Add ListContainer::AppendByMoving

cc/base/list_container.h

 // Copyright 2014 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 CC_BASE_LIST_CONTAINER_H_
 #define CC_BASE_LIST_CONTAINER_H_
 
 #include "base/logging.h"
 #include "base/macros.h"
 #include "base/memory/scoped_ptr.h"
@@ skipping 143 matching lines @@
   ConstIterator cend() const;
   Iterator begin();
   Iterator end();
 
   Iterator IteratorAt(size_t index);
   ConstIterator IteratorAt(size_t index) const;
 
   size_t size() const;
   bool empty() const;
 
+  size_t MaxSizeForDerivedClass() const;
+
   // Unlike the ListContainer method, this one does not invoke element
   // destructors.
   void clear();
 
   size_t AvailableSizeWithoutAnotherAllocationForTesting() const;
 
   // Hands out memory location for an element at the end of data structure.
   void* Allocate(size_t size_of_actual_element_in_bytes);
 
   scoped_ptr<ListContainerCharAllocator> data_;
@@ skipping 89 matching lines @@
   const BaseElementType* ElementAt(size_t index) const {
     return *ConstIterator(IteratorAt(index));
   }
 
   // Take in derived element type and construct it at location generated by
   // Allocate().
   template <typename DerivedElementType>
   DerivedElementType* AllocateAndConstruct() {
     return new (Allocate(sizeof(DerivedElementType))) DerivedElementType;
   }
+
   // Take in derived element type and copy construct it at location generated by
   // Allocate().
   template <typename DerivedElementType>
   DerivedElementType* AllocateAndCopyFrom(const DerivedElementType* source) {
     return new (Allocate(sizeof(DerivedElementType)))
         DerivedElementType(*source);
   }
+
   // Construct a new element on top of an existing one.
   template <typename DerivedElementType>
   DerivedElementType* ReplaceExistingElement(Iterator at) {
     at->~BaseElementType();
     return new (*at) DerivedElementType();
   }
 
+  // Appends a new item without copying. The original item will not be
+  // destructed and will be replaced with a new DerivedElementType. The
+  // DerivedElementType does not have to match the moved type as a full block
+  // of memory will be moved (up to MaxSizeForDerivedClass()).
+  template <typename DerivedElementType>
+  void AppendByMoving(DerivedElementType* item) {
+    size_t max_size_for_derived_class = MaxSizeForDerivedClass();
+    void* new_item = Allocate(max_size_for_derived_class);
+    memcpy(new_item, static_cast<void*>(item), max_size_for_derived_class);
+    // Construct a new element in-place so it can be destructed safely.
+    new (item) DerivedElementType;
+  }
+
   using ListContainerBase::size;
   using ListContainerBase::empty;
 
   void clear() {
     for (Iterator i = begin(); i != end(); ++i) {
       i->~BaseElementType();
     }
     ListContainerBase::clear();
   }
 
@@ skipping 150 matching lines @@
         ListContainerBase::ConstReverseIterator base_iterator)
         : ListContainerBase::ConstReverseIterator(base_iterator) {}
     friend ConstReverseIterator ListContainer<BaseElementType>::crbegin() const;
     friend ConstReverseIterator ListContainer<BaseElementType>::crend() const;
   };
 };
 
 }  // namespace cc
 
 #endif  // CC_BASE_LIST_CONTAINER_H_