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@@ -48,7 +48,7 @@ struct hash *
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hash_create (unsigned int (*hash_key) (void *),
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int (*hash_cmp) (const void *, const void *))
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{
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- return hash_create_size (HASHTABSIZE, hash_key, hash_cmp);
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+ return hash_create_size (HASH_INITIAL_SIZE, hash_key, hash_cmp);
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}
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/* Utility function for hash_get(). When this function is specified
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@@ -60,6 +60,52 @@ hash_alloc_intern (void *arg)
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return arg;
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}
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+/* Expand hash if the chain length exceeds the threshold. */
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+static void hash_expand (struct hash *hash)
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+{
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+ unsigned int i, new_size, losers;
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+ struct hash_backet *hb, *hbnext, **new_index;
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+
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+ new_size = hash->size * 2;
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+ new_index = XCALLOC(MTYPE_HASH_INDEX, sizeof(struct hash_backet *) * new_size);
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+ if (new_index == NULL)
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+ return;
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+
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+ for (i = 0; i < hash->size; i++)
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+ for (hb = hash->index[i]; hb; hb = hbnext)
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+ {
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+ unsigned int h = hb->key & (new_size - 1);
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+
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+ hbnext = hb->next;
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+ hb->next = new_index[h];
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+ new_index[h] = hb;
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+ }
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+
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+ /* Switch to new table */
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+ XFREE(MTYPE_HASH_INDEX, hash->index);
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+ hash->size = new_size;
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+ hash->index = new_index;
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+
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+ /* Ideally, new index should have chains half as long as the original.
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+ If expansion didn't help, then not worth expanding again,
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+ the problem is the hash function. */
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+ losers = 0;
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+ for (i = 0; i < hash->size; i++)
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+ {
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+ unsigned int len = 0;
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+ for (hb = hash->index[i]; hb; hb = hb->next)
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+ {
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+ if (++len > HASH_THRESHOLD/2)
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+ ++losers;
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+ if (len >= HASH_THRESHOLD)
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+ hash->no_expand = 1;
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+ }
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+ }
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+
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+ if (losers > hash->count / 2)
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+ hash->no_expand = 1;
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+}
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+
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/* Lookup and return hash backet in hash. If there is no
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corresponding hash backet and alloc_func is specified, create new
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hash backet. */
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@@ -69,14 +115,19 @@ hash_get (struct hash *hash, void *data, void * (*alloc_func) (void *))
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unsigned int key;
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unsigned int index;
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void *newdata;
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+ unsigned int len;
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struct hash_backet *backet;
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key = (*hash->hash_key) (data);
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index = key & (hash->size - 1);
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+ len = 0;
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- for (backet = hash->index[index]; backet != NULL; backet = backet->next)
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- if (backet->key == key && (*hash->hash_cmp) (backet->data, data))
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- return backet->data;
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+ for (backet = hash->index[index]; backet != NULL; backet = backet->next)
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+ {
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+ if (backet->key == key && (*hash->hash_cmp) (backet->data, data))
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+ return backet->data;
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+ ++len;
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+ }
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if (alloc_func)
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{
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@@ -84,6 +135,12 @@ hash_get (struct hash *hash, void *data, void * (*alloc_func) (void *))
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if (newdata == NULL)
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return NULL;
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+ if (len > HASH_THRESHOLD && !hash->no_expand)
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+ {
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+ hash_expand (hash);
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+ index = key & (hash->size - 1);
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+ }
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+
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backet = XMALLOC (MTYPE_HASH_BACKET, sizeof (struct hash_backet));
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backet->data = newdata;
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backet->key = key;
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