cygwin fork()

clayne@anodized.com clayne@anodized.com
Fri Sep 1 17:47:00 GMT 2006


On Fri, Sep 01, 2006 at 01:24:57PM -0400, Christopher Faylor wrote:
> >In regards to setting the fd to textmode as a way of stripping CRs.
> >Only problem is that it's making 213,110 syscalls for a 213k libtool
> >script.  That cannot be an efficient way to remove CRs from input.
> 
> Opening a file with O_TEXT should not, AFAIK, cause a bunch of one-byte
> reads.
> 
> A simple test case (tm) seems to confirm that.
> 
> cgf

You're right. I also verified this.

I found the real culprit, which I had also ifdef'd out because it looked
bogus and crufty:

/* Return 1 if a seek on FD will succeed. */
#ifndef __CYGWIN__
#  define fd_is_seekable(fd) (lseek ((fd), 0L, SEEK_CUR) >= 0)
#else
#  define fd_is_seekable(fd) 0
#endif /* __CYGWIN__ */

/* Take FD, a file descriptor, and create and return a buffered stream
   corresponding to it.  If something is wrong and the file descriptor
   is invalid, return a NULL stream. */
BUFFERED_STREAM *
fd_to_buffered_stream (fd)
     int fd;
{
  char *buffer;
  size_t size;
  struct stat sb;

  if (fstat (fd, &sb) < 0)
    {
      close (fd);
      return ((BUFFERED_STREAM *)NULL);
    }

  size = (fd_is_seekable (fd)) ? min (sb.st_size, MAX_INPUT_BUFFER_SIZE) : 1;
  if (size == 0)
    size = 1;
  buffer = (char *)xmalloc (size);

  return (make_buffered_stream (fd, buffer, size));
}



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