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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 <stddef.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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