Added new class LinkedListInVector

LinkedListInVector maintains a linked list in a vector.
It uses prev/next indices instead of pointers.
Implemented iterators and insert functions.

Change-Id: I7e15734b5c209618c4760efe65b7e68f1f827b62
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2089543Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Commit-Queue: Kei Nakashima <keinakashima@google.com>
Cr-Commit-Position: refs/heads/master@{#748125}

third_party/blink/renderer/platform/wtf/BUILD.gn

@@ -175,6 +175,7 @@ jumbo_component("wtf") {
     "uuid.cc",
     "uuid.h",
     "vector.h",
+    "vector_backed_linked_list.h",
     "vector_traits.h",
     "wtf.cc",
     "wtf.h",
@@ -296,6 +297,7 @@ jumbo_source_set("wtf_unittests_sources") {
     "tree_node_test.cc",
     "type_traits_test.cc",
     "uuid_test.cc",
+    "vector_backed_linked_list_test.cc",
     "vector_test.cc",
   ]
 

third_party/blink/renderer/platform/wtf/vector_backed_linked_list_test.cc

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "third_party/blink/renderer/platform/wtf/vector_backed_linked_list.h"
+
+#include "testing/gtest/include/gtest/gtest.h"
+
+namespace WTF {
+
+TEST(VectorBackedLinkedListTest, Insert) {
+  using List = VectorBackedLinkedList<int>;
+  List list;
+
+  EXPECT_TRUE(list.empty());
+  EXPECT_TRUE(list.begin() == list.end());
+  list.insert(list.end(), 1);
+  list.insert(list.begin(), -2);
+  list.insert(list.end(), 2);
+
+  List::iterator it = list.begin();
+  ++it;
+  list.insert(it, -1);
+  list.insert(it, 0);
+
+  EXPECT_EQ(list.front(), -2);
+  EXPECT_EQ(list.back(), 2);
+  EXPECT_EQ(list.size(), 5u);
+
+  int i = -2;
+  for (auto element : list) {
+    EXPECT_EQ(element, i);
+    i++;
+  }
+}
+
+TEST(VectorBackedLinkedList, PushFront) {
+  using List = VectorBackedLinkedList<int>;
+  List list;
+
+  EXPECT_TRUE(list.empty());
+  list.push_front(3);
+  EXPECT_EQ(list.front(), 3);
+  list.push_front(2);
+  EXPECT_EQ(list.front(), 2);
+  list.push_front(1);
+  EXPECT_EQ(list.front(), 1);
+
+  int i = 1;
+  for (auto element : list) {
+    EXPECT_EQ(element, i);
+    i++;
+  }
+}
+
+TEST(VectorBackedLinkedList, PushBack) {
+  using List = VectorBackedLinkedList<int>;
+  List list;
+
+  EXPECT_TRUE(list.empty());
+  list.push_back(1);
+  EXPECT_EQ(list.back(), 1);
+  list.push_back(2);
+  EXPECT_EQ(list.back(), 2);
+  list.push_back(3);
+  EXPECT_EQ(list.back(), 3);
+
+  int i = 1;
+  for (auto element : list) {
+    EXPECT_EQ(element, i);
+    i++;
+  }
+}
+
+TEST(VectorBackedLinkedList, Iterator) {
+  using List = VectorBackedLinkedList<int>;
+  List list;
+
+  list.push_back(1);
+  list.push_back(2);
+  list.push_back(3);
+
+  List::iterator it = list.begin();
+
+  EXPECT_EQ(*it, 1);
+  ++it;
+  EXPECT_EQ(*it, 2);
+  ++it;
+  EXPECT_EQ(*it, 3);
+  *it = 4;  // list: {1, 2, 4}
+  EXPECT_EQ(list.back(), 4);
+  ++it;
+  EXPECT_TRUE(it == list.end());
+  --it;
+  --it;
+  --it;
+  EXPECT_TRUE(it == list.begin());
+  EXPECT_EQ(list.front(), 1);
+  *it = 0;
+  EXPECT_EQ(list.front(), 0);  // list: {0, 2, 4}
+
+  List::reverse_iterator rit = list.rbegin();
+
+  EXPECT_EQ(*rit, 4);
+  ++rit;
+  EXPECT_EQ(*rit, 2);
+  ++rit;
+  EXPECT_EQ(*rit, 0);
+  EXPECT_FALSE(rit == list.rend());
+  *rit = 1;  // list: {1, 2, 4}
+  EXPECT_EQ(list.front(), 1);
+  ++rit;
+  EXPECT_TRUE(rit == list.rend());
+  --rit;
+  EXPECT_EQ(*rit, 1);
+}
+
+TEST(VectorBackedLinkedList, ConstIterator) {
+  using List = VectorBackedLinkedList<int>;
+  List list;
+
+  list.push_back(1);
+  list.push_back(2);
+  list.push_back(3);
+
+  List::const_iterator cit = list.cbegin();
+
+  EXPECT_EQ(*cit, 1);
+  ++cit;
+  EXPECT_EQ(*cit, 2);
+  ++cit;
+  EXPECT_EQ(*cit, 3);
+  ++cit;
+  EXPECT_TRUE(cit == list.cend());
+  --cit;
+  --cit;
+  --cit;
+  EXPECT_TRUE(cit == list.cbegin());
+  EXPECT_EQ(list.front(), 1);
+
+  List::const_reverse_iterator crit = list.crbegin();
+
+  EXPECT_EQ(*crit, 3);
+  ++crit;
+  EXPECT_EQ(*crit, 2);
+  ++crit;
+  EXPECT_EQ(*crit, 1);
+  ++crit;
+  EXPECT_TRUE(crit == list.crend());
+  --crit;
+  EXPECT_EQ(*crit, 1);
+}
+
+}  // namespace WTF