summaryrefslogtreecommitdiff
path: root/src/hash.c
diff options
context:
space:
mode:
Diffstat (limited to 'src/hash.c')
-rw-r--r--src/hash.c307
1 files changed, 307 insertions, 0 deletions
diff --git a/src/hash.c b/src/hash.c
new file mode 100644
index 0000000..1dbee82
--- /dev/null
+++ b/src/hash.c
@@ -0,0 +1,307 @@
+/*
+ * Copyright © 2009 Intel Corporation
+ * Copyright © 1988-2004 Keith Packard and Bart Massey.
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
+ * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
+ * IN THE SOFTWARE.
+ *
+ * Except as contained in this notice, the names of the authors
+ * or their institutions shall not be used in advertising or
+ * otherwise to promote the sale, use or other dealings in this
+ * Software without prior written authorization from the
+ * authors.
+ *
+ * Authors:
+ * Eric Anholt <eric@anholt.net>
+ * Keith Packard <keithp@keithp.com>
+ */
+
+#include <stdlib.h>
+#include <stdint.h>
+
+#include "hash.h"
+
+struct hash_entry {
+ uint32_t hash;
+ void *data;
+};
+
+struct hash_table {
+ struct hash_entry *table;
+ uint32_t size;
+ uint32_t rehash;
+ uint32_t max_entries;
+ uint32_t size_index;
+ uint32_t entries;
+ uint32_t deleted_entries;
+};
+
+#define ARRAY_SIZE(array) (sizeof(array) / sizeof(array[0]))
+
+/*
+ * From Knuth -- a good choice for hash/rehash values is p, p-2 where
+ * p and p-2 are both prime. These tables are sized to have an extra 10%
+ * free to avoid exponential performance degradation as the hash table fills
+ */
+
+static const uint32_t deleted_data;
+
+static const struct {
+ uint32_t max_entries, size, rehash;
+} hash_sizes[] = {
+ { 2, 5, 3 },
+ { 4, 7, 5 },
+ { 8, 13, 11 },
+ { 16, 19, 17 },
+ { 32, 43, 41 },
+ { 64, 73, 71 },
+ { 128, 151, 149 },
+ { 256, 283, 281 },
+ { 512, 571, 569 },
+ { 1024, 1153, 1151 },
+ { 2048, 2269, 2267 },
+ { 4096, 4519, 4517 },
+ { 8192, 9013, 9011 },
+ { 16384, 18043, 18041 },
+ { 32768, 36109, 36107 },
+ { 65536, 72091, 72089 },
+ { 131072, 144409, 144407 },
+ { 262144, 288361, 288359 },
+ { 524288, 576883, 576881 },
+ { 1048576, 1153459, 1153457 },
+ { 2097152, 2307163, 2307161 },
+ { 4194304, 4613893, 4613891 },
+ { 8388608, 9227641, 9227639 },
+ { 16777216, 18455029, 18455027 },
+ { 33554432, 36911011, 36911009 },
+ { 67108864, 73819861, 73819859 },
+ { 134217728, 147639589, 147639587 },
+ { 268435456, 295279081, 295279079 },
+ { 536870912, 590559793, 590559791 },
+ { 1073741824, 1181116273, 1181116271},
+ { 2147483648ul, 2362232233ul, 2362232231ul}
+};
+
+static int
+entry_is_free(struct hash_entry *entry)
+{
+ return entry->data == NULL;
+}
+
+static int
+entry_is_deleted(struct hash_entry *entry)
+{
+ return entry->data == &deleted_data;
+}
+
+static int
+entry_is_present(struct hash_entry *entry)
+{
+ return entry->data != NULL && entry->data != &deleted_data;
+}
+
+struct hash_table *
+hash_table_create(void)
+{
+ struct hash_table *ht;
+
+ ht = malloc(sizeof(*ht));
+ if (ht == NULL)
+ return NULL;
+
+ ht->size_index = 0;
+ ht->size = hash_sizes[ht->size_index].size;
+ ht->rehash = hash_sizes[ht->size_index].rehash;
+ ht->max_entries = hash_sizes[ht->size_index].max_entries;
+ ht->table = calloc(ht->size, sizeof(*ht->table));
+ ht->entries = 0;
+ ht->deleted_entries = 0;
+
+ if (ht->table == NULL) {
+ free(ht);
+ return NULL;
+ }
+
+ return ht;
+}
+
+/**
+ * Frees the given hash table.
