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-rw-r--r--hashmap.c266
1 files changed, 266 insertions, 0 deletions
diff --git a/hashmap.c b/hashmap.c
new file mode 100644
index 0000000..f693839
--- /dev/null
+++ b/hashmap.c
@@ -0,0 +1,266 @@
+/*
+ * Generic implementation of hash-based key value mappings.
+ */
+#include "cache.h"
+#include "hashmap.h"
+
+#define FNV32_BASE ((unsigned int) 0x811c9dc5)
+#define FNV32_PRIME ((unsigned int) 0x01000193)
+
+unsigned int strhash(const char *str)
+{
+ unsigned int c, hash = FNV32_BASE;
+ while ((c = (unsigned char) *str++))
+ hash = (hash * FNV32_PRIME) ^ c;
+ return hash;
+}
+
+unsigned int strihash(const char *str)
+{
+ unsigned int c, hash = FNV32_BASE;
+ while ((c = (unsigned char) *str++)) {
+ if (c >= 'a' && c <= 'z')
+ c -= 'a' - 'A';
+ hash = (hash * FNV32_PRIME) ^ c;
+ }
+ return hash;
+}
+
+unsigned int memhash(const void *buf, size_t len)
+{
+ unsigned int hash = FNV32_BASE;
+ unsigned char *ucbuf = (unsigned char *) buf;
+ while (len--) {
+ unsigned int c = *ucbuf++;
+ hash = (hash * FNV32_PRIME) ^ c;
+ }
+ return hash;
+}
+
+unsigned int memihash(const void *buf, size_t len)
+{
+ unsigned int hash = FNV32_BASE;
+ unsigned char *ucbuf = (unsigned char *) buf;
+ while (len--) {
+ unsigned int c = *ucbuf++;
+ if (c >= 'a' && c <= 'z')
+ c -= 'a' - 'A';
+ hash = (hash * FNV32_PRIME) ^ c;
+ }
+ return hash;
+}
+
+#define HASHMAP_INITIAL_SIZE 64
+/* grow / shrink by 2^2 */
+#define HASHMAP_RESIZE_BITS 2
+/* load factor in percent */
+#define HASHMAP_LOAD_FACTOR 80
+
+static void alloc_table(struct hashmap *map, unsigned int size)
+{
+ map->tablesize = size;
+ map->table = xcalloc(size, sizeof(struct hashmap_entry *));
+
+ /* calculate resize thresholds for new size */
+ map->grow_at = (unsigned int) ((uint64_t) size * HASHMAP_LOAD_FACTOR / 100);
+ if (size <= HASHMAP_INITIAL_SIZE)
+ map->shrink_at = 0;
+ else
+ /*
+ * The shrink-threshold must be slightly smaller than
+ * (grow-threshold / resize-factor) to prevent erratic resizing,
+ * thus we divide by (resize-factor + 1).
+ */
+ map->shrink_at = map->grow_at / ((1 << HASHMAP_RESIZE_BITS) + 1);
+}
+
+static inline int entry_equals(const struct hashmap *map,
+ const struct hashmap_entry *e1, const struct hashmap_entry *e2,
+ const void *keydata)
+{
+ return (e1 == e2) || (e1->hash == e2->hash && !map->cmpfn(e1, e2, keydata));
+}
+
+static inline unsigned int bucket(const struct hashmap *map,
+ const struct hashmap_entry *key)
+{
+ return key->hash & (map->tablesize - 1);
+}
+
+static void rehash(struct hashmap *map, unsigned int newsize)
+{
+ unsigned int i, oldsize = map->tablesize;
+ struct hashmap_entry **oldtable = map->table;
+
+ alloc_table(map, newsize);
+ for (i = 0; i < oldsize; i++) {
+ struct hashmap_entry *e = oldtable[i];
+ while (e) {
+ struct hashmap_entry *next = e->next;
+ unsigned int b = bucket(map, e);
+ e->next = map->table[b];
+ map->table[b] = e;
+ e = next;
+ }
+ }
+ free(oldtable);
+}
+
+static inline struct hashmap_entry **find_entry_ptr(const struct hashmap *map,
+ const struct hashmap_entry *key, const void *keydata)
+{
+ struct hashmap_entry **e = &map->table[bucket(map, key)];
+ while (*e && !entry_equals(map, *e, key, keydata))
+ e = &(*e)->next;
+ return e;
+}
+
+static int always_equal(const void *unused1, const void *unused2, const void *unused3)
+{
+ return 0;
+}
+
+void hashmap_init(struct hashmap *map, hashmap_cmp_fn equals_function,
