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/*
* 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.
* You may obtain a copy of the License at:
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
#include <config.h>
#include "tag.h"
#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 tag deterministically generated from 'seed'.
*
* 'seed' should have data in all of its bits; if it has data only in its
* low-order bits then the resulting tags will be poorly distributed. Use a
* hash function such as hash_bytes() to generate 'seed' if necessary. */
tag_type
tag_create_deterministic(uint32_t seed)
{
int x = seed & (N_TAG_BITS - 1);
int y = (seed >> LOG2_N_TAG_BITS) % (N_TAG_BITS - 1);
y += y >= x;
return (1u << x) | (1u << y);
}
/* Initializes 'tracker'. */
void
tag_tracker_init(struct tag_tracker *tracker)
{
memset(tracker, 0, sizeof *tracker);
}
/* 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)
{
*tags |= add;
for (; add; add = zero_rightmost_1bit(add)) {
tracker->counts[rightmost_1bit_idx(add)]++;
}
}
/* Removes 'sub' from 'tracker' and unsets any bits in '*tags' that no
* remaining tag includes. */
void
tag_tracker_subtract(struct tag_tracker *tracker, tag_type *tags, tag_type sub)
{
for (; sub; sub = zero_rightmost_1bit(sub)) {
if (!--tracker->counts[rightmost_1bit_idx(sub)]) {
*tags &= ~rightmost_1bit(sub);
}
}
}
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