It is like backupfile, except it avoids some race conditions,
and it does not output to stderr or exit.
* MODULES.html.sh: Add backup-rename.
* lib/backup-find.c, lib/backup-internal.h, lib/backup-rename.c:
* modules/backup-rename: New files.
* lib/backupfile.c: Turn this into an internals file, which
contains code common to backupfile and backup_rename. Do not
include argmatch.h or xalloc.h: include xalloc-oversized.h.
Include renameat2.h and fcntl.h.
(BACKUP_NOMEM): New constant.
(numbered_backup): New args BASE_OFFSET and *DIRPP. Do not exit
on memory exhaustion; just return BACKUP_NOMEM. Caller changed.
(backupfile_internal): Rename from find_backup_file_name.
Support new arg RENAME.
(backup_args, backup_types, get_version, xget_version):
Move to lib/backup-find.c.
* lib/backupfile.h (backup_file_rename): New decl.
* modules/backupfile (Files): Add lib/backup-internal.h,
lib/backup-find.c.
(Depends-on): Add dirfd, fcntl, renameat2.
(lib_SOURCES): Add backup-find.c.
---
ChangeLog | 24 ++++++
MODULES.html.sh | 1 +
lib/backup-find.c | 91 +++++++++++++++++++++
lib/backup-internal.h | 3 +
lib/backup-rename.c | 31 ++++++++
lib/backupfile.c | 213 ++++++++++++++++++++++++++------------------------
lib/backupfile.h | 1 +
modules/backup-rename | 38 +++++++++
modules/backupfile | 12 ++-
9 files changed, 308 insertions(+), 106 deletions(-)
create mode 100644 lib/backup-find.c
create mode 100644 lib/backup-internal.h
create mode 100644 lib/backup-rename.c
create mode 100644 modules/backup-rename
diff --git a/ChangeLog b/ChangeLog
index ce7c46b..a6909f6 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,29 @@
2017-07-30 Paul Eggert <egg...@cs.ucla.edu>
+ backup-rename: new module
+ It is like backupfile, except it avoids some race conditions,
+ and it does not output to stderr or exit.
+ * MODULES.html.sh: Add backup-rename.
+ * lib/backup-find.c, lib/backup-internal.h, lib/backup-rename.c:
+ * modules/backup-rename: New files.
+ * lib/backupfile.c: Turn this into an internals file, which
+ contains code common to backupfile and backup_rename. Include
+ backupfile-internal.h instead of backupfile.h. Do not include
+ argmatch.h or xalloc.h: include xalloc-oversized.h. Include
+ renameat2.h and fcntl.h.
+ (BACKUP_NOMEM): New constant.
+ (numbered_backup): New args BASE_OFFSET and *DIRPP. Do not exit
+ on memory exhaustion; just return BACKUP_NOMEM. Caller changed.
+ (backupfile_internal): Rename from find_backup_file_name.
+ Support new arg RENAME.
+ (backup_args, backup_types, get_version, xget_version):
+ Move to lib/backup-find.c.
+ * lib/backupfile.h (backup_file_rename): New decl.
+ * modules/backupfile (Files): Add lib/backup-internal.h,
+ lib/backup-find.c.
+ (Depends-on): Add dirfd, fcntl, renameat2.
+ (lib_SOURCES): Add backup-find.c.
+
renameat2: port better to older Solaris
* lib/renameat2.c (renameat2): Set ret_val properly on old Solaris.
Add goto to use a label, to silence picky compilers.
diff --git a/MODULES.html.sh b/MODULES.html.sh
index 102223d..a64b999 100755
--- a/MODULES.html.sh
+++ b/MODULES.html.sh
@@ -2637,6 +2637,7 @@ func_all_modules ()
func_module areadlinkat
func_module areadlinkat-with-size
func_module backupfile
+ func_module backup-rename
func_module canonicalize
func_module canonicalize-lgpl
func_module chdir-safer
diff --git a/lib/backup-find.c b/lib/backup-find.c
new file mode 100644
index 0000000..fbfb54e
--- /dev/null
+++ b/lib/backup-find.c
@@ -0,0 +1,91 @@
+/* backupfile.c -- make Emacs style backup file names
+
+ Copyright 2017 Free Software Foundation, Inc.
