Joerg Sonnenberger wrote:
> Attached is a replacement version of fflush that is the least intrusive
> version I can think of. No further replacements for ftello/fseeko are
> needed. It should work with all BSD derived stdio implementations,
> directly tested are NetBSD and DragonFly.
Thanks for this idea. Eric, here is a proposed patch for gnulib, that
additionally:
- uses the #ifdef for BSD systems,
- not only sets __SNPT but also resets __SOPT. __SOPT tells fseek that
it can use block-alignment as for regular files, __SNPT tells fseek
that it must not do so. Since it is undocumented which of the two
flags is tested first by fseek(), it is safer to reset __SOPT.
- restores the previous flags after calling fseeko. Setting __SNPT
means to disable block-aligned reading for *all* future fseek calls,
but we need it only for the next one.
Tested on MacOS X.
If someone wants to submit a patch handling the __FILE_public, please do
"gnulib-tool --create-testdir --dir=... fbufmode fflush fpurge freadable \
freading fseeko fseterr ftello fwritable fwriting"
to see which files need to be adjusted for this special situation.
Bruno
2007-07-27 Bruno Haible <[EMAIL PROTECTED]>
* lib/fflush.c (rpl_fflush): On BSD systems, use the __SNPT flag.
Suggested by Joerg Sonnenberger <[EMAIL PROTECTED]>.
*** lib/fflush.c 27 Apr 2007 18:05:08 -0000 1.8
--- lib/fflush.c 27 Jul 2007 21:54:28 -0000
***************
*** 77,91 ****
if (result != 0)
return result;
pos = lseek (fileno (stream), pos, SEEK_SET);
if (pos == -1)
return EOF;
/* After a successful lseek, update the file descriptor's position cache
in the stream. */
! #if defined __sferror /* FreeBSD, NetBSD, OpenBSD, MacOS X, Cygwin
*/
stream->_offset = pos;
stream->_flags |= __SOFF;
! #endif
return 0;
}
--- 77,111 ----
if (result != 0)
return result;
+ #if defined __sferror && defined __SNPT /* FreeBSD, NetBSD, OpenBSD, MacOS X,
Cygwin */
+
+ {
+ /* Disable seek optimization for the next fseeko call. This tells the
+ following fseeko call to seek to the desired position directly, rather
+ than to seek to a block-aligned boundary. */
+ int saved_flags = stream->_flags & (__SOPT | __SNPT);
+ stream->_flags &= ~__SOPT;
+ stream->_flags |= __SNPT;
+
+ result = fseeko (stream, pos, SEEK_SET);
+
+ stream->_flags = (stream->_flags & ~(__SOPT | __SNPT)) | saved_flags;
+ }
+ return result;
+
+ #else
+
pos = lseek (fileno (stream), pos, SEEK_SET);
if (pos == -1)
return EOF;
/* After a successful lseek, update the file descriptor's position cache
in the stream. */
! # if defined __sferror /* FreeBSD, NetBSD, OpenBSD, MacOS X, Cygwin
*/
stream->_offset = pos;
stream->_flags |= __SOFF;
! # endif
return 0;
+
+ #endif
}
