X-Git-Url: http://git.ozlabs.org/?a=blobdiff_plain;f=ccan%2Fhtable%2Fhtable.c;h=0371e81d0fac4837c221fcb7cb57fff5a12b8fdf;hb=5971ec743ffa28a0eaae65929475226c703678b9;hp=b27d063f207000b65fbbdd14aed05f171c279d09;hpb=d615e534e870a911f11b7b88021242220ea053bf;p=ccan

diff --git a/ccan/htable/htable.c b/ccan/htable/htable.c
index b27d063f..0371e81d 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);
@@ -53,18 +56,73 @@ static inline uintptr_t make_hval(const struct htable *ht,
 	return ((uintptr_t)p & ~ht->common_mask) | bits;
 }
 
-static inline bool entry_is_valid(uintptr_t e)
+static inline uintptr_t *actually_valid_pair(const struct htable *ht)
+{
+	return ht->table + ((size_t)1 << ht->bits);
+}
+
+/* We have have two entries which look deleted, but we remember
+ * they are not! */
+static inline bool entry_actually_valid(const struct htable *ht, size_t off)
+{
+	const uintptr_t *valid = actually_valid_pair(ht);
+	/* Empty table looks like this! */
+	if (valid == &ht->common_bits + 1)
+		return false;
+	return valid[0] == off || valid[1] == off;
+}
+
+/* Initialize the "actually valid" pair. */
+static inline void init_actually_valid(struct htable *ht)
+{
+	uintptr_t *valid = actually_valid_pair(ht);
+	valid[0] = valid[1] = ((size_t)1 << ht->bits);
+}
+
+/* Add to the "actually valid" pair: there can only ever be two! */
+static COLD void add_actually_valid(struct htable *ht, size_t off)
+{
+	uintptr_t *valid = actually_valid_pair(ht);
+	if (valid[0] == ((size_t)1 << ht->bits))
+		valid[0] = off;
+	else {
+		assert(valid[1] == ((size_t)1 << ht->bits));
+		valid[1] = off;
+	}
+}
+
+static COLD void del_actually_valid(struct htable *ht, size_t off)
+{
+	uintptr_t *validpair = actually_valid_pair(ht);
+	if (validpair[0] == off)
+		validpair[0] = ((size_t)1 << ht->bits);
+	else {
+		assert(validpair[1] == off);
+		validpair[1] = ((size_t)1 << ht->bits);
+	}
+}
+
+/* If this entry looks invalid, check entry_actually_valid! */
+static inline bool entry_looks_invalid(const struct htable *ht, size_t off)
+{
+	return ht->table[off] <= HTABLE_DELETED;
+}
+
+static inline bool entry_is_valid(const struct htable *ht, size_t off)
+{
+	if (!entry_looks_invalid(ht, off))
+		return true;
+	return entry_actually_valid(ht, off);
+}
+
+static inline bool entry_is_deleted(const struct htable *ht, size_t off)
 {
-	return e > HTABLE_DELETED;
+	return ht->table[off] == HTABLE_DELETED && !entry_actually_valid(ht, off);
 }
 
-/* We use 0 to mean we don't have a perfect bit, otherwise it's
- * bit n - 1 */
 static inline uintptr_t ht_perfect_mask(const struct htable *ht)
 {
-	if (ht->perfect_bitnum > 0)
-		return (uintptr_t)1 << (ht->perfect_bitnum - 1);
-	return 0;
+	return (uintptr_t)2 << ht->perfect_bitnum;
 }
 
 static inline uintptr_t get_hash_ptr_bits(const struct htable *ht,
@@ -97,6 +155,12 @@ static inline size_t ht_max_with_deleted(const struct htable *ht)
 	return ((size_t)9 << ht->bits) / 10;
 }
 
+/* Includes the two trailing "not-deleted" entries */
+static size_t htable_alloc_size(size_t bits)
+{
+	return (sizeof(size_t) << bits) + 2 * sizeof(size_t);
+}
+
 bool htable_init_sized(struct htable *ht,
 		       size_t (*rehash)(const void *, void *),
 		       void *priv, size_t expect)
@@ -109,11 +173,12 @@ bool htable_init_sized(struct htable *ht,
 			break;
 	}
 
-	ht->table = htable_alloc(ht, sizeof(size_t) << ht->bits);
+	ht->table = htable_alloc(ht, htable_alloc_size(ht->bits));
 	if (!ht->table) {
 		ht->table = &ht->common_bits;
 		return false;
 	}
+	init_actually_valid(ht);
 	(void)htable_debug(ht, HTABLE_LOC);
 	return true;
 }
@@ -127,14 +192,14 @@ void htable_clear(struct htable *ht)
 
 bool htable_copy_(struct htable *dst, const struct htable *src)
 {
-	uintptr_t *htable = htable_alloc(dst, sizeof(size_t) << src->bits);
+	uintptr_t *htable = htable_alloc(dst, htable_alloc_size(src->bits));
 
 	if (!htable)
 		return false;
 