+
+ 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 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
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ 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, see <http://www.gnu.org/licenses/>. */
+
+#include <config.h>
+
+#include "backup-internal.h"
+
+#include "argmatch.h"
+#include "xalloc.h"
+
+#include <stdlib.h>
+
+/* Return the name of a backup file for the existing file FILE,
+ allocated with malloc. Report an error and exit if out of memory.
+ Do not call this function if backup_type == no_backups. */
+
+char *
+find_backup_file_name (char const *file, enum backup_type backup_type)
+{
+ char *result = backupfile_internal (file, backup_type, false);
+ if (!result)
+ xalloc_die ();
+ return result;
+}
+
+static char const *const backup_args[] =
+{
+ /* In a series of synonyms, present the most meaningful first, so
+ that argmatch_valid be more readable. */
+ "none", "off",
+ "simple", "never",
+ "existing", "nil",
+ "numbered", "t",
+ NULL
+};
+
+static const enum backup_type backup_types[] =
+{
+ no_backups, no_backups,
+ simple_backups, simple_backups,
+ numbered_existing_backups, numbered_existing_backups,
+ numbered_backups, numbered_backups
+};
+
+/* Ensure that these two vectors have the same number of elements,
+ not counting the final NULL in the first one. */
+ARGMATCH_VERIFY (backup_args, backup_types);
+
+/* Return the type of backup specified by VERSION.
+ If VERSION is NULL or the empty string, return numbered_existing_backups.
+ If VERSION is invalid or ambiguous, fail with a diagnostic appropriate
+ for the specified CONTEXT. Unambiguous abbreviations are accepted. */
+
+enum backup_type
+get_version (char const *context, char const *version)
+{
+ if (version == 0 || *version == 0)
+ return numbered_existing_backups;
+ else
+ return XARGMATCH (context, version, backup_args, backup_types);
+}
+
+
+/* Return the type of backup specified by VERSION.
+ If VERSION is NULL, use the value of the envvar VERSION_CONTROL.
+ If the specified string is invalid or ambiguous, fail with a diagnostic
+ appropriate for the specified CONTEXT.
+ Unambiguous abbreviations are accepted. */
+
+enum backup_type
+xget_version (char const *context, char const *version)
+{
+ if (version && *version)
+ return get_version (context, version);
+ else
+ return get_version ("$VERSION_CONTROL", getenv ("VERSION_CONTROL"));
+}
diff --git a/lib/backup-internal.h b/lib/backup-internal.h
new file mode 100644
index 0000000..2401c07
--- /dev/null
+++ b/lib/backup-internal.h
@@ -0,0 +1,3 @@
+#include "backupfile.h"
+#include <stdbool.h>
+extern char *backupfile_internal (char const *, enum backup_type, bool);
diff --git a/lib/backup-rename.c b/lib/backup-rename.c
new file mode 100644
index 0000000..628542b
--- /dev/null
+++ b/lib/backup-rename.c
@@ -0,0 +1,31 @@
+/* Rename a file to a backup name, Emacs style.
+
+ Copyright 2017 Free Software Foundation, Inc.
