Implement incremental hash table resizing in isc_ht

Previously, an incremental hash table resizing was implemented for the dns_rbt_t hash table implementation. Using that as a base, also implement the incremental hash table resizing also for isc_ht API hashtables: 1. During the resize, allocate the new hash table, but keep the old table unchanged. 2. In each lookup, delete, or iterator operation, check both tables. 3. Perform insertion operations only in the new table. 4. At each insertion also move <r> elements from the old table to the new table. 5. When all elements are removed from the old table, deallocate it. To ensure that the old table is completely copied over before the new table itself needs to be enlarged, it is necessary to increase the size of the table by a factor of at least (<r> + 1)/<r> during resizing. In our implementation <r> is equal to 1. The downside of this approach is that the old table and the new table could stay in memory for longer when there are no new insertions into the hash table for prolonged periods of time as the incremental rehashing happens only during the insertions.
2025-08-31 06:25:31 +00:00 · 2022-03-15 21:45:33 +01:00
parent 7ba3a06935
commit e42cb1f198
2 changed files with 377 additions and 146 deletions
--- a/lib/isc/ht.c
+++ b/lib/isc/ht.c
@@ -27,9 +27,22 @@ typedef struct isc_ht_node isc_ht_node_t;
 #define ISC_HT_MAGIC	 ISC_MAGIC('H', 'T', 'a', 'b')
 #define ISC_HT_VALID(ht) ISC_MAGIC_VALID(ht, ISC_HT_MAGIC)

+#define HT_NO_BITS    0
+#define HT_MIN_BITS   1
+#define HT_MAX_BITS   32
+#define HT_OVERCOMMIT 3
+
+#define HT_NEXTTABLE(idx)      ((idx == 0) ? 1 : 0)
+#define TRY_NEXTTABLE(idx, ht) (idx == ht->hindex && rehashing_in_progress(ht))
+
+#define GOLDEN_RATIO_32 0x61C88647
+
+#define HASHSIZE(bits) (UINT64_C(1) << (bits))
+
 struct isc_ht_node {
 	void *value;
 	isc_ht_node_t *next;
+	uint32_t hashval;
 	size_t keysize;
 	unsigned char key[];
 };
@@ -37,41 +50,203 @@ struct isc_ht_node {
 struct isc_ht {
 	unsigned int magic;
 	isc_mem_t *mctx;
-	size_t size;
-	size_t mask;
-	unsigned int count;
-	isc_ht_node_t **table;
+	size_t count;
+	size_t size[2];
+	uint8_t hashbits[2];
+	isc_ht_node_t **table[2];
+	uint8_t hindex;
+	uint32_t hiter; /* rehashing iterator */
 };

 struct isc_ht_iter {
 	isc_ht_t *ht;
 	size_t i;
+	uint8_t hindex;
 	isc_ht_node_t *cur;
 };

