X-Git-Url: http://git.ozlabs.org/?p=ccan;a=blobdiff_plain;f=ccan%2Fhtable%2Fhtable.c;h=b7e65d11966acc96be83dffbb25a273fec153145;hp=dec53127470a9f6b06a53555286a9fcbb153dbef;hb=e0529e15e0c7f9251af5465ef03f208d279affc1;hpb=78e983a7a6e5250ebf963d5d93fe34c1d27d5a39

diff --git a/ccan/htable/htable.c b/ccan/htable/htable.c
index dec53127..b7e65d11 100644
--- a/ccan/htable/htable.c
+++ b/ccan/htable/htable.c
@@ -1,27 +1,14 @@
+/* Licensed under LGPLv2+ - see LICENSE file for details */
 #include <ccan/htable/htable.h>
 #include <ccan/compiler/compiler.h>
-#include <stdint.h>
 #include <stdlib.h>
+#include <limits.h>
 #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)
 
-struct htable {
-	size_t (*rehash)(const void *elem, void *priv);
-	void *priv;
-	unsigned int bits;
-	size_t elems, deleted, max, max_with_deleted;
-	/* These are the bits which are the same in all pointers. */
-	uintptr_t common_mask, common_bits;
-	uintptr_t perfect_bit;
-	uintptr_t *table;
-};
-
 /* We clear out the bits which are always the same, and put metadata there. */
 static inline uintptr_t get_extra_ptr_bits(const struct htable *ht,
 					   uintptr_t e)
@@ -55,35 +42,21 @@ static inline uintptr_t get_hash_ptr_bits(const struct htable *ht,
 		& ht->common_mask & ~ht->perfect_bit;
 }
 
-struct htable *htable_new(size_t (*rehash)(const void *elem, void *priv),
-			  void *priv)
+void htable_init(struct htable *ht,
+		 size_t (*rehash)(const void *elem, void *priv), void *priv)
 {
-	struct htable *ht = malloc(sizeof(struct htable));
-	if (ht) {
-		ht->bits = HTABLE_BASE_BITS;
-		ht->rehash = rehash;
-		ht->priv = priv;
-		ht->elems = 0;
-		ht->deleted = 0;
-		ht->max = (1 << ht->bits) * 2 / 3;
-		ht->max_with_deleted = (1 << ht->bits) * 4 / 5;
-		/* 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;
-		}
-	}
-	return ht;
+	struct htable empty = HTABLE_INITIALIZER(empty, NULL, NULL);
+	*ht = empty;
+	ht->rehash = rehash;
+	ht->priv = priv;
+	ht->table = &ht->perfect_bit;
 }
 
-void htable_free(const struct htable *ht)
+void htable_clear(struct htable *ht)
 {
-	free((void *)ht->table);
-	free((void *)ht);
+	if (ht->table != &ht->perfect_bit)
+		free((void *)ht->table);
+	htable_init(ht, ht->rehash, ht->priv);
 }
 
 static size_t hash_bucket(const struct htable *ht, size_t h)
@@ -154,7 +127,7 @@ static void ht_add(struct htable *ht, const void *new, size_t h)
 	ht->table[i] = make_hval(ht, new, get_hash_ptr_bits(ht, h)|perfect);
 }
 
-static COLD_ATTRIBUTE bool double_table(struct htable *ht)
+static COLD bool double_table(struct htable *ht)
 {
 	unsigned int i;
 	size_t oldnum = (size_t)1 << ht->bits;
@@ -167,22 +140,33 @@ static COLD_ATTRIBUTE 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) {
+		for (i = 0; i < sizeof(ht->common_mask) * CHAR_BIT; i++) {
+			if (ht->common_mask & ((size_t)1 << i)) {
+				ht->perfect_bit = (size_t)1 << i;
+				break;
+			}
+		}
+	}
 
-	/* FIXME: If we lost our perfect bit, we could reclaim it here! */
-	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;
 }
 
-static COLD_ATTRIBUTE void rehash_table(struct htable *ht)
+static COLD void rehash_table(struct htable *ht)
 {
 	size_t start, i;
 	uintptr_t e;
@@ -207,14 +191,23 @@ static COLD_ATTRIBUTE void rehash_table(struct htable *ht)
 }
 
 /* We stole some bits, now we need to put them back... */
-static COLD_ATTRIBUTE void update_common(struct htable *ht, const void *p)
+static COLD void update_common(struct htable *ht, const void *p)
 {
 	unsigned int i;
 	uintptr_t maskdiff, bitsdiff;
 
 	if (ht->elems == 0) {
-		ht->common_mask = -1;
-		ht->common_bits = (uintptr_t)p;
+		/* Always reveal one bit of the pointer in the bucket,
+		 * so it's not zero or HTABLE_DELETED (1), even if
+		 * hash happens to be 0.  Assumes (void *)1 is not a
+		 * valid pointer. */
+		for (i = sizeof(uintptr_t)*CHAR_BIT - 1; i > 0; i--) {
+			if ((uintptr_t)p & ((uintptr_t)1 << i))
+				break;
+		}
+
+		ht->common_mask = ~((uintptr_t)1 << i);
+		ht->common_bits = ((uintptr_t)p & ht->common_mask);
 		ht->perfect_bit = 1;
 		return;
 	}