X-Git-Url: http://git.ozlabs.org/?a=blobdiff_plain;f=ccan%2Fhtable%2Fhtable.c;h=3247bea0879af34e2db5f47e1a3c5f9ac8a9fa9f;hb=e03b68c761b870fd9e4c165bfe2358f5df82e49c;hp=e6dc4fd817f886fa2676d0cefd9774f0fd9a690a;hpb=7a353c03e5e8cdd55cbc0917f9ecff5cf9beefdb;p=ccan

diff --git a/ccan/htable/htable.c b/ccan/htable/htable.c
index e6dc4fd8..3247bea0 100644
--- a/ccan/htable/htable.c
+++ b/ccan/htable/htable.c
@@ -11,6 +11,9 @@
 /* We use 0x1 as deleted marker. */
 #define HTABLE_DELETED (0x1)
 
+/* perfect_bitnum 63 means there's no perfect bitnum */
+#define NO_PERFECT_BIT (sizeof(uintptr_t) * CHAR_BIT - 1)
+
 static void *htable_default_alloc(struct htable *ht, size_t len)
 {
 	return calloc(len, 1);
@@ -58,6 +61,11 @@ static inline bool entry_is_valid(uintptr_t e)
 	return e > HTABLE_DELETED;
 }
 
+static inline uintptr_t ht_perfect_mask(const struct htable *ht)
+{
+	return (uintptr_t)2 << ht->perfect_bitnum;
+}
+
 static inline uintptr_t get_hash_ptr_bits(const struct htable *ht,
 					  size_t hash)
 {
@@ -65,7 +73,7 @@ static inline uintptr_t get_hash_ptr_bits(const struct htable *ht,
 	 * end is quite expensive.  But the lower bits are redundant, so
 	 * we fold the value first. */
 	return (hash ^ (hash >> ht->bits))
-		& ht->common_mask & ~ht->perfect_bit;
+		& ht->common_mask & ~ht_perfect_mask(ht);
 }
 
 void htable_init(struct htable *ht,
@@ -75,14 +83,17 @@ void htable_init(struct htable *ht,
 	*ht = empty;
 	ht->rehash = rehash;
 	ht->priv = priv;
-	ht->table = &ht->perfect_bit;
+	ht->table = &ht->common_bits;
 }
 
-/* We've changed ht->bits, update ht->max and ht->max_with_deleted */
-static void htable_adjust_capacity(struct htable *ht)
+static inline size_t ht_max(const struct htable *ht)
 {
-	ht->max = ((size_t)3 << ht->bits) / 4;
-	ht->max_with_deleted = ((size_t)9 << ht->bits) / 10;
+	return ((size_t)3 << ht->bits) / 4;
+}
+
+static inline size_t ht_max_with_deleted(const struct htable *ht)
+{
+	return ((size_t)9 << ht->bits) / 10;
 }
 
 bool htable_init_sized(struct htable *ht,
@@ -99,17 +110,16 @@ bool htable_init_sized(struct htable *ht,
 
 	ht->table = htable_alloc(ht, sizeof(size_t) << ht->bits);
 	if (!ht->table) {
-		ht->table = &ht->perfect_bit;
+		ht->table = &ht->common_bits;
 		return false;
 	}
-	htable_adjust_capacity(ht);
 	(void)htable_debug(ht, HTABLE_LOC);
 	return true;
 }
 	
 void htable_clear(struct htable *ht)
 {
-	if (ht->table != &ht->perfect_bit)
+	if (ht->table != &ht->common_bits)
 		htable_free(ht, (void *)ht->table);
 	htable_init(ht, ht->rehash, ht->priv);
 }
@@ -152,7 +162,7 @@ void *htable_firstval_(const struct htable *ht,
 		       struct htable_iter *i, size_t hash)
 {
 	i->off = hash_bucket(ht, hash);
-	return htable_val(ht, i, hash, ht->perfect_bit);
+	return htable_val(ht, i, hash, ht_perfect_mask(ht));
 }
 
 void *htable_nextval_(const struct htable *ht,
@@ -185,17 +195,88 @@ void *htable_prev_(const struct htable *ht, struct htable_iter *i)
 	for (;;) {
 		if (!i->off)
 			return NULL;
-		i->off --;
+		i->off--;
 		if (entry_is_valid(ht->table[i->off]))
 			return get_raw_ptr(ht, ht->table[i->off]);
 	}
 }
 
