htable: start empty.

There's no real reason to start with 128 entries.

ccan/htable/htable.c

@@ -7,9 +7,6 @@
 #include <stdbool.h>
 #include <assert.h>
 
-/* This means a struct htable takes at least 512 bytes / 1k (32/64 bits). */
-#define HTABLE_BASE_BITS 7
-
 /* We use 0x1 as deleted marker. */
 #define HTABLE_DELETED (0x1)
 
@@ -62,29 +59,27 @@ struct htable *htable_new(size_t (*rehash)(const void *elem, void *priv),
 {
 	struct htable *ht = malloc(sizeof(struct htable));
 	if (ht) {
-		ht->bits = HTABLE_BASE_BITS;
+		ht->bits = 0;
 		ht->rehash = rehash;
 		ht->priv = priv;
 		ht->elems = 0;
 		ht->deleted = 0;
-		ht->max = ((size_t)1 << ht->bits) * 3 / 4;
-		ht->max_with_deleted = ((size_t)1 << ht->bits) * 9 / 10;
+		ht->max = 0;
+		ht->max_with_deleted = 0;
 		/* This guarantees we enter update_common first add. */
 		ht->common_mask = -1;
 		ht->common_bits = 0;
 		ht->perfect_bit = 0;
-		ht->table = calloc(1 << ht->bits, sizeof(uintptr_t));
-		if (!ht->table) {
-			free(ht);
-			ht = NULL;
-		}
+		/* Dummy table until first insert. */
+		ht->table = &ht->perfect_bit;
 	}
 	return ht;
 }
 
 void htable_free(const struct htable *ht)
 {
-	free((void *)ht->table);
+	if (ht->table != &ht->perfect_bit)
+		free((void *)ht->table);
 	free((void *)ht);
 }
 
@@ -169,8 +164,8 @@ static COLD bool double_table(struct htable *ht)
 		return false;
 	}
 	ht->bits++;
-	ht->max *= 2;
-	ht->max_with_deleted *= 2;
+	ht->max = ((size_t)3 << ht->bits) / 4;
+	ht->max_with_deleted = ((size_t)9 << ht->bits) / 10;
 
 	/* If we lost our "perfect bit", get it back now. */
 	if (!ht->perfect_bit && ht->common_mask) {
@@ -182,14 +177,16 @@ static COLD bool double_table(struct htable *ht)
 		}
 	}
 
-	for (i = 0; i < oldnum; i++) {
-		if (entry_is_valid(e = oldtable[i])) {
-			void *p = get_raw_ptr(ht, e);
-			ht_add(ht, p, ht->rehash(p, ht->priv));
+	if (oldtable != &ht->perfect_bit) {
+		for (i = 0; i < oldnum; i++) {
+			if (entry_is_valid(e = oldtable[i])) {
+				void *p = get_raw_ptr(ht, e);
+				ht_add(ht, p, ht->rehash(p, ht->priv));
+			}
 		}
+		free(oldtable);
 	}
 	ht->deleted = 0;
-	free(oldtable);
 	return true;
 }
 

ccan/htable/test/run-size.c

@@ -0,0 +1,36 @@
+#include <ccan/htable/htable.h>
+#include <ccan/htable/htable.c>
+#include <ccan/tap/tap.h>
+#include <stdbool.h>
+#include <string.h>
+
+#define NUM_VALS 512
+
+/* We use the number divided by two as the hash (for lots of
+   collisions). */
+static size_t hash(const void *elem, void *unused)
+{
+	size_t h = *(uint64_t *)elem / 2;
+	return h;
+}
+
+int main(int argc, char *argv[])
+{
+	struct htable *ht;
+	uint64_t val[NUM_VALS];
+	unsigned int i;
+
+	plan_tests((NUM_VALS) * 2);
+	for (i = 0; i < NUM_VALS; i++)
+		val[i] = i;
+
+	ht = htable_new(hash, NULL);
+	for (i = 0; i < NUM_VALS; i++) {
+		ok1(ht->max >= i);
+		ok1(ht->max <= i * 2);
+		htable_add(ht, hash(&val[i], NULL), &val[i]);
+	}
+	htable_free(ht);
+
+	return exit_status();
+}

ccan/htable/test/run-type.c

@@ -4,7 +4,8 @@
 #include <stdbool.h>
 #include <string.h>
 
-#define NUM_VALS (1 << HTABLE_BASE_BITS)
+#define NUM_BITS 7
+#define NUM_VALS (1 << NUM_BITS)
 
 struct obj {
 	/* Makes sure we don't try to treat and obj as a key or vice versa */
@@ -23,7 +24,7 @@ static const unsigned int *objkey(const struct obj *obj)
 static size_t objhash(const unsigned int *key)
 {
 	size_t h = *key / 2;
-	h |= -1UL << HTABLE_BASE_BITS;
+	h |= -1UL << NUM_BITS;
 	return h;
 }
 
