private void runReadOnBackground() {
m_SyncStart.waitAndSync();
while (!m_StopThread) {
// In Linux read() from a HID device we always try to read at least as many bytes as there can
// be in a report
// the kernel will return with the actual number of bytes in the report (plus one if numbered
// reports are used)
// and the data will be preceded with the report number if and only if numbered reports are
// used, which is
// kind of stupid because then we need to know this and to know that it is necessary to (be
// able to!) read
// the HID descriptor AND parse it. I like the Mac OS and Windows ways better, what a mess the
// world is!
int bytes_read = read(m_DeviceHandle, m_InputReportBytes, m_InputReportBytes.length);
if (m_InputReportListener != null) {
byte reportID = 0;
if (m_UsesNumberedReports) {
reportID = m_InputReportBytes[0];
bytes_read--;
System.arraycopy(m_InputReportBytes, 1, m_InputReportBytes, 0, bytes_read);
}
m_InputReportListener.onInputReport(this, reportID, m_InputReportBytes, bytes_read);
}
}
m_SyncShutdown.waitAndSync();
}
@Override
public synchronized int setOutputReport(byte reportID, byte[] data, int length) {
if (!m_Open) throw new IllegalStateException("device not open");
// In Linux write() to HID device data is preceded with the report number only if numbered
// reports are used
//
// "The first byte of the buffer passed to write() should be set to the report
// number. If the device does not use numbered reports, the first byte should
// be set to 0. The report data itself should begin at the second byte."
//
// References:
// - https://www.kernel.org/doc/Documentation/hid/hidraw.txt
// - http://www.usb.org/developers/hidpage/HID1_11.pdf
if (m_UsesNumberedReports) m_OutputReportBytes[0] = reportID;
else m_OutputReportBytes[0] = 0;
System.arraycopy(data, 0, m_OutputReportBytes, 1, length);
int len = write(m_DeviceHandle, m_OutputReportBytes, length + 1);
if (len < 0) return len;
return len - 1;
}