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