AVL: creation, destroy, add
diff --git a/src/core/support/avl.c b/src/core/support/avl.c
new file mode 100644
index 0000000..b1f5585
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+++ b/src/core/support/avl.c
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+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ * * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include <grpc/support/avl.h>
+
+#include <assert.h>
+#include <stdlib.h>
+
+#include <grpc/support/alloc.h>
+#include <grpc/support/string_util.h>
+#include <grpc/support/useful.h>
+
+gpr_avl gpr_avl_create(const gpr_avl_vtable *vtable) {
+ gpr_avl out;
+ out.vtable = vtable;
+ out.root = NULL;
+ return out;
+}
+
+static gpr_avl_node *ref_node(gpr_avl_node *node) {
+ if (node) {
+ gpr_ref(&node->refs);
+ }
+ return node;
+}
+
+static void unref_node(const gpr_avl_vtable *vtable, gpr_avl_node *node) {
+ if (node == NULL) {
+ return;
+ }
+ if (gpr_unref(&node->refs)) {
+ vtable->destroy_key(node->key);
+ vtable->destroy_value(node->value);
+ unref_node(vtable, node->left);
+ unref_node(vtable, node->right);
+ gpr_free(node);
+ }
+}
+
+static long node_height(gpr_avl_node *node) {
+ return node == NULL ? 0 : node->height;
+}
+
+static long calculate_height(gpr_avl_node *node) {
+ return node == NULL ? 0 : 1 + GPR_MAX(calculate_height(node->left),
+ calculate_height(node->right));
+}
+
+static void assert_invariants(gpr_avl_node *n) {
+ if (n == NULL) return;
+ assert_invariants(n->left);
+ assert_invariants(n->right);
+ assert(calculate_height(n) == n->height);
+ assert(labs(node_height(n->left) - node_height(n->right)) <= 1);
+}
+
+gpr_avl_node *new_node(void *key, void *value, gpr_avl_node *left,
+ gpr_avl_node *right) {
+ gpr_avl_node *node = gpr_malloc(sizeof(*node));
+ gpr_ref_init(&node->refs, 1);
+ node->key = key;
+ node->value = value;
+ node->left = left;
+ node->right = right;
+ node->height = 1 + GPR_MAX(node_height(left), node_height(right));
+ return node;
+}
+
+static gpr_avl_node *get(const gpr_avl_vtable *vtable, gpr_avl_node *node,
+ void *key) {
+ long cmp;
+
+ if (node == NULL) {
+ return NULL;
+ }
+
+ cmp = vtable->compare_keys(node->key, key);
+ if (cmp == 0) {
+ return node;
+ } else if (cmp > 0) {
+ return get(vtable, node->left, key);
+ } else {
+ return get(vtable, node->right, key);
+ }
+}
+
+void *gpr_avl_get(gpr_avl avl, void *key) {
+ gpr_avl_node *node = get(avl.vtable, avl.root, key);
+ return node ? node->value : NULL;
+}
+
+static gpr_avl_node *rotate_left(const gpr_avl_vtable *vtable, void *key,
+ void *value, gpr_avl_node *left,
+ gpr_avl_node *right) {
+ gpr_avl_node *n =
+ new_node(vtable->copy_key(right->key), vtable->copy_value(right->value),
+ new_node(key, value, left, ref_node(right->left)),
+ ref_node(right->right));
+ unref_node(vtable, right);
+ return n;
+}
+
+static gpr_avl_node *rotate_right(const gpr_avl_vtable *vtable, void *key,
+ void *value, gpr_avl_node *left,
+ gpr_avl_node *right) {
+ gpr_avl_node *n = new_node(
+ vtable->copy_key(left->key), vtable->copy_value(left->value),
+ ref_node(left->left), new_node(key, value, ref_node(left->right), right));
+ unref_node(vtable, left);
+ return n;
+}
+
+static gpr_avl_node *rotate_left_right(const gpr_avl_vtable *vtable, void *key,
+ void *value, gpr_avl_node *left,
+ gpr_avl_node *right) {
+ /* rotate_right(..., rotate_left(left), right) */
+ /* TODO(ctiller): elide first allocation */
+ gpr_avl_node *leftp = new_node(
+ vtable->copy_key(left->right->key),
+ vtable->copy_value(left->right->value),
+ new_node(vtable->copy_key(left->key), vtable->copy_value(left->value),
+ ref_node(left->left), ref_node(left->right->left)),
+ ref_node(left->right->right));
+ gpr_avl_node *n =
+ new_node(vtable->copy_key(leftp->key), vtable->copy_value(leftp->value),
+ ref_node(leftp->left),
+ new_node(key, value, ref_node(leftp->right), right));
+ unref_node(vtable, left);
+ unref_node(vtable, leftp);
+ return n;
+}
+
+static gpr_avl_node *rotate_right_left(const gpr_avl_vtable *vtable, void *key,
+ void *value, gpr_avl_node *left,
+ gpr_avl_node *right) {
+ /* rotate_left(..., left, rotate_right(right)) */
+ /* TODO(ctiller): elide first allocation */
+ gpr_avl_node *rightp = new_node(
+ vtable->copy_key(right->left->key),
+ vtable->copy_value(right->left->value), ref_node(right->left->left),
+ new_node(vtable->copy_key(right->key), vtable->copy_key(right->value),
+ ref_node(right->left->right), ref_node(right->right)));
+ gpr_avl_node *n =
+ new_node(vtable->copy_key(rightp->key), vtable->copy_value(rightp->value),
+ new_node(key, value, left, ref_node(rightp->left)),
+ ref_node(rightp->right));
+ unref_node(vtable, right);
+ unref_node(vtable, rightp);
+ return n;
+}
+
+static gpr_avl_node *add(const gpr_avl_vtable *vtable, gpr_avl_node *node,
+ void *key, void *value) {
+ long cmp;
+ gpr_avl_node *l;
+ gpr_avl_node *r;
+ if (node == NULL) {
+ return new_node(key, value, NULL, NULL);
+ }
+ cmp = vtable->compare_keys(node->key, key);
+ if (cmp == 0) {
+ return new_node(key, value, NULL, NULL);
+ }
+ l = node->left;
+ r = node->right;
+ if (cmp > 0) {
+ l = add(vtable, l, key, value);
+ ref_node(r);
+ } else {
+ r = add(vtable, r, key, value);
+ ref_node(l);
+ }
+
+ key = vtable->copy_key(node->key);
+ value = vtable->copy_value(node->value);
+
+ switch (node_height(l) - node_height(r)) {
+ case 2:
+ if (node_height(l->left) - node_height(l->right) == 1) {
+ return rotate_right(vtable, key, value, l, r);
+ } else {
+ return rotate_left_right(vtable, key, value, l, r);
+ }
+ case -2:
+ if (node_height(r->left) - node_height(r->right) == 1) {
+ return rotate_right_left(vtable, key, value, l, r);
+ } else {
+ return rotate_left(vtable, key, value, l, r);
+ }
+ default:
+ return new_node(key, value, l, r);
+ }
+}
+
+gpr_avl gpr_avl_add(gpr_avl avl, void *key, void *value) {
+ gpr_avl_node *old_root = avl.root;
+ avl.root = add(avl.vtable, avl.root, key, value);
+ assert_invariants(avl.root);
+ unref_node(avl.vtable, old_root);
+ return avl;
+}
+
+void gpr_avl_destroy(gpr_avl avl) { unref_node(avl.vtable, avl.root); }