/*
	ringbuffer.h

	ring buffer

	Copyright (C) 2020  Bill Currie <bill@taniwha.org>

	This program is free software; you can redistribute it and/or
	modify it under the terms of the GNU General Public License
	as published by the Free Software Foundation; either version 2
	of the License, or (at your option) any later version.

	This program is distributed in the hope that it will be useful,
	but WITHOUT ANY WARRANTY; without even the implied warranty of
	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

	See the GNU General Public License for more details.

	You should have received a copy of the GNU General Public License
	along with this program; if not, write to:

		Free Software Foundation, Inc.
		59 Temple Place - Suite 330
		Boston, MA  02111-1307, USA

*/

#ifndef __QF_ringbuffer_h
#define __QF_ringbuffer_h

#define RING_BUFFER(type, size) 	\
	struct {						\
		type        buffer[size];	\
		unsigned    head;			\
		unsigned    tail;			\
	}

#define RB_buffer_size(ring_buffer)						\
	({	__auto_type rb = (ring_buffer);					\
		sizeof (rb->buffer) / sizeof (rb->buffer[0]);	\
	})

#define RB_SPACE_AVAILABLE(ring_buffer)										\
	({	__auto_type rb = &(ring_buffer);									\
		(rb->tail + RB_buffer_size(rb) - rb->head - 1) % RB_buffer_size(rb);\
	})

#define RB_DATA_AVAILABLE(ring_buffer)										\
	({	__auto_type rb = &(ring_buffer);									\
		(rb->head + RB_buffer_size (rb) - rb->tail) % RB_buffer_size (rb);	\
	})

#define RB_WRITE_DATA(ring_buffer, data, count)								\
	({	__auto_type rb = &(ring_buffer);									\
		const typeof (rb->buffer[0]) *d = (data);							\
		unsigned    c = (count);											\
		unsigned    h = rb->head;											\
		rb->head = (h + c) % RB_buffer_size (rb);							\
		if (c > RB_buffer_size (rb) - h) {									\
			memcpy (rb->buffer + h, d,										\
					(RB_buffer_size (rb) - h) * sizeof (rb->buffer[0]));	\
			c -= RB_buffer_size (rb) - h;									\
			d += RB_buffer_size (rb) - h;									\
			h = 0;															\
		}																	\
		memcpy (rb->buffer + h, d, c * sizeof (rb->buffer[0]));				\
	})

#define RB_READ_DATA(ring_buffer, data, count)								\
	({	__auto_type rb = &(ring_buffer);									\
		typeof (&rb->buffer[0]) d = (data);									\
		unsigned    c = (count);											\
		unsigned    oc = c;													\
		unsigned    t = rb->tail;											\
		if (c > RB_buffer_size (rb) - t) {									\
			memcpy (d, rb->buffer + t,										\
					(RB_buffer_size (rb) - t) * sizeof (rb->buffer[0]));	\
			c -= RB_buffer_size (rb) - t;									\
			d += RB_buffer_size (rb) - t;									\
			t = 0;															\
		}																	\
		memcpy (d, rb->buffer + t, c * sizeof (rb->buffer[0]));				\
		rb->tail = (t + oc) % RB_buffer_size (rb);							\
	})

#define RB_DROP_DATA(ring_buffer, count)									\
	({	__auto_type rb = &(ring_buffer);									\
		unsigned    c = (count);											\
		unsigned    t = rb->tail;											\
		rb->tail = (t + c) % RB_buffer_size (rb);							\
	})

#define RB_PEEK_DATA(ring_buffer, ahead)						\
	({	__auto_type rb = &(ring_buffer);						\
		rb->buffer[(rb->tail + ahead) % RB_buffer_size (rb)];	\
	})

#define RB_POKE_DATA(ring_buffer, ahead, data)							\
	({	__auto_type rb = &(ring_buffer);								\
		rb->buffer[(rb->tail + ahead) % RB_buffer_size (rb)] = (data);	\
	})

#endif//__QF_ringbuffer_h