STLP_ASSERT(__status == _Codecvt::ok)
    _STLP_ASSERT(__inext == __ibegin + __ipos)
    _STLP_ASSERT(equal(this->eback(), this->gptr(), __ibegin, _STLP_PRIV _Eq_traits<traits_type>()))
#endif
    // Get the current position (at the end of the external buffer),
    // then adjust it.  Again, it might be a text-oriented stream.
    streamoff __cur = _M_base._M_seek(0, ios_base::cur);
    streamoff __adj = _M_base._M_get_offset(_M_ext_buf, _M_ext_buf + __epos) -
                      _M_base._M_get_offset(_M_ext_buf, _M_ext_buf_end);
    if (__cur != -1 && __cur + __adj >= 0)
      return __off == 0 ? pos_type(__cur + __adj)
                        : _M_seek_return(__cur + __adj, __state);
  }

  return pos_type(-1);
}


template <class _CharT, class _Traits>
__BF_pos_type__
basic_filebuf<_CharT, _Traits>::seekpos(pos_type __pos,