fstream_win32io.cpp

来自「stl的源码」· C++ 代码 · 共 630 行 · 第 1/2 页

  _M_regular_file = _STLP_PRIV __is_regular_file(_M_file_id);

  return true;
#else
  (void)__id;
  (void)init_mode;    // dwa 4/27/00 - suppress unused parameter warning

  // not available for the API
  return false;

#endif
}

// Associated the filebuf with a file descriptor pointing to an already-
// open file.  Mode is set to be consistent with the way that the file
// was opened.
bool _Filebuf_base::_M_open(int file_no, ios_base::openmode init_mode) {
  if (_M_is_open || file_no < 0)
    return false;

#if (defined (_STLP_MSVC_LIB) && !defined (_STLP_WCE)) || \
    (defined (__MINGW32__) && defined (__MSVCRT__)) || defined (__DMC__)

  HANDLE oshandle = (HANDLE)_get_osfhandle(file_no);
  if (oshandle == INVALID_STLP_FD)
    return false;

  if (init_mode != ios_base::__default_mode)
    _M_openmode = init_mode;
  else
    _M_openmode = _get_osfflags(file_no, oshandle);

  _M_file_id = oshandle;
  _M_is_open = true;
  _M_should_close = false;
  _M_regular_file = _STLP_PRIV __is_regular_file(_M_file_id);
  return true;
#else
  _STLP_MARK_PARAMETER_AS_UNUSED(&init_mode)
  // not available for the API
  return false;
#endif
}

bool _Filebuf_base::_M_close() {
  if (!_M_is_open)
    return false;

  bool ok;

  if (!_M_should_close)
    ok = true;
  else {
    if (_M_file_id != INVALID_STLP_FD) {
      ok = (CloseHandle(_M_file_id) != 0);
    }
    else {
      ok = false;
    }
  }

  _M_is_open = _M_should_close = false;
  _M_openmode = 0;
  return ok;
}


#define _STLP_LF 10
#define _STLP_CR 13
#define _STLP_CTRLZ 26

// Read up to n characters into a buffer.  Return value is number of
// characters read.
ptrdiff_t _Filebuf_base::_M_read(char* buf, ptrdiff_t n) {
  ptrdiff_t readen = 0;
  //Here cast to size_t is safe as n cannot be negative.
  size_t chunkSize = (min)(size_t(0xffffffff), __STATIC_CAST(size_t, n));
  // The following, while validating that we are still able to extract chunkSize
  // charaters to the buffer, avoids extraction of too small chunk of datas
  // which would be counter performant.
  while (__STATIC_CAST(size_t, (n - readen)) >= chunkSize) {
    DWORD numberOfBytesRead;
    ReadFile(_M_file_id, buf + readen, __STATIC_CAST(DWORD, chunkSize), &numberOfBytesRead, 0);

    if (numberOfBytesRead == 0)
      break;

    if (!(_M_openmode & ios_base::binary)) {
      // translate CR-LFs to LFs in the buffer
      char *to = buf + readen;
      char *from = to;
      char *last = from + numberOfBytesRead - 1;
      for (; from <= last && *from != _STLP_CTRLZ; ++from) {
        if (*from != _STLP_CR)
          *to++ = *from;
        else { // found CR
          if (from < last) { // not at buffer end
            if (*(from + 1) != _STLP_LF)
              *to++ = _STLP_CR;
          }
          else { // last char is CR, peek for LF
            char peek = ' ';
            DWORD NumberOfBytesPeeked;
            ReadFile(_M_file_id, (LPVOID)&peek, 1, &NumberOfBytesPeeked, 0);
            if (NumberOfBytesPeeked != 0) {
              if (peek != _STLP_LF) { //not a <CR><LF> combination
                *to++ = _STLP_CR;
                if ((to < buf + n) && (peek != _STLP_CR))
                  //We have enough place to store peek and it is no a special
                  //_STLP_CR character, we can store it.
                  *to++ = peek;
                else
                  SetFilePointer(_M_file_id, (LONG)-1, 0, FILE_CURRENT);
              }
              else {
                // A <CR><LF> combination, we keep the <LF>:
                *to++ = _STLP_LF;
              }
            }
            else {
              /* This case is tedious, we could
               *  - put peek back in the file but this would then generate an infinite loop
               *  - report an error as we don't know if in a future call to ReadFile we won't then
               *    get a <LF>. Doing so would make all files with a <CR> last an invalid file
               *    for STLport, a hard solution for STLport clients.
               *  - store the <CR> in the returned buffer, the chosen solution, even if in this
               *    case we could miss a <CR><LF> combination.
               */
              *to++ = _STLP_CR;
            }
          }
        } // found CR
      } // for
      readen = to - buf;
      // seek back to TEXT end of file if hit CTRL-Z
      if (from <= last) { // terminated due to CTRLZ
        SetFilePointer(_M_file_id, -(LONG)((last + 1) - from), 0, FILE_CURRENT);
        break;
      }
    }
    else
      readen += numberOfBytesRead;
  }
  return readen;
}

// Write n characters from a buffer.  Return value: true if we managed
// to write the entire buffer, false if we didn't.
bool _Filebuf_base::_M_write(char* buf, ptrdiff_t n) {
  for (;;) {
    ptrdiff_t written;

    //In the following implementation we are going to cast most of the ptrdiff_t
    //values in size_t to work with coherent unsigned values. Doing so make code
    //more simple especially in the min function call.