+/* Another bit currently in mask needs to be exposed, so that a bucket with p in
+ * it won't appear invalid */
+static COLD void unset_another_common_bit(struct htable *ht,
+					  uintptr_t *maskdiff,
+					  const void *p)
+{
+	size_t i;
+
+	for (i = sizeof(uintptr_t) * CHAR_BIT - 1; i > 0; i--) {
+		if (((uintptr_t)p & ((uintptr_t)1 << i))
+		    && ht->common_mask & ~*maskdiff & ((uintptr_t)1 << i))
+			break;
+	}
+	/* There must have been one, right? */
+	assert(i > 0);
+
+	*maskdiff |= ((uintptr_t)1 << i);
+}
+
+/* We want to change the common mask: this fixes up the table */
+static COLD void fixup_table_common(struct htable *ht, uintptr_t maskdiff)
+{
+	size_t i;
+	uintptr_t bitsdiff;
+
+again:
+	bitsdiff = ht->common_bits & maskdiff;
+
+	for (i = 0; i < (size_t)1 << ht->bits; i++) {
+		uintptr_t e;
+		if (!entry_is_valid(e = ht->table[i]))
+			continue;
+
+		/* Clear the bits no longer in the mask, set them as
+		 * expected. */
+		e &= ~maskdiff;
+		e |= bitsdiff;
+		/* If this made it invalid, restart with more exposed */
+		if (!entry_is_valid(e)) {
+			unset_another_common_bit(ht, &maskdiff, get_raw_ptr(ht, e));
+			goto again;
+		}
+		ht->table[i] = e;
+	}
+
+	/* Take away those bits from our mask, bits and perfect bit. */
+	ht->common_mask &= ~maskdiff;
+	ht->common_bits &= ~maskdiff;
+	if (ht_perfect_mask(ht) & maskdiff)
+		ht->perfect_bitnum = NO_PERFECT_BIT;
+}
+
+/* Limited recursion */
+static void ht_add(struct htable *ht, const void *new, size_t h);
+
+/* We tried to add this entry, but it looked invalid!  We need to
+ * let another pointer bit through mask */
+static COLD void update_common_fix_invalid(struct htable *ht, const void *p, size_t h)
+{
+	uintptr_t maskdiff;
+
+	assert(ht->elems != 0);
+
+	maskdiff = 0;
+	unset_another_common_bit(ht, &maskdiff, p);
+	fixup_table_common(ht, maskdiff);
+
+	/* Now won't recurse */
+	ht_add(ht, p, h);
+}
+
 /* This does not expand the hash table, that's up to caller. */
 static void ht_add(struct htable *ht, const void *new, size_t h)
 {
 	size_t i;
-	uintptr_t perfect = ht->perfect_bit;
+	uintptr_t perfect = ht_perfect_mask(ht);
 
 	i = hash_bucket(ht, h);
 
@@ -204,6 +285,8 @@ static void ht_add(struct htable *ht, const void *new, size_t h)
 		i = (i + 1) & ((1 << ht->bits)-1);
 	}
 	ht->table[i] = make_hval(ht, new, get_hash_ptr_bits(ht, h)|perfect);
+	if (!entry_is_valid(ht->table[i]))
+		update_common_fix_invalid(ht, new, h);
 }
 
 static COLD bool double_table(struct htable *ht)
@@ -219,19 +302,18 @@ static COLD bool double_table(struct htable *ht)
 		return false;
 	}
 	ht->bits++;
-	htable_adjust_capacity(ht);
 
 	/* If we lost our "perfect bit", get it back now. */
-	if (!ht->perfect_bit && ht->common_mask) {
+	if (ht->perfect_bitnum == NO_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;
+			if (ht->common_mask & ((size_t)2 << i)) {
+				ht->perfect_bitnum = i;
 				break;
 			}
 		}
 	}
 
