RingBuffer.h

// SPDX-License-Identifier: MIT
/**
   Copyright (c) 2015 - 2022 Beckhoff Automation GmbH & Co. KG
 */

#pragma once

#include <cassert>
#include <cstdint>
#include <memory>

struct RingBuffer {
	friend struct RingBufferTransaction;

	RingBuffer(size_t N)
		: dataSize(N + 1)
		, data(new uint8_t[N + 1])
		, write(data.get())
		, read(data.get())
	{
	}

	size_t BytesFree() const
	{
		return (write < read) ? read - write - 1 :
					dataSize - 1 - (write - read);
	}

	size_t BytesAvailable() const
	{
		return dataSize - BytesFree() - 1;
	}

	size_t WriteChunk() const
	{
		return (write < read) ? read - write - 1 :
					data.get() + dataSize - write -
						(data.get() == read);
	}

	void Write(size_t n)
	{
		assert(n <= BytesFree());
		write = Increment(write, n);
	}

	template <class T> T ReadFromLittleEndian()
	{
		T result = 0;
		for (size_t i = 0; i < sizeof(T); ++i) {
			result += (((T)(*read)) << (8 * i));
			read = Increment(read, 1);
		}
		return result;
	}

	void Read(size_t n)
	{
		assert(n <= BytesAvailable());
		read = Increment(read, n);
	}

    private:
	const size_t dataSize;
	const std::unique_ptr<uint8_t[]> data;

	inline uint8_t *Increment(const uint8_t *ptr, size_t n)
	{
		return data.get() + ((ptr - data.get() + n) % dataSize);
	}

    public:
	uint8_t *write;
	const uint8_t *read;
};