Hashtable routines.

[ccan] / ccan / hashtable / hashtable.c

diff --git a/ccan/hashtable/hashtable.c b/ccan/hashtable/hashtable.c
new file mode 100644 (file)
index 0000000..46f85ac
--- /dev/null
+++ b/ccan/hashtable/hashtable.c
@@ -0,0 +1,201 @@
+#include <ccan/hashtable/hashtable.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <assert.h>
+
+/* This means a struct hashtable takes at least 512 bytes / 1k (32/64 bits). */
+#define HASHTABLE_BASE_BITS 7
+
+/* We use 0x1 as deleted marker. */
+#define HASHTABLE_DELETED ((void *)0x1)
+
+/* Number of redundant bits in a pointer. */
+#define PTR_STEAL_BITS 3
+
+static inline uintptr_t get_extra_ptr_bits(const void *p)
+{
+       return (uintptr_t)p & (((uintptr_t)1 << PTR_STEAL_BITS)-1);
+}
+
+static inline void *get_raw_ptr(const void *p)
+{
+       return (void *)((uintptr_t)p & ~(((uintptr_t)1 << PTR_STEAL_BITS)-1));
+}
+
+static inline void *make_ptr(const void *p, uintptr_t bits)
+{
+       return (void *)((uintptr_t)p | bits);
+}
+
+struct hashtable {
+       unsigned long (*rehash)(const void *elem, void *priv);
+       void *priv;
+       unsigned int bits;
+       unsigned long elems, max;
+       void **table;
+};
+
+static inline bool ptr_is_valid(const void *e)
+{
+       return e > HASHTABLE_DELETED;
+}
+
+struct hashtable *hashtable_new(unsigned long (*rehash)(const void *elem,
+                                                       void *priv),
+                               void *priv)
+{
+       struct hashtable *ht = malloc(sizeof(struct hashtable));
+       if (ht) {
+               ht->bits = HASHTABLE_BASE_BITS;
+               ht->rehash = rehash;
+               ht->priv = priv;
+               ht->elems = 0;
+               ht->max = (1 << ht->bits) * 3 / 4;
+               ht->table = calloc(1 << ht->bits, sizeof(void *));
+               if (!ht->table) {
+                       free(ht);
+                       ht = NULL;
+               }
+       }
+       return ht;
+}
+
+void hashtable_free(struct hashtable *ht)
+{
+       free(ht->table);
+       free(ht);
+}
+
+static unsigned long hash_bucket(const struct hashtable *ht,
+                                unsigned long h, unsigned long *ptrbits)
+{
+       *ptrbits = (h >> ht->bits) & (((uintptr_t)1 << PTR_STEAL_BITS)-1);
+       return h & ((1 << ht->bits)-1);
+}
+
+/* This does not expand the hash table, that's up to caller. */
+static void ht_add(struct hashtable *ht, const void *new, unsigned long h)
+{
+       unsigned long i, h2;
+
+       i = hash_bucket(ht, h, &h2);
+
+       while (ptr_is_valid(ht->table[i])) {
+               i = (i + 1) & ((1 << ht->bits)-1);
+       }
+       ht->table[i] = make_ptr(new, h2);
+}
+
+static bool double_table(struct hashtable *ht)
+{
+       unsigned int i;
+       size_t oldnum = (size_t)1 << ht->bits;
+       void **oldtable, *e;
+
+       oldtable = ht->table;
+       ht->table = calloc(1 << (ht->bits+1), sizeof(void *));
+       if (!ht->table) {
+               ht->table = oldtable;
+               return false;
+       }
+       ht->bits++;
+       ht->max *= 2;
+
+       for (i = 0; i < oldnum; i++) {
+               if (ptr_is_valid(e = oldtable[i])) {
+                       e = get_raw_ptr(e);
+                       ht_add(ht, e, ht->rehash(e, ht->priv));
+               }
+       }
+       free(oldtable);
+       return true;
+}
+
+bool hashtable_add(struct hashtable *ht, unsigned long hash, const void *p)
+{
+       if (ht->elems+1 > ht->max && !double_table(ht))
+               return false;
+       ht->elems++;
+       assert(p);
+       assert(((uintptr_t)p & (((uintptr_t)1 << PTR_STEAL_BITS)-1)) == 0);
+       ht_add(ht, p, hash);
+       return true;
+}
+
+/* Find bucket for an element. */
+static size_t ht_find(struct hashtable *ht,
+                     unsigned long hash,
+                     bool (*cmp)(const void *htelem, void *cmpdata),
+                     void *cmpdata)
+{
+       void *e;
+       unsigned long i, h2;
+
+       i = hash_bucket(ht, hash, &h2);
+
+       while ((e = ht->table[i]) != NULL) {
+               if (e != HASHTABLE_DELETED
+                   && h2 == get_extra_ptr_bits(e)
+                   && cmp(get_raw_ptr(ht->table[i]), cmpdata))
+                       return i;
+               i = (i + 1) & ((1 << ht->bits)-1);
+       }
+       return (size_t)-1;
+}
+
+
+/* If every one of the following buckets are DELETED (up to the next unused
+   one), we can actually mark them all unused. */
+static void delete_run(struct hashtable *ht, unsigned int num)
+{
+       unsigned int i, last = num + 1;
+
+       while (ht->table[last & ((1 << ht->bits)-1)]) {
+               if (ptr_is_valid(ht->table[last & ((1 << ht->bits)-1)]))
+                       return;
+               last++;
+       }
+       for (i = num; i < last; i++)
+               ht->table[i & ((1 << ht->bits)-1)] = NULL;
+}
+
+void *hashtable_find(struct hashtable *ht,
+                    unsigned long hash,
+                    bool (*cmp)(const void *htelem, void *cmpdata),
+                    void *cmpdata)
+{
+       size_t i = ht_find(ht, hash, cmp, cmpdata);
+       if (i != (size_t)-1)
+               return get_raw_ptr(ht->table[i]);
+       return NULL;
+}
+
+static bool ptr_cmp(const void *htelem, void *cmpdata)
+{
+       return htelem == cmpdata;
+}
+
+bool hashtable_del(struct hashtable *ht, unsigned long hash, const void *p)
+{
+       size_t i = ht_find(ht, hash, ptr_cmp, (void *)p);
+       if (i == (size_t)-1)
+               return false;
+
+       ht->elems--;
+       ht->table[i] = HASHTABLE_DELETED;
+       delete_run(ht, i);
+       return true;
+}
+       
+       
+void hashtable_traverse(struct hashtable *ht, bool (*cb)(void *p, void *cbarg),
+                       void *cbarg)
+{
+       size_t i;
+
+       for (i = 0; i < (1 << ht->bits); i++) {
+               if (ptr_is_valid(ht->table[i]))
+                       if (cb(get_raw_ptr(ht->table[i]), cbarg))
+                               return;
+       }
+}