 	*dst = *src;
 	dst->table = htable;
-	memcpy(dst->table, src->table, sizeof(size_t) << src->bits);
+	memcpy(dst->table, src->table, htable_alloc_size(src->bits));
 	return true;
 }
 
@@ -148,8 +213,8 @@ static void *htable_val(const struct htable *ht,
 {
 	uintptr_t h2 = get_hash_ptr_bits(ht, hash) | perfect;
 
-	while (ht->table[i->off]) {
-		if (ht->table[i->off] != HTABLE_DELETED) {
+	while (ht->table[i->off] || entry_actually_valid(ht, i->off)) {
+		if (!entry_is_deleted(ht, i->off)) {
 			if (get_extra_ptr_bits(ht, ht->table[i->off]) == h2)
 				return get_raw_ptr(ht, ht->table[i->off]);
 		}
@@ -176,7 +241,7 @@ void *htable_nextval_(const struct htable *ht,
 void *htable_first_(const struct htable *ht, struct htable_iter *i)
 {
 	for (i->off = 0; i->off < (size_t)1 << ht->bits; i->off++) {
-		if (entry_is_valid(ht->table[i->off]))
+		if (entry_is_valid(ht, i->off))
 			return get_raw_ptr(ht, ht->table[i->off]);
 	}
 	return NULL;
@@ -185,7 +250,7 @@ void *htable_first_(const struct htable *ht, struct htable_iter *i)
 void *htable_next_(const struct htable *ht, struct htable_iter *i)
 {
 	for (i->off++; i->off < (size_t)1 << ht->bits; i->off++) {
-		if (entry_is_valid(ht->table[i->off]))
+		if (entry_is_valid(ht, i->off))
 			return get_raw_ptr(ht, ht->table[i->off]);
 	}
 	return NULL;
@@ -196,8 +261,8 @@ void *htable_prev_(const struct htable *ht, struct htable_iter *i)
 	for (;;) {
 		if (!i->off)
 			return NULL;
-		i->off --;
-		if (entry_is_valid(ht->table[i->off]))
+		i->off--;
+		if (entry_is_valid(ht, i->off))
 			return get_raw_ptr(ht, ht->table[i->off]);
 	}
 }
@@ -210,45 +275,49 @@ static void ht_add(struct htable *ht, const void *new, size_t h)
 
 	i = hash_bucket(ht, h);
 
-	while (entry_is_valid(ht->table[i])) {
+	while (entry_is_valid(ht, i)) {
 		perfect = 0;
 		i = (i + 1) & ((1 << ht->bits)-1);
 	}
 	ht->table[i] = make_hval(ht, new, get_hash_ptr_bits(ht, h)|perfect);
+
+	/* If it looks invalid, add it to exceptions */
+	if (ht->table[i] <= HTABLE_DELETED)
+		add_actually_valid(ht, i);
 }
 
 static COLD bool double_table(struct htable *ht)
 {
-	unsigned int i;
-	size_t oldnum = (size_t)1 << ht->bits;
-	uintptr_t *oldtable, e;
+	size_t i;
+	struct htable oldht = *ht;
 
-	oldtable = ht->table;
-	ht->table = htable_alloc(ht, sizeof(size_t) << (ht->bits+1));
+	ht->table = htable_alloc(ht, htable_alloc_size(ht->bits+1));
 	if (!ht->table) {
-		ht->table = oldtable;
+		ht->table = oldht.table;
 		return false;
 	}
 	ht->bits++;
+	init_actually_valid(ht);
 
 	/* If we lost our "perfect bit", get it back now. */
-	if (ht->perfect_bitnum == 0 && 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_bitnum = i + 1;
+			if (ht->common_mask & ((size_t)2 << i)) {
+				ht->perfect_bitnum = i;
 				break;
 			}
 		}
 	}
 
-	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);
+	if (oldht.table != &ht->common_bits) {
+		for (i = 0; i < (size_t)1 << oldht.bits; i++) {
+			if (entry_is_valid(&oldht, i)) {
+				void *p = get_raw_ptr(&oldht, oldht.table[i]);
 				ht_add(ht, p, ht->rehash(p, ht->priv));
 			}
 		}
-		htable_free(ht, oldtable);
+		/* Pass ht here to callback: oldht is an internal figment */
+		htable_free(ht, oldht.table);
 	}
 	ht->deleted = 0;
 
