htable: allow htable_type keys to be non-pointers.

[ccan] / ccan / htable / htable.h

diff --git a/ccan/htable/htable.h b/ccan/htable/htable.h
index b3962ac050251747706c3de25259b781e3b026ca..61ed9170fda461779840f63db55295757a9bce8a 100644 (file)
--- a/ccan/htable/htable.h
+++ b/ccan/htable/htable.h
@@ -24,7 +24,26 @@ struct htable {
 };
 
 /**
- * htable_init - initialize an empty hash tree.
+ * HTABLE_INITIALIZER - static initialization for a hash table.
+ * @name: name of this htable.
+ * @rehash: hash function to use for rehashing.
+ * @priv: private argument to @rehash function.
+ *
+ * This is useful for setting up static and global hash tables.
+ *
+ * Example:
+ *     // For simplicity's sake, say hash value is contents of elem.
+ *     static size_t rehash(const void *elem, void *unused)
+ *     {
+ *             return *(size_t *)elem;
+ *     }
+ *     static struct htable ht = HTABLE_INITIALIZER(ht, rehash, NULL);
+ */
+#define HTABLE_INITIALIZER(name, rehash, priv)                         \
+       { rehash, priv, 0, 0, 0, 0, 0, -1, 0, 0, &name.perfect_bit }
+
+/**
+ * htable_init - initialize an empty hash table.
  * @ht: the hash table to initialize
  * @rehash: hash function to use for rehashing.
  * @priv: private argument to @rehash function.
@@ -33,13 +52,47 @@ void htable_init(struct htable *ht,
                 size_t (*rehash)(const void *elem, void *priv), void *priv);
 
 /**
- * htable_clear - empty a hash tree.
+ * htable_init_sized - initialize an empty hash table of given size.
+ * @ht: the hash table to initialize
+ * @rehash: hash function to use for rehashing.
+ * @priv: private argument to @rehash function.
+ * @size: the number of element.
+ *
+ * If this returns false, @ht is still usable, but may need to do reallocation
+ * upon an add.  If this returns true, it will not need to reallocate within
+ * @size htable_adds.
+ */
+bool htable_init_sized(struct htable *ht,
+                      size_t (*rehash)(const void *elem, void *priv),
+                      void *priv, size_t size);
+
+/**
+ * htable_clear - empty a hash table.
  * @ht: the hash table to clear
  *
  * This doesn't do anything to any pointers left in it.
  */
 void htable_clear(struct htable *ht);
 
+/**
+ * htable_copy - duplicate a hash table.
+ * @dst: the hash table to overwrite
+ * @src: the hash table to copy
+ *
+ * Only fails on out-of-memory.
+ *
+ * Equivalent to (but faster than):
+ *    if (!htable_init_sized(dst, src->rehash, src->priv, 1U << src->bits))
+ *        return false;
+ *    v = htable_first(src, &i);
+ *    while (v) {
+ *             htable_add(dst, v);
+ *             v = htable_next(src, i);
+ *    }
+ *    return true;
+ */
+bool htable_copy(struct htable *dst, const struct htable *src);
+
 /**
  * htable_rehash - use a hashtree's rehash function
  * @elem: the argument to rehash()
@@ -48,7 +101,7 @@ void htable_clear(struct htable *ht);
 size_t htable_rehash(const void *elem);
 
 /**
- * htable_add - add a pointer into a hash tree.
+ * htable_add - add a pointer into a hash table.
  * @ht: the htable
  * @hash: the hash value of the object
  * @p: the non-NULL pointer
@@ -59,7 +112,7 @@ size_t htable_rehash(const void *elem);
 bool htable_add(struct htable *ht, size_t hash, const void *p);
 
 /**
- * htable_del - remove a pointer from a hash tree
+ * htable_del - remove a pointer from a hash table
  * @ht: the htable
  * @hash: the hash value of the object
  * @p: the pointer
@@ -145,7 +198,22 @@ void *htable_first(const struct htable *htable, struct htable_iter *i);
 void *htable_next(const struct htable *htable, struct htable_iter *i);
 
 /**
- * htable_delval - remove an iterated pointer from a hash tree
+ * htable_prev - find the previous entry in the hash table
+ * @ht: the hashtable
+ * @i: the struct htable_iter to use
+ *
+ * Get previous entry in the hashtable; NULL if all done.
+ *
+ * "previous" here only means the item that would have been returned by
+ * htable_next() before the item it returned most recently.
+ *
+ * This is usually used in the middle of (or after) a htable_next iteration and
+ * to "unwind" actions taken.
+ */
+void *htable_prev(const struct htable *htable, struct htable_iter *i);
+
+/**
+ * htable_delval - remove an iterated pointer from a hash table
  * @ht: the htable
  * @i: the htable_iter
  *