+static isc_ht_node_t *
+isc__ht_find(const isc_ht_t *ht, const unsigned char *key,
+	     const uint32_t keysize, const uint32_t hashval, const uint8_t idx);
+static void
+isc__ht_add(isc_ht_t *ht, const unsigned char *key, const uint32_t keysize,
+	    const uint32_t hashval, const uint8_t idx, void *value);
+static isc_result_t
+isc__ht_delete(isc_ht_t *ht, const unsigned char *key, const uint32_t keysize,
+	       const uint32_t hashval, const uint8_t idx);
+
+static uint32_t
+rehash_bits(isc_ht_t *ht, size_t newcount);
+
+static void
+hashtable_new(isc_ht_t *ht, const uint8_t idx, const uint8_t bits);
+static void
+hashtable_free(isc_ht_t *ht, const uint8_t idx);
+static void
+hashtable_rehash(isc_ht_t *ht, uint32_t newbits);
+static void
+hashtable_rehash_one(isc_ht_t *ht);
+static void
+maybe_rehash(isc_ht_t *ht, size_t newcount);
+
+static isc_result_t
+isc__ht_iter_next(isc_ht_iter_t *it);
+
+static bool
+isc__ht_node_match(isc_ht_node_t *node, const uint32_t hashval,
+		   const uint8_t *key, uint32_t keysize) {
+	return (node->hashval == hashval && node->keysize == keysize &&
+		memcmp(node->key, key, keysize) == 0);
+}
+
+static uint32_t
+hash_32(uint32_t val, unsigned int bits) {
+	REQUIRE(bits <= HT_MAX_BITS);
+	/* High bits are more random. */
+	return (val * GOLDEN_RATIO_32 >> (32 - bits));
+}
+
+static bool
+rehashing_in_progress(const isc_ht_t *ht) {
+	return (ht->table[HT_NEXTTABLE(ht->hindex)] != NULL);
+}
+
+static bool
+hashtable_is_overcommited(isc_ht_t *ht) {
+	return (ht->count >= (ht->size[ht->hindex] * HT_OVERCOMMIT));
+}
+
+static uint32_t
+rehash_bits(isc_ht_t *ht, size_t newcount) {
+	uint32_t newbits = ht->hashbits[ht->hindex];
+
+	while (newcount >= HASHSIZE(newbits) && newbits <= HT_MAX_BITS) {
+		newbits += 1;
+	}
+
+	return (newbits);
+}
+
+/*
+ * Rebuild the hashtable to reduce the load factor
+ */
+static void
+hashtable_rehash(isc_ht_t *ht, uint32_t newbits) {
+	uint8_t oldindex = ht->hindex;
+	uint32_t oldbits = ht->hashbits[oldindex];
+	uint8_t newindex = HT_NEXTTABLE(oldindex);
+
+	REQUIRE(ht->hashbits[oldindex] >= HT_MIN_BITS);
+	REQUIRE(ht->hashbits[oldindex] <= HT_MAX_BITS);
+	REQUIRE(ht->table[oldindex] != NULL);
+
+	REQUIRE(newbits <= HT_MAX_BITS);
+	REQUIRE(ht->hashbits[newindex] == HT_NO_BITS);
+	REQUIRE(ht->table[newindex] == NULL);
+
+	REQUIRE(newbits > oldbits);
+
+	hashtable_new(ht, newindex, newbits);
+
+	ht->hindex = newindex;
+
+	hashtable_rehash_one(ht);
+}
+
+static void
+hashtable_rehash_one(isc_ht_t *ht) {
+	isc_ht_node_t **newtable = ht->table[ht->hindex];
+	uint32_t oldsize = ht->size[HT_NEXTTABLE(ht->hindex)];
+	isc_ht_node_t **oldtable = ht->table[HT_NEXTTABLE(ht->hindex)];
+	isc_ht_node_t *node = NULL;
+	isc_ht_node_t *nextnode;
+
+	/* Find first non-empty node */
+	while (ht->hiter < oldsize && oldtable[ht->hiter] == NULL) {
+		ht->hiter++;
+	}
+
+	/* Rehashing complete */
+	if (ht->hiter == oldsize) {
+		hashtable_free(ht, HT_NEXTTABLE(ht->hindex));
+		ht->hiter = 0;
+		return;
+	}
+
+	/* Move the first non-empty node from old hashtable to new hashtable */
+	for (node = oldtable[ht->hiter]; node != NULL; node = nextnode) {
+		uint32_t hash = hash_32(node->hashval,
+					ht->hashbits[ht->hindex]);
+		nextnode = node->next;
+		node->next = newtable[hash];
+		newtable[hash] = node;
+	}
+
+	oldtable[ht->hiter] = NULL;
+
+	ht->hiter++;
+}
+
+static void
+maybe_rehash(isc_ht_t *ht, size_t newcount) {
+	uint32_t newbits = rehash_bits(ht, newcount);
+
+	if (ht->hashbits[ht->hindex] < newbits && newbits <= HT_MAX_BITS) {
+		hashtable_rehash(ht, newbits);
+	}
+}
+
+static void
+hashtable_new(isc_ht_t *ht, const uint8_t idx, const uint8_t bits) {
+	size_t size;
+	REQUIRE(ht->hashbits[idx] == HT_NO_BITS);
+	REQUIRE(ht->table[idx] == NULL);
+	REQUIRE(bits >= HT_MIN_BITS);
+	REQUIRE(bits <= HT_MAX_BITS);
+
+	ht->hashbits[idx] = bits;
+	ht->size[idx] = HASHSIZE(ht->hashbits[idx]);
+
+	size = ht->size[idx] * sizeof(isc_ht_node_t *);
+
+	ht->table[idx] = isc_mem_get(ht->mctx, size);
+	memset(ht->table[idx], 0, size);
+}
+
+static void
+hashtable_free(isc_ht_t *ht, const uint8_t idx) {
+	size_t size = ht->size[idx] * sizeof(isc_ht_node_t *);
+
+	for (size_t i = 0; i < ht->size[idx]; i++) {
+		isc_ht_node_t *node = ht->table[idx][i];
+		while (node != NULL) {
+			isc_ht_node_t *next = node->next;
+			ht->count--;
+			isc_mem_put(ht->mctx, node,
+				    sizeof(*node) + node->keysize);
+			node = next;
+		}
+	}
+
+	isc_mem_put(ht->mctx, ht->table[idx], size);
+	ht->hashbits[idx] = HT_NO_BITS;
+	ht->table[idx] = NULL;
+}
+
 void
 isc_ht_init(isc_ht_t **htp, isc_mem_t *mctx, uint8_t bits) {
 	isc_ht_t *ht = NULL;
-	size_t i;

