Port to GNU/kFreeBSD - FreeBSD kernel + GNU libc,

[gnulib.git] / lib / fflush.c

diff --git a/lib/fflush.c b/lib/fflush.c
old mode 100755 (executable)
new mode 100644 (file)
index 9361c09..be97769
--- a/lib/fflush.c
+++ b/lib/fflush.c
@@ -1,10 +1,10 @@
 /* fflush.c -- allow flushing input streams
    Copyright (C) 2007 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
@@ -12,8 +12,7 @@
    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. */
 
@@ -38,15 +37,31 @@ rpl_fflush (FILE *stream)
   int result;
   off_t pos;
 
-  /* When stream is NULL, POSIX only requires flushing of output
-     streams.  C89 guarantees behavior of output streams, and fflush
-     should be safe on read-write streams that are not currently
-     reading.  */
-  if (! stream || ! freading (stream))
+  /* 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.
+
+     When stream is "an output stream or an update stream in which the most
+     recent operation was not input", POSIX and C99 requires that fflush
+     writes out any buffered data, and all implementations do this.
+
+     When stream is, however, an input stream or an update stream in
+     which the most recent operation was input, C99 specifies nothing,
+     and POSIX only specifies behavior if the stream is seekable.
+     mingw, in particular, drops the input buffer, leaving the file
+     descriptor positioned at the end of the input buffer. I.e. ftell
+     (stream) is lost.  We don't want to call the implementation's
+     fflush in this case.
+
+     We test ! freading (stream) here, rather than fwriting (stream), because
+     what we need to know is whether the stream holds a "read buffer", and on
+     mingw this is indicated by _IOREAD, regardless of _IOWRT.  */
+  if (stream == NULL || ! freading (stream))
     return fflush (stream);
 
   /* POSIX does not specify fflush behavior for non-seekable input
-     streams.  */
+     streams.  Some implementations purge unread data, some return
+     EBADF, some do nothing.  */
   pos = ftello (stream);
   if (pos == -1)
     {
@@ -60,12 +75,35 @@ rpl_fflush (FILE *stream)
   result = fpurge (stream);
   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 = (stream->_flags & ~__SOPT) | __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;
-#if defined __sferror               /* FreeBSD, NetBSD, OpenBSD, MacOS X, Cygwin */
+  /* 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
+# endif
+
   return 0;
+
+#endif
 }