public override int Read(byte[] dest, int timeoutMillis)
{
if (mEnableAsyncReads)
{
UsbRequest request = new UsbRequest();
try
{
request.Initialize(mConnection, mReadEndpoint);
// CJM: Xamarin bug: ByteBuffer.Wrap is supposed to be a two way update
// Changes made to one buffer should reflect in the other. It's not working
// As a work around, I added a new method as an extension that uses JNI to turn
// a new byte[] array. I then used BlockCopy to copy the bytes back the original array
// see https://forums.xamarin.com/discussion/comment/238396/#Comment_238396
//
// Old work around:
// as a work around, we populate dest with a call to buf.Get()
// see https://bugzilla.xamarin.com/show_bug.cgi?id=20772
// and https://bugzilla.xamarin.com/show_bug.cgi?id=31260
ByteBuffer buf = ByteBuffer.Wrap(dest);
if (!request.Queue(buf, dest.Length))
{
throw new IOException("Error queueing request.");
}
UsbRequest response = mConnection.RequestWait();
if (response == null)
{
throw new IOException("Null response");
}
int nread = buf.Position();
if (nread > 0)
{
// CJM: This differs from the Java implementation. The dest buffer was
// not getting the data back.
// 1st work around, no longer used
//buf.Rewind();
//buf.Get(dest, 0, dest.Length);
System.Buffer.BlockCopy(buf.ToByteArray(), 0, dest, 0, dest.Length);
//Log.Debug(TAG, HexDump.DumpHexString(dest, 0, Math.Min(32, dest.Length)));
return(nread);
}
else
{
return(0);
}
}
finally
{
request.Close();
request.Dispose();//richard: dispose request
}
}
int numBytesRead;
lock (mReadBufferLock)
{
int readAmt = Math.Min(dest.Length, mReadBuffer.Length);
numBytesRead = mConnection.BulkTransfer(mReadEndpoint, mReadBuffer, readAmt,
timeoutMillis);
if (numBytesRead < 0)
{
// This sucks: we get -1 on timeout, not 0 as preferred.
// We *should* use UsbRequest, except it has a bug/api oversight
// where there is no way to determine the number of bytes read
// in response :\ -- http://b.android.com/28023
if (timeoutMillis == Integer.MaxValue)
{
// Hack: Special case "~infinite timeout" as an error.
return(-1);
}
return(0);
}
System.Buffer.BlockCopy(mReadBuffer, 0, dest, 0, numBytesRead);
}
return(numBytesRead);
}