[Emacs-diffs] /srv/bzr/emacs/trunk r111559: * fileio.c: Use O_APPEND to append.

[Paul Eggert]

------------------------------------------------------------
revno: 111559
committer: Paul Eggert <address@hidden>
branch nick: trunk
timestamp: Sat 2013-01-19 10:58:40 -0800
message:
  * fileio.c: Use O_APPEND to append.
  
  This corresponds better to the natural interpretation of "append",
  and avoids the need to open the output file twice, or to invoke
  lseek when APPEND is neither nil nor a number.
  This relies on POSIX 1003.1-1988 or later, which is OK nowadays.
  (Fwrite_region): Simplify.  Use O_APPEND instead of opening the
  file possibly twice, and lseeking to its end; this avoids the
  need to lseek on non-regular files.  Do not use O_EXCL and O_TRUNC
  at the same time: the combination is never needed and apparently
  it doesn't work with DOS_NT.
modified:
  src/ChangeLog
  src/fileio.c

=== modified file 'src/ChangeLog'
--- a/src/ChangeLog     2013-01-19 12:29:10 +0000
+++ b/src/ChangeLog     2013-01-19 18:58:40 +0000
@@ -1,5 +1,16 @@
 2013-01-19  Paul Eggert  <address@hidden>
 
+       * fileio.c: Use O_APPEND to append.
+       This corresponds better to the natural interpretation of "append",
+       and avoids the need to open the output file twice, or to invoke
+       lseek when APPEND is neither nil nor a number.
+       This relies on POSIX 1003.1-1988 or later, which is OK nowadays.
+       (Fwrite_region): Simplify.  Use O_APPEND instead of opening the
+       file possibly twice, and lseeking to its end; this avoids the
+       need to lseek on non-regular files.  Do not use O_EXCL and O_TRUNC
+       at the same time: the combination is never needed and apparently
+       it doesn't work with DOS_NT.
+
        Fix size bug on DOS_NT introduced by CIFS workaround (Bug#13149).
        * fileio.c (Fwrite_region): Use O_BINARY in checking code, too.
 

=== modified file 'src/fileio.c'
--- a/src/fileio.c      2013-01-19 12:29:10 +0000
+++ b/src/fileio.c      2013-01-19 18:58:40 +0000
@@ -4741,7 +4741,9 @@
   (Lisp_Object start, Lisp_Object end, Lisp_Object filename, Lisp_Object 
append, Lisp_Object visit, Lisp_Object lockname, Lisp_Object mustbenew)
 {
   int desc;
-  off_t offset;
+  int open_flags;
+  int mode;
+  off_t offset IF_LINT (= 0);
   bool ok;
   int save_errno = 0;
   const char *fn;
@@ -4861,28 +4863,20 @@
 #endif /* CLASH_DETECTION */
 
   encoded_filename = ENCODE_FILE (filename);
-
   fn = SSDATA (encoded_filename);
-  offset = 0;
-  desc = -1;
-  if (!NILP (append))
-    {
-      if (NUMBERP (append))
-       offset = file_offset (append);
-      desc = emacs_open (fn, O_WRONLY | O_BINARY, 0);
-    }
-
-  if (desc < 0 && (NILP (append) || errno == ENOENT))
+  open_flags = O_WRONLY | O_BINARY | O_CREAT;
+  open_flags |= EQ (mustbenew, Qexcl) ? O_EXCL : !NILP (append) ? 0 : O_TRUNC;
+  if (NUMBERP (append))
+    offset = file_offset (append);
+  else if (!NILP (append))
+    open_flags |= O_APPEND;
 #ifdef DOS_NT
-  desc = emacs_open (fn,
-                    O_WRONLY | O_CREAT | O_BINARY
-                    | (EQ (mustbenew, Qexcl) ? O_EXCL : O_TRUNC),
-                    S_IREAD | S_IWRITE);
-#else  /* not DOS_NT */
-  desc = emacs_open (fn, O_WRONLY | O_TRUNC | O_CREAT
-                    | (EQ (mustbenew, Qexcl) ? O_EXCL : 0),
-                    auto_saving ? auto_save_mode_bits : 0666);
-#endif /* not DOS_NT */
+  mode = S_IREAD | S_IWRITE;
+#else
+  mode = auto_saving ? auto_save_mode_bits : 0666;
+#endif
+
+  desc = emacs_open (fn, open_flags, mode);
 
   if (desc < 0)
     {
@@ -4897,9 +4891,9 @@
 
   record_unwind_protect (close_file_unwind, make_number (desc));
 
-  if (!NILP (append))
+  if (NUMBERP (append))
     {
-      off_t ret = lseek (desc, offset, NUMBERP (append) ? SEEK_SET : SEEK_END);
+      off_t ret = lseek (desc, offset, SEEK_SET);
       if (ret < 0)
        {
 #ifdef CLASH_DETECTION