@@ -259,21 +328,34 @@ 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);
+	uintptr_t *validpair = actually_valid_pair(ht);
 
 	/* Beware wrap cases: we need to start from first empty bucket. */
 	for (start = 0; ht->table[start]; start++);
 
 	for (i = 0; i < (size_t)1 << ht->bits; i++) {
 		size_t h = (i + start) & ((1 << ht->bits)-1);
+		uintptr_t *actually = NULL;
 		e = ht->table[h];
-		if (!e)
-			continue;
-		if (e == HTABLE_DELETED)
-			ht->table[h] = 0;
-		else if (!(e & ht_perfect_mask(ht))) {
+		if (e <= HTABLE_DELETED) {
+			/* If it's actually valid, remember in case we move it! */
+			if (validpair[0] == h) {
+				actually = &validpair[0];
+			} else if (validpair[1] == h) {
+				actually = &validpair[1];
+			} else {
+				ht->table[h] = 0;
+				continue;
+			}
+		}
+
+		if (!(e & perfect)) {
 			void *p = get_raw_ptr(ht, e);
 			ht->table[h] = 0;
+			/* Clear actuallyvalid, let ht_add refill */
+			if (actually)
+				*actually = ((size_t)1 << ht->bits);
 			ht_add(ht, p, ht->rehash(p, ht->priv));
 		}
 	}
@@ -288,18 +370,9 @@ static COLD void update_common(struct htable *ht, const void *p)
 	uintptr_t maskdiff, bitsdiff;
 
 	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_bitnum = 1;
+		ht->perfect_bitnum = 0;
 		(void)htable_debug(ht, HTABLE_LOC);
 		return;
 	}
@@ -311,19 +384,23 @@ static COLD void update_common(struct htable *ht, const void *p)
 	bitsdiff = ht->common_bits & maskdiff;
 
 	for (i = 0; i < (size_t)1 << ht->bits; i++) {
-		if (!entry_is_valid(ht->table[i]))
+		if (!entry_is_valid(ht, i))
 			continue;
 		/* Clear the bits no longer in the mask, set them as
 		 * expected. */
 		ht->table[i] &= ~maskdiff;
 		ht->table[i] |= bitsdiff;
+
+		/* Make sure it's not newly falsely invalid */
+		if (ht->table[i] <= HTABLE_DELETED && !entry_actually_valid(ht, i))
+			add_actually_valid(ht, i);
 	}
 
 	/* 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 = 0;
+		ht->perfect_bitnum = NO_PERFECT_BIT;
 	(void)htable_debug(ht, HTABLE_LOC);
 }
 
@@ -359,18 +436,35 @@ bool htable_del_(struct htable *ht, size_t h, const void *p)
 void htable_delval_(struct htable *ht, struct htable_iter *i)
 {
 	assert(i->off < (size_t)1 << ht->bits);
-	assert(entry_is_valid(ht->table[i->off]));
+
+	if (entry_looks_invalid(ht, i->off))
+		del_actually_valid(ht, i->off);
 
 	ht->elems--;
 	ht->table[i->off] = HTABLE_DELETED;
 	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;
 	struct htable_iter i;
 	size_t n = 0;
+	const uintptr_t *validpair = actually_valid_pair(ht);
 
 	/* Use non-DEBUG versions here, to avoid infinite recursion with
 	 * CCAN_HTABLE_DEBUG! */
@@ -413,5 +507,35 @@ struct htable *htable_check(const struct htable *ht, const char *abortstr)
 		return NULL;
 	}
 
+	/* Check validpair does actually override invalid-looking entries! */
+	if (ht->table != &ht->common_bits) {
+		size_t i;
+		for (i = 0; i < 2; i++) {
+			if (validpair[i] == ((size_t)1 << ht->bits))
+				continue;
+			if (validpair[i] > ((size_t)1 << ht->bits)) {
+				if (abortstr) {
+					fprintf(stderr,
+						"%s: validpair[%zu] points at %zu"
+						" which is out of bounds\n",
+						abortstr, i, validpair[i]);
+					abort();
+				}
+				return NULL;
+			}
+			if (entry_looks_invalid(ht, validpair[i]))
+				continue;
+
+			if (abortstr) {
+				fprintf(stderr,
+					"%s: validpair[%zu] points at %zu"
+					" which seems valid\n",
+					abortstr, i, validpair[i]);
+				abort();
+			}
+			return NULL;
+		}
+	}
+
 	return (struct htable *)ht;
 }