0

cc: Add RandomAccessListContainer, which has more restricted API.

This patch adds RandomAccessListContainer, which is similar to
ListContainer with two important differences:
- It supports random access via operator[]
  - This is important for DisplayItemList use-case where an access into
    an rtree returns indices of elements to be rasterized. With this,
    we can access those elements directly.
- It doesn't support middle-of-list operations (inserts/deletes)
  - This is done in order to simplify maintaining random access capabilities

BUG=527245
R=weiliangc, danakj
CQ_INCLUDE_TRYBOTS=tryserver.blink:linux_blink_rel

Review URL: https://codereview.chromium.org/1340703002

Cr-Commit-Position: refs/heads/master@{#349564}
This commit is contained in:
vmpstr
2015-09-17 18:10:12 -07:00
committed by Commit bot
parent 37b4bf3f64
commit b10241fcd5
7 changed files with 208 additions and 0 deletions

@@ -725,6 +725,7 @@ test("cc_unittests") {
"base/histograms_unittest.cc",
"base/list_container_unittest.cc",
"base/math_util_unittest.cc",
"base/random_access_list_container_unittest.cc",
"base/region_unittest.cc",
"base/rolling_time_delta_history_unittest.cc",
"base/scoped_ptr_vector_unittest.cc",

@@ -18,6 +18,7 @@ source_set("base") {
"list_container_helper.h",
"math_util.cc",
"math_util.h",
"random_access_list_container.h",
"region.cc",
"region.h",
"resource_id.h",

@@ -18,6 +18,9 @@ class CC_EXPORT ListContainerHelper final {
template <typename T>
friend class ListContainer;
template <typename T>
friend class RandomAccessListContainer;
explicit ListContainerHelper(size_t max_size_for_derived_class);
ListContainerHelper(size_t max_size_for_derived_class,
size_t num_of_elements_to_reserve_for);

@@ -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_

@@ -0,0 +1,107 @@
// 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.
#include "cc/base/random_access_list_container.h"
#include <algorithm>
#include <vector>
#include "testing/gmock/include/gmock/gmock.h"
#include "testing/gtest/include/gtest/gtest.h"
namespace cc {
namespace {
class Base {
public:
virtual ~Base() {}
int get_value() const { return value_; }
protected:
explicit Base(int value) : value_(value) {}
int value_;
};
const int kMagicNumberOne = 1;
const int kMagicNumberTwo = 2;
const int kMagicNumberThree = 3;
class Derived1 : public Base {
public:
Derived1() : Base(kMagicNumberOne) {}
};
class Derived2 : public Base {
public:
Derived2() : Base(kMagicNumberTwo) {}
};
class Derived3 : public Base {
public:
Derived3() : Base(kMagicNumberThree) {}
};
size_t LargestDerivedElementSize() {
static_assert(sizeof(Derived1) >= sizeof(Derived2),
"Derived2 is larger than Derived1");
static_assert(sizeof(Derived1) >= sizeof(Derived3),
"Derived3 is larger than Derived1");
return sizeof(Derived1);
}
TEST(RandomAccessListContainerTest, RandomAccess) {
RandomAccessListContainer<Base> list(LargestDerivedElementSize(), 1);
list.AllocateAndConstruct<Derived1>();
list.AllocateAndConstruct<Derived2>();
list.AllocateAndConstruct<Derived3>();
list.AllocateAndConstruct<Derived1>();
list.AllocateAndConstruct<Derived2>();
list.AllocateAndConstruct<Derived3>();
EXPECT_EQ(kMagicNumberOne, list[0]->get_value());
EXPECT_EQ(kMagicNumberTwo, list[1]->get_value());
EXPECT_EQ(kMagicNumberThree, list[2]->get_value());
EXPECT_EQ(kMagicNumberOne, list[3]->get_value());
EXPECT_EQ(kMagicNumberTwo, list[4]->get_value());
EXPECT_EQ(kMagicNumberThree, list[5]->get_value());
list.RemoveLast();
list.RemoveLast();
list.RemoveLast();
EXPECT_EQ(kMagicNumberOne, list[0]->get_value());
EXPECT_EQ(kMagicNumberTwo, list[1]->get_value());
EXPECT_EQ(kMagicNumberThree, list[2]->get_value());
list.AllocateAndConstruct<Derived3>();
list.AllocateAndConstruct<Derived2>();
list.AllocateAndConstruct<Derived1>();
EXPECT_EQ(kMagicNumberOne, list[0]->get_value());
EXPECT_EQ(kMagicNumberTwo, list[1]->get_value());
EXPECT_EQ(kMagicNumberThree, list[2]->get_value());
EXPECT_EQ(kMagicNumberThree, list[3]->get_value());
EXPECT_EQ(kMagicNumberTwo, list[4]->get_value());
EXPECT_EQ(kMagicNumberOne, list[5]->get_value());
}
TEST(RandomAccessListContainerTest, Clear) {
RandomAccessListContainer<Base> list(LargestDerivedElementSize(), 1);
list.AllocateAndConstruct<Derived1>();
list.AllocateAndConstruct<Derived2>();
EXPECT_EQ(kMagicNumberOne, list[0]->get_value());
EXPECT_EQ(kMagicNumberTwo, list[1]->get_value());
list.clear();
list.AllocateAndConstruct<Derived3>();
EXPECT_EQ(kMagicNumberThree, list[0]->get_value());
}
} // namespace
} // namespace cc

@@ -85,6 +85,7 @@
'base/list_container_helper.h',
'base/math_util.cc',
'base/math_util.h',
'base/random_access_list_container.h',
'base/region.cc',
'base/region.h',
'base/resource_id.h',

@@ -22,6 +22,7 @@
'base/histograms_unittest.cc',
'base/list_container_unittest.cc',
'base/math_util_unittest.cc',
'base/random_access_list_container_unittest.cc',
'base/region_unittest.cc',
'base/rolling_time_delta_history_unittest.cc',
'base/scoped_ptr_vector_unittest.cc',