ported avl trees (tsearch) from musl

include/search.h

@@ -46,6 +46,12 @@ void *	lfind(const void *_key, void *_base, size_t *_nelp, size_t _width,
 void *	lsearch(const void *_key, void *_base, size_t *_nelp, size_t _width,
 		int(*_compar)(const void *, const void *));
 
+typedef enum { preorder, postorder, endorder, leaf } VISIT;
+void *tdelete(const void *, void **, int(*)(const void *, const void *));
+void *tfind(const void *, void *const *, int(*)(const void *, const void *));
+void *tsearch(const void *, void **, int (*)(const void *, const void *));
+void twalk(const void *, void (*)(const void *, VISIT, int));
+
 #ifndef _POSIX_SOURCE
 
 /* qelem type for insque and remque. */

src/libc/posix/search/makefile

@@ -5,5 +5,6 @@ TOP=../..
 SRC += _hash2v.c
 SRC += hcreate.c
 SRC += lfind.c
+SRC += tsearch_avl.c
 
 include $(TOP)/../makefile.inc

src/libc/posix/search/tsearch_avl.c

@@ -0,0 +1,204 @@
+#include <stdlib.h>
+#include <search.h>
+
+/*
+avl tree implementation using recursive functions
+the height of an n node tree is less than 1.44*log2(n+2)-1
+(so the max recursion depth in case of a tree with 2^32 nodes is 45)
+*/
+
+struct node {
+	const void *key;
+	struct node *left;
+	struct node *right;
+	int height;
+};
+
+static int delta(struct node *n) {
+	return (n->left ? n->left->height:0) - (n->right ? n->right->height:0);
+}
+
+static void updateheight(struct node *n) {
+	n->height = 0;
+	if (n->left && n->left->height > n->height)
+		n->height = n->left->height;
+	if (n->right && n->right->height > n->height)
+		n->height = n->right->height;
+	n->height++;
+}
+
+static struct node *rotl(struct node *n) {
+	struct node *r = n->right;
+	n->right = r->left;
+	r->left = n;
+	updateheight(n);
+	updateheight(r);
+	return r;
+}
+
+static struct node *rotr(struct node *n) {
+	struct node *l = n->left;
+	n->left = l->right;
+	l->right = n;
+	updateheight(n);
+	updateheight(l);
+	return l;
+}
+
+static struct node *balance(struct node *n) {
+	int d = delta(n);
+
+	if (d < -1) {
+		if (delta(n->right) > 0)
+			n->right = rotr(n->right);
+		return rotl(n);
+	} else if (d > 1) {
+		if (delta(n->left) < 0)
+			n->left = rotl(n->left);
+		return rotr(n);
+	}
+	updateheight(n);
+	return n;
+}
+
+static struct node *find(struct node *n, const void *k,
+	int (*cmp)(const void *, const void *))
+{
+	int c;
+
+	if (!n)
+		return 0;
+	c = cmp(k, n->key);
+	if (c == 0)
+		return n;
+	if (c < 0)
+		return find(n->left, k, cmp);
+	else
+		return find(n->right, k, cmp);
+}
+
+static struct node *insert(struct node *n, const void *k,
+	int (*cmp)(const void *, const void *), struct node **found)
+{
+	struct node *r;
+	int c;
+
+	if (!n) {
+		n = malloc(sizeof *n);
+		if (n) {
+			n->key = k;
+			n->left = n->right = 0;
+			n->height = 1;
+		}
+		*found = n;
+		return n;
+	}
+	c = cmp(k, n->key);
+	if (c == 0) {
+		*found = n;
+		return 0;
+	}
+	r = insert(c < 0 ? n->left : n->right, k, cmp, found);
+	if (r) {
+		if (c < 0)
+			n->left = r;
+		else
+			n->right = r;
+		r = balance(n);
+	}
+	return r;
+}
+
+static struct node *remove_rightmost(struct node *n, struct node **rightmost)
+{
+	if (!n->right) {
+		*rightmost = n;
+		return n->left;
+	}
+	n->right = remove_rightmost(n->right, rightmost);
+	return balance(n);
+}
+
+static struct node *remove(struct node **n, const void *k,
+	int (*cmp)(const void *, const void *), struct node *parent)
+{
+	int c;
+
+	if (!*n)
+		return 0;
+	c = cmp(k, (*n)->key);
+	if (c == 0) {
+		struct node *r = *n;
+		if (r->left) {
+			r->left = remove_rightmost(r->left, n);
+			(*n)->left = r->left;
+			(*n)->right = r->right;
+			*n = balance(*n);
+		} else
+			*n = r->right;
+		free(r);
+		return parent;
+	}
+	if (c < 0)
+		parent = remove(&(*n)->left, k, cmp, *n);
+	else
+		parent = remove(&(*n)->right, k, cmp, *n);
+	if (parent)
+		*n = balance(*n);
+	return parent;
+}
+
+void *tdelete(const void *restrict key, void **restrict rootp,
+	int(*compar)(const void *, const void *))
+{
+	if (!rootp)
+		return 0;
+	struct node *n = *rootp;
+	struct node *ret;
+	/* last argument is arbitrary non-null pointer
+	   which is returned when the root node is deleted */
+	ret = remove(&n, key, compar, n);
+	*rootp = n;
+	return ret;
+}
+
+void *tfind(const void *key, void *const *rootp,
+	int(*compar)(const void *, const void *))
+{
+	if (!rootp)
+		return 0;
+	return find(*rootp, key, compar);
+}
+
+void *tsearch(const void *key, void **rootp,
+	int (*compar)(const void *, const void *))
+{
+	struct node *update;
+	struct node *ret;
+	if (!rootp)
+		return 0;
+	update = insert(*rootp, key, compar, &ret);
+	if (update)
+		*rootp = update;
+	return ret;
+}
+
+static void walk(const struct node *r, void (*action)(const void *, VISIT, int), int d)
+{
+	if (r == 0)
+		return;
+	if (r->left == 0 && r->right == 0)
+		action(r, leaf, d);
+	else {
+		action(r, preorder, d);
+		walk(r->left, action, d+1);
+		action(r, postorder, d);
+		walk(r->right, action, d+1);
+		action(r, endorder, d);
+	}
+}
+
+void twalk(const void *root, void (*action)(const void *, VISIT, int))
+{
+	walk(root, action, 0);
+}