Add a hash_table_foreach() macro.

I kept rewriting this in an user of this code.

2 files changed, 12 insertions, 6 deletions

diff --git a/hash_table.c b/hash_table.c
index efe15e9..a7d182a 100644
--- a/hash_table.c
+++ b/hash_table.c
@@ -144,9 +144,7 @@ hash_table_destroy(struct hash_table *ht,
 	if (delete_function) {
 		struct hash_entry *entry;
 
-		for (entry = hash_table_next_entry(ht, NULL);
-		     entry != NULL;
-		     entry = hash_table_next_entry(ht, entry)) {
+		hash_table_foreach(ht, entry) {
 			delete_function(entry);
 		}
 	}
@@ -210,9 +208,7 @@ hash_table_rehash(struct hash_table *ht, int new_size_index)
 	ht->entries = 0;
 	ht->deleted_entries = 0;
 
-	for (entry = old_ht.table;
-	     entry != old_ht.table + old_ht.size;
-	     entry++) {
+	hash_table_foreach(&old_ht, entry) {
 		if (entry_is_present(entry)) {
 			hash_table_insert(ht, entry->hash,
 					  entry->key, entry->data);
diff --git a/hash_table.h b/hash_table.h
index ffa3ec7..9afb4cd 100644
--- a/hash_table.h
+++ b/hash_table.h
@@ -60,3 +60,13 @@ struct hash_entry *hash_table_next_entry(struct hash_table *ht,
 struct hash_entry *
 hash_table_random_entry(struct hash_table *ht,
 			int (*predicate)(struct hash_entry *entry));
+
+/**
+ * This foreach function is safe against deletion (which just replaces
+ * an entry's data with the deleted marker), but not against insertion
+ * (which may rehash the table, making entry a dangling pointer).
+ */
+#define hash_table_foreach(ht, entry)				\
+	for (entry = hash_table_next_entry(ht, NULL);		\
+	     entry != NULL;					\
+	     entry = hash_table_next_entry(ht, entry))