/*
- * Copyright (c) 2008, 2009, 2010 Nicira Networks.
+ * Copyright (c) 2008, 2009, 2010, 2011, 2013 Nicira, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
#include <config.h>
#include "tag.h"
-#include <limits.h>
-#include "random.h"
-#include "type-props.h"
-#include "util.h"
-
-#define N_TAG_BITS (CHAR_BIT * sizeof(tag_type))
-BUILD_ASSERT_DECL(IS_POW2(N_TAG_BITS));
#define LOG2_N_TAG_BITS (N_TAG_BITS == 32 ? 5 : N_TAG_BITS == 64 ? 6 : 0)
BUILD_ASSERT_DECL(LOG2_N_TAG_BITS > 0);
-/* Returns a randomly selected tag. */
-tag_type
-tag_create_random(void)
-{
- int x, y;
- do {
- uint16_t r = random_uint16();
- x = r & (N_TAG_BITS - 1);
- y = r >> (16 - LOG2_N_TAG_BITS);
- } while (x == y);
- return (1u << x) | (1u << y);
-}
-
/* Returns a tag deterministically generated from 'seed'.
*
* 'seed' should have data in all of its bits; if it has data only in its
return (1u << x) | (1u << y);
}
-/* Initializes 'set' as an empty tag set. */
+/* Initializes 'tracker'. */
void
-tag_set_init(struct tag_set *set)
+tag_tracker_init(struct tag_tracker *tracker)
{
- memset(set, 0, sizeof *set);
+ memset(tracker, 0, sizeof *tracker);
}
-static bool
-tag_is_worth_adding(const struct tag_set *set, tag_type tag)
+/* Adds 'add' to '*tags' and records the bits added in 'tracker'. */
+void
+tag_tracker_add(struct tag_tracker *tracker, tag_type *tags, tag_type add)
{
- 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;
+ *tags |= add;
+ for (; add; add = zero_rightmost_1bit(add)) {
+ tracker->counts[rightmost_1bit_idx(add)]++;
}
}
-/* Adds 'tag' to 'set'. */
+/* Removes 'sub' from 'tracker' and unsets any bits in '*tags' that no
+ * remaining tag includes. */
void
-tag_set_add(struct tag_set *set, tag_type tag)
+tag_tracker_subtract(struct tag_tracker *tracker, tag_type *tags, tag_type sub)
{
- 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
- * whereas four 1-bits match 4 * 3 / 2 = 6 unique tags. */
- tag_type *t = &set->tags[set->n++ % TAG_SET_SIZE];
- *t |= tag;
- if (*t == TYPE_MAXIMUM(tag_type)) {
- set->tags[0] = *t;
+ for (; sub; sub = zero_rightmost_1bit(sub)) {
+ if (!--tracker->counts[rightmost_1bit_idx(sub)]) {
+ *tags &= ~rightmost_1bit(sub);
}
-
- set->total |= tag;
}
}
-