+
+/* Parses a key or a key-value pair from '*stringp'.
+ *
+ * On success: Stores the key into '*keyp'. Stores the value, if present, into
+ * '*valuep', otherwise an empty string. Advances '*stringp' past the end of
+ * the key-value pair, preparing it for another call. '*keyp' and '*valuep'
+ * are substrings of '*stringp' created by replacing some of its bytes by null
+ * terminators. Returns true.
+ *
+ * If '*stringp' is just white space or commas, sets '*keyp' and '*valuep' to
+ * NULL and returns false. */
+bool
+ofputil_parse_key_value(char **stringp, char **keyp, char **valuep)
+{
+ char *pos, *key, *value;
+ size_t key_len;
+
+ pos = *stringp;
+ pos += strspn(pos, ", \t\r\n");
+ if (*pos == '\0') {
+ *keyp = *valuep = NULL;
+ return false;
+ }
+
+ key = pos;
+ key_len = strcspn(pos, ":=(, \t\r\n");
+ if (key[key_len] == ':' || key[key_len] == '=') {
+ /* The value can be separated by a colon. */
+ size_t value_len;
+
+ value = key + key_len + 1;
+ value_len = strcspn(value, ", \t\r\n");
+ pos = value + value_len + (value[value_len] != '\0');
+ value[value_len] = '\0';
+ } else if (key[key_len] == '(') {
+ /* The value can be surrounded by balanced parentheses. The outermost
+ * set of parentheses is removed. */
+ int level = 1;
+ size_t value_len;
+
+ value = key + key_len + 1;
+ for (value_len = 0; level > 0; value_len++) {
+ switch (value[value_len]) {
+ case '\0':
+ ovs_fatal(0, "unbalanced parentheses in argument to %s", key);
+
+ case '(':
+ level++;
+ break;
+
+ case ')':
+ level--;
+ break;
+ }
+ }
+ value[value_len - 1] = '\0';
+ pos = value + value_len;
+ } else {
+ /* There might be no value at all. */
+ value = key + key_len; /* Will become the empty string below. */
+ pos = key + key_len + (key[key_len] != '\0');
+ }
+ key[key_len] = '\0';
+
+ *stringp = pos;
+ *keyp = key;
+ *valuep = value;
+ return true;
+}