o Trivial binary tree

1 files changed, 130 insertions, 0 deletions

diff --git a/lib/datastruct/btree.c b/lib/datastruct/btree.c
new file mode 100644
index 00000000..6392a643
--- /dev/null
+++ b/lib/datastruct/btree.c
@@ -0,0 +1,130 @@
+/*
+ * Copyright (C) 2001 Sistina Software (UK) Limited.
+ *
+ * This file is released under the GPL.
+ */
+
+#include "btree.h"
+#include "log.h"
+
+struct node {
+	uint32_t key;
+	struct node *l, *r, *p;
+
+	void *data;
+};
+
+struct btree {
+	struct pool *mem;
+	struct node *root;
+};
+
+struct btree *btree_create(struct pool *mem)
+{
+	struct btree *t = pool_alloc(mem, sizeof(*t));
+
+	if (t) {
+		t->mem = mem;
+		t->root = NULL;
+	}
+
+	return t;
+}
+
+/*
+ * Shuffle the bits in a key, to try and remove
+ * any ordering.
+ */
+static uint32_t _shuffle(uint32_t k)
+{
+#if 0
+	return ((k & 0xff) << 24 |
+		(k & 0xff00) << 16 |
+		(k & 0xff0000) >> 8 |
+		(k & 0xff000000) >> 24);
+#else
+	return k;
+#endif
+}
+
+struct node **_lookup(struct node **c, uint32_t key, struct node **p)
+{
+	*p = NULL;
+	while (*c) {
+		*p = *c;
+		if ((*c)->key == key)
+			break;
+
+		if (key < (*c)->key)
+			c = &(*c)->l;
+
+		else
+			c = &(*c)->r;
+	}
+
+	return c;
+}
+
+void *btree_lookup(struct btree *t, uint32_t k)
+{
+	uint32_t key = _shuffle(k);
+	struct node *p, **c = _lookup(&t->root, key, &p);
+	return (*c) ? (*c)->data : NULL;
+}
+
+int btree_insert(struct btree *t, uint32_t k, void *data)
+{
+	uint32_t key = _shuffle(k);
+	struct node *p, **c = _lookup(&t->root, key, &p), *n;
+
+	if (!*c) {
+		if (!(n = pool_alloc(t->mem, sizeof(*n)))) {
+			stack;
+			return 0;
+		}
+
+		n->key = key;
+		n->data = data;
+		n->l = n->r = NULL;
+		n->p = p;
+
+		*c = n;
+	}
+
+	return 1;
+}
+
+void *btree_get_data(struct btree_iter *it)
+{
+	return ((struct node *) it)->data;
+}
+
+static inline struct node *_left(struct node *n)
+{
+	while (n->l)
+		n = n->l;
+	return n;
+}
+
+struct btree_iter *btree_first(struct btree *t)
+{
+	if (!t->root)
+		return NULL;
+
+	return (struct btree_iter *) _left(t->root);
+}
+
+struct btree_iter *btree_next(struct btree_iter *it)
+{
+	struct node *n = (struct node *) it;
+	uint32_t k = n->key;
+
+	if (n->r)
+		return (struct btree_iter *) _left(n->r);
+
+	do
+		n = n->p;
+	while (n && k > n->key);
+
+	return (struct btree_iter *) n;
+}