htable: first implementation

ccan/htable/LICENSE

+../../licenses/GPL-2
\ No newline at end of file

ccan/htable/_info

+#include <string.h>
+#include <stdio.h>
+
+/**
+ * htable - hash table routines
+ *
+ * A hash table is an efficient structure for looking up keys.  This version
+ * grows with usage and allows efficient deletion.
+ *
+ * Example:
+ *	#include <ccan/htable/htable.h>
+ *	#include <ccan/hash/hash.h>
+ *	#include <stdio.h>
+ *	#include <err.h>
+ *	#include <string.h>
+ *
+ *	struct name_to_digit {
+ *		const char *name;
+ *		unsigned int val;
+ *	};
+ *
+ *	static struct name_to_digit map[] = {
+ *		{ "zero", 0},
+ *		{ "one", 1 },
+ *		{ "two", 2 },
+ *		{ "three", 3 },
+ *		{ "four", 4 },
+ *		{ "five", 5 },
+ *		{ "six", 6 },
+ *		{ "seven", 7 },
+ *		{ "eight", 8 },
+ *		{ "nine", 9 }
+ *	};
+ *
+ *	// Wrapper for rehash function pointer.
+ *	static size_t rehash(const void *e, void *unused)
+ *	{
+ *		return hash_string(((struct name_to_digit *)e)->name);
+ *	}
+ *
+ *	// Comparison function.
+ *	static bool streq(const void *e, void *string)
+ *	{
+ *		return strcmp(((struct name_to_digit *)e)->name, string) == 0;
+ *	}
+ *
+ *	// We let them add their own aliases, eg. --alias=v=5
+ *	static void add_alias(struct htable *ht, const char *alias)
+ *	{
+ *		char *eq;
+ *		struct name_to_digit *n;
+ *
+ *		n = malloc(sizeof(*n));
+ *		n->name = strdup(alias);
+ *
+ *		eq = strchr(n->name, '=');
+ *		if (!eq || ((n->val = atoi(eq+1)) == 0 && !strcmp(eq+1, "0")))
+ *			errx(1, "Usage: --alias=<name>=<value>");
+ *		*eq = '\0';
+ *		htable_add(ht, hash_string(n->name), n);
+ *	}
+ *
+ *	int main(int argc, char *argv[])
+ *	{
+ *		struct htable *ht;
+ *		unsigned int i;
+ *		unsigned long val;
+ *
+ *		if (argc < 2)
+ *			errx(1, "Usage: %s [--alias=<name>=<val>]... <str>...",
+ *			     argv[0]);
+ *
+ *		// Create and populate hash table.
+ *		ht = htable_new(rehash, NULL);
+ *		for (i = 0; i < sizeof(map)/sizeof(map[0]); i++)
+ *			htable_add(ht, hash_string(map[i].name), &map[i]);
+ *
+ *		// Add any aliases to the hash table.
+ *		for (i = 1; i < argc; i++) {
+ *			if (!strncmp(argv[i], "--alias=", strlen("--alias=")))
+ *				add_alias(ht, argv[i] + strlen("--alias="));
+ *			else
+ *				break;
+ *		}
+ *
+ *		// Find the other args in the hash table.
+ *		for (val = 0; i < argc; i++) {
+ *			struct name_to_digit *n;
+ *			n = htable_get(ht, hash_string(argv[i]),
+ *				       streq, argv[i]);
+ *			if (!n)
+ *				errx(1, "Invalid digit name %s", argv[i]);
+ *			// Append it to the value we are building up.
+ *			val *= 10;
+ *			val += n->val;
+ *		}
+ *		printf("%lu\n", val);
+ *		return 0;
+ *	}
+ *
+ * License: GPLv2 (or later)
+ * Author: Rusty Russell <rusty@rustcorp.com.au>
+ */
+int main(int argc, char *argv[])
+{
+	if (argc != 2)
+		return 1;
+
+	if (strcmp(argv[1], "depends") == 0) {
+		printf("ccan/compiler\n");
+		return 0;
+	}
+
+	return 1;
+}

