*dst = '\0';
return dst - buf;
}
+
+/*
+ * path = Canonical absolute path
+ * prefix_list = Colon-separated list of absolute paths
+ *
+ * Determines, for each path in parent_list, whether the "prefix" really
+ * is an ancestor directory of path. Returns the length of the longest
+ * ancestor directory, excluding any trailing slashes, or -1 if no prefix
+ * is an ancestor. (Note that this means 0 is returned if prefix_list is
+ * "/".) "/foo" is not considered an ancestor of "/foobar". Directories
+ * are not considered to be their own ancestors. path must be in a
+ * canonical form: empty components, or "." or ".." components are not
+ * allowed. prefix_list may be null, which is like "".
+ */
+int longest_ancestor_length(const char *path, const char *prefix_list)
+{
+ char buf[PATH_MAX+1];
+ const char *ceil, *colon;
+ int len, max_len = -1;
+
+ if (prefix_list == NULL || !strcmp(path, "/"))
+ return -1;
+
+ for (colon = ceil = prefix_list; *colon; ceil = colon+1) {
+ for (colon = ceil; *colon && *colon != ':'; colon++);
+ len = colon - ceil;
+ if (len == 0 || len > PATH_MAX || !is_absolute_path(ceil))
+ continue;
+ strlcpy(buf, ceil, len+1);
+ len = normalize_absolute_path(buf, buf);
+ /* Strip "trailing slashes" from "/". */
+ if (len == 1)
+ len = 0;
+
+ if (!strncmp(path, buf, len) &&
+ path[len] == '/' &&
+ len > max_len) {
+ max_len = len;
+ }
+ }
+
+ return max_len;
+}