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diff --git a/third_party/wasm2c/include/wabt/circular-array.h b/third_party/wasm2c/include/wabt/circular-array.h
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+/*
+ * Copyright 2017 WebAssembly Community Group participants
+ *
+ * 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 WABT_CIRCULAR_ARRAY_H_
+#define WABT_CIRCULAR_ARRAY_H_
+
+#include <array>
+#include <cassert>
+#include <cstddef>
+#include <type_traits>
+
+namespace wabt {
+
+// TODO(karlschimpf) Complete the API
+// Note: Capacity must be a power of 2.
+template <class T, size_t kCapacity>
+class CircularArray {
+ public:
+  using value_type = T;
+  using reference = value_type&;
+  using const_reference = const value_type&;
+  using size_type = size_t;
+  using difference_type = ptrdiff_t;
+
+  CircularArray() {
+    static_assert(kCapacity && ((kCapacity & (kCapacity - 1)) == 0),
+                  "Capacity must be a power of 2.");
+  }
+
+  CircularArray(const CircularArray&) = default;
+  CircularArray& operator=(const CircularArray&) = default;
+
+  CircularArray(CircularArray&&) = default;
+  CircularArray& operator=(CircularArray&&) = default;
+
+  ~CircularArray() { clear(); }
+
+  reference at(size_type index) {
+    assert(index < size_);
+    return (*this)[index];
+  }
+
+  const_reference at(size_type index) const {
+    assert(index < size_);
+    return (*this)[index];
+  }
+
+  reference operator[](size_type index) { return contents_[position(index)]; }
+
+  const_reference operator[](size_type index) const {
+    return contents_[position(index)];
+  }
+
+  reference back() { return at(size_ - 1); }
+
+  const_reference back() const { return at(size_ - 1); }
+
+  bool empty() const { return size_ == 0; }
+
+  reference front() { return at(0); }
+
+  const_reference front() const { return at(0); }
+
+  size_type max_size() const { return kCapacity; }
+
+  void pop_back() {
+    assert(size_ > 0);
+    SetElement(back());
+    --size_;
+  }
+
+  void pop_front() {
+    assert(size_ > 0);
+    SetElement(front());
+    front_ = (front_ + 1) & kMask;
+    --size_;
+  }
+
+  void push_back(const value_type& value) {
+    assert(size_ < kCapacity);
+    SetElement(at(size_++), value);
+  }
+
+  size_type size() const { return size_; }
+
+  void clear() {
+    while (!empty()) {
+      pop_back();
+    }
+  }
+
+ private:
+  static constexpr size_type kMask = kCapacity - 1;
+
+  size_t position(size_t index) const { return (front_ + index) & kMask; }
+
+  template <typename... Args>
+  void SetElement(reference element, Args&&... args) {
+    element.~T();
+    new (&element) T(std::forward<Args>(args)...);
+  }
+
+  std::array<T, kCapacity> contents_;
+  size_type size_ = 0;
+  size_type front_ = 0;
+};
+
+}  // namespace wabt
+
+#endif  // WABT_CIRCULAR_ARRAY_H_