ccan/htable/htable.c

+#include <ccan/htable/htable.h>
+#include <ccan/compiler/compiler.h>
+#include <stdint.h>
+#include <stdlib.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, max;
+	/* These are the bits which are the same in all pointers. */
+	uintptr_t common_mask, common_bits;
+	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)
+{
+	return e & ht->common_mask;
+}
+
+static inline void *get_raw_ptr(const struct htable *ht, uintptr_t e)
+{
+	return (void *)((e & ~ht->common_mask) | ht->common_bits);
+}
+
+static inline uintptr_t make_hval(const struct htable *ht,
+				  const void *p, uintptr_t bits)
+{
+	return ((uintptr_t)p & ~ht->common_mask) | bits;
+}
+
+static inline bool entry_is_valid(uintptr_t e)
+{
+	return e > HTABLE_DELETED;
+}
+
+static inline uintptr_t get_hash_ptr_bits(const struct htable *ht,
+					  size_t hash)
+{
+	/* Shuffling the extra bits (as specified in mask) down the
+	 * end is quite expensive.  But the lower bits are redundant, so
+	 * we fold the value first. */
+	return (hash ^ (hash >> ht->bits)) & ht->common_mask;
+}
+
+struct htable *htable_new(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->max = (1 << ht->bits) * 3 / 4;
+		/* This guarantees we enter update_common first add. */
+		ht->common_mask = -1;
+		ht->common_bits = 0;
+		ht->table = calloc(1 << ht->bits, sizeof(uintptr_t));
+		if (!ht->table) {
+			free(ht);
+			ht = NULL;
+		}
+	}
+	return ht;
+}
+
+void htable_free(const struct htable *ht)
+{
+	free((void *)ht->table);
+	free((void *)ht);
+}
+
+static size_t hash_bucket(const struct htable *ht, size_t h)
+{
+	return h & ((1 << ht->bits)-1);
+}
+
+static void *htable_val(const struct htable *ht,
+			struct htable_iter *i, size_t hash)
+{
+	uintptr_t h2 = get_hash_ptr_bits(ht, hash);
+
+	while (ht->table[i->off]) {
+		if (ht->table[i->off] != HTABLE_DELETED) {
+			if (get_extra_ptr_bits(ht, ht->table[i->off]) == h2)
+				return get_raw_ptr(ht, ht->table[i->off]);
+		}
+		i->off = (i->off + 1) & ((1 << ht->bits)-1);
+	}
+	return NULL;
+}
+
+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);
+}
+
+void *htable_nextval(const struct htable *ht,
+		     struct htable_iter *i, size_t hash)
+{
+	i->off = (i->off + 1) & ((1 << ht->bits)-1);
+	return htable_val(ht, i, hash);
+}
+
+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]))
+			return get_raw_ptr(ht, ht->table[i->off]);
+	}
+	return NULL;
+}
+
+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]))
+			return get_raw_ptr(ht, ht->table[i->off]);
+	}
+	return NULL;
+}
+
+/* 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;
+
+	i = hash_bucket(ht, h);
+
+	while (entry_is_valid(ht->table[i]))
+		i = (i + 1) & ((1 << ht->bits)-1);
+
+	ht->table[i] = make_hval(ht, new, get_hash_ptr_bits(ht, h));
+}
+
+static COLD_ATTRIBUTE bool double_table(struct htable *ht)
+{
+	unsigned int i;
+	size_t oldnum = (size_t)1 << ht->bits;
+	size_t *oldtable, e;
+
+	oldtable = ht->table;
+	ht->table = calloc(1 << (ht->bits+1), sizeof(size_t));
+	if (!ht->table) {
+		ht->table = oldtable;
+		return false;
+	}
+	ht->bits++;
+	ht->max *= 2;
+
+	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);
+	return true;
+}
+
+/* We stole some bits, now we need to put them back... */
+static COLD_ATTRIBUTE 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;
+		return;
+	}
+
+	/* 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 and set. */
+	ht->common_mask &= ~maskdiff;
+	ht->common_bits &= ~maskdiff;
+}
+
+bool htable_add(struct htable *ht, size_t hash, const void *p)
+{
+	if (ht->elems+1 > ht->max && !double_table(ht))
+		return false;
+	assert(p);
+	if (((uintptr_t)p & ht->common_mask) != ht->common_bits)
+		update_common(ht, p);
+
+	ht_add(ht, p, hash);
+	ht->elems++;
+	return true;
+}
+
+/* If every one of the following buckets are DELETED (up to the next unused
+   one), we can actually mark them all unused. */
+static void delete_run(struct htable *ht, unsigned int num)
+{
+	unsigned int i, last = num + 1;
+	size_t mask = (((size_t)1 << ht->bits)-1);
+
+	while (ht->table[last & mask]) {
+		if (entry_is_valid(ht->table[last & mask]))
+			return;
+		last++;
+	}
+
+	/* Now see if we can step backwards to find previous deleted ones. */
+	for (i = num-1; ht->table[i & mask] == HTABLE_DELETED; i--);
+
+	for (i++; i < last; i++)
+		ht->table[i & ((1 << ht->bits)-1)] = 0;
+}
+
+bool htable_del(struct htable *ht, size_t h, const void *p)
+{
+	struct htable_iter i;
+	void *c;
+
+	for (c = htable_firstval(ht,&i,h); c; c = htable_nextval(ht,&i,h)) {
+		if (c == p) {
+			htable_delval(ht, &i);
+			return true;
+		}
+	}
+	return false;
+}
+
+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]));
+
+	ht->elems--;
+	ht->table[i->off] = HTABLE_DELETED;
+	delete_run(ht, i->off);
+}

