virtualx-engine/core/ring_buffer.h

/*************************************************************************/
/*  ring_buffer.h                                                        */
/*************************************************************************/
/*                       This file is part of:                           */
/*                           GODOT ENGINE                                */
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/* Copyright (c) 2007-2020 Juan Linietsky, Ariel Manzur.                 */
/* Copyright (c) 2014-2020 Godot Engine contributors (cf. AUTHORS.md).   */
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#ifndef RING_BUFFER_H
#define RING_BUFFER_H

#include "core/vector.h"

template <typename T>
class RingBuffer {
	Vector<T> data;
	int read_pos = 0;
	int write_pos = 0;
	int size_mask;

	inline int inc(int &p_var, int p_size) const {
		int ret = p_var;
		p_var += p_size;
		p_var = p_var & size_mask;
		return ret;
	}

public:
	T read() {
		ERR_FAIL_COND_V(space_left() < 1, T());
		return data.ptr()[inc(read_pos, 1)];
	}

	int read(T *p_buf, int p_size, bool p_advance = true) {
		int left = data_left();
		p_size = MIN(left, p_size);
		int pos = read_pos;
		int to_read = p_size;
		int dst = 0;
		while (to_read) {
			int end = pos + to_read;
			end = MIN(end, size());
			int total = end - pos;
			const T *read = data.ptr();
			for (int i = 0; i < total; i++) {
				p_buf[dst++] = read[pos + i];
			}
			to_read -= total;
			pos = 0;
		}
		if (p_advance) {
			inc(read_pos, p_size);
		}
		return p_size;
	}

	int copy(T *p_buf, int p_offset, int p_size) const {
		int left = data_left();
		if ((p_offset + p_size) > left) {
			p_size -= left - p_offset;
			if (p_size <= 0) {
				return 0;
			}
		}
		p_size = MIN(left, p_size);
		int pos = read_pos;
		inc(pos, p_offset);
		int to_read = p_size;
		int dst = 0;
		while (to_read) {
			int end = pos + to_read;
			end = MIN(end, size());
			int total = end - pos;
			for (int i = 0; i < total; i++) {
				p_buf[dst++] = data[pos + i];
			}
			to_read -= total;
			pos = 0;
		}
		return p_size;
	}

	int find(const T &t, int p_offset, int p_max_size) const {
		int left = data_left();
		if ((p_offset + p_max_size) > left) {
			p_max_size -= left - p_offset;
			if (p_max_size <= 0) {
				return 0;
			}
		}
		p_max_size = MIN(left, p_max_size);
		int pos = read_pos;
		inc(pos, p_offset);
		int to_read = p_max_size;
		while (to_read) {
			int end = pos + to_read;
			end = MIN(end, size());
			int total = end - pos;
			for (int i = 0; i < total; i++) {
				if (data[pos + i] == t) {
					return i + (p_max_size - to_read);
				}
			}
			to_read -= total;
			pos = 0;
		}
		return -1;
	}

	inline int advance_read(int p_n) {
		p_n = MIN(p_n, data_left());
		inc(read_pos, p_n);
		return p_n;
	}

	inline int decrease_write(int p_n) {
		p_n = MIN(p_n, data_left());
		inc(write_pos, size_mask + 1 - p_n);
		return p_n;
	}

	Error write(const T &p_v) {
		ERR_FAIL_COND_V(space_left() < 1, FAILED);
		data.write[inc(write_pos, 1)] = p_v;
		return OK;
	}

	int write(const T *p_buf, int p_size) {
		int left = space_left();
		p_size = MIN(left, p_size);

		int pos = write_pos;
		int to_write = p_size;
		int src = 0;
		while (to_write) {
			int end = pos + to_write;
			end = MIN(end, size());
			int total = end - pos;

			for (int i = 0; i < total; i++) {
				data.write[pos + i] = p_buf[src++];
			}
			to_write -= total;
			pos = 0;
		}

		inc(write_pos, p_size);
		return p_size;
	}

	inline int space_left() const {
		int left = read_pos - write_pos;
		if (left < 0) {
			return size() + left - 1;
		}
		if (left == 0) {
			return size() - 1;
		}
		return left - 1;
	}
	inline int data_left() const {
		return size() - space_left() - 1;
	}

	inline int size() const {
		return data.size();
	}

	inline void clear() {
		read_pos = 0;
		write_pos = 0;
	}

	void resize(int p_power) {
		int old_size = size();
		int new_size = 1 << p_power;
		int mask = new_size - 1;
		data.resize(1 << p_power);
		if (old_size < new_size && read_pos > write_pos) {
			for (int i = 0; i < write_pos; i++) {
				data.write[(old_size + i) & mask] = data[i];
			}
			write_pos = (old_size + write_pos) & mask;
		} else {
			read_pos = read_pos & mask;
			write_pos = write_pos & mask;
		}

		size_mask = mask;
	}

	RingBuffer<T>(int p_power = 0) {
		resize(p_power);
	}
	~RingBuffer<T>() {}
};

#endif // RING_BUFFER_H