How do you implement a circular buffer in C?

Question

I have a need for a fixed-size (selectable at run-time when creating it, not compile-time) circular buffer which can hold objects of any type and it needs to be very

Answer 1

Extending adam-rosenfield's solution, i think the following will work for multithreaded single producer - single consumer scenario.

int cb_push_back(circular_buffer *cb, const void *item)
{
  void *new_head = (char *)cb->head + cb->sz;
  if (new_head == cb>buffer_end) {
      new_head = cb->buffer;
  }
  if (new_head == cb->tail) {
    return 1;
  }
  memcpy(cb->head, item, cb->sz);
  cb->head = new_head;
  return 0;
}

int cb_pop_front(circular_buffer *cb, void *item)
{
  void *new_tail = cb->tail + cb->sz;
  if (cb->head == cb->tail) {
    return 1;
  }
  memcpy(item, cb->tail, cb->sz);
  if (new_tail == cb->buffer_end) {
    new_tail = cb->buffer;
  }
  cb->tail = new_tail;
  return 0;
}