/*-
* Copyright (c) 2015 Nuxi, https://nuxi.nl/
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
* IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
* ARE DISCLAIMED. IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
* FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
* DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
* OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
* HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
* LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
* OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
* SUCH DAMAGE.
*/
#include <sys/cdefs.h>
__FBSDID("$FreeBSD$");
#include <errno.h>
#include <limits.h>
#include <search.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include "hsearch.h"
/*
* Look up an unused entry in the hash table for a given hash. For this
* implementation we use quadratic probing. Quadratic probing has the
* advantage of preventing primary clustering.
*/
static ENTRY *
hsearch_lookup_free(struct __hsearch *hsearch, size_t hash)
{
size_t index, i;
for (index = hash, i = 0;; index += ++i) {
ENTRY *entry = &hsearch->entries[index & hsearch->index_mask];
if (entry->key == NULL)
return (entry);
}
}
/*
* Computes an FNV-1a hash of the key. Depending on the pointer size, this
* either uses the 32- or 64-bit FNV prime.
*/
static size_t
hsearch_hash(size_t offset_basis, const char *str)
{
size_t hash;
hash = offset_basis;
while (*str != '\0') {
hash ^= (uint8_t)*str++;
if (sizeof(size_t) * CHAR_BIT <= 32)
hash *= UINT32_C(16777619);
else
hash *= UINT64_C(1099511628211);
}
return (hash);
}
int
hsearch_r(ENTRY item, ACTION action, ENTRY **retval, struct hsearch_data *htab)
{
struct __hsearch *hsearch;
ENTRY *entry, *old_entries, *new_entries;
size_t hash, index, i, old_hash, old_count, new_count;
hsearch = htab->__hsearch;
hash = hsearch_hash(hsearch->offset_basis, item.key);
/*
* Search the hash table for an existing entry for this key.
* Stop searching if we run into an unused hash table entry.
*/
for (index = hash, i = 0;; index += ++i) {
entry = &hsearch->entries[index & hsearch->index_mask];
if (entry->key == NULL)
break;
if (strcmp(entry->key, item.key) == 0) {
*retval = entry;
return (1);
}
}
/* Only perform the insertion if action is set to ENTER. */
if (action == FIND) {
errno = ESRCH;
return (0);
}
if (hsearch->entries_used * 2 >= hsearch->index_mask) {
/* Preserve the old hash table entries. */
old_count = hsearch->index_mask + 1;
old_entries = hsearch->entries;
/*
* Allocate and install a new table if insertion would
* yield a hash table that is more than 50% used. By
* using 50% as a threshold, a lookup will only take up
* to two steps on average.
*/
new_count = (hsearch->index_mask + 1) * 2;
new_entries = calloc(new_count, sizeof(ENTRY));
if (new_entries == NULL)
return (0);
hsearch->entries = new_entries;
hsearch->index_mask = new_count - 1;
/* Copy over the entries from the old table to the new table. */
for (i = 0; i < old_count; ++i) {
entry = &old_entries[i];
if (entry->key != NULL) {
old_hash = hsearch_hash(hsearch->offset_basis,
entry->key);
*hsearch_lookup_free(hsearch, old_hash) =
*entry;
}
}
/* Destroy the old hash table entries. */
free(old_entries);
/*
* Perform a new lookup for a free table entry, so that
* we insert the entry into the new hash table.
*/
hsearch = htab->__hsearch;
entry = hsearch_lookup_free(hsearch, hash);
}
/* Insert the new entry into the hash table. */
*entry = item;
++hsearch->entries_used;
*retval = entry;
return (1);
}
