app/ring.c


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#include "project.h"


static inline size_t
ring_next (volatile ring_t *r, size_t p)
{
  p++;

  if (p >= r->size)
    p -= r->size;

  return p;
}

void
ring_init (volatile ring_t *r, uint8_t *buf, size_t len)
{
  r->data = buf;
  r->size = len;
  r->write = 0;
  r->read = 0;
}

int
ring_write_byte (volatile ring_t *r, uint8_t c)
{
  size_t n = ring_next (r, r->write);

  if (n == r->read)
    return -EAGAIN;

  r->data[r->write] = c;

  r->write = n;

  return 0;
}


int
ring_read_byte (volatile ring_t *r, uint8_t *c)
{
  size_t n = ring_next (r, r->read);

  if (r->read == r->write)
    return -EAGAIN;

  *c = r->data[r->read];
  r->read = n;

  return 0;
}

int
ring_write (volatile ring_t *r, uint8_t *buf, size_t len, int blocking)
{
  while (len--) {
    if (blocking) {
      while (ring_write_byte (r, *buf));

      buf++;
    } else {
      if (ring_write_byte (r, * (buf++)))
        return -EAGAIN;
    }
  }

  return 0;
}


int
ring_empty (volatile ring_t *r)
{
  return (r->read == r->write) ? 1 : 0;
}