Index: cc/base/random_access_list_container.h |
diff --git a/cc/base/random_access_list_container.h b/cc/base/random_access_list_container.h |
new file mode 100644 |
index 0000000000000000000000000000000000000000..b2baf3064d27e6938b6e3c5c93c70fd3223f8aac |
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+++ b/cc/base/random_access_list_container.h |
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+// Copyright 2015 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_RANDOM_ACCESS_LIST_CONTAINER_H_ |
+#define CC_BASE_RANDOM_ACCESS_LIST_CONTAINER_H_ |
+ |
+#include <vector> |
+ |
+#include "base/logging.h" |
+#include "cc/base/list_container_helper.h" |
+ |
+namespace cc { |
+ |
+// RandomAccessListContainer is a container similar to ListContainer (see |
+// list_container.h), but it allows random access into its elements via |
+// operator[]. In order to have efficient support for random access, some |
+// functionality is not available for RandomAccessListContainers, such as |
+// insert/deletes in the middle of the list. |
+template <class BaseElementType> |
+class RandomAccessListContainer { |
+ public: |
+ // BaseElementType is the type of raw pointers this class hands out; however, |
+ // its derived classes might require different memory sizes. |
+ // max_size_for_derived_class the largest memory size required for all the |
+ // derived classes to use for allocation. |
+ explicit RandomAccessListContainer(size_t max_size_for_derived_class) |
+ : helper_(max_size_for_derived_class) {} |
+ |
+ // This constructor reserves the requested memory up front so only a single |
+ // allocation is needed. When num_of_elements_to_reserve_for is zero, use the |
+ // default size. |
+ RandomAccessListContainer(size_t max_size_for_derived_class, |
+ size_t num_of_elements_to_reserve_for) |
+ : helper_(max_size_for_derived_class, num_of_elements_to_reserve_for) { |
+ items_.reserve(num_of_elements_to_reserve_for); |
+ } |
+ |
+ ~RandomAccessListContainer() { |
+ for (BaseElementType* item : items_) |
+ item->~BaseElementType(); |
+ } |
+ |
+ void clear() { |
+ for (BaseElementType* item : items_) |
+ item->~BaseElementType(); |
+ helper_.clear(); |
+ items_.clear(); |
+ } |
+ |
+ bool empty() const { return helper_.empty(); } |
+ size_t size() const { return helper_.size(); } |
+ size_t GetCapacityInBytes() const { return helper_.GetCapacityInBytes(); } |
+ |
+ template <typename DerivedElementType> |
+ DerivedElementType* AllocateAndConstruct() { |
+ auto* value = |
+ new (helper_.Allocate(sizeof(DerivedElementType))) DerivedElementType; |
+ items_.push_back(value); |
+ return value; |
+ } |
+ |
+ void RemoveLast() { |
+ items_.back()->~BaseElementType(); |
+ items_.pop_back(); |
+ helper_.RemoveLast(); |
+ } |
+ |
+ const BaseElementType* operator[](size_t index) const { |
+ DCHECK_GE(index, 0u); |
+ DCHECK_LT(index, items_.size()); |
+ return items_[index]; |
+ } |
+ |
+ BaseElementType* operator[](size_t index) { |
+ DCHECK_GE(index, 0u); |
+ DCHECK_LT(index, items_.size()); |
+ return items_[index]; |
+ } |
+ |
+ // Note that although BaseElementType objects can change, the pointer itself |
+ // (in the vector) cannot. So this class only supports a const iterator. |
+ using ConstIterator = typename std::vector<BaseElementType*>::const_iterator; |
+ ConstIterator begin() const { return items_.begin(); } |
+ ConstIterator end() const { return items_.end(); } |
+ |
+ private: |
+ ListContainerHelper helper_; |
+ std::vector<BaseElementType*> items_; |
+}; |
+ |
+} // namespace cc |
+ |
+#endif // CC_BASE_RANDOM_ACCESS_LIST_CONTAINER_H_ |