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Unified Diff: cc/base/random_access_list_container.h

Issue 1340703002: cc: Add RandomAccessListContainer, which has more restricted API. (Closed) Base URL: https://chromium.googlesource.com/chromium/src.git@master
Patch Set: Created 5 years, 3 months ago
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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
--- /dev/null
+++ b/cc/base/random_access_list_container.h
@@ -0,0 +1,94 @@
+// 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_
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