int submit()

in src/kernel_aio.cc [203:256]
36 lines of code
6 McCabe index (conditional complexity)

			int submit(int group_id) {
				if (!started) assert(!"IOManager not started!");

				groups_mutex.lock();
				auto group = groups[group_id];
				groups_mutex.unlock();

				// create the array
				auto array = std::make_shared<CbArray>();
				array->size = group->op_queue.size();
				array->items_left = array->size;
				array->array = (iocb**)malloc(sizeof(iocb*)*array->size);

				int i = 0;
				for (auto& op : group->op_queue) {
					op->cb_array = array;	// copy pointer to the array struct so we can find it later

					// add the op to the in_flight map with a unique id
					while(group->in_flight.count(group->next_flight)) {
						group->next_flight = (void *)((size_t)(group->next_flight) + 1);
					}
					op->cb.data = group->next_flight;
					group->in_flight[group->next_flight] = op;
					group->next_flight = (void *)((size_t)(group->next_flight) + 1);

					// add the ops's cb to the array
					array->array[i++] = &(op->cb);
				}

				// do the actual io submission!
				int err = io_submit(group->ctx, array->size, array->array);
				// clean up and return an error
				if (err != array->size) {

					// clean up all the ops we tried to submit
					for (int j = 0; j < array->size; ++j) {
						io_cancel(group->ctx, array->array[j], nullptr);// cancel the op, ignore errors
						void * in_flight_id = array->array[j]->data;	// get the in flight id
						group->in_flight.erase(in_flight_id);			// remove from map
					}

					free(array->array); // free the malloc'd memory
					group->arrays.erase(array); // remove from the set of cbarrays

					d_printf("IOManager failed: io_submit returned %d instead of %lu\n", err, array->size);
					errno = -err; // libaio returns the error code negated so we convert it
					return err;
				}

				// clear the queued ops
				group->op_queue.clear();

				return 0;
			}