ccan/htable/htable.h

+#ifndef CCAN_HTABLE_H
+#define CCAN_HTABLE_H
+#include "config.h"
+#include <stdbool.h>
+#include <stdlib.h>
+
+struct htable;
+
+/**
+ * htable_new - allocate a hash tree.
+ * @rehash: hash function to use for rehashing.
+ * @priv: private argument to @rehash function.
+ */
+struct htable *htable_new(size_t (*hash)(const void *elem, void *priv),
+			  void *priv);
+
+/**
+ * htable_free - dellocate a hash tree.
+ *
+ * This doesn't do anything to any pointers left in it.
+ */
+void htable_free(const struct htable *);
+
+/**
+ * htable_rehash - use a hashtree's rehash function
+ * @elem: the argument to rehash()
+ *
+ */
+size_t htable_rehash(const void *elem);
+
+/**
+ * htable_add - add a pointer into a hash tree.
+ * @ht: the htable
+ * @hash: the hash value of the object
+ * @p: the non-NULL pointer
+ *
+ * Also note that this can only fail due to allocation failure.  Otherwise, it
+ * returns true.
+ */
+bool htable_add(struct htable *ht, size_t hash, const void *p);
+
+/**
+ * htable_del - remove a pointer from a hash tree
+ * @ht: the htable
+ * @hash: the hash value of the object
+ * @p: the pointer
+ *
+ * Returns true if the pointer was found (and deleted).
+ */
+bool htable_del(struct htable *ht, size_t hash, const void *p);
+
+/**
+ * struct htable_iter - iterator or htable_first or htable_firstval etc.
+ *
+ * This refers to a location inside the hashtable.
+ */
+struct htable_iter {
+	size_t off;
+};
+
+/**
+ * htable_firstval - find a candidate for a given hash value
+ * @htable: the hashtable
+ * @i: the struct htable_iter to initialize
+ * @hash: the hash value
+ *
+ * You'll need to check the value is what you want; returns NULL if none.
+ * See Also:
+ *	htable_delval()
+ */
+void *htable_firstval(const struct htable *htable,
+		      struct htable_iter *i, size_t hash);
+
+/**
+ * htable_nextval - find another candidate for a given hash value
+ * @htable: the hashtable
+ * @i: the struct htable_iter to initialize
+ * @hash: the hash value
+ *
+ * You'll need to check the value is what you want; returns NULL if no more.
+ */
+void *htable_nextval(const struct htable *htable,
+		     struct htable_iter *i, size_t hash);
+
+/**
+ * htable_get - find an entry in the hash table
+ * @ht: the hashtable
+ * @h: the hash value of the entry
+ * @cmp: the comparison function
+ * @ptr: the pointer to hand to the comparison function.
+ *
+ * Convenient inline wrapper for htable_firstval/htable_nextval loop.
+ */
+static inline void *htable_get(const struct htable *ht,
+			       size_t h,
+			       bool (*cmp)(const void *candidate, void *ptr),
+			       const void *ptr)
+{
+	struct htable_iter i;
+	void *c;
+
+	for (c = htable_firstval(ht,&i,h); c; c = htable_nextval(ht,&i,h)) {
+		if (cmp(c, (void *)ptr))
+			return c;
+	}
+	return NULL;
+}
+
+/**
+ * htable_first - find an entry in the hash table
+ * @ht: the hashtable
+ * @i: the struct htable_iter to initialize
+ *
+ * Get an entry in the hashtable; NULL if empty.
+ */
+void *htable_first(const struct htable *htable, struct htable_iter *i);
+
+/**
+ * htable_next - find another entry in the hash table
+ * @ht: the hashtable
+ * @i: the struct htable_iter to use
+ *
+ * Get another entry in the hashtable; NULL if all done.
+ * This is usually used after htable_first or prior non-NULL htable_next.
+ */
+void *htable_next(const struct htable *htable, struct htable_iter *i);
+
+/**
+ * htable_delval - remove an iterated pointer from a hash tree
+ * @ht: the htable
+ * @i: the htable_iter
+ *
+ * Usually used to delete a hash entry after it has been found with
+ * htable_firstval etc.
+ */
+void htable_delval(struct htable *ht, struct htable_iter *i);
+
+#endif /* CCAN_HTABLE_H */