+
+ 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 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
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ 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, see <http://www.gnu.org/licenses/>. */
+
+#include <config.h>
+
+#include "backup-internal.h"
+
+/* Rename the existing file FILE to a backup name, allocated with
+ malloc, and return the backup name. On failure return a null
+ pointer, setting errno. Do not call this function if backup_type
+ == no_backups. */
+
+char *
+backup_file_rename (char const *file, enum backup_type backup_type)
+{
+ return backupfile_internal (file, backup_type, true);
+}
diff --git a/lib/backupfile.c b/lib/backupfile.c
index 2d0c750..9773fe2 100644
--- a/lib/backupfile.c
+++ b/lib/backupfile.c
@@ -20,12 +20,13 @@
#include <config.h>
-#include "backupfile.h"
+#include "backup-internal.h"
-#include "argmatch.h"
#include "dirname.h"
-#include "xalloc.h"
+#include "renameat2.h"
+#include "xalloc-oversized.h"
+#include <fcntl.h>
#include <errno.h>
#include <stdbool.h>
#include <stdlib.h>
@@ -155,7 +156,10 @@ enum numbered_backup_result
/* There are no existing backup names. The new name's length
should be checked. */
- BACKUP_IS_NEW
+ BACKUP_IS_NEW,
+
+ /* Memory allocation failure. */
+ BACKUP_NOMEM
};
/* *BUFFER contains a file name. Store into *BUFFER the next backup
@@ -164,33 +168,45 @@ enum numbered_backup_result
initial allocated size is BUFFER_SIZE, which must be at least 4
bytes longer than the file name to make room for the initially
appended ".~1". FILELEN is the length of the original file name.
+ BASE_OFFSET is the offset of the basename in *BUFFER.
The returned value indicates what kind of backup was found. If an
I/O or other read error occurs, use the highest backup number that
- was found. */
+ was found.
+
+ *DIRPP is the destination directory. If *DIRPP is null, open the
+ destination directory and store the resulting stream into *DIRPP
+ without closing the stream. */
static enum numbered_backup_result
-numbered_backup (char **buffer, size_t buffer_size, size_t filelen)
+numbered_backup (char **buffer, size_t buffer_size, size_t filelen,
+ ptrdiff_t base_offset, DIR **dirpp)
{
enum numbered_backup_result result = BACKUP_IS_NEW;
- DIR *dirp;
+ DIR *dirp = *dirpp;
struct dirent *dp;
char *buf = *buffer;
size_t versionlenmax = 1;
- char *base = last_component (buf);
- size_t base_offset = base - buf;
+ char *base = buf + base_offset;
size_t baselen = base_len (base);
- /* Temporarily modify the buffer into its parent directory name,
- open the directory, and then restore the buffer. */
- char tmp[sizeof "."];
- memcpy (tmp, base, sizeof ".");
- strcpy (base, ".");
- dirp = opendir (buf);
- memcpy (base, tmp, sizeof ".");
- strcpy (base + baselen, ".~1~");
-
- if (!dirp)
- return result;
+ if (dirp)
+ rewinddir (dirp);
+ else
+ {
+ /* Temporarily modify the buffer into its parent directory name,
+ open the directory, and then restore the buffer. */
+ char tmp[sizeof "."];
+ memcpy (tmp, base, sizeof ".");
+ strcpy (base, ".");
+ dirp = opendir (buf);
+ if (!dirp && errno == ENOMEM)
+ result = BACKUP_NOMEM;
+ memcpy (base, tmp, sizeof ".");
+ strcpy (base + baselen, ".~1~");
+ if (!dirp)
+ return result;
+ *dirpp = dirp;
+ }
while ((dp = readdir (dirp)) != NULL)
{
@@ -198,7 +214,6 @@ numbered_backup (char **buffer, size_t buffer_size, size_t
filelen)
char *q;
bool all_9s;
size_t versionlen;
- size_t new_buflen;
if (! REAL_DIR_ENTRY (dp) || _D_EXACT_NAMLEN (dp) < baselen + 4)
continue;
@@ -224,17 +239,25 @@ numbered_backup (char **buffer, size_t buffer_size,
size_t filelen)
&& memcmp (buf + filelen + 2, p, versionlen) <= 0))))
continue;
- /* This directory has the largest version number seen so far.
+ /* This entry has the largest version number seen so far.
