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