-/* Return the number of the highest-numbered backup file for file
- FILE in directory DIR. If there are no numbered backups
- of FILE in DIR, or an error occurs reading DIR, return 0.
- */
-
-static int
-max_backup_version (const char *file, const char *dir)
+/* Returned values for NUMBERED_BACKUP. */
+
+enum numbered_backup_result
+ {
+ /* The new backup name is the same length as an existing backup
+ name, so it's valid for that directory. */
+ BACKUP_IS_SAME_LENGTH,
+
+ /* Some backup names already exist, but the returned name is longer
+ than any of them, and its length should be checked. */
+ BACKUP_IS_LONGER,
+
+ /* There are no existing backup names. The new name's length
+ should be checked. */
+ BACKUP_IS_NEW
+ };
+
+/* *BUFFER contains a file name. Store into *BUFFER the next backup
+ name for the named file, with a version number greater than all the
+ existing numbered backups. Reallocate *BUFFER as necessary; its
+ 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.
+ 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. */
+
+static enum numbered_backup_result
+numbered_backup (char **buffer, size_t buffer_size, size_t filelen)