Append this highest numbered extension to the file name,
prepending '0' to the number if it is all 9s. */
versionlenmax = all_9s + versionlen;
result = (all_9s ? BACKUP_IS_LONGER : BACKUP_IS_SAME_LENGTH);
- new_buflen = filelen + 2 + versionlenmax + 1;
- if (buffer_size <= new_buflen)
+ size_t new_buffer_size = filelen + 2 + versionlenmax + 2;
+ if (buffer_size < new_buffer_size)
{
- buf = xnrealloc (buf, 2, new_buflen);
- buffer_size = new_buflen * 2;
+ if (! xalloc_oversized (new_buffer_size, 2))
+ new_buffer_size *= 2;
+ char *new_buf = realloc (buf, new_buffer_size);
+ if (!new_buf)
+ {
+ *buffer = buf;
+ return BACKUP_NOMEM;
+ }
+ buf = new_buf;
+ buffer_size = new_buffer_size;
}
q = buf + filelen;
*q++ = '.';
@@ -251,22 +274,20 @@ numbered_backup (char **buffer, size_t buffer_size,
size_t filelen)
++*q;
}
- closedir (dirp);
*buffer = buf;
return result;
}
/* Return the name of the new backup file for the existing file FILE,
- allocated with malloc. Report an error and fail if out of memory.
+ allocated with malloc. If RENAME, also rename FILE to the new name.
+ On failure, return NULL and set errno.
Do not call this function if backup_type == no_backups. */
char *
-find_backup_file_name (char const *file, enum backup_type backup_type)
+backupfile_internal (char const *file, enum backup_type backup_type, bool
rename)
{
- size_t filelen = strlen (file);
- char *s;
- size_t ssize;
- bool simple = true;
+ ptrdiff_t base_offset = last_component (file) - file;
+ size_t filelen = base_offset + strlen (file + base_offset);
/* Initialize the default simple backup suffix. */
if (! simple_backup_suffix)
@@ -286,80 +307,68 @@ find_backup_file_name (char const *file, enum backup_type
backup_type)
if (backup_suffix_size_guess < GUESS)
backup_suffix_size_guess = GUESS;
- ssize = filelen + backup_suffix_size_guess + 1;
- s = xmalloc (ssize);
- memcpy (s, file, filelen + 1);
+ ssize_t ssize = filelen + backup_suffix_size_guess + 1;
+ char *s = malloc (ssize);
+ if (!s)
+ return s;
- if (backup_type != simple_backups)
- switch (numbered_backup (&s, ssize, filelen))
- {
- case BACKUP_IS_SAME_LENGTH:
- return s;
+ DIR *dirp = NULL;
+ while (true)
+ {
+ memcpy (s, file, filelen + 1);
- case BACKUP_IS_LONGER:
- simple = false;
+ if (backup_type == simple_backups)
+ memcpy (s + filelen, simple_backup_suffix, simple_backup_suffix_size);
+ else
+ switch (numbered_backup (&s, ssize, filelen, base_offset, &dirp))
+ {
+ case BACKUP_IS_SAME_LENGTH:
+ break;
+
+ case BACKUP_IS_NEW:
+ if (backup_type == numbered_existing_backups)
+ {
+ backup_type = simple_backups;
+ memcpy (s + filelen, simple_backup_suffix,
+ simple_backup_suffix_size);
+ }
+ check_extension (s, filelen, '~');
+ break;
+
+ case BACKUP_IS_LONGER:
+ check_extension (s, filelen, '~');
+ break;
+
+ case BACKUP_NOMEM:
+ free (s);
+ errno = ENOMEM;
+ return NULL;
+ }
+
+ if (! rename)
break;
- case BACKUP_IS_NEW:
- simple = (backup_type == numbered_existing_backups);
+ int sdir = dirp ? dirfd (dirp) : -1;
+ if (sdir < 0)
+ {
+ sdir = AT_FDCWD;
+ base_offset = 0;
+ }
+ unsigned flags = backup_type == simple_backups ? 0 : RENAME_NOREPLACE;
+ if (renameat2 (AT_FDCWD, file, sdir, s + base_offset, flags) == 0)
break;
- }
+ int e = errno;
+ if (e != EEXIST)
+ {
+ if (dirp)
+ closedir (dirp);
+ free (s);
+ errno = e;
+ return NULL;
+ }
+ }
- if (simple)
- memcpy (s + filelen, simple_backup_suffix, simple_backup_suffix_size);
- check_extension (s, filelen, '~');
+ if (dirp)
+ closedir (dirp);
return s;
}
-
-static char const * const backup_args[] =
-{
- /* In a series of synonyms, present the most meaningful first, so
- that argmatch_valid be more readable. */
- "none", "off",
- "simple", "never",
- "existing", "nil",
- "numbered", "t",
- NULL
-};
-
-static const enum backup_type backup_types[] =
-{
- no_backups, no_backups,
- simple_backups, simple_backups,
- numbered_existing_backups, numbered_existing_backups,
- numbered_backups, numbered_backups
-};
-
-/* Ensure that these two vectors have the same number of elements,
- not counting the final NULL in the first one. */
-ARGMATCH_VERIFY (backup_args, backup_types);
-
-/* Return the type of backup specified by VERSION.
