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+/*
+ * Copyright (C) 2013 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef ART_LIBARTBASE_BASE_BOUNDED_FIFO_H_
+#define ART_LIBARTBASE_BASE_BOUNDED_FIFO_H_
+
+#include <android-base/logging.h>
+
+#include "base/bit_utils.h"
+
+namespace art {
+
+// A bounded fifo is a fifo which has a bounded size. The power of two version uses a bit mask to
+// avoid needing to deal with wrapping integers around or using a modulo operation.
+template <typename T, const size_t kMaxSize>
+class BoundedFifoPowerOfTwo {
+ static_assert(IsPowerOfTwo(kMaxSize), "kMaxSize must be a power of 2.");
+
+ public:
+ BoundedFifoPowerOfTwo() {
+ clear();
+ }
+
+ void clear() {
+ back_index_ = 0;
+ size_ = 0;
+ }
+
+ bool empty() const {
+ return size() == 0;
+ }
+
+ size_t size() const {
+ return size_;
+ }
+
+ void push_back(const T& value) {
+ ++size_;
+ DCHECK_LE(size_, kMaxSize);
+ // Relies on integer overflow behavior.
+ data_[back_index_++ & mask_] = value;
+ }
+
+ const T& front() const {
+ DCHECK_GT(size_, 0U);
+ return data_[(back_index_ - size_) & mask_];
+ }
+
+ void pop_front() {
+ DCHECK_GT(size_, 0U);
+ --size_;
+ }
+
+ private:
+ static const size_t mask_ = kMaxSize - 1;
+ size_t back_index_, size_;
+ T data_[kMaxSize];
+};
+
+} // namespace art
+
+#endif // ART_LIBARTBASE_BASE_BOUNDED_FIFO_H_