memory_pool_impl.h revision f025d4a118047d7763d75ff50c37fdd2819ba8eb 
1/*
2 * Copyright (C) 2016 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17#ifndef CHRE_UTIL_MEMORY_POOL_IMPL_H_
18#define CHRE_UTIL_MEMORY_POOL_IMPL_H_
19
20#include "chre/util/memory_pool.h"
21
22#include <utility>
23
24namespace chre {
25
26template<typename ElementType, size_t kSize>
27MemoryPool<ElementType, kSize>::MemoryPool() {
28  // Initialize the free block list. The initial condition is such that each
29  // block points to the next as being empty. The mFreeBlockCount is used to
30  // ensure that we never allocate out of bounds so we don't need to worry about
31  // the last block referring to one that is non-existent.
32  for (size_t i = 0; i < kSize; i++) {
33    mBlocks.emplace_back(i + 1);
34  }
35}
36
37template<typename ElementType, size_t kSize>
38template<typename... Args>
39ElementType *MemoryPool<ElementType, kSize>::allocate(Args&&... args) {
40  if (mFreeBlockCount == 0) {
41    return nullptr;
42  }
43
44  size_t blockIndex = mNextFreeBlockIndex;
45  mNextFreeBlockIndex = mBlocks[blockIndex].mNextFreeBlockIndex;
46  mFreeBlockCount--;
47
48  return new (&mBlocks[blockIndex].mElement)
49      ElementType(std::forward<Args>(args)...);
50}
51
52template<typename ElementType, size_t kSize>
53void MemoryPool<ElementType, kSize>::deallocate(ElementType *element) {
54  uintptr_t elementAddress = reinterpret_cast<uintptr_t>(element);
55  uintptr_t baseAddress = reinterpret_cast<uintptr_t>(&mBlocks[0].mElement);
56  size_t blockIndex = (elementAddress - baseAddress) / sizeof(MemoryPoolBlock);
57
58  mBlocks[blockIndex].mElement.~ElementType();
59  mBlocks[blockIndex].mNextFreeBlockIndex = mNextFreeBlockIndex;
60  mNextFreeBlockIndex = blockIndex;
61  mFreeBlockCount++;
62}
63
64template<typename ElementType, size_t kSize>
65MemoryPool<ElementType, kSize>::MemoryPoolBlock::MemoryPoolBlock(
66    size_t nextFreeBlockIndex) : mNextFreeBlockIndex(nextFreeBlockIndex) {}
67
68}  // namespace chre
69
70#endif  // CHRE_UTIL_MEMORY_POOL_IMPL_H_
71