-	if (oldtable != &ht->perfect_bit) {
+	if (oldtable != &ht->common_bits) {
 		for (i = 0; i < oldnum; i++) {
 			if (entry_is_valid(e = oldtable[i])) {
 				void *p = get_raw_ptr(ht, e);
@@ -249,7 +331,7 @@ static COLD bool double_table(struct htable *ht)
 static COLD void rehash_table(struct htable *ht)
 {
 	size_t start, i;
-	uintptr_t e;
+	uintptr_t e, perfect = ht_perfect_mask(ht);
 
 	/* Beware wrap cases: we need to start from first empty bucket. */
 	for (start = 0; ht->table[start]; start++);
@@ -261,7 +343,7 @@ static COLD void rehash_table(struct htable *ht)
 			continue;
 		if (e == HTABLE_DELETED)
 			ht->table[h] = 0;
-		else if (!(e & ht->perfect_bit)) {
+		else if (!(e & perfect)) {
 			void *p = get_raw_ptr(ht, e);
 			ht->table[h] = 0;
 			ht_add(ht, p, ht->rehash(p, ht->priv));
@@ -274,22 +356,12 @@ static COLD void rehash_table(struct htable *ht)
 /* We stole some bits, now we need to put them back... */
 static COLD void update_common(struct htable *ht, const void *p)
 {
-	unsigned int i;
-	uintptr_t maskdiff, bitsdiff;
+	uintptr_t maskdiff;
 
 	if (ht->elems == 0) {
-		/* 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_mask = -1;
 		ht->common_bits = ((uintptr_t)p & ht->common_mask);
-		ht->perfect_bit = 1;
+		ht->perfect_bitnum = 0;
 		(void)htable_debug(ht, HTABLE_LOC);
 		return;
 	}
@@ -297,32 +369,20 @@ static COLD void update_common(struct htable *ht, const void *p)
 	/* Find bits which are unequal to old common set. */
 	maskdiff = ht->common_bits ^ ((uintptr_t)p & ht->common_mask);
 
-	/* These are the bits which go there in existing entries. */
-	bitsdiff = ht->common_bits & maskdiff;
-
-	for (i = 0; i < (size_t)1 << ht->bits; i++) {
-		if (!entry_is_valid(ht->table[i]))
-			continue;
-		/* Clear the bits no longer in the mask, set them as
-		 * expected. */
-		ht->table[i] &= ~maskdiff;
-		ht->table[i] |= bitsdiff;
-	}
-
-	/* Take away those bits from our mask, bits and perfect bit. */
-	ht->common_mask &= ~maskdiff;
-	ht->common_bits &= ~maskdiff;
-	ht->perfect_bit &= ~maskdiff;
+	fixup_table_common(ht, maskdiff);
 	(void)htable_debug(ht, HTABLE_LOC);
 }
 
 bool htable_add_(struct htable *ht, size_t hash, const void *p)
 {
-	if (ht->elems+1 > ht->max && !double_table(ht))
+	/* Cannot insert NULL, or (void *)1. */
+	assert(p);
+	assert(entry_is_valid((uintptr_t)p));
+
+	if (ht->elems+1 > ht_max(ht) && !double_table(ht))
 		return false;
-	if (ht->elems+1 + ht->deleted > ht->max_with_deleted)
+	if (ht->elems+1 + ht->deleted > ht_max_with_deleted(ht))
 		rehash_table(ht);
-	assert(p);
 	if (((uintptr_t)p & ht->common_mask) != ht->common_bits)
 		update_common(ht, p);
 
@@ -355,6 +415,20 @@ void htable_delval_(struct htable *ht, struct htable_iter *i)
 	ht->deleted++;
 }
 
+void *htable_pick_(const struct htable *ht, size_t seed, struct htable_iter *i)
+{
+	void *e;
+	struct htable_iter unwanted;
+
+	if (!i)
+		i = &unwanted;
+	i->off = seed % ((size_t)1 << ht->bits);
+	e = htable_next(ht, i);
+	if (!e)
+		e = htable_first(ht, i);
+	return e;
+}
+
 struct htable *htable_check(const struct htable *ht, const char *abortstr)
 {
 	void *p;