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/*
* Copyright 2019 The libgav1 Authors
*
* 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 LIBGAV1_SRC_UTILS_QUEUE_H_
#define LIBGAV1_SRC_UTILS_QUEUE_H_
#include <cassert>
#include <cstddef>
#include <memory>
#include <new>
#include <utility>
#include "src/utils/compiler_attributes.h"
namespace libgav1 {
// A FIFO queue of a fixed capacity.
//
// WARNING: No error checking is performed.
template <typename T>
class Queue {
public:
LIBGAV1_MUST_USE_RESULT bool Init(size_t capacity) {
elements_.reset(new (std::nothrow) T[capacity]);
if (elements_ == nullptr) return false;
capacity_ = capacity;
return true;
}
// Pushes the element |value| to the end of the queue. It is an error to call
// Push() when the queue is full.
void Push(T&& value) {
assert(size_ < capacity_);
elements_[end_++] = std::move(value);
if (end_ == capacity_) end_ = 0;
++size_;
}
// Removes the element at the front of the queue. It is an error to call Pop()
// when the queue is empty.
void Pop() {
assert(size_ != 0);
const T element = std::move(elements_[begin_++]);
static_cast<void>(element);
if (begin_ == capacity_) begin_ = 0;
--size_;
}
// Returns a reference to the element at the front of the queue. It is an
// error to call Front() when the queue is empty.
T& Front() {
assert(size_ != 0);
return elements_[begin_];
}
// Returns a reference to the element at the back of the queue. It is an error
// to call Back() when the queue is empty.
T& Back() {
assert(size_ != 0);
const size_t back = ((end_ == 0) ? capacity_ : end_) - 1;
return elements_[back];
}
// Clears the queue.
void Clear() {
while (!Empty()) {
Pop();
}
}
// Returns true if the queue is empty.
bool Empty() const { return size_ == 0; }
// Returns true if the queue is full.
bool Full() const { return size_ >= capacity_; }
// Returns the number of elements in the queue.
size_t Size() const { return size_; }
private:
// An array of |capacity| elements. Used as a circular array.
std::unique_ptr<T[]> elements_;
size_t capacity_ = 0;
// The index of the element to be removed by Pop().
size_t begin_ = 0;
// The index where the new element is inserted by Push().
size_t end_ = 0;
size_t size_ = 0;
};
} // namespace libgav1
#endif // LIBGAV1_SRC_UTILS_QUEUE_H_
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