 	REQUIRE(htp != NULL && *htp == NULL);
 	REQUIRE(mctx != NULL);
-	REQUIRE(bits >= 1 && bits <= (sizeof(size_t) * 8 - 1));
+	REQUIRE(bits >= 1 && bits <= HT_MAX_BITS);

-	ht = isc_mem_get(mctx, sizeof(struct isc_ht));
+	ht = isc_mem_get(mctx, sizeof(*ht));
+	*ht = (isc_ht_t){ 0 };

-	ht->mctx = NULL;
 	isc_mem_attach(mctx, &ht->mctx);

-	ht->size = ((size_t)1 << bits);
-	ht->mask = ((size_t)1 << bits) - 1;
-	ht->count = 0;
-
-	ht->table = isc_mem_get(ht->mctx, ht->size * sizeof(isc_ht_node_t *));
-
-	for (i = 0; i < ht->size; i++) {
-		ht->table[i] = NULL;
-	}
+	hashtable_new(ht, 0, bits);

 	ht->magic = ISC_HT_MAGIC;

@@ -81,123 +256,180 @@ isc_ht_init(isc_ht_t **htp, isc_mem_t *mctx, uint8_t bits) {
 void
 isc_ht_destroy(isc_ht_t **htp) {
 	isc_ht_t *ht;
-	size_t i;

 	REQUIRE(htp != NULL);
+	REQUIRE(ISC_HT_VALID(*htp));

 	ht = *htp;
 	*htp = NULL;
-
-	REQUIRE(ISC_HT_VALID(ht));
-
 	ht->magic = 0;

-	for (i = 0; i < ht->size; i++) {
-		isc_ht_node_t *node = ht->table[i];
-		while (node != NULL) {
-			isc_ht_node_t *next = node->next;
-			ht->count--;
-			isc_mem_put(ht->mctx, node,
-				    offsetof(isc_ht_node_t, key) +
-					    node->keysize);
-			node = next;
+	for (size_t i = 0; i <= 1; i++) {
+		if (ht->table[i] != NULL) {
+			hashtable_free(ht, i);
 		}
 	}

 	INSIST(ht->count == 0);

-	isc_mem_put(ht->mctx, ht->table, ht->size * sizeof(isc_ht_node_t *));
-	isc_mem_putanddetach(&ht->mctx, ht, sizeof(struct isc_ht));
+	isc_mem_putanddetach(&ht->mctx, ht, sizeof(*ht));
+}
+
+static void
+isc__ht_add(isc_ht_t *ht, const unsigned char *key, const uint32_t keysize,
+	    const uint32_t hashval, const uint8_t idx, void *value) {
+	isc_ht_node_t *node;
+	uint32_t hash;
+
+	hash = hash_32(hashval, ht->hashbits[idx]);
+
+	node = isc_mem_get(ht->mctx, sizeof(*node) + keysize);
+	*node = (isc_ht_node_t){
+		.keysize = keysize,
+		.hashval = hashval,
+		.next = ht->table[idx][hash],
+		.value = value,
+	};
+
+	memmove(node->key, key, keysize);
+
+	ht->count++;
+	ht->table[idx][hash] = node;
 }

 isc_result_t
-isc_ht_add(isc_ht_t *ht, const unsigned char *key, uint32_t keysize,
+isc_ht_add(isc_ht_t *ht, const unsigned char *key, const uint32_t keysize,
 	   void *value) {
-	isc_ht_node_t *node;
-	uint32_t hash;
+	uint32_t hashval;

 	REQUIRE(ISC_HT_VALID(ht));
 	REQUIRE(key != NULL && keysize > 0);

-	hash = isc_hash_function(key, keysize, true);
-	node = ht->table[hash & ht->mask];
-	while (node != NULL) {
-		if (keysize == node->keysize &&
-		    memcmp(key, node->key, keysize) == 0) {
-			return (ISC_R_EXISTS);
-		}
-		node = node->next;
+	if (rehashing_in_progress(ht)) {
+		/* Rehash in progress */
+		hashtable_rehash_one(ht);
+	} else if (hashtable_is_overcommited(ht)) {
+		/* Rehash requested */
+		maybe_rehash(ht, ht->count);
 	}

