+/* Turns multiple adjacent slashes into a single slash (possible exception:
+ * the preserving of two leading slashes at the start), drops all leading or
+ * interior "." elements unless CFN_KEEP_DOT_DIRS is flagged. Will also drop
+ * a trailing '.' after a '/' if CFN_DROP_TRAILING_DOT_DIR is flagged, removes
+ * a trailing slash (perhaps after removing the aforementioned dot) unless
+ * CFN_KEEP_TRAILING_SLASH is flagged, and will also collapse ".." elements
+ * (except at the start) if CFN_COLLAPSE_DOT_DOT_DIRS is flagged. If the
+ * resulting name would be empty, returns ".". */
+unsigned int clean_fname(char *name, int flags)
+{
+ char *limit = name - 1, *t = name, *f = name;
+ int anchored;
+
+ if (!name)
+ return 0;
+
+ if ((anchored = *f == '/') != 0) {
+ *t++ = *f++;
+#ifdef __CYGWIN__
+ /* If there are exactly 2 slashes at the start, preserve
+ * them. Would break daemon excludes unless the paths are
+ * really treated differently, so used this sparingly. */
+ if (*f == '/' && f[1] != '/')
+ *t++ = *f++;
+#endif
+ } else if (flags & CFN_KEEP_DOT_DIRS && *f == '.' && f[1] == '/') {
+ *t++ = *f++;
+ *t++ = *f++;
+ }
+ while (*f) {
+ /* discard extra slashes */
+ if (*f == '/') {
+ f++;
+ continue;
+ }
+ if (*f == '.') {
+ /* discard interior "." dirs */
+ if (f[1] == '/' && !(flags & CFN_KEEP_DOT_DIRS)) {
+ f += 2;
+ continue;
+ }
+ if (f[1] == '\0' && flags & CFN_DROP_TRAILING_DOT_DIR)
+ break;
+ /* collapse ".." dirs */
+ if (flags & CFN_COLLAPSE_DOT_DOT_DIRS
+ && f[1] == '.' && (f[2] == '/' || !f[2])) {
+ char *s = t - 1;
+ if (s == name && anchored) {
+ f += 2;
+ continue;
+ }
+ while (s > limit && *--s != '/') {}
+ if (s != t - 1 && (s < name || *s == '/')) {
+ t = s + 1;
+ f += 2;
+ continue;
+ }
+ limit = t + 2;
+ }
+ }
+ while (*f && (*t++ = *f++) != '/') {}