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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:
typedef T value_type;
typedef value_type& reference;
typedef const value_type& const_reference;
typedef size_t size_type;
typedef ptrdiff_t difference_type;
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 const 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_
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