upload android base code part3

android/art/runtime/base/bounded_fifo.h

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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_RUNTIME_BASE_BOUNDED_FIFO_H_
+#define ART_RUNTIME_BASE_BOUNDED_FIFO_H_
+
+#include "base/bit_utils.h"
+#include "base/logging.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_RUNTIME_BASE_BOUNDED_FIFO_H_