Function hid_write

dependencies/hidapi/hidapi.c:872–920

int HID_API_EXPORT hid_write(hid_device *dev, const unsigned char *data, size_t length)
{
	int res;
	int report_number = data[0];
	int skipped_report_id = 0;

	if (report_number == 0x0) {
		data++;
		length--;
		skipped_report_id = 1;
	}


	if (dev->output_endpoint <= 0) {
		/* No interrupt out endpoint. Use the Control Endpoint */
		res = libusb_control_transfer(dev->device_handle,
			LIBUSB_REQUEST_TYPE_CLASS|LIBUSB_RECIPIENT_INTERFACE|LIBUSB_ENDPOINT_OUT,
			0x09/*HID Set_Report*/,
			(2/*HID output*/ << 8) | report_number,
			dev->interface,
			(unsigned char *)data, length,
			1000/*timeout millis*/);

		if (res < 0)
			return -1;

		if (skipped_report_id)
			length++;

		return length;
	}
	else {
		/* Use the interrupt out endpoint */
		int actual_length;
		res = libusb_interrupt_transfer(dev->device_handle,
			dev->output_endpoint,
			(unsigned char*)data,
			length,
			&actual_length, 1000);

		if (res < 0)
			return -1;

		if (skipped_report_id)
			actual_length++;

		return actual_length;
	}
}

/* Helper function, to simplify hid_read().
   This should be called with dev->mutex locked. */