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[z180-stamp.git] / include / ring.h

#ifndef RING_H
#define RING_H

struct ring {
	uint8_t *data;
	uint_fast8_t mask;
	volatile uint_fast8_t begin;
	volatile uint_fast8_t end;
};


static inline
void ring_init(struct ring *ring, uint8_t *buf, int size)
{
	ring->data = buf;
	ring->mask = (size-1) & 0xff;
	ring->begin = 0;
	ring->end = 0;
}

static inline
int ring_write_ch(struct ring *ring, uint8_t ch)
{
	uint_fast8_t ep = ring->end;

	ring->data[ep] = ch;
	ep = (ep + 1) & ring->mask;

	if ((ep) != ring->begin) {
		ring->end = ep;
		return 1;
	}

	return -1;
}

#if 0
static inline
int ring_write(struct ring *ring, uint8_t *data, int size)
{
	int i;

	for (i = 0; i < size; i++) {
		if (ring_write_ch(ring, data[i]) < 0)
			return -i;
	}

	return i;
}
#endif

static inline
int ring_read_ch(struct ring *ring)
{
	int ret = -1;
	uint_fast8_t bp = ring->begin;

	if (bp != ring->end) {
		ret = ring->data[bp];
		ring->begin = (bp + 1) & ring->mask;
	}

	return ret;
}


static inline
int_fast8_t ring_is_empty(struct ring *ring)
{
	return ring->begin == ring->end;
}

#endif /* RING_H */