+ */
+void
+hash_table_destroy(struct hash_table *ht)
+{
+ if (!ht)
+ return;
+
+ free(ht->table);
+ free(ht);
+}
+
+/**
+ * Finds a hash table entry with the given key and hash of that key.
+ *
+ * Returns NULL if no entry is found. Note that the data pointer may be
+ * modified by the user.
+ */
+static void *
+hash_table_search(struct hash_table *ht, uint32_t hash)
+{
+ uint32_t hash_address;
+
+ hash_address = hash % ht->size;
+ do {
+ uint32_t double_hash;
+
+ struct hash_entry *entry = ht->table + hash_address;
+
+ if (entry_is_free(entry)) {
+ return NULL;
+ } else if (entry_is_present(entry) && entry->hash == hash) {
+ return entry;
+ }
+
+ double_hash = 1 + hash % ht->rehash;
+
+ hash_address = (hash_address + double_hash) % ht->size;
+ } while (hash_address != hash % ht->size);
+
+ return NULL;
+}
+
+void
+hash_table_for_each(struct hash_table *ht,
+ hash_table_iterator_func_t func, void *data)
+{
+ struct hash_entry *entry;
+ uint32_t i;
+
+ for (i = 0; i < ht->size; i++) {
+ entry = ht->table + i;
+ if (entry_is_present(entry))
+ func(entry->data, data);
+ }
+}
+
+void *
+hash_table_lookup(struct hash_table *ht, uint32_t hash)
+{
+ struct hash_entry *entry;
+
+ entry = hash_table_search(ht, hash);
+ if (entry != NULL)
+ return entry->data;
+
+ return NULL;
+}
+
+static void
+hash_table_rehash(struct hash_table *ht, int new_size_index)
+{
+ struct hash_table old_ht;
+ struct hash_entry *table, *entry;
+
+ if (new_size_index >= ARRAY_SIZE(hash_sizes))
+ return;
+
+ table = calloc(hash_sizes[new_size_index].size, sizeof(*ht->table));
+ if (table == NULL)
+ return;
+
+ old_ht = *ht;
+
+ ht->table = table;
+ ht->size_index = new_size_index;
+ ht->size = hash_sizes[ht->size_index].size;
+ ht->rehash = hash_sizes[ht->size_index].rehash;
+ ht->max_entries = hash_sizes[ht->size_index].max_entries;
+ ht->entries = 0;
+ ht->deleted_entries = 0;
+
+ for (entry = old_ht.table;
+ entry != old_ht.table + old_ht.size;
+ entry++) {
+ if (entry_is_present(entry)) {
+ hash_table_insert(ht, entry->hash, entry->data);
+ }
+ }
+
+ free(old_ht.table);
+}
+
+/**
+ * Inserts the data with the given hash into the table.
+ *
+ * Note that insertion may rearrange the table on a resize or rehash,
+ * so previously found hash_entries are no longer valid after this function.
+ */
+int
+hash_table_insert(struct hash_table *ht, uint32_t hash, void *data)
+{
+ uint32_t hash_address;
+
+ if (ht->entries >= ht->max_entries) {
+ hash_table_rehash(ht, ht->size_index + 1);
+ } else if (ht->deleted_entries + ht->entries >= ht->max_entries) {
+ hash_table_rehash(ht, ht->size_index);
+ }
+
+ hash_address = hash % ht->size;
+ do {
+ struct hash_entry *entry = ht->table + hash_address;
+ uint32_t double_hash;
+
+ if (!entry_is_present(entry)) {
+ if (entry_is_deleted(entry))
+ ht->deleted_entries--;
+ entry->hash = hash;
+ entry->data = data;
+ ht->entries++;
+ return 0;
+ }
+
+ double_hash = 1 + hash % ht->rehash;
+
+ hash_address = (hash_address + double_hash) % ht->size;
+ } while (hash_address != hash % ht->size);
+
+ /* We could hit here if a required resize failed. An unchecked-malloc
+ * application could ignore this result.
+ */
+ return -1;
+}
+
+/**
+ * This function deletes the given hash table entry.
+ *
+ * Note that deletion doesn't otherwise modify the table, so an iteration over
+ * the table deleting entries is safe.
+ */
+void
+hash_table_remove(struct hash_table *ht, uint32_t hash)
+{
+ struct hash_entry *entry;
+
+ entry = hash_table_search(ht, hash);
+ if (entry != NULL) {
+ entry->data = (void *) &deleted_data;
+ ht->entries--;
+ ht->deleted_entries++;
+ }
+}
generated by cgit v1.2.3 (git 2.39.1) at 2024-11-23 15:58:07 +0000