Function CircularBuffer_Reserve

src/util/circular_buffer.c:145–168

reserve a slot within buffer returns a pointer to a 'item size' slot within the buffer this function is thread-safe and lock-free

// returns a pointer to a 'item size' slot within the buffer
// this function is thread-safe and lock-free
void *CircularBuffer_Reserve
(
	CircularBuffer cb  // buffer to populate
) {
	ASSERT(cb != NULL);

	// atomic update buffer item count
	// item is not added if buffer is full
	uint64_t item_count = atomic_fetch_add(&cb->item_count, 1);
	if(unlikely(item_count >= cb->item_cap)) {
		cb->item_count = cb->item_cap;
	}

	// determine current and next write position
	uint64_t curr = atomic_fetch_add(&cb->write, cb->item_size);
	if(unlikely(cb->data + curr >= cb->end_marker)) {
		uint64_t old_curr = curr + cb->item_size;
		curr -= cb->item_size * cb->item_cap;
		// advance write position atomicly
		atomic_compare_exchange_weak(&cb->write, &old_curr, curr + cb->item_size);
	}

	return cb->data + curr;
}

// read oldest item from buffer
void *CircularBuffer_Read