ring buffer from gba fifo

ring_buf.c

struct RingBuf
{
    uint32_t buf[8];
    uint32_t r_index;
    uint32_t w_index;
};

static void ringbuf_reset(struct RingBuf* ring)
{
    ring->r_index = ring->w_index;
}

static uint32_t ringbuf_capacity(const struct RingBuf* ring)
{
    return sizeof(ring->buf) / sizeof(ring->buf[0]);
}

static unsigned ringbuf_size(const struct RingBuf* ring)
{
    return (ring->w_index - ring->r_index) % (ringbuf_capacity(ring) * 2U);
}

static unsigned ringbuf_free(const struct RingBuf* ring)
{
    return ringbuf_capacity(ring) - ringbuf_size(ring);
}

static uint32_t ringbuf_read(const struct RingBuf* ring)
{
    return ring->buf[ring->r_index % ringbuf_capacity(ring)];
}

static void ringbuf_push(struct RingBuf* ring, uint32_t value)
{
    ring->buf[ring->w_index % ringbuf_capacity(ring)] = value;
    ring->w_index = (ring->w_index + 1U) % (ringbuf_capacity(ring) * 2U);
}

static uint32_t ringbuf_pop(struct RingBuf* ring)
{
    const uint32_t value = ring->buf[ring->r_index % ringbuf_capacity(ring)];
    ring->r_index = (ring->r_index + 1U) % (ringbuf_capacity(ring) * 2U);
}