4d646dac46
This hsearch(3) implementation is (with very minor changes) taken from FreeBSD 11.1. Also fix compilation errors due to calls to index(). This should probably be fixed upstream.
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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