-	node = isc_mem_get(ht->mctx, offsetof(isc_ht_node_t, key) + keysize);
+	hashval = isc_hash32(key, keysize, true);

-	memmove(node->key, key, keysize);
-	node->keysize = keysize;
-	node->next = ht->table[hash & ht->mask];
-	node->value = value;
+	if (isc__ht_find(ht, key, keysize, hashval, ht->hindex) != NULL) {
+		return (ISC_R_EXISTS);
+	}
+
+	isc__ht_add(ht, key, keysize, hashval, ht->hindex, value);

-	ht->count++;
-	ht->table[hash & ht->mask] = node;
 	return (ISC_R_SUCCESS);
 }

-isc_result_t
-isc_ht_find(const isc_ht_t *ht, const unsigned char *key, uint32_t keysize,
-	    void **valuep) {
-	isc_ht_node_t *node;
+static isc_ht_node_t *
+isc__ht_find(const isc_ht_t *ht, const unsigned char *key,
+	     const uint32_t keysize, const uint32_t hashval,
+	     const uint8_t idx) {
 	uint32_t hash;
+	uint8_t findex = idx;
+
+nexttable:
+	hash = hash_32(hashval, ht->hashbits[findex]);
+	for (isc_ht_node_t *node = ht->table[findex][hash]; node != NULL;
+	     node = node->next)
+	{
+		if (isc__ht_node_match(node, hashval, key, keysize)) {
+			return (node);
+		}
+	}
+	if (TRY_NEXTTABLE(findex, ht)) {
+		/*
+		 * Rehashing in progress, check the other table
+		 */
+		findex = HT_NEXTTABLE(findex);
+		goto nexttable;
+	}
+
+	return (NULL);
+}
+
+isc_result_t
+isc_ht_find(const isc_ht_t *ht, const unsigned char *key,
+	    const uint32_t keysize, void **valuep) {
+	uint32_t hashval;
+	isc_ht_node_t *node;

 	REQUIRE(ISC_HT_VALID(ht));
 	REQUIRE(key != NULL && keysize > 0);
 	REQUIRE(valuep == NULL || *valuep == NULL);

-	hash = isc_hash_function(key, keysize, true);
-	node = ht->table[hash & ht->mask];
-	while (node != NULL) {
-		if (keysize == node->keysize &&
-		    memcmp(key, node->key, keysize) == 0) {
-			if (valuep != NULL) {
-				*valuep = node->value;
+	hashval = isc_hash32(key, keysize, true);
+
+	node = isc__ht_find(ht, key, keysize, hashval, ht->hindex);
+	if (node == NULL) {
+		return (ISC_R_NOTFOUND);
+	}
+
+	if (valuep != NULL) {
+		*valuep = node->value;
+	}
+	return (ISC_R_SUCCESS);
+}
+
+static isc_result_t
+isc__ht_delete(isc_ht_t *ht, const unsigned char *key, const uint32_t keysize,
+	       const uint32_t hashval, const uint8_t idx) {
+	isc_ht_node_t *prev = NULL;
+	uint32_t hash;
+
+	hash = hash_32(hashval, ht->hashbits[idx]);
+
+	for (isc_ht_node_t *node = ht->table[idx][hash]; node != NULL;
+	     prev = node, node = node->next)
+	{
+		if (isc__ht_node_match(node, hashval, key, keysize)) {
+			if (prev == NULL) {
+				ht->table[idx][hash] = node->next;
+			} else {
+				prev->next = node->next;
 			}
+			isc_mem_put(ht->mctx, node,
+				    sizeof(*node) + node->keysize);
+			ht->count--;
+
 			return (ISC_R_SUCCESS);
 		}
-		node = node->next;
 	}

 	return (ISC_R_NOTFOUND);
 }

 isc_result_t
-isc_ht_delete(isc_ht_t *ht, const unsigned char *key, uint32_t keysize) {
-	isc_ht_node_t *node, *prev;
-	uint32_t hash;
+isc_ht_delete(isc_ht_t *ht, const unsigned char *key, const uint32_t keysize) {
+	uint32_t hashval;
+	uint8_t hindex;
+	isc_result_t result;

 	REQUIRE(ISC_HT_VALID(ht));
 	REQUIRE(key != NULL && keysize > 0);

