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* fileio.c: Use O_APPEND to append.

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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.
This commit is contained in:
Paul Eggert 2013-01-19 10:58:40 -08:00
parent 20de6ab6a5
commit 3a955a1f86
2 changed files with 28 additions and 23 deletions
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11
src/ChangeLog
View file

@ -1,5 +1,16 @@
2013-01-19 Paul Eggert <eggert@cs.ucla.edu>
* 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.

40
src/fileio.c
View file

@ -4741,7 +4741,9 @@ This calls `write-region-annotate-functions' at the start, and
(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 @@ This calls `write-region-annotate-functions' at the start, and
#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 @@ This calls `write-region-annotate-functions' at the start, and
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