ccan/htable/htable_type.h

+#ifndef CCAN_HTABLE_TYPE_H
+#define CCAN_HTABLE_TYPE_H
+#include <ccan/htable/htable.h>
+#include "config.h"
+
+/**
+ * HTABLE_DEFINE_TYPE - create a set of htable ops for a type
+ * @type: a type whose pointers will be values in the hash.
+ * @keyof: a function/macro to extract a key from a @type element.
+ * @hashfn: a hash function for a @key
+ * @cmpfn: a comparison function for two keyof()s.
+ * @name: a name for all the functions to define (of form htable_<name>_*)
+ *
+ * NULL values may not be placed into the hash table.
+ *
+ * The following wrapper functions are defined; each one is a
+ * simplified version of the htable.h equivalent:
+ *
+ *	// Creating and freeing.
+ *	struct htable_@name *htable_@name_new(void);
+ *	void htable_@name_free(const struct htable_@name *ht);
+ *
+ *	// Add, delete and find.
+ *	bool htable_@name_add(struct htable_@name *ht, const type *e);
+ *	bool htable_@name_del(struct htable_@name *ht, const type *e);
+ *	bool htable_@name_delkey(struct htable_@name *ht, const ktype *k);
+ *	type *htable_@name_get(const struct htable_@name *ht, const ktype *k);
+ *
+ *	// Iteration.
+ *	struct htable_@name_iter;
+ *	type *htable_@name_first(const struct htable_@name *ht,
+ *				 struct htable_@name_iter *i);
+ *	type *htable_@name_next(const struct htable_@name *ht,
+ *				struct htable_@name_iter *i);
+ */
+#define HTABLE_DEFINE_TYPE(type, keyof, hashfn, cmpfn, name)		\
+struct htable_##name;							\
+struct htable_##name##_iter { struct htable_iter i; };			\
+static inline size_t htable_##name##_hash(const void *elem, void *priv)	\
+{									\
+	return hashfn(keyof((const type *)elem));			\
+}									\
+static inline struct htable_##name *htable_##name##_new(void)		\
+{									\
+	return (struct htable_##name *)htable_new(htable_##name##_hash,	\
+						  NULL);		\
+}									\
+static inline void htable_##name##_free(const struct htable_##name *ht)	\
+{									\
+	htable_free((const struct htable *)ht);				\
+}									\
+static inline bool htable_##name##_add(struct htable_##name *ht,	\
+				       const type *elem)		\
+{									\
+	return htable_add((struct htable *)ht, hashfn(keyof(elem)), elem); \
+}									\
+static inline bool htable_##name##_del(const struct htable_##name *ht,	\
+				       const type *elem)		\
+{									\
+	return htable_del((struct htable *)ht, hashfn(keyof(elem)), elem); \
+}									\
+static inline type *htable_##name##_get(const struct htable_##name *ht,	\
+					const HTABLE_KTYPE(keyof) k)	\
+{									\
+	/* Typecheck for cmpfn */					\
+	(void)sizeof(cmpfn(keyof((const type *)NULL),			\
+			   keyof((const type *)NULL)));			\
+	return (type *)htable_get((const struct htable *)ht,		\
+				  hashfn(k),				\
+				  (bool (*)(const void *, void *))(cmpfn), \
+				  k);					\
+}									\
+static inline bool htable_##name##_delkey(struct htable_##name *ht,	\
+					  const HTABLE_KTYPE(keyof) k) \
+{									\
+	type *elem = htable_##name##_get(ht, k);			\
+	if (elem)							\
+		return htable_##name##_del(ht, elem);			\
+	return false;							\
+}									\
+static inline type *htable_##name##_first(const struct htable_##name *ht, \
+					  struct htable_##name##_iter *iter) \
+{									\
+	return htable_first((const struct htable *)ht, &iter->i);	\
+}									\
+static inline type *htable_##name##_next(const struct htable_##name *ht, \
+					 struct htable_##name##_iter *iter) \
+{									\
+	return htable_next((const struct htable *)ht, &iter->i);	\
+}
+
+#if HAVE_TYPEOF
+#define HTABLE_KTYPE(keyof) typeof(keyof(NULL))
+#else
+#define HTABLE_KTYPE(keyof) void *
+#endif
+#endif /* CCAN_HTABLE_TYPE_H */

