1 /* 2 * Copyright (C) 2013 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 ART_LIBARTBASE_BASE_BOUNDED_FIFO_H_ 18 #define ART_LIBARTBASE_BASE_BOUNDED_FIFO_H_ 19 20 #include <android-base/logging.h> 21 22 #include "bit_utils.h" 23 24 namespace art { 25 26 // A bounded fifo is a fifo which has a bounded size. The power of two version uses a bit mask to 27 // avoid needing to deal with wrapping integers around or using a modulo operation. 28 template <typename T, const size_t kMaxSize> 29 class BoundedFifoPowerOfTwo { 30 static_assert(IsPowerOfTwo(kMaxSize), "kMaxSize must be a power of 2."); 31 32 public: BoundedFifoPowerOfTwo()33 BoundedFifoPowerOfTwo() { 34 clear(); 35 } 36 clear()37 void clear() { 38 back_index_ = 0; 39 size_ = 0; 40 } 41 empty()42 bool empty() const { 43 return size() == 0; 44 } 45 size()46 size_t size() const { 47 return size_; 48 } 49 push_back(const T & value)50 void push_back(const T& value) { 51 ++size_; 52 DCHECK_LE(size_, kMaxSize); 53 // Relies on integer overflow behavior. 54 data_[back_index_++ & mask_] = value; 55 } 56 front()57 const T& front() const { 58 DCHECK_GT(size_, 0U); 59 return data_[(back_index_ - size_) & mask_]; 60 } 61 pop_front()62 void pop_front() { 63 DCHECK_GT(size_, 0U); 64 --size_; 65 } 66 67 private: 68 static const size_t mask_ = kMaxSize - 1; 69 size_t back_index_, size_; 70 T data_[kMaxSize]; 71 }; 72 73 } // namespace art 74 75 #endif // ART_LIBARTBASE_BASE_BOUNDED_FIFO_H_ 76