-	prev = NULL;
-	hash = isc_hash_function(key, keysize, true);
-	node = ht->table[hash & ht->mask];
-	while (node != NULL) {
-		if (keysize == node->keysize &&
-		    memcmp(key, node->key, keysize) == 0) {
-			if (prev == NULL) {
-				ht->table[hash & ht->mask] = node->next;
-			} else {
-				prev->next = node->next;
-			}
-			isc_mem_put(ht->mctx, node,
-				    offsetof(isc_ht_node_t, key) +
-					    node->keysize);
-			ht->count--;
-
-			return (ISC_R_SUCCESS);
-		}
-
-		prev = node;
-		node = node->next;
+	if (rehashing_in_progress(ht)) {
+		/* Rehash in progress */
+		hashtable_rehash_one(ht);
 	}
-	return (ISC_R_NOTFOUND);
+
+	hindex = ht->hindex;
+	hashval = isc_hash32(key, keysize, true);
+nexttable:
+	result = isc__ht_delete(ht, key, keysize, hashval, hindex);
+
+	if (result == ISC_R_NOTFOUND && TRY_NEXTTABLE(hindex, ht)) {
+		/*
+		 * Rehashing in progress, check the other table
+		 */
+		hindex = HT_NEXTTABLE(hindex);
+		goto nexttable;
+	}
+
+	return (result);
 }

 void
@@ -208,10 +440,10 @@ isc_ht_iter_create(isc_ht_t *ht, isc_ht_iter_t **itp) {
 	REQUIRE(itp != NULL && *itp == NULL);

 	it = isc_mem_get(ht->mctx, sizeof(isc_ht_iter_t));
-
-	it->ht = ht;
-	it->i = 0;
-	it->cur = NULL;
+	*it = (isc_ht_iter_t){
+		.ht = ht,
+		.hindex = ht->hindex,
+	};

 	*itp = it;
 }
@@ -226,25 +458,45 @@ isc_ht_iter_destroy(isc_ht_iter_t **itp) {
 	it = *itp;
 	*itp = NULL;
 	ht = it->ht;
-	isc_mem_put(ht->mctx, it, sizeof(isc_ht_iter_t));
+	isc_mem_put(ht->mctx, it, sizeof(*it));
 }

 isc_result_t
 isc_ht_iter_first(isc_ht_iter_t *it) {
+	isc_ht_t *ht;
+
 	REQUIRE(it != NULL);

+	ht = it->ht;
+
+	it->hindex = ht->hindex;
 	it->i = 0;
-	while (it->i < it->ht->size && it->ht->table[it->i] == NULL) {
+
+	return (isc__ht_iter_next(it));
+}
+
+static isc_result_t
+isc__ht_iter_next(isc_ht_iter_t *it) {
+	isc_ht_t *ht = it->ht;
+
+	while (it->i < ht->size[it->hindex] &&
+	       ht->table[it->hindex][it->i] == NULL) {
 		it->i++;
 	}

-	if (it->i == it->ht->size) {
-		return (ISC_R_NOMORE);
+	if (it->i < ht->size[it->hindex]) {
+		it->cur = ht->table[it->hindex][it->i];
+
+		return (ISC_R_SUCCESS);
 	}

-	it->cur = it->ht->table[it->i];
+	if (TRY_NEXTTABLE(it->hindex, ht)) {
+		it->hindex = HT_NEXTTABLE(it->hindex);
+		it->i = 0;
+		return (isc__ht_iter_next(it));
+	}

-	return (ISC_R_SUCCESS);
+	return (ISC_R_NOMORE);
 }

 isc_result_t
@@ -253,60 +505,36 @@ isc_ht_iter_next(isc_ht_iter_t *it) {
 	REQUIRE(it->cur != NULL);

 	it->cur = it->cur->next;
-	if (it->cur == NULL) {
-		do {
-			it->i++;
-		} while (it->i < it->ht->size && it->ht->table[it->i] == NULL);
-		if (it->i >= it->ht->size) {
-			return (ISC_R_NOMORE);
-		}
-		it->cur = it->ht->table[it->i];
+
+	if (it->cur != NULL) {
+		return (ISC_R_SUCCESS);
 	}

