Add the FOREACH and FOREACH_SAFE macros

1 files changed, 32 insertions, 0 deletions

diff --git a/src/gehashmap.h b/src/gehashmap.h
index 311c2c3..1f24943 100644
--- a/src/gehashmap.h
+++ b/src/gehashmap.h
@@ -11,6 +11,38 @@
 #define GEHASHMAP_INITIAL_SIZE 16
 #define GEHASHMAP_LOAD_FACTOR  0.75
 
+/* The GEHASHMAP_FOREACH() macro takes 2 arguments.  The first argument “entry”
+ * is a “struct n##_entry *”.  This variable will be set to point to the next
+ * hashmap entry each iteration.  The second argument “map” is a pointer to the
+ * hashmap to iterate over.
+ *
+ * This macro is unsafe to use when modifying the hashmap inplace (i.e. when
+ * calling n##_remove() in the loop).
+ */
+#define GEHASHMAP_FOREACH(entry, map) \
+	for (size_t _gehashmap_i = 0; \
+	     _gehashmap_i < (map)->capacity; \
+	     (_gehashmap_i)++) \
+		for ((entry) = (map)->entries[_gehashmap_i]; \
+		     (entry) != NULL; \
+		     (entry) = (entry)->next)
+
+/* The GEHASHMAP_FOREACH_SAFE() macro is identical to the GEHASHMAP_FOREACH()
+ * macro except it takes an additional “tmp” argument.  This argument is of the
+ * same type as “entry” (a “struct n##_entry *”) and shouldn’t be interacted
+ * with by the library user.  This macro allows you to modify the hashmap
+ * inplace while iterating.
+ */
+#define GEHASHMAP_FOREACH_SAFE(entry, tmp, map) \
+	for (size_t _gehashmap_i = 0; \
+	     _gehashmap_i < (map)->capacity; \
+	     (_gehashmap_i)++) \
+		for ((entry) = (map)->entries[_gehashmap_i], \
+		     (tmp) = (entry) ? (entry)->next : NULL; \
+		     (entry) != NULL; \
+		     (entry) = (tmp), \
+		     (tmp) = (entry) ? (entry)->next : NULL)
+
 #define GEHASHMAP_API(k, v, n) \
 	struct n##_entry { \
 		k key; \