    // In append mode, every write does an implicit seek to the end
    // of the file.
    if (_M_openmode & ios_base::app)
      _M_seek(0, ios_base::end);

    if (_M_openmode & ios_base::binary) {
      // binary mode
      size_t bytes_to_write = (size_t)n;
      DWORD NumberOfBytesWritten;
      written = 0;
      for (; bytes_to_write != 0;) {
        WriteFile(_M_file_id, buf + written,
                  __STATIC_CAST(DWORD, (min)(size_t(0xffffffff), bytes_to_write)),
                  &NumberOfBytesWritten, 0);
        if (NumberOfBytesWritten == 0)
          return false;
        bytes_to_write -= NumberOfBytesWritten;
        written += NumberOfBytesWritten;
      }
    }
    else {
      char textbuf[_TEXTBUF_SIZE + 1]; // extra 1 in case LF at end
      char * nextblock = buf, * ptrtextbuf = textbuf;
      char * endtextbuf = textbuf + _TEXTBUF_SIZE;
      char * endblock = buf + n;
      ptrdiff_t nextblocksize = (min) (n, (ptrdiff_t)_TEXTBUF_SIZE);
      char * nextlf;

      while ( (nextblocksize > 0) &&
              (nextlf = (char *)memchr(nextblock, _STLP_LF, nextblocksize)) != 0) {
        ptrdiff_t linelength = nextlf - nextblock;
        memcpy(ptrtextbuf, nextblock, linelength);
        ptrtextbuf += linelength;
        nextblock += (linelength + 1);
        * ptrtextbuf ++ = _STLP_CR;
        * ptrtextbuf ++ = _STLP_LF;
        nextblocksize = (min) (ptrdiff_t(endblock - nextblock),
                               (max) (ptrdiff_t(0), ptrdiff_t(endtextbuf - ptrtextbuf)));
      }
      // write out what's left, > condition is here since for LF at the end ,
      // endtextbuf may get < ptrtextbuf ...
      if (nextblocksize > 0) {
        memcpy(ptrtextbuf, nextblock, nextblocksize);
        ptrtextbuf += nextblocksize;
        nextblock += nextblocksize;
      }
      // now write out the translated buffer
      char * writetextbuf = textbuf;
      for (size_t NumberOfBytesToWrite = (size_t)(ptrtextbuf - textbuf);
           NumberOfBytesToWrite;) {
        DWORD NumberOfBytesWritten;
        WriteFile((HANDLE)_M_file_id, writetextbuf,
                  __STATIC_CAST(DWORD, (min)(size_t(0xffffffff), NumberOfBytesToWrite)),
                  &NumberOfBytesWritten, 0);
        if (!NumberOfBytesWritten) // write shortfall
          return false;
        writetextbuf += NumberOfBytesWritten;
        NumberOfBytesToWrite -= NumberOfBytesWritten;
      }
      // count non-translated characters
      written = (nextblock - buf);
    }

    if (n == written)
      return true;
    else if (written > 0 && written < n) {
      n -= written;
      buf += written;
    }
    else
      return false;
  }
}

// Wrapper for lseek or the like.
streamoff _Filebuf_base::_M_seek(streamoff offset, ios_base::seekdir dir) {
  streamoff result = -1;
  int whence;

  switch(dir) {
  case ios_base::beg:
    if (offset < 0 /* || offset > _M_file_size() */ )
      return streamoff(-1);
    whence = FILE_BEGIN;
    break;
  case ios_base::cur:
    whence = FILE_CURRENT;
    break;
  case ios_base::end:
    if (/* offset > 0 || */  -offset > _M_file_size() )
      return streamoff(-1);
    whence = FILE_END;
    break;
  default:
    return streamoff(-1);
  }

  LARGE_INTEGER li;
  li.QuadPart = offset;
  li.LowPart = SetFilePointer(_M_file_id, li.LowPart, &li.HighPart, whence);
  if (li.LowPart != INVALID_SET_FILE_POINTER || GetLastError() == NO_ERROR)
    result = li.QuadPart;

  return result;
}


// Attempts to memory-map len bytes of the current file, starting
// at position offset.  Precondition: offset is a multiple of the
// page size.  Postcondition: return value is a null pointer if the
// memory mapping failed.  Otherwise the return value is a pointer to
// the memory-mapped file and the file position is set to offset.
void* _Filebuf_base::_M_mmap(streamoff offset, streamoff len) {
  void* base;
  _M_view_id = CreateFileMapping(_M_file_id, (PSECURITY_ATTRIBUTES)0 ,
                                 PAGE_READONLY, 0 /* len >> 32 */ ,
                                 0 /* len & 0xFFFFFFFF */ , // low-order DWORD of size
                                 0);

  if (_M_view_id) {
#if 0
/*
    printf("view %x created from file %x, error = %d, size = %d, map_offset = %d map_len = %d\n",
     _M_view_id, _M_file_id, GetLastError(),
     (int)cur_filesize, ULL(offset) & 0xffffffff, len);
*/
#endif
    LARGE_INTEGER li;
    li.QuadPart = offset;
    base = MapViewOfFile(_M_view_id, FILE_MAP_READ, li.HighPart, li.LowPart,
#if !defined (__DMC__)
                         __STATIC_CAST(SIZE_T, len));
#else
                         __STATIC_CAST(DWORD, len));
#endif
    // check if mapping succeded and is usable
    if (base == 0  || _M_seek(offset + len, ios_base::beg) < 0) {
      this->_M_unmap(base, len);
      base = 0;
    }
  } else
    base = 0;

  return base;
}

void _Filebuf_base::_M_unmap(void* base, streamoff len) {
  // precondition : there is a valid mapping at the moment
  if (base != NULL)
    UnmapViewOfFile(base);
  // destroy view handle as well
  if (_M_view_id != NULL)
    CloseHandle(_M_view_id);
  _M_view_id = NULL;
  (void)len; //unused variable
}

_STLP_END_NAMESPACE