@@ -121,15 +122,15 @@ int main(int argc, char *argv[])
 	dne = i;
 
 	ht = htable_obj_new();
-	ok1(((struct htable *)ht)->max < (1 << ((struct htable *)ht)->bits));
-	ok1(((struct htable *)ht)->bits == HTABLE_BASE_BITS);
+	ok1(((struct htable *)ht)->max == 0);
+	ok1(((struct htable *)ht)->bits == 0);
 
 	/* We cannot find an entry which doesn't exist. */
 	ok1(!htable_obj_get(ht, &dne));
 
-	/* Fill it, it should increase in size (once). */
+	/* Fill it, it should increase in size. */
 	add_vals(ht, val, NUM_VALS);
-	ok1(((struct htable *)ht)->bits == HTABLE_BASE_BITS + 1);
+	ok1(((struct htable *)ht)->bits == NUM_BITS + 1);
 	ok1(((struct htable *)ht)->max < (1 << ((struct htable *)ht)->bits));
 
 	/* Mask should be set. */

ccan/htable/test/run.c

@@ -4,7 +4,8 @@
 #include <stdbool.h>
 #include <string.h>
 
-#define NUM_VALS (1 << HTABLE_BASE_BITS)
+#define NUM_BITS 7
+#define NUM_VALS (1 << NUM_BITS)
 
 /* We use the number divided by two as the hash (for lots of
    collisions), plus set all the higher bits so we can detect if they
@@ -12,7 +13,7 @@
 static size_t hash(const void *elem, void *unused)
 {
 	size_t h = *(uint64_t *)elem / 2;
-	h |= -1UL << HTABLE_BASE_BITS;
+	h |= -1UL << NUM_BITS;
 	return h;
 }
 
@@ -22,11 +23,12 @@ static bool objcmp(const void *htelem, void *cmpdata)
 }
 
 static void add_vals(struct htable *ht,
-		     const uint64_t val[], unsigned int num)
+		     const uint64_t val[],
+		     unsigned int off, unsigned int num)
 {
 	uint64_t i;
 
-	for (i = 0; i < num; i++) {
+	for (i = off; i < off+num; i++) {
 		if (htable_get(ht, hash(&i, NULL), objcmp, &i)) {
 			fail("%llu already in hash", (long long)i);
 			return;
@@ -103,27 +105,39 @@ int main(int argc, char *argv[])
 	void *p;
 	struct htable_iter iter;
 
-	plan_tests(23);
+	plan_tests(29);
 	for (i = 0; i < NUM_VALS; i++)
 		val[i] = i;
 	dne = i;
 
 	ht = htable_new(hash, NULL);
-	ok1(ht->max < (1 << ht->bits));
-	ok1(ht->bits == HTABLE_BASE_BITS);
+	ok1(ht->max == 0);
+	ok1(ht->bits == 0);
 
 	/* We cannot find an entry which doesn't exist. */
 	ok1(!htable_get(ht, hash(&dne, NULL), objcmp, &dne));
 
-	/* Fill it, it should increase in size (once). */
-	add_vals(ht, val, NUM_VALS);
-	ok1(ht->bits == HTABLE_BASE_BITS + 1);
-	ok1(ht->max < (1 << ht->bits));
+	/* This should increase it once. */
+	add_vals(ht, val, 0, 1);
+	ok1(ht->bits == 1);
+	ok1(ht->max == 1);
+	ok1(ht->common_mask == -1);
+
+	/* Mask should be set. */
+	ok1(check_mask(ht, val, 1));
+
+	/* This should increase it again. */
+	add_vals(ht, val, 1, 1);
+	ok1(ht->bits == 2);
+	ok1(ht->max == 3);
 
 	/* Mask should be set. */
 	ok1(ht->common_mask != 0);
 	ok1(ht->common_mask != -1);
-	ok1(check_mask(ht, val, NUM_VALS));
+	ok1(check_mask(ht, val, 2));
+
+	/* Now do the rest. */
+	add_vals(ht, val, 2, NUM_VALS - 2);
 
 	/* Find all. */
 	find_vals(ht, val, NUM_VALS);
@@ -148,7 +162,7 @@ int main(int argc, char *argv[])
 	htable_del(ht, 0, (void *)~(uintptr_t)&val[NUM_VALS-1]);
 
 	/* Add the rest. */
-	add_vals(ht, val, NUM_VALS-1);
+	add_vals(ht, val, 0, NUM_VALS-1);
 
 	/* Check we can find them all. */
 	find_vals(ht, val, NUM_VALS);
@@ -167,7 +181,7 @@ int main(int argc, char *argv[])
 	htable_del(ht, 0, (void *)((uintptr_t)&val[NUM_VALS-1] | perfect_bit));
 
 	/* Enlarging should restore it... */
-	add_vals(ht, val, NUM_VALS-1);
+	add_vals(ht, val, 0, NUM_VALS-1);
 
 	ok1(ht->perfect_bit != 0);
 	htable_free(ht);