#define RBUF_SIZE 5                         

typedef struct                             
{
    uint8_t buf[RBUF_SIZE];
    uint8_t head;                           
    uint8_t tail;                           
    uint8_t count;                         
}RingBuffer_t;


void ringbuf_init(RingBuffer_t *buffer);
uint8_t ringbuf_get(RingBuffer_t *buffer);
void ringbuf_put(RingBuffer_t *buffer, uint8_t item);
uint8_t ringbuf_adv(const uint8_t value, const uint8_t max);

void main(void) {
   
    RingBuffer_t buffer;
    ringbuf_init(&buffer);
    ringbuf_put(&buffer, 18);
    while(1);
    return;
}


void ringbuf_put(RingBuffer_t *buffer, uint8_t item)
{
    if(buffer->count < RBUF_SIZE)
    {
        buffer->buf[buffer->head] = item;
        buffer->head = ringbuf_adv(buffer->head, RBUF_SIZE);
        ++buffer->count;
    }
}


uint8_t ringbuf_adv(const uint8_t value, const uint8_t max)
{
    unsigned int index = value + 1;
    if(index >= max)
    {
        index = 0;
    }

    return index;
}


uint8_t ringbuf_get(RingBuffer_t *buffer)
{
    int item;
    if(buffer->count > 0)
    {
        item = buffer->buf[buffer->tail];
        buffer->tail = ringbuf_adv(buffer->tail, RBUF_SIZE);
        --buffer->count;
    }
    else
    {
        item = 0;
    }

    return item;
}


void ringbuf_init(RingBuffer_t *buffer)
{
    buffer->count = 0;
    buffer->head = 0;
    buffer->tail = 0;
   
    uint8_t i;
    for(i=0; i<RBUF_SIZE; i++)
    {
        buffer->buf[i] = 0;
    }
}