ccan/htable/test/run-type.c

+#include <ccan/htable/htable_type.h>
+#include <ccan/htable/htable.c>
+#include <ccan/tap/tap.h>
+#include <stdbool.h>
+#include <string.h>
+
+#define NUM_VALS (1 << HTABLE_BASE_BITS)
+
+struct obj {
+	unsigned int key;
+};
+
+static const unsigned int *objkey(const struct obj *obj)
+{
+	return &obj->key;
+}
+
+/* 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
+   don't get masked out. */
+static size_t objhash(const unsigned int *key)
+{
+	size_t h = *key / 2;
+	h |= -1UL << HTABLE_BASE_BITS;
+	return h;
+}
+
+static bool cmp(const unsigned int *key1, const unsigned int *key2)
+{
+	return *key1 == *key2;
+}
+
+HTABLE_DEFINE_TYPE(struct obj, objkey, objhash, cmp, obj);
+
+static void add_vals(struct htable_obj *ht,
+		     struct obj val[], unsigned int num)
+{
+	unsigned int i;
+
+	for (i = 0; i < num; i++) {
+		if (htable_obj_get(ht, &i)) {
+			fail("%u already in hash", i);
+			return;
+		}
+		htable_obj_add(ht, &val[i]);
+		if (htable_obj_get(ht, &i) != &val[i]) {
+			fail("%u not added to hash", i);
+			return;
+		}
+	}
+	pass("Added %u numbers to hash", i);
+}
+
+static void find_vals(const struct htable_obj *ht,
+		      const struct obj val[], unsigned int num)
+{
+	unsigned int i;
+
+	for (i = 0; i < num; i++) {
+		if (htable_obj_get(ht, &i) != &val[i]) {
+			fail("%u not found in hash", i);
+			return;
+		}
+	}
+	pass("Found %u numbers in hash", i);
+}
+
+static void del_vals(struct htable_obj *ht,
+		     const struct obj val[], unsigned int num)
+{
+	unsigned int i;
+
+	for (i = 0; i < num; i++) {
+		if (!htable_obj_delkey(ht, &val[i].key)) {
+			fail("%u not deleted from hash", i);
+			return;
+		}
+	}
+	pass("Deleted %u numbers in hash", i);
+}
+
+static void del_vals_bykey(struct htable_obj *ht,
+			   const struct obj val[], unsigned int num)
+{
+	unsigned int i;
+
+	for (i = 0; i < num; i++) {
+		if (!htable_obj_delkey(ht, &i)) {
+			fail("%u not deleted by key from hash", i);
+			return;
+		}
+	}
+	pass("Deleted %u numbers by key from hash", i);
+}
+
+static bool check_mask(struct htable *ht, const struct obj val[], unsigned num)
