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/*
* Copyright (c) 2008, 2009 Nicira Networks.
*
* Permission to use, copy, modify, and/or distribute this software for any
* purpose with or without fee is hereby granted, provided that the above
* copyright notice and this permission notice appear in all copies.
*
* THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
* WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
* MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
* ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
* WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
* ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
* OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
*/
#include <config.h>
#include "hmap.h"
#include <assert.h>
#include <stdint.h>
#include "coverage.h"
#include "util.h"
/* Initializes 'hmap' as an empty hash table. */
void
hmap_init(struct hmap *hmap)
{
hmap->buckets = &hmap->one;
hmap->one = NULL;
hmap->mask = 0;
hmap->n = 0;
}
/* Frees memory reserved by 'hmap'. It is the client's responsibility to free
* the nodes themselves, if necessary. */
void
hmap_destroy(struct hmap *hmap)
{
if (hmap && hmap->buckets != &hmap->one) {
free(hmap->buckets);
}
}
/* Exchanges hash maps 'a' and 'b'. */
void
hmap_swap(struct hmap *a, struct hmap *b)
{
struct hmap tmp = *a;
*a = *b;
*b = tmp;
if (a->buckets == &b->one) {
a->buckets = &a->one;
}
if (b->buckets == &a->one) {
b->buckets = &b->one;
}
}
static void
resize(struct hmap *hmap, size_t new_mask)
{
struct hmap tmp;
size_t i;
assert(!(new_mask & (new_mask + 1)));
assert(new_mask != SIZE_MAX);
hmap_init(&tmp);
if (new_mask) {
tmp.buckets = xmalloc(sizeof *tmp.buckets * (new_mask + 1));
tmp.mask = new_mask;
for (i = 0; i <= tmp.mask; i++) {
tmp.buckets[i] = NULL;
}
}
for (i = 0; i <= hmap->mask; i++) {
struct hmap_node *node, *next;
int count = 0;
for (node = hmap->buckets[i]; node; node = next) {
next = node->next;
hmap_insert_fast(&tmp, node, node->hash);
count++;
}
if (count > 5) {
COVERAGE_INC(hmap_pathological);
}
}
hmap_swap(hmap, &tmp);
hmap_destroy(&tmp);
}
static size_t
calc_mask(size_t capacity)
{
size_t mask = capacity / 2;
mask |= mask >> 1;
mask |= mask >> 2;
mask |= mask >> 4;
mask |= mask >> 8;
mask |= mask >> 16;
#if SIZE_MAX > UINT32_MAX
mask |= mask >> 32;
#endif
/* If we need to dynamically allocate buckets we might as well allocate at
* least 4 of them. */
mask |= (mask & 1) << 1;
return mask;
}
/* Expands 'hmap', if necessary, to optimize the performance of searches. */
void
hmap_expand(struct hmap *hmap)
{
size_t new_mask = calc_mask(hmap->n);
if (new_mask > hmap->mask) {
COVERAGE_INC(hmap_expand);
resize(hmap, new_mask);
}
}
/* Shrinks 'hmap', if necessary, to optimize the performance of iteration. */
void
hmap_shrink(struct hmap *hmap)
{
size_t new_mask = calc_mask(hmap->n);
if (new_mask < hmap->mask) {
COVERAGE_INC(hmap_shrink);
resize(hmap, new_mask);
}
}
/* Expands 'hmap', if necessary, to optimize the performance of searches when
* it has up to 'n' elements. (But iteration will be slow in a hash map whose
* allocated capacity is much higher than its current number of nodes.) */
void
hmap_reserve(struct hmap *hmap, size_t n)
{
size_t new_mask = calc_mask(n);
if (new_mask > hmap->mask) {
COVERAGE_INC(hmap_reserve);
resize(hmap, new_mask);
}
}
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