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/* $OpenBSD: hash.c,v 1.2 2017/08/11 14:58:56 jasper Exp $ */
/* Copyright (c) 1999, 2004 Marc Espie <espie@openbsd.org>
*
* Permission to use, copy, modify, and 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 <stddef.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <limits.h>
#include "hash.h"
struct _hash_record {
uint32_t hv;
struct hash_entry *p;
};
struct hash {
struct _hash_record *t;
unsigned int size;
unsigned int total;
unsigned int deleted;
};
#define DELETED ((struct hash_entry *)h)
#define NONE (h->size)
/* Don't bother changing the hash table if the change is small enough. */
#define MINSIZE (1UL << 4)
#define MINDELETED 4
static void hash_resize(struct hash *);
static uint32_t hash_interval(const char *, const char **);
static unsigned int hash_qlookup(struct hash *, const char *);
/* hash_delete only frees the hash structure. Use hash_first/hash_next
* to free entries as well. */
void
hash_delete(struct hash *h)
{
free(h->t);
h->t = NULL;
}
static void
hash_resize(struct hash *h)
{
struct _hash_record *n;
size_t ns;
unsigned int j;
unsigned int i, incr;
if (4 * h->deleted < h->total) {
if (h->size >= (UINT_MAX >> 1U))
ns = UINT_MAX;
else
ns = h->size << 1U;
} else if (3 * h->deleted > 2 * h->total)
ns = h->size >> 1U;
else
ns = h->size;
if (ns < MINSIZE)
ns = MINSIZE;
n = calloc(ns, sizeof(struct _hash_record));
if (!n)
return;
for (j = 0; j < h->size; j++) {
if (h->t[j].p != NULL && h->t[j].p != DELETED) {
i = h->t[j].hv % ns;
incr = ((h->t[j].hv % (ns - 2)) & ~1) + 1;
while (n[i].p != NULL) {
i += incr;
if (i >= ns)
i -= ns;
}
n[i].hv = h->t[j].hv;
n[i].p = h->t[j].p;
}
}
free(h->t);
h->t = n;
h->size = ns;
h->total -= h->deleted;
h->deleted = 0;
}
void *
hash_remove(struct hash *h, unsigned int i)
{
void *result = (void *)h->t[i].p;
if (result == NULL || result == DELETED)
return NULL;
h->t[i].p = DELETED;
h->deleted++;
if (h->deleted >= MINDELETED && 4 * h->deleted > h->total)
hash_resize(h);
return result;
}
void
hash_insert(struct hash *h, unsigned int i, struct hash_entry *p,
const char *key)
{
p->hkey = key;
if (h->t[i].p == DELETED) {
h->deleted--;
h->t[i].p = p;
} else {
h->t[i].p = p;
/* Arbitrary resize boundary. Tweak if not efficient enough. */
if (++h->total * 4 > h->size * 3)
hash_resize(h);
}
}
void *
hash_first(struct hash *h, unsigned int *pos)
{
*pos = 0;
return hash_next(h, pos);
}
void *
hash_next(struct hash *h, unsigned int *pos)
{
for (; *pos < h->size; (*pos)++)
if (h->t[*pos].p != DELETED && h->t[*pos].p != NULL)
return (void *)h->t[(*pos)++].p;
return NULL;
}
struct hash *
hash_init(unsigned int size)
{
struct hash *h;
h = calloc(1, sizeof(*h));
if (h == NULL)
return NULL;
h->size = 1UL << size;
if (h->size < MINSIZE)
h->size = MINSIZE;
/* Copy info so that caller may free it. */
h->total = h->deleted = 0;
h->t = calloc(h->size, sizeof(struct _hash_record));
if (h->t == NULL) {
free(h);
return NULL;
}
return h;
}
static uint32_t
hash_interval(const char *s, const char **e)
{
uint32_t k;
if (!*e)
*e = s + strlen(s);
if (s == *e)
k = 0;
else
k = *s++;
while (s != *e)
k = ((k << 2) | (k >> 30)) ^ *s++;
return k;
}
static unsigned int
hash_qlookup(struct hash *h, const char *start)
{
const char *end = NULL;
unsigned int i, incr;
unsigned int empty;
uint32_t hv;
hv = hash_interval(start, &end);
empty = NONE;
i = hv % h->size;
incr = ((hv % (h->size-2)) & ~1) + 1;
while (h->t[i].p != NULL) {
if (h->t[i].p == DELETED) {
if (empty == NONE)
empty = i;
} else if (h->t[i].hv == hv &&
strncmp(h->t[i].p->hkey, start, end - start) == 0 &&
(h->t[i].p->hkey)[end-start] == '\0') {
if (empty != NONE) {
h->t[empty].hv = hv;
h->t[empty].p = h->t[i].p;
h->t[i].p = DELETED;
return empty;
} else {
return i;
}
}
i += incr;
if (i >= h->size)
i -= h->size;
}
/* Found an empty position. */
if (empty != NONE)
i = empty;
h->t[i].hv = hv;
return i;
}
struct hash_entry *
hash_find(struct hash *h, const char *start, unsigned int *slot)
{
unsigned int i;
i = hash_qlookup(h, start);
if (slot != NULL)
*slot = i;
if (h->t[i].p == DELETED)
return NULL;
return h->t[i].p;
}
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