+{
+	uint64_t i;
+
+	for (i = 0; i < num; i++) {
+		if (((uintptr_t)&val[i] & ht->common_mask) != ht->common_bits)
+			return false;
+	}
+	return true;
+}
+
+int main(int argc, char *argv[])
+{
+	unsigned int i;
+	struct htable_obj *ht;
+	struct obj val[NUM_VALS];
+	unsigned int dne;
+	void *p;
+	struct htable_obj_iter iter;
+
+	plan_tests(20);
+	for (i = 0; i < NUM_VALS; i++)
+		val[i].key = i;
+	dne = i;
+
+	ht = htable_obj_new();
+	ok1(((struct htable *)ht)->max < (1 << ((struct htable *)ht)->bits));
+	ok1(((struct htable *)ht)->bits == HTABLE_BASE_BITS);
+
+	/* We cannot find an entry which doesn't exist. */
+	ok1(!htable_obj_get(ht, &dne));
+
+	/* Fill it, it should increase in size (once). */
+	add_vals(ht, val, NUM_VALS);
+	ok1(((struct htable *)ht)->bits == HTABLE_BASE_BITS + 1);
+	ok1(((struct htable *)ht)->max < (1 << ((struct htable *)ht)->bits));
+
+	/* Mask should be set. */
+	ok1(((struct htable *)ht)->common_mask != 0);
+	ok1(((struct htable *)ht)->common_mask != -1);
+	ok1(check_mask((struct htable *)ht, val, NUM_VALS));
+
+	/* Find all. */
+	find_vals(ht, val, NUM_VALS);
+	ok1(!htable_obj_get(ht, &dne));
+
+	/* Walk once, should get them all. */
+	i = 0;
+	for (p = htable_obj_first(ht,&iter); p; p = htable_obj_next(ht, &iter))
+		i++;
+	ok1(i == NUM_VALS);
+
+	/* Delete all. */
+	del_vals(ht, val, NUM_VALS);
+	ok1(!htable_obj_get(ht, &val[0].key));
+
+	/* Worst case, a "pointer" which doesn't have any matching bits. */
+	htable_add((struct htable *)ht, 0,
+		   (void *)~(uintptr_t)&val[NUM_VALS-1]);
+	htable_obj_add(ht, &val[NUM_VALS-1]);
+	ok1(((struct htable *)ht)->common_mask == 0);
+	ok1(((struct htable *)ht)->common_bits == 0);
+	/* Delete the bogus one before we trip over it. */
+	htable_del((struct htable *)ht, 0,
+		   (void *)~(uintptr_t)&val[NUM_VALS-1]);
+
+	/* Add the rest. */
+	add_vals(ht, val, NUM_VALS-1);
+
+	/* Check we can find them all. */
+	find_vals(ht, val, NUM_VALS);
+	ok1(!htable_obj_get(ht, &dne));
+
+	/* Delete them all by key. */
+	del_vals_bykey(ht, val, NUM_VALS);
+	htable_obj_free(ht);
+
+	return exit_status();
+}

