[ovs-dev] [learning v2 06/19] ofp-util: New function for parsing key-value pairs.

[Ben Pfaff]

This will soon have a new user, but it's a worthwhile cleanup on its own.
---
 lib/ofp-parse.c |   63 ++++---------------------------------------------
 lib/ofp-util.c  |   69 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 lib/ofp-util.h  |    3 ++
 3 files changed, 78 insertions(+), 57 deletions(-)

diff --git a/lib/ofp-parse.c b/lib/ofp-parse.c
index 7e38565..77d3f19 100644
--- a/lib/ofp-parse.c
+++ b/lib/ofp-parse.c
@@ -495,80 +495,29 @@ parse_named_action(enum ofputil_action_code code, struct ofpbuf *b, char *arg)
 static void
 str_to_action(char *str, struct ofpbuf *b)
 {
-    bool drop = false;
+    char *pos, *act, *arg;
     int n_actions;
-    char *pos;
 
     pos = str;
     n_actions = 0;
-    for (;;) {
-        char empty_string[] = "";
-        char *act, *arg;
-        size_t actlen;
+    while (ofputil_parse_key_value(&pos, &act, &arg)) {
         uint16_t port;
         int code;
 
-        pos += strspn(pos, ", \t\r\n");
-        if (*pos == '\0') {
-            break;
-        }
-
-        if (drop) {
-            ovs_fatal(0, "Drop actions must not be followed by other actions");
-        }
-
-        act = pos;
-        actlen = strcspn(pos, ":(, \t\r\n");
-        if (act[actlen] == ':') {
-            /* The argument can be separated by a colon. */
-            size_t arglen;
-
-            arg = act + actlen + 1;
-            arglen = strcspn(arg, ", \t\r\n");
-            pos = arg + arglen + (arg[arglen] != '\0');
-            arg[arglen] = '\0';
-        } else if (act[actlen] == '(') {
-            /* The argument can be surrounded by balanced parentheses.  The
-             * outermost set of parentheses is removed. */
-            int level = 1;
-            size_t arglen;
-
-            arg = act + actlen + 1;
-            for (arglen = 0; level > 0; arglen++) {
-                switch (arg[arglen]) {
-                case '\0':
-                    ovs_fatal(0, "unbalanced parentheses in argument to %s "
-                              "action", act);
-
-                case '(':
-                    level++;
-                    break;
-
-                case ')':
-                    level--;
-                    break;
-                }
-            }
-            arg[arglen - 1] = '\0';
-            pos = arg + arglen;
-        } else {
-            /* There might be no argument at all. */
-            arg = empty_string;
-            pos = act + actlen + (act[actlen] != '\0');
-        }
-        act[actlen] = '\0';
-
         code = ofputil_action_code_from_name(act);
         if (code >= 0) {
             parse_named_action(code, b, arg);
         } else if (!strcasecmp(act, "drop")) {
             /* A drop action in OpenFlow occurs by just not setting
              * an action. */
-            drop = true;
             if (n_actions) {
                 ovs_fatal(0, "Drop actions must not be preceded by other "
                           "actions");
+            } else if (ofputil_parse_key_value(&pos, &act, &arg)) {
+                ovs_fatal(0, "Drop actions must not be followed by other "
+                          "actions");
             }
+            break;
         } else if (!strcasecmp(act, "CONTROLLER")) {
             struct ofp_action_output *oao;
             oao = put_output_action(b, OFPP_CONTROLLER);
diff --git a/lib/ofp-util.c b/lib/ofp-util.c
index 5cc1d40..a97a0e3 100644
--- a/lib/ofp-util.c
+++ b/lib/ofp-util.c
@@ -2735,3 +2735,72 @@ ofputil_actions_clone(const union ofp_action *actions, size_t n)
 {
     return n ? xmemdup(actions, n * sizeof *actions) : NULL;
 }
+
+/* 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;
+}
diff --git a/lib/ofp-util.h b/lib/ofp-util.h
index a658df1..ecd77cc 100644
--- a/lib/ofp-util.h
+++ b/lib/ofp-util.h
@@ -547,4 +547,7 @@ int ofputil_decode_error_msg(const struct ofp_header *, size_t *payload_ofs);
 void ofputil_format_error(struct ds *, int error);
 char *ofputil_error_to_string(int error);
 
+/* Handy utility for parsing flows and actions. */
+bool ofputil_parse_key_value(char **stringp, char **keyp, char **valuep);
+
 #endif /* ofp-util.h */
-- 
1.7.4.4