#include <stddef.h>
#include "libpspp/cast.h"
-/* Returns the data structure corresponding to the given NODE,
- assuming that NODE is embedded as the given MEMBER name in
- data type STRUCT. */
-#define bt_data(NODE, STRUCT, MEMBER) \
- (CHECK_POINTER_HAS_TYPE (NODE, struct bt_node *), \
- UP_CAST (NODE, STRUCT, MEMBER))
+/* Returns the data structure corresponding to the given NODE, assuming that
+ NODE is embedded as the given MEMBER name in data type STRUCT. NODE must
+ not be a null pointer. */
+#define BT_DATA(NODE, STRUCT, MEMBER) \
+ (CHECK_POINTER_HAS_TYPE (NODE, struct bt_node *), \
+ UP_CAST (NODE, STRUCT, MEMBER))
+
+/* Like BT_DATA, except that a null NODE yields a null pointer result. */
+#define BT_NULLABLE_DATA(NODE, STRUCT, MEMBER) \
+ ((STRUCT *) bt_nullable_data__ (NODE, offsetof (STRUCT, MEMBER)))
/* Node in a balanced binary tree. */
struct bt_node
size_t size; /* Current node count. */
size_t max_size; /* Max size since last complete rebalance. */
};
+#define BT_INITIALIZER(COMPARE, AUX) { .compare = COMPARE, .aux = AUX }
void bt_init (struct bt *, bt_compare_func *, const void *aux);
struct bt_node *bt_changed (struct bt *, struct bt_node *);
void bt_moved (struct bt *, struct bt_node *);
+/* Convenience macros for iteration.
+
+ These macros automatically use BT_DATA to obtain the data elements that
+ encapsulate bt nodes, which often saves typing and can make code easier to
+ read. Refer to the large comment near the top of this file for an example.
+
+ These macros evaluate their arguments many times. */
+#define BT_FIRST(STRUCT, MEMBER, BT) \
+ BT_NULLABLE_DATA (bt_first (BT), STRUCT, MEMBER)
+#define BT_NEXT(DATA, STRUCT, MEMBER, BT) \
+ BT_NULLABLE_DATA (bt_next (BT, &(DATA)->MEMBER), STRUCT, MEMBER)
+#define BT_FOR_EACH(DATA, STRUCT, MEMBER, BT) \
+ for ((DATA) = BT_FIRST (STRUCT, MEMBER, BT); \
+ (DATA) != NULL; \
+ (DATA) = BT_NEXT (DATA, STRUCT, MEMBER, BT))
+#define BT_FOR_EACH_SAFE(DATA, NEXT, STRUCT, MEMBER, BT) \
+ for ((DATA) = BT_FIRST (STRUCT, MEMBER, BT); \
+ ((DATA) != NULL \
+ ? ((NEXT) = BT_NEXT (DATA, STRUCT, MEMBER, BT), 1) \
+ : 0); \
+ (DATA) = (NEXT))
+
/* Returns the number of nodes currently in BT. */
static inline size_t bt_count (const struct bt *bt)
{
return bt->size == 0;
}
+/* Helper for BT_NULLABLE_DATA (to avoid evaluating its NODE argument more than
+ once). */
+static inline void *
+bt_nullable_data__ (struct bt_node *node, size_t member_offset)
+{
+ return node != NULL ? (char *) node - member_offset : NULL;
+}
+
#endif /* libpspp/bt.h */