+ /* Strip the basename and any redundant slashes before it. */
+ for (length = last_component (file) - file;
+ prefix_length < length; length--)
+ if (! ISSLASH (file[length - 1]))
+ break;
+ return length;
+}
+
+
+/* In general, we can't use the builtin `dirname' function if available,
+ since it has different meanings in different environments.
+ In some environments the builtin `dirname' modifies its argument.
+
+ Return the leading directories part of FILE, allocated with xmalloc.
+ Works properly even if there are trailing slashes (by effectively
+ ignoring them). Unlike POSIX dirname(), FILE cannot be NULL.
+
+ If lstat (FILE) would succeed, then { chdir (dir_name (FILE));
+ lstat (base_name (FILE)); } will access the same file. Likewise,
+ if the sequence { chdir (dir_name (FILE));
+ rename (base_name (FILE), "foo"); } succeeds, you have renamed FILE
+ to "foo" in the same directory FILE was in. */
+
+char *
+dir_name (char const *file)
+{
+ size_t length = dir_len (file);
+ bool append_dot = (length == 0
+ || (FILE_SYSTEM_DRIVE_PREFIX_CAN_BE_RELATIVE
+ && length == FILE_SYSTEM_PREFIX_LEN (file)
+ && file[2] != '\0' && ! ISSLASH (file[2])));
+ char *dir = xmalloc (length + append_dot + 1);
+ memcpy (dir, file, length);
+ if (append_dot)
+ dir[length++] = '.';
+ dir[length] = '\0';
+ return dir;