1 files changed, 300 insertions, 0 deletions
diff --git a/src/core/lib/gpr/avl.cc b/src/core/lib/gpr/avl.cc
new file mode 100644
index 0000000000..0b67a21f2f
--- /dev/null
+++ b/src/core/lib/gpr/avl.cc
@@ -0,0 +1,300 @@
+/*
+ *
+ * Copyright 2015 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+#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 = nullptr;
+  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,
+                       void* user_data) {
+  if (node == nullptr) {
+    return;
+  }
+  if (gpr_unref(&node->refs)) {
+    vtable->destroy_key(node->key, user_data);
+    vtable->destroy_value(node->value, user_data);
+    unref_node(vtable, node->left, user_data);
+    unref_node(vtable, node->right, user_data);
+    gpr_free(node);
+  }
+}
+
+static long node_height(gpr_avl_node* node) {
+  return node == nullptr ? 0 : node->height;
+}
+
+#ifndef NDEBUG
+static long calculate_height(gpr_avl_node* node) {
+  return node == nullptr ? 0
+                         : 1 + GPR_MAX(calculate_height(node->left),
+                                       calculate_height(node->right));
+}
+
+static gpr_avl_node* assert_invariants(gpr_avl_node* n) {
+  if (n == nullptr) return nullptr;
+  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);
+  return n;
+}
+#else
+static gpr_avl_node* assert_invariants(gpr_avl_node* n) { return n; }
+#endif
+
+gpr_avl_node* new_node(void* key, void* value, gpr_avl_node* left,
+                       gpr_avl_node* right) {
+  gpr_avl_node* node = (gpr_avl_node*)gpr_malloc(sizeof(*node));
+  gpr_ref_init(&node->refs, 1);
+  node->key = key;
+  node->value = value;
+  node->left = assert_invariants(left);
+  node->right = assert_invariants(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, void* user_data) {
+  long cmp;
+
+  if (node == nullptr) {
+    return nullptr;
+  }
+
+  cmp = vtable->compare_keys(node->key, key, user_data);
+  if (cmp == 0) {
+    return node;
+  } else if (cmp > 0) {
+    return get(vtable, node->left, key, user_data);
+  } else {
+    return get(vtable, node->right, key, user_data);
+  }
+}
+
+void* gpr_avl_get(gpr_avl avl, void* key, void* user_data) {
+  gpr_avl_node* node = get(avl.vtable, avl.root, key, user_data);
+  return node ? node->value : nullptr;
+}
+
+int gpr_avl_maybe_get(gpr_avl avl, void* key, void** value, void* user_data) {
+  gpr_avl_node* node = get(avl.vtable, avl.root, key, user_data);
+  if (node != nullptr) {
+    *value = node->value;
+    return 1;
+  }
+  return 0;
+}
+
+static gpr_avl_node* rotate_left(const gpr_avl_vtable* vtable, void* key,
+                                 void* value, gpr_avl_node* left,
+                                 gpr_avl_node* right, void* user_data) {
+  gpr_avl_node* n = new_node(vtable->copy_key(right->key, user_data),
+                             vtable->copy_value(right->value, user_data),
+                             new_node(key, value, left, ref_node(right->left)),
+                             ref_node(right->right));
+  unref_node(vtable, right, user_data);
+  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, void* user_data) {
+  gpr_avl_node* n =
+      new_node(vtable->copy_key(left->key, user_data),
+               vtable->copy_value(left->value, user_data), ref_node(left->left),
+               new_node(key, value, ref_node(left->right), right));
+  unref_node(vtable, left, user_data);
+  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, void* user_data) {
+  /* rotate_right(..., rotate_left(left), right) */
+  gpr_avl_node* n =
+      new_node(vtable->copy_key(left->right->key, user_data),
+               vtable->copy_value(left->right->value, user_data),
+               new_node(vtable->copy_key(left->key, user_data),
+                        vtable->copy_value(left->value, user_data),
+                        ref_node(left->left), ref_node(left->right->left)),
+               new_node(key, value, ref_node(left->right->right), right));
+  unref_node(vtable, left, user_data);
+  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, void* user_data) {
+  /* rotate_left(..., left, rotate_right(right)) */
+  gpr_avl_node* n =
+      new_node(vtable->copy_key(right->left->key, user_data),
+               vtable->copy_value(right->left->value, user_data),
+               new_node(key, value, left, ref_node(right->left->left)),
+               new_node(vtable->copy_key(right->key, user_data),
+                        vtable->copy_value(right->value, user_data),
+                        ref_node(right->left->right), ref_node(right->right)));
+  unref_node(vtable, right, user_data);
+  return n;
+}
+
+static gpr_avl_node* rebalance(const gpr_avl_vtable* vtable, void* key,
