ofp-util: Work on decoding OF1.1 flow_mods.

[openvswitch] / lib / tag.c

diff --git a/lib/tag.c b/lib/tag.c
index 955cf30e1c37d52d05b89fc57965f2f161b80f96..f064d17867f485900684ad013e495a4ab02d61ed 100644 (file)
--- a/lib/tag.c
+++ b/lib/tag.c
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2008, 2009 Nicira Networks.
+ * Copyright (c) 2008, 2009, 2010, 2011 Nicira, Inc.
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -49,7 +49,7 @@ tag_type
 tag_create_deterministic(uint32_t seed)
 {
     int x = seed & (N_TAG_BITS - 1);
-    int y = (seed >> LOG2_N_TAG_BITS) % 31;
+    int y = (seed >> LOG2_N_TAG_BITS) % (N_TAG_BITS - 1);
     y += y >= x;
     return (1u << x) | (1u << y);
 }
@@ -61,11 +61,36 @@ tag_set_init(struct tag_set *set)
     memset(set, 0, sizeof *set);
 }
 
+static bool
+tag_is_worth_adding(const struct tag_set *set, tag_type tag)
+{
+    if (!tag) {
+        /* Nothing to add. */
+        return false;
+    } else if ((set->total & tag) != tag) {
+        /* 'set' doesn't have all the bits in 'tag', so we need to add it. */
+        return true;
+    } else {
+        /* We can drop it if some member of 'set' already includes all of the
+         * 1-bits in 'tag'.  (tag_set_intersects() does a different test:
+         * whether some member of 'set' has at least two 1-bit in common with
+         * 'tag'.) */
+        int i;
+
+        for (i = 0; i < TAG_SET_SIZE; i++) {
+            if ((set->tags[i] & tag) == tag) {
+                return false;
+            }
+        }
+        return true;
+    }
+}
+
 /* Adds 'tag' to 'set'. */
 void
 tag_set_add(struct tag_set *set, tag_type tag)
 {
-    if (tag && (!tag_is_valid(tag) || !tag_set_intersects(set, tag))) {
+    if (tag_is_worth_adding(set, tag)) {
         /* XXX We could do better by finding the set member to which we would
          * add the fewest number of 1-bits.  This would reduce the amount of
          * ambiguity, since e.g. three 1-bits match 3 * 2 / 2 = 3 unique tags
@@ -80,3 +105,13 @@ tag_set_add(struct tag_set *set, tag_type tag)
     }
 }
 
+/* Adds all the tags in 'other' to 'set'. */
+void
+tag_set_union(struct tag_set *set, const struct tag_set *other)
+{
+    size_t i;
+
+    for (i = 0; i < TAG_SET_SIZE; i++) {
+        tag_set_add(set, other->tags[i]);
+    }
+}