-	return (ISC_R_SUCCESS);
+	it->i++;
+
+	return (isc__ht_iter_next(it));
 }

 isc_result_t
 isc_ht_iter_delcurrent_next(isc_ht_iter_t *it) {
 	isc_result_t result = ISC_R_SUCCESS;
-	isc_ht_node_t *to_delete = NULL;
-	isc_ht_node_t *prev = NULL;
-	isc_ht_node_t *node = NULL;
-	uint32_t hash;
+	isc_ht_node_t *dnode = NULL;
+	uint8_t dindex;
 	isc_ht_t *ht;
+	isc_result_t dresult;
+
 	REQUIRE(it != NULL);
 	REQUIRE(it->cur != NULL);
-	to_delete = it->cur;
+
 	ht = it->ht;
+	dnode = it->cur;
+	dindex = it->hindex;

-	it->cur = it->cur->next;
-	if (it->cur == NULL) {
-		do {
-			it->i++;
-		} while (it->i < ht->size && ht->table[it->i] == NULL);
-		if (it->i >= ht->size) {
-			result = ISC_R_NOMORE;
-		} else {
-			it->cur = ht->table[it->i];
-		}
-	}
+	result = isc_ht_iter_next(it);

-	hash = isc_hash_function(to_delete->key, to_delete->keysize, true);
-	node = ht->table[hash & ht->mask];
-	while (node != to_delete) {
-		prev = node;
-		node = node->next;
-		INSIST(node != NULL);
-	}
-
-	if (prev == NULL) {
-		ht->table[hash & ht->mask] = node->next;
-	} else {
-		prev->next = node->next;
-	}
-	isc_mem_put(ht->mctx, node,
-		    offsetof(isc_ht_node_t, key) + node->keysize);
-	ht->count--;
+	dresult = isc__ht_delete(ht, dnode->key, dnode->keysize, dnode->hashval,
+				 dindex);
+	INSIST(dresult == ISC_R_SUCCESS);

 	return (result);
 }
@@ -331,8 +559,8 @@ isc_ht_iter_currentkey(isc_ht_iter_t *it, unsigned char **key,
 	*keysize = it->cur->keysize;
 }

-unsigned int
-isc_ht_count(isc_ht_t *ht) {
+size_t
+isc_ht_count(const isc_ht_t *ht) {
 	REQUIRE(ISC_HT_VALID(ht));

 	return (ht->count);
--- a/lib/isc/include/isc/ht.h
+++ b/lib/isc/include/isc/ht.h
@@ -51,6 +51,7 @@ isc_ht_destroy(isc_ht_t **htp);
 *
 * Requires:
 *\li	'ht' is a valid hashtable
+ *\li   write-lock
 *
 * Returns:
 *\li	#ISC_R_NOMEMORY		-- not enough memory to create pool
@@ -58,7 +59,7 @@ isc_ht_destroy(isc_ht_t **htp);
 *\li	#ISC_R_SUCCESS		-- all is well.
 */
 isc_result_t
-isc_ht_add(isc_ht_t *ht, const unsigned char *key, uint32_t keysize,
+isc_ht_add(isc_ht_t *ht, const unsigned char *key, const uint32_t keysize,
 	   void *value);

 /*%
@@ -69,27 +70,29 @@ isc_ht_add(isc_ht_t *ht, const unsigned char *key, uint32_t keysize,
 *
 * Requires:
 * \li	'ht' is a valid hashtable
+ * \li  read-lock
 *
 * Returns:
 * \li	#ISC_R_SUCCESS		-- success
 * \li	#ISC_R_NOTFOUND		-- key not found
 */
 isc_result_t
-isc_ht_find(const isc_ht_t *ht, const unsigned char *key, uint32_t keysize,
-	    void **valuep);
+isc_ht_find(const isc_ht_t *ht, const unsigned char *key,
+	    const uint32_t keysize, void **valuep);

 /*%
 * Delete node from hashtable
 *
 * Requires:
 *\li	ht is a valid hashtable
+ *\li   write-lock
 *
 * Returns:
 *\li	#ISC_R_NOTFOUND		-- key not found
 *\li	#ISC_R_SUCCESS		-- all is well
 */
 isc_result_t
-isc_ht_delete(isc_ht_t *ht, const unsigned char *key, uint32_t keysize);
+isc_ht_delete(isc_ht_t *ht, const unsigned char *key, const uint32_t keysize);

 /*%
 * Create an iterator for the hashtable; point '*itp' to it.
@@ -177,5 +180,5 @@ isc_ht_iter_currentkey(isc_ht_iter_t *it, unsigned char **key, size_t *keysize);
 * Requires:
 *\li	'ht' is a valid hashtable
 */
-unsigned int
-isc_ht_count(isc_ht_t *ht);
+size_t
+isc_ht_count(const isc_ht_t *ht);