ccan/htable/test/run.c

+#include <ccan/htable/htable.h>
+#include <ccan/htable/htable.c>
+#include <ccan/tap/tap.h>
+#include <stdbool.h>
+#include <string.h>
+
+#define NUM_VALS (1 << HTABLE_BASE_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
+   don't get masked out. */
+static size_t hash(const void *elem, void *unused)
+{
+	size_t h = *(uint64_t *)elem / 2;
+	h |= -1UL << HTABLE_BASE_BITS;
+	return h;
+}
+
+static bool objcmp(const void *htelem, void *cmpdata)
+{
+	return *(uint64_t *)htelem == *(uint64_t *)cmpdata;
+}
+
+static void add_vals(struct htable *ht,
+		     const uint64_t val[], unsigned int num)
+{
+	uint64_t i;
+
+	for (i = 0; i < num; i++) {
+		if (htable_get(ht, hash(&i, NULL), objcmp, &i)) {
+			fail("%llu already in hash", (long long)i);
+			return;
+		}
+		htable_add(ht, hash(&val[i], NULL), &val[i]);
+		if (htable_get(ht, hash(&i, NULL), objcmp, &i) != &val[i]) {
+			fail("%llu not added to hash", (long long)i);
+			return;
+		}
+	}
+	pass("Added %llu numbers to hash", (long long)i);
+}
+
+#if 0
+static void refill_vals(struct htable *ht,
+			const uint64_t val[], unsigned int num)
+{
+	uint64_t i;
+
+	for (i = 0; i < num; i++) {
+		if (htable_get(ht, hash(&i, NULL), objcmp, &i))
+			continue;
+		htable_add(ht, hash(&val[i], NULL), &val[i]);
+	}
+}
+#endif
+
+static void find_vals(struct htable *ht,
+		      const uint64_t val[], unsigned int num)
+{
+	uint64_t i;
+
+	for (i = 0; i < num; i++) {
+		if (htable_get(ht, hash(&i, NULL), objcmp, &i) != &val[i]) {
+			fail("%llu not found in hash", (long long)i);
+			return;
+		}
+	}
+	pass("Found %llu numbers in hash", (long long)i);
+}
+
+static void del_vals(struct htable *ht,
+		     const uint64_t val[], unsigned int num)
+{
+	uint64_t i;
+
+	for (i = 0; i < num; i++) {
+		if (!htable_del(ht, hash(&val[i], NULL), &val[i])) {
+			fail("%llu not deleted from hash", (long long)i);
+			return;
+		}
+	}
+	pass("Deleted %llu numbers in hash", (long long)i);
+}
+
+static bool check_mask(struct htable *ht, uint64_t val[], unsigned num)
+{
+	uint64_t i;
+
+	for (i = 0; i < num; i++) {
+		if (((uintptr_t)&val[i] & ht->common_mask) != ht->common_bits)
+			return false;
+	}
+	return true;
+}
+
+int main(int argc, char *argv[])
+{
+	unsigned int i;
+	struct htable *ht;
+	uint64_t val[NUM_VALS];
+	uint64_t dne;
+	void *p;
+	struct htable_iter iter;
+
+	plan_tests(19);
+	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);
+
+	/* 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));
+
+	/* Mask should be set. */
+	ok1(ht->common_mask != 0);
+	ok1(ht->common_mask != -1);
+	ok1(check_mask(ht, val, NUM_VALS));
+
+	/* Find all. */
+	find_vals(ht, val, NUM_VALS);
+	ok1(!htable_get(ht, hash(&dne, NULL), objcmp, &dne));
+
+	/* Walk once, should get them all. */
+	i = 0;
+	for (p = htable_first(ht,&iter); p; p = htable_next(ht, &iter))
+		i++;
+	ok1(i == NUM_VALS);
+
+	/* Delete all. */
+	del_vals(ht, val, NUM_VALS);
+	ok1(!htable_get(ht, hash(&val[0], NULL), objcmp, &val[0]));
+
+	/* Worst case, a "pointer" which doesn't have any matching bits. */
+	htable_add(ht, 0, (void *)~(uintptr_t)&val[NUM_VALS-1]);
+	htable_add(ht, hash(&val[NUM_VALS-1], NULL), &val[NUM_VALS-1]);
+	ok1(ht->common_mask == 0);
+	ok1(ht->common_bits == 0);
+
+	/* Add the rest. */
+	add_vals(ht, val, NUM_VALS-1);
+
+	/* Check we can find them all. */
+	find_vals(ht, val, NUM_VALS);
+	ok1(!htable_get(ht, hash(&dne, NULL), objcmp, &dne));
+
+	return exit_status();
+}