- If VERSION is NULL or the empty string, return numbered_existing_backups.
- If VERSION is invalid or ambiguous, fail with a diagnostic appropriate
- for the specified CONTEXT. Unambiguous abbreviations are accepted. */
-
-enum backup_type
-get_version (char const *context, char const *version)
-{
- if (version == 0 || *version == 0)
- return numbered_existing_backups;
- else
- return XARGMATCH (context, version, backup_args, backup_types);
-}
-
-
-/* Return the type of backup specified by VERSION.
- If VERSION is NULL, use the value of the envvar VERSION_CONTROL.
- If the specified string is invalid or ambiguous, fail with a diagnostic
- appropriate for the specified CONTEXT.
- Unambiguous abbreviations are accepted. */
-
-enum backup_type
-xget_version (char const *context, char const *version)
-{
- if (version && *version)
- return get_version (context, version);
- else
- return get_version ("$VERSION_CONTROL", getenv ("VERSION_CONTROL"));
-}
diff --git a/lib/backupfile.h b/lib/backupfile.h
index ccd168c..d578a65 100644
--- a/lib/backupfile.h
+++ b/lib/backupfile.h
@@ -46,6 +46,7 @@ enum backup_type
extern char const *simple_backup_suffix;
+char *backup_file_rename (char const *, enum backup_type);
char *find_backup_file_name (char const *, enum backup_type);
enum backup_type get_version (char const *context, char const *arg);
enum backup_type xget_version (char const *context, char const *arg);
diff --git a/modules/backup-rename b/modules/backup-rename
new file mode 100644
index 0000000..4d8932d
--- /dev/null
+++ b/modules/backup-rename
@@ -0,0 +1,38 @@
+Description:
+Rename a file to a backup name.
+
+Files:
+lib/backup-internal.h
+lib/backup-rename.c
+lib/backupfile.c
+lib/backupfile.h
+m4/backupfile.m4
+
+Depends-on:
+argmatch
+closedir
+d-ino
+dirent-safer
+dirfd
+dirname-lgpl
+fcntl
+memcmp
+opendir
+renameat2
+readdir
+stdbool
+
+configure.ac:
+gl_BACKUPFILE
+
+Makefile.am:
+lib_SOURCES += backupfile.c backup-rename.c
+
+Include:
+"backupfile.h"
+
+License:
+GPL
+
+Maintainer:
+Paul Eggert, Jim Meyering
diff --git a/modules/backupfile b/modules/backupfile
index dbd26b6..9e4efd7 100644
--- a/modules/backupfile
+++ b/modules/backupfile
@@ -1,10 +1,11 @@
Description:
-Determination of the filename of a backup file, according to user environment
-variables.
+Determine the name of a backup file.
Files:
-lib/backupfile.h
+lib/backup-internal.h
+lib/backup-find.c
lib/backupfile.c
+lib/backupfile.h
m4/backupfile.m4
Depends-on:
@@ -12,9 +13,12 @@ argmatch
closedir
d-ino
dirent-safer
+dirfd
dirname-lgpl
+fcntl
memcmp
opendir
+renameat2
readdir
stdbool
@@ -22,7 +26,7 @@ configure.ac:
gl_BACKUPFILE
Makefile.am:
-lib_SOURCES += backupfile.c
+lib_SOURCES += backupfile.c backup-find.c
Include:
"backupfile.h"
--
2.7.4
