/* fflush.c -- allow flushing input streams
- Copyright (C) 2007 Free Software Foundation, Inc.
+ Copyright (C) 2007-2011 Free Software Foundation, Inc.
- This program is free software; you can redistribute it and/or modify
+ This program 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.
+ the Free Software Foundation; either version 3 of the License, or
+ (at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
- along with this program; if not, write to the Free Software Foundation,
- Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA. */
+ along with this program. If not, see <http://www.gnu.org/licenses/>. */
/* Written by Eric Blake. */
#include <unistd.h>
#include "freading.h"
-#include "fpurge.h"
+
+#include "stdio-impl.h"
#undef fflush
+
+#if defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Haiku, Linux libc5 */
+
+/* Clear the stream's ungetc buffer, preserving the value of ftello (fp). */
+static inline void
+clear_ungetc_buffer_preserving_position (FILE *fp)
+{
+ if (fp->_flags & _IO_IN_BACKUP)
+ /* _IO_free_backup_area is a bit complicated. Simply call fseek. */
+ fseeko (fp, 0, SEEK_CUR);
+}
+
+#else
+
+/* Clear the stream's ungetc buffer. May modify the value of ftello (fp). */
+static inline void
+clear_ungetc_buffer (FILE *fp)
+{
+# if defined __sferror || defined __DragonFly__ /* FreeBSD, NetBSD, OpenBSD, DragonFly, MacOS X, Cygwin */
+ if (HASUB (fp))
+ {
+ fp_->_p += fp_->_r;
+ fp_->_r = 0;
+ }
+# elif defined __EMX__ /* emx+gcc */
+ if (fp->_ungetc_count > 0)
+ {
+ fp->_ungetc_count = 0;
+ fp->_rcount = - fp->_rcount;
+ }
+# elif defined _IOERR /* Minix, AIX, HP-UX, IRIX, OSF/1, Solaris, OpenServer, mingw, NonStop Kernel */
+ /* Nothing to do. */
+# else /* other implementations */
+ fseeko (fp, 0, SEEK_CUR);
+# endif
+}
+
+#endif
+
+#if (defined __sferror || defined __DragonFly__) && defined __SNPT /* FreeBSD, NetBSD, OpenBSD, DragonFly, MacOS X, Cygwin */
+
+static inline int
+disable_seek_optimization (FILE *fp)
+{
+ int saved_flags = fp_->_flags & (__SOPT | __SNPT);
+ fp_->_flags = (fp_->_flags & ~__SOPT) | __SNPT;
+ return saved_flags;
+}
+
+static inline void
+restore_seek_optimization (FILE *fp, int saved_flags)
+{
+ fp_->_flags = (fp_->_flags & ~(__SOPT | __SNPT)) | saved_flags;
+}
+
+#endif
+
+static inline void
+update_fpos_cache (FILE *fp, off_t pos)
+{
+#if defined __sferror || defined __DragonFly__ /* FreeBSD, NetBSD, OpenBSD, DragonFly, MacOS X, Cygwin */
+# if defined __CYGWIN__
+ /* fp_->_offset is typed as an integer. */
+ fp_->_offset = pos;
+# else
+ /* fp_->_offset is an fpos_t. */
+ /* Use a union, since on NetBSD, the compilation flags determine
+ whether fpos_t is typedef'd to off_t or a struct containing a
+ single off_t member. */
+ union
+ {
+ fpos_t f;
+ off_t o;
+ } u;
+ u.o = pos;
+ fp_->_offset = u.f;
+# endif
+ fp_->_flags |= __SOFF;
+#endif
+}
+
/* Flush all pending data on STREAM according to POSIX rules. Both
output and seekable input streams are supported. */
int
rpl_fflush (FILE *stream)
{
- int result;
- off_t pos;
-
/* When stream is NULL, POSIX and C99 only require flushing of "output
streams and update streams in which the most recent operation was not
input", and all implementations do this.
if (stream == NULL || ! freading (stream))
return fflush (stream);
- /* POSIX does not specify fflush behavior for non-seekable input
- streams. Some implementations purge unread data, some return
- EBADF, some do nothing. */
- pos = ftello (stream);
- if (pos == -1)
- {
- errno = EBADF;
- return EOF;
- }
+#if defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Haiku, Linux libc5 */
- /* To get here, we must be flushing a seekable input stream, so the
- semantics of fpurge are now appropriate to clear the buffer. To
- avoid losing data, the lseek is also necessary. */
- result = fpurge (stream);
- if (result != 0)
- return result;
+ clear_ungetc_buffer_preserving_position (stream);
-#if defined __sferror && defined __SNPT /* FreeBSD, NetBSD, OpenBSD, MacOS X, Cygwin */
+ return fflush (stream);
+#else
{
- /* 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 = (stream->_flags & ~__SOPT) | __SNPT;
+ /* Notes about the file-position indicator:
+ 1) The file position indicator is incremented by fgetc() and decremented
+ by ungetc():
+ <http://www.opengroup.org/susv3/functions/fgetc.html>
+ "... the fgetc() function shall ... advance the associated file
+ position indicator for the stream ..."
+ <http://www.opengroup.org/susv3/functions/ungetc.html>
+ "The file-position indicator is decremented by each successful
+ call to ungetc()..."
+ 2) <http://www.opengroup.org/susv3/functions/ungetc.html> says:
+ "The value of the file-position indicator for the stream after
+ reading or discarding all pushed-back bytes shall be the same
+ as it was before the bytes were pushed back."
+ Here we are discarding all pushed-back bytes. But more specifically,
+ 3) <http://www.opengroup.org/austin/aardvark/latest/xshbug3.txt> says:
+ "[After fflush(),] the file offset of the underlying open file
+ description shall be set to the file position of the stream, and
+ any characters pushed back onto the stream by ungetc() ... shall
+ be discarded." */
+
+ /* POSIX does not specify fflush behavior for non-seekable input
+ streams. Some implementations purge unread data, some return
+ EBADF, some do nothing. */
+ off_t pos = ftello (stream);
+ if (pos == -1)
+ {
+ errno = EBADF;
+ return EOF;
+ }
+
+ /* Clear the ungetc buffer. */
+ clear_ungetc_buffer (stream);
+
+ /* To get here, we must be flushing a seekable input stream, so the
+ semantics of fpurge are now appropriate to clear the buffer. To
+ avoid losing data, the lseek is also necessary. */
+ {
+ int result = fpurge (stream);
+ if (result != 0)
+ return result;
+ }
- result = fseeko (stream, pos, SEEK_SET);
+# if (defined __sferror || defined __DragonFly__) && defined __SNPT /* FreeBSD, NetBSD, OpenBSD, DragonFly, MacOS X, Cygwin */
- stream->_flags = (stream->_flags & ~(__SOPT | __SNPT)) | saved_flags;
- }
- return result;
+ {
+ /* 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 = disable_seek_optimization (stream);
+ int result = fseeko (stream, pos, SEEK_SET);
+
+ restore_seek_optimization (stream, saved_flags);
+ return result;
+ }
-#else
+# 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
+ 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. */
+ update_fpos_cache (stream, pos);
- return 0;
+ return 0;
+# endif
+ }
#endif
}