gettimeofday: port recent C++ fix to Emacs

[gnulib.git] / lib / fflush.c

diff --git a/lib/fflush.c b/lib/fflush.c
old mode 100755 (executable)
new mode 100644 (file)
index 2d81495..8ac5dea
--- a/lib/fflush.c
+++ b/lib/fflush.c
@@ -1,10 +1,10 @@
 /* fflush.c -- allow flushing input streams
 /* fflush.c -- allow flushing input streams

-   Copyright (C) 2007 Free Software Foundation, Inc.
+   Copyright (C) 2007-2013 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
    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
 
    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
    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. */
 
 
 /* Written by Eric Blake. */
 


@@ -26,18 +25,104 @@
 #include <unistd.h>
 
 #include "freading.h"
 #include <unistd.h>
 
 #include "freading.h"

-#include "fpurge.h"
+
+#include "stdio-impl.h"
+
+#include "unused-parameter.h"

 
 #undef fflush
 
 
 #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 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 void
+clear_ungetc_buffer (FILE *fp)
+{
+# if defined __sferror || defined __DragonFly__ /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS 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 _IO_ftrylockfile || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Haiku, Linux libc5 */)
+
+# if (defined __sferror || defined __DragonFly__) && defined __SNPT /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS X, Cygwin */
+
+static int
+disable_seek_optimization (FILE *fp)
+{
+  int saved_flags = fp_->_flags & (__SOPT | __SNPT);
+  fp_->_flags = (fp_->_flags & ~__SOPT) | __SNPT;
+  return saved_flags;
+}
+
+static void
+restore_seek_optimization (FILE *fp, int saved_flags)
+{
+  fp_->_flags = (fp_->_flags & ~(__SOPT | __SNPT)) | saved_flags;
+}
+
+# else
+
+static void
+update_fpos_cache (FILE *fp _GL_UNUSED_PARAMETER,
+                   off_t pos _GL_UNUSED_PARAMETER)
+{
+#  if defined __sferror || defined __DragonFly__ /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS 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
+}
+# endif
+#endif
+

 /* Flush all pending data on STREAM according to POSIX rules.  Both
    output and seekable input streams are supported.  */
 int
 rpl_fflush (FILE *stream)
 {
 /* 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.
   /* 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.


@@ -46,11 +131,13 @@ rpl_fflush (FILE *stream)
      recent operation was not input", POSIX and C99 requires that fflush
      writes out any buffered data, and all implementations do this.
 
      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, POSIX and C99 specify nothing.
-     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.
+     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
 
      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


@@ -58,31 +145,81 @@ rpl_fflush (FILE *stream)
   if (stream == NULL || ! freading (stream))
     return fflush (stream);
 
   if (stream == NULL || ! freading (stream))
     return fflush (stream);
 

-  /* POSIX does not specify fflush behavior for non-seekable input
-     streams.  */
-  pos = ftello (stream);
-  if (pos == -1)
+#if defined _IO_ftrylockfile || __GNU_LIBRARY__ == 1 /* GNU libc, BeOS, Haiku, Linux libc5 */
+
+  clear_ungetc_buffer_preserving_position (stream);
+
+  return fflush (stream);
+
+#else
+  {
+    /* 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.  */

     {
     {

-      errno = EBADF;
-      return EOF;
+      int result = fpurge (stream);
+      if (result != 0)
+        return result;

     }
 
     }
 

-  /* 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;
-
-  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
+# if (defined __sferror || defined __DragonFly__) && defined __SNPT /* FreeBSD, NetBSD, OpenBSD, DragonFly, Mac OS 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 = disable_seek_optimization (stream);
+      int result = fseeko (stream, pos, SEEK_SET);
+
+      restore_seek_optimization (stream, saved_flags);
+      return result;
+    }

 
 

-  return 0;
+# 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.  */
+    update_fpos_cache (stream, pos);
+
+    return 0;
+
+# endif
+  }
+#endif

 }
 }