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// Copyright 2021 The Pigweed 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
//
// https://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.
#pragma once
#include <cstdint>
#include <optional>
#include "pw_assert/assert.h"
#include "pw_span/span.h"
namespace pw::work_queue::internal {
// TODO(hepler): Replace this with a std::deque like container.
template <typename T>
class CircularBuffer {
public:
explicit constexpr CircularBuffer(span<T> buffer)
: buffer_(buffer), head_(0), tail_(0), count_(0) {}
bool empty() const { return count_ == 0; }
bool full() const { return count_ == buffer_.size(); }
size_t size() const { return count_; }
size_t capacity() const { return buffer_.size(); }
template <typename Ty>
bool Push(Ty&& value) {
PW_DASSERT(tail_ < buffer_.size());
if (full()) {
return false;
}
buffer_[tail_] = std::forward<Ty>(value);
IncrementWithWrap(tail_);
++count_;
return true;
}
std::optional<T> Pop() {
PW_DASSERT(head_ < buffer_.size());
if (empty()) {
return std::nullopt;
}
T entry = std::move(buffer_[head_]);
IncrementWithWrap(head_);
--count_;
return entry;
}
private:
void IncrementWithWrap(size_t& index) const {
index++;
// Note: branch is faster than mod (%) on common embedded architectures.
if (index == buffer_.size()) {
index = 0;
}
}
span<T> buffer_;
size_t head_;
size_t tail_;
size_t count_;
};
} // namespace pw::work_queue::internal
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