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◆ main openmsx / src / utils / CircularBuffer.hh
2.3 KiB · C++ · last changed chore(): initial commit 1 month ago source blame history raw
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#ifndef CIRCULARBUFFER_HH
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#define CIRCULARBUFFER_HH
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#include <array>
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#include <cassert>
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#include <cstddef>
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#include <utility>
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namespace openmsx {
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template<typename T, size_t MAXSIZE>
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class CircularBuffer
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{
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public:
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	constexpr CircularBuffer() = default;
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	constexpr void push_front(const T& element) {
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		assert(!full());
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		first = prev(first);
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		buffer[first] = element;
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	}
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	constexpr void push_front(T&& element) {
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		assert(!full());
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		first = prev(first);
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		buffer[first] = std::move(element);
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	}
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	constexpr void push_back(const T& element) {
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		assert(!full());
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		buffer[last] = element;
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		last = next(last);
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	}
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	constexpr void push_back(T&& element) {
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		assert(!full());
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		buffer[last] = std::move(element);
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		last = next(last);
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	}
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	constexpr T& pop_front() {
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		assert(!empty());
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		auto tmp = first;
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		first = next(first);
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		return buffer[tmp];
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	}
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	constexpr T& pop_back() {
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		assert(!empty());
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		last = prev(last);
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		return buffer[last];
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	}
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	[[nodiscard]] constexpr T& operator[](size_t pos) {
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		assert(pos < size());
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		auto tmp = first + pos;
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		if (tmp > MAXSIZE) {
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			tmp -= (MAXSIZE + 1);
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		}
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		return buffer[tmp];
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	}
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	[[nodiscard]] constexpr const T& operator[](size_t pos) const {
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		assert(pos < size());
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		auto tmp = first + pos;
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		if (tmp > MAXSIZE) {
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			tmp -= (MAXSIZE + 1);
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		}
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		return buffer[tmp];
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	}
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	[[nodiscard]] constexpr T& front() {
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		assert(!empty());
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		return buffer[first];
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	}
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	[[nodiscard]] constexpr const T& front() const {
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		assert(!empty());
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		return buffer[first];
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	}
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	[[nodiscard]] constexpr T& back() {
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		assert(!empty());
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		return buffer[prev(last)];
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	}
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	[[nodiscard]] constexpr const T& back() const {
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		assert(!empty());
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		return buffer[prev(last)];
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	}
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	[[nodiscard]] constexpr bool empty() const {
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		return (first == last);
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	}
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	[[nodiscard]] constexpr bool full() const {
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		return (first == next(last));
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	}
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	[[nodiscard]] constexpr size_t size() const {
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		if (first > last) {
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			return MAXSIZE + 1 - first + last;
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		} else {
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			return last - first;
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		}
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	}
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	void clear() {
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		first = last = 0;
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	}
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private:
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	[[nodiscard]] constexpr size_t next(size_t a) const {
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		return (a != MAXSIZE) ? a + 1 : 0;
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	}
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	[[nodiscard]] constexpr size_t prev(size_t a) const {
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		return (a != 0) ? a - 1 : MAXSIZE;
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	}
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	size_t first = 0;
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	size_t last = 0;
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	// one extra to be able to distinguish full and empty
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	std::array<T, MAXSIZE + 1> buffer;
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};
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} // namespace openmsx
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#endif