Function hid_write

lib/hidapi/windows/hid.c:1006–1075

}

int HID_API_EXPORT HID_API_CALL hid_write(hid_device *dev, const unsigned char *data, size_t length)
{
	DWORD bytes_written = 0;
	int function_result = -1;
	BOOL res;
	BOOL overlapped = FALSE;

	unsigned char *buf;

	if (!data || !length) {
		register_string_error(dev, L"Zero buffer/length");
		return function_result;
	}

	register_string_error(dev, NULL);

	/* Make sure the right number of bytes are passed to WriteFile. Windows
	   expects the number of bytes which are in the _longest_ report (plus
	   one for the report number) bytes even if the data is a report
	   which is shorter than that. Windows gives us this value in
	   caps.OutputReportByteLength. If a user passes in fewer bytes than this,
	   use cached temporary buffer which is the proper size. */
	if (length >= dev->output_report_length) {
		/* The user passed the right number of bytes. Use the buffer as-is. */
		buf = (unsigned char *) data;
	} else {
		if (dev->write_buf == NULL)
			dev->write_buf = (unsigned char *) malloc(dev->output_report_length);
		buf = dev->write_buf;
		memcpy(buf, data, length);
		memset(buf + length, 0, dev->output_report_length - length);
		length = dev->output_report_length;
	}

	res = WriteFile(dev->device_handle, buf, (DWORD) length, NULL, &dev->write_ol);

	if (!res) {
		if (GetLastError() != ERROR_IO_PENDING) {
			/* WriteFile() failed. Return error. */
			register_winapi_error(dev, L"WriteFile");
			goto end_of_function;
		}
		overlapped = TRUE;
	}

	if (overlapped) {
		/* Wait for the transaction to complete. This makes
		   hid_write() synchronous. */
		res = WaitForSingleObject(dev->write_ol.hEvent, 1000);
		if (res != WAIT_OBJECT_0) {
			/* There was a Timeout. */
			register_winapi_error(dev, L"hid_write/WaitForSingleObject");
			goto end_of_function;
		}

		/* Get the result. */
		res = GetOverlappedResult(dev->device_handle, &dev->write_ol, &bytes_written, FALSE/*wait*/);
		if (res) {