Move stack_container and linked_list to the new containers subdirectory.

This also replaces the StackWString with StackString16 and adds a char traits definition to the string16 header file to make this possible without ifdefs.

BUG=

Review URL: https://codereview.chromium.org/11360174

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@167022 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 164 insertions, 0 deletions

diff --git a/base/containers/linked_list.h b/base/containers/linked_list.h
new file mode 100644
index 0000000..25bbe76
--- /dev/null
+++ b/base/containers/linked_list.h
@@ -0,0 +1,164 @@
+// Copyright (c) 2009 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.
+
+#ifndef BASE_CONTAINERS_LINKED_LIST_H_
+#define BASE_CONTAINERS_LINKED_LIST_H_
+
+// Simple LinkedList type. (See the Q&A section to understand how this
+// differs from std::list).
+//
+// To use, start by declaring the class which will be contained in the linked
+// list, as extending LinkNode (this gives it next/previous pointers).
+//
+//   class MyNodeType : public LinkNode<MyNodeType> {
+//     ...
+//   };
+//
+// Next, to keep track of the list's head/tail, use a LinkedList instance:
+//
+//   LinkedList<MyNodeType> list;
+//
+// To add elements to the list, use any of LinkedList::Append,
+// LinkNode::InsertBefore, or LinkNode::InsertAfter:
+//
+//   LinkNode<MyNodeType>* n1 = ...;
+//   LinkNode<MyNodeType>* n2 = ...;
+//   LinkNode<MyNodeType>* n3 = ...;
+//
+//   list.Append(n1);
+//   list.Append(n3);
+//   n3->InsertBefore(n3);
+//
+// Lastly, to iterate through the linked list forwards:
+//
+//   for (LinkNode<MyNodeType>* node = list.head();
+//        node != list.end();
+//        node = node->next()) {
+//     MyNodeType* value = node->value();
+//     ...
+//   }
+//
+// Or to iterate the linked list backwards:
+//
+//   for (LinkNode<MyNodeType>* node = list.tail();
+//        node != list.end();
+//        node = node->previous()) {
+//     MyNodeType* value = node->value();
+//     ...
+//   }
+//
+// Questions and Answers:
+//
+// Q. Should I use std::list or base::LinkedList?
+//
+// A. The main reason to use base::LinkedList over std::list is
+//    performance. If you don't care about the performance differences
+//    then use an STL container, as it makes for better code readability.
+//
+//    Comparing the performance of base::LinkedList<T> to std::list<T*>:
+//
+//    * Erasing an element of type T* from base::LinkedList<T> is
+//      an O(1) operation. Whereas for std::list<T*> it is O(n).
+//      That is because with std::list<T*> you must obtain an
+//      iterator to the T* element before you can call erase(iterator).
+//
+//    * Insertion operations with base::LinkedList<T> never require
+//      heap allocations.
+//
+// Q. How does base::LinkedList implementation differ from std::list?
+//
+// A. Doubly-linked lists are made up of nodes that contain "next" and
+//    "previous" pointers that reference other nodes in the list.
+//
+//    With base::LinkedList<T>, the type being inserted already reserves
+//    space for the "next" and "previous" pointers (base::LinkNode<T>*).
+//    Whereas with std::list<T> the type can be anything, so the implementation
+//    needs to glue on the "next" and "previous" pointers using
+//    some internal node type.
+
+namespace base {
+
+template <typename T>
+class LinkNode {
+ public:
+  LinkNode() : previous_(0), next_(0) {}
+  LinkNode(LinkNode<T>* previous, LinkNode<T>* next)
+      : previous_(previous), next_(next) {}
+
+  // Insert |this| into the linked list, before |e|.
+  void InsertBefore(LinkNode<T>* e) {
+    this->next_ = e;
+    this->previous_ = e->previous_;
+    e->previous_->next_ = this;
+    e->previous_ = this;
+  }
+
+  // Insert |this| into the linked list, after |e|.
+  void InsertAfter(LinkNode<T>* e) {
+    this->next_ = e->next_;
+    this->previous_ = e;
+    e->next_->previous_ = this;
+    e->next_ = this;
+  }
+
+  // Remove |this| from the linked list.
+  void RemoveFromList() {
+    this->previous_->next_ = this->next_;
+    this->next_->previous_ = this->previous_;
+  }
+
+  LinkNode<T>* previous() const {
+    return previous_;
+  }
+
+  LinkNode<T>* next() const {
+    return next_;
+  }
+
+  // Cast from the node-type to the value type.
+  const T* value() const {
+    return static_cast<const T*>(this);
+  }
+
+  T* value() {
+    return static_cast<T*>(this);
+  }
+
+ private:
+  LinkNode<T>* previous_;
+  LinkNode<T>* next_;
+};
+
+template <typename T>
+class LinkedList {
+ public:
+  // The "root" node is self-referential, and forms the basis of a circular
+  // list (root_.next() will point back to the start of the list,
+  // and root_->previous() wraps around to the end of the list).
+  LinkedList() : root_(&root_, &root_) {}
+
+  // Appends |e| to the end of the linked list.
+  void Append(LinkNode<T>* e) {
+    e->InsertBefore(&root_);
+  }
+
+  LinkNode<T>* head() const {
+    return root_.next();
+  }
+
+  LinkNode<T>* tail() const {
+    return root_.previous();
+  }
+
+  const LinkNode<T>* end() const {
+    return &root_;
+  }
+
+ private:
+  LinkNode<T> root_;
+};
+
+}  // namespace base
+
+#endif  // BASE_CONTAINERS_LINKED_LIST_H_