+                               void* value, gpr_avl_node* left,
+                               gpr_avl_node* right, void* user_data) {
+  switch (node_height(left) - node_height(right)) {
+    case 2:
+      if (node_height(left->left) - node_height(left->right) == -1) {
+        return assert_invariants(
+            rotate_left_right(vtable, key, value, left, right, user_data));
+      } else {
+        return assert_invariants(
+            rotate_right(vtable, key, value, left, right, user_data));
+      }
+    case -2:
+      if (node_height(right->left) - node_height(right->right) == 1) {
+        return assert_invariants(
+            rotate_right_left(vtable, key, value, left, right, user_data));
+      } else {
+        return assert_invariants(
+            rotate_left(vtable, key, value, left, right, user_data));
+      }
+    default:
+      return assert_invariants(new_node(key, value, left, right));
+  }
+}
+
+static gpr_avl_node* add_key(const gpr_avl_vtable* vtable, gpr_avl_node* node,
+                             void* key, void* value, void* user_data) {
+  long cmp;
+  if (node == nullptr) {
+    return new_node(key, value, nullptr, nullptr);
+  }
+  cmp = vtable->compare_keys(node->key, key, user_data);
+  if (cmp == 0) {
+    return new_node(key, value, ref_node(node->left), ref_node(node->right));
+  } else if (cmp > 0) {
+    return rebalance(vtable, vtable->copy_key(node->key, user_data),
+                     vtable->copy_value(node->value, user_data),
+                     add_key(vtable, node->left, key, value, user_data),
+                     ref_node(node->right), user_data);
+  } else {
+    return rebalance(
+        vtable, vtable->copy_key(node->key, user_data),
+        vtable->copy_value(node->value, user_data), ref_node(node->left),
+        add_key(vtable, node->right, key, value, user_data), user_data);
+  }
+}
+
+gpr_avl gpr_avl_add(gpr_avl avl, void* key, void* value, void* user_data) {
+  gpr_avl_node* old_root = avl.root;
+  avl.root = add_key(avl.vtable, avl.root, key, value, user_data);
+  assert_invariants(avl.root);
+  unref_node(avl.vtable, old_root, user_data);
+  return avl;
+}
+
+static gpr_avl_node* in_order_head(gpr_avl_node* node) {
+  while (node->left != nullptr) {
+    node = node->left;
+  }
+  return node;
+}
+
+static gpr_avl_node* in_order_tail(gpr_avl_node* node) {
+  while (node->right != nullptr) {
+    node = node->right;
+  }
+  return node;
+}
+
+static gpr_avl_node* remove_key(const gpr_avl_vtable* vtable,
+                                gpr_avl_node* node, void* key,
+                                void* user_data) {
+  long cmp;
+  if (node == nullptr) {
+    return nullptr;
+  }
+  cmp = vtable->compare_keys(node->key, key, user_data);
+  if (cmp == 0) {
+    if (node->left == nullptr) {
+      return ref_node(node->right);
+    } else if (node->right == nullptr) {
+      return ref_node(node->left);
+    } else if (node->left->height < node->right->height) {
+      gpr_avl_node* h = in_order_head(node->right);
+      return rebalance(
+          vtable, vtable->copy_key(h->key, user_data),
+          vtable->copy_value(h->value, user_data), ref_node(node->left),
+          remove_key(vtable, node->right, h->key, user_data), user_data);
+    } else {
+      gpr_avl_node* h = in_order_tail(node->left);
+      return rebalance(vtable, vtable->copy_key(h->key, user_data),
+                       vtable->copy_value(h->value, user_data),
+                       remove_key(vtable, node->left, h->key, user_data),
+                       ref_node(node->right), user_data);
+    }
+  } else if (cmp > 0) {
+    return rebalance(vtable, vtable->copy_key(node->key, user_data),
+                     vtable->copy_value(node->value, user_data),
+                     remove_key(vtable, node->left, key, user_data),
+                     ref_node(node->right), user_data);
+  } else {
+    return rebalance(
+        vtable, vtable->copy_key(node->key, user_data),
+        vtable->copy_value(node->value, user_data), ref_node(node->left),
+        remove_key(vtable, node->right, key, user_data), user_data);
+  }
+}
+
+gpr_avl gpr_avl_remove(gpr_avl avl, void* key, void* user_data) {
+  gpr_avl_node* old_root = avl.root;
+  avl.root = remove_key(avl.vtable, avl.root, key, user_data);
+  assert_invariants(avl.root);
+  unref_node(avl.vtable, old_root, user_data);
+  return avl;
+}
+
+gpr_avl gpr_avl_ref(gpr_avl avl, void* user_data) {
+  ref_node(avl.root);
+  return avl;
+}
+
+void gpr_avl_unref(gpr_avl avl, void* user_data) {
+  unref_node(avl.vtable, avl.root, user_data);
+}
+
+int gpr_avl_is_empty(gpr_avl avl) { return avl.root == nullptr; }