+ size_t initial_size)
+{
+ unsigned int size = HASHMAP_INITIAL_SIZE;
+ map->size = 0;
+ map->cmpfn = equals_function ? equals_function : always_equal;
+
+ /* calculate initial table size and allocate the table */
+ initial_size = (unsigned int) ((uint64_t) initial_size * 100
+ / HASHMAP_LOAD_FACTOR);
+ while (initial_size > size)
+ size <<= HASHMAP_RESIZE_BITS;
+ alloc_table(map, size);
+}
+
+void hashmap_free(struct hashmap *map, int free_entries)
+{
+ if (!map || !map->table)
+ return;
+ if (free_entries) {
+ struct hashmap_iter iter;
+ struct hashmap_entry *e;
+ hashmap_iter_init(map, &iter);
+ while ((e = hashmap_iter_next(&iter)))
+ free(e);
+ }
+ free(map->table);
+ memset(map, 0, sizeof(*map));
+}
+
+void *hashmap_get(const struct hashmap *map, const void *key, const void *keydata)
+{
+ return *find_entry_ptr(map, key, keydata);
+}
+
+void *hashmap_get_next(const struct hashmap *map, const void *entry)
+{
+ struct hashmap_entry *e = ((struct hashmap_entry *) entry)->next;
+ for (; e; e = e->next)
+ if (entry_equals(map, entry, e, NULL))
+ return e;
+ return NULL;
+}
+
+void hashmap_add(struct hashmap *map, void *entry)
+{
+ unsigned int b = bucket(map, entry);
+
+ /* add entry */
+ ((struct hashmap_entry *) entry)->next = map->table[b];
+ map->table[b] = entry;
+
+ /* fix size and rehash if appropriate */
+ map->size++;
+ if (map->size > map->grow_at)
+ rehash(map, map->tablesize << HASHMAP_RESIZE_BITS);
+}
+
+void *hashmap_remove(struct hashmap *map, const void *key, const void *keydata)
+{
+ struct hashmap_entry *old;
+ struct hashmap_entry **e = find_entry_ptr(map, key, keydata);
+ if (!*e)
+ return NULL;
+
+ /* remove existing entry */
+ old = *e;
+ *e = old->next;
+ old->next = NULL;
+
+ /* fix size and rehash if appropriate */
+ map->size--;
+ if (map->size < map->shrink_at)
+ rehash(map, map->tablesize >> HASHMAP_RESIZE_BITS);
+ return old;
+}
+
+void *hashmap_put(struct hashmap *map, void *entry)
+{
+ struct hashmap_entry *old = hashmap_remove(map, entry, NULL);
+ hashmap_add(map, entry);
+ return old;
+}
+
+void hashmap_iter_init(struct hashmap *map, struct hashmap_iter *iter)
+{
+ iter->map = map;
+ iter->tablepos = 0;
+ iter->next = NULL;
+}
+
+void *hashmap_iter_next(struct hashmap_iter *iter)
+{
+ struct hashmap_entry *current = iter->next;
+ for (;;) {
+ if (current) {
+ iter->next = current->next;
+ return current;
+ }
+
+ if (iter->tablepos >= iter->map->tablesize)
+ return NULL;
+
+ current = iter->map->table[iter->tablepos++];
+ }
+}
+
+struct pool_entry {
+ struct hashmap_entry ent;
+ size_t len;
+ unsigned char data[FLEX_ARRAY];
+};
+
+static int pool_entry_cmp(const struct pool_entry *e1,
+ const struct pool_entry *e2,
+ const unsigned char *keydata)
+{
+ return e1->data != keydata &&
+ (e1->len != e2->len || memcmp(e1->data, keydata, e1->len));
+}
+
+const void *memintern(const void *data, size_t len)
+{
+ static struct hashmap map;
+ struct pool_entry key, *e;
+
+ /* initialize string pool hashmap */
+ if (!map.tablesize)
+ hashmap_init(&map, (hashmap_cmp_fn) pool_entry_cmp, 0);
+
+ /* lookup interned string in pool */
+ hashmap_entry_init(&key, memhash(data, len));
+ key.len = len;
+ e = hashmap_get(&map, &key, data);
+ if (!e) {
+ /* not found: create it */
+ e = xmallocz(sizeof(struct pool_entry) + len);
+ hashmap_entry_init(e, key.ent.hash);
+ e->len = len;
+ memcpy(e->data, data, len);
+ hashmap_add(&map, e);
+ }
+ return e->data;
+}