public const int RESPONSE_CRC = -0x0002; // UInt16BE
// returns the dycrypted response payload only
protected byte[] Decode(MedtronicCnlSession pumpSession, byte[] payload)
{
if (payload.Length < MM_PAYLOAD + NGP_PAYLOAD + NGP55_PAYLOAD + RESPONSE_PAYLOAD ||
payload[MM_COMMAND] == (byte)CommandType.READ_INFO ||
payload[MM_COMMAND] == (byte)CommandType.REQUEST_LINK_KEY_RESPONSE)
{
throw new EncryptionException("Message received for decryption wrong type/size");
}
byte encryptedPayloadSize = payload[MM_PAYLOAD + NGP_PAYLOAD + NGP55_ENCRYPTED_SIZE];
if (encryptedPayloadSize == 0)
{
throw new EncryptionException("Could not decrypt Medtronic Message (encryptedPayloadSize == 0)");
}
var encryptedPayload = new MedtronicMessageBuffer(encryptedPayloadSize);
encryptedPayload.Put(payload, MM_PAYLOAD + NGP_PAYLOAD + NGP55_PAYLOAD, encryptedPayloadSize);
var decryptedPayload = Decrypt(pumpSession.getKey(), pumpSession.getIV(), encryptedPayload);
if (decryptedPayload == null)
{
throw new EncryptionException("Could not decrypt Medtronic Message (decryptedPayload == null)");
}
#if DEBUG
string outputstring = HexDump.DumpHexstring(decryptedPayload);
Log.d(TAG, "DECRYPTED: " + outputstring);
#endif
return(decryptedPayload);
}
protected async Task <byte[]> ReadMessage(UsbHidDriver mDevice, int timeout = READ_TIMEOUT_MS)
{
ByteArrayOutputStream responseMessage = new ByteArrayOutputStream();
int messageSize = 0;
int bytesRead;
do
{
var rawBytes = await mDevice.Read(timeout);
bytesRead = rawBytes?.Length ?? -1;
if (bytesRead == -1)
{
throw new TimeoutException("Timeout waiting for response from pump");
}
else if (bytesRead > 0)
{
// Validate the header
var responseBuffer = new MedtronicMessageBuffer(bytesRead);
ValidateHeader(responseBuffer);
messageSize = responseBuffer.MessageLength;
responseMessage.write(responseBuffer, 4, messageSize);
}
else
{
Log.w(TAG, "readMessage: got a zero-sized response.");
}
} while (bytesRead > 0 && messageSize == USB_MAX_MESSAGE_SIZE);
string responsestring = HexDump.DumpHexstring(responseMessage.toByteArray());
Log.d(TAG, "READ: " + responsestring);
return(responseMessage.toByteArray());
}
protected void SendMessage(UsbHidDriver mDevice)
{
int pos = 0;
var message = Encode();
// chop into pieces and send each individual piece
while (message.Length > pos)
{
var outputBuffer = new MedtronicMessageBuffer(USB_BLOCKSIZE);
int sendLength = (pos + USB_MAX_MESSAGE_SIZE > message.Length)
? message.Length - pos
: USB_MAX_MESSAGE_SIZE;
outputBuffer.Put(HeaderBytes);
outputBuffer.Put((byte)sendLength);
outputBuffer.Put(message, pos, sendLength);
// separate the send concern
mDevice.Write(outputBuffer, WRITE_TIMEOUT_MS);
pos += sendLength;
string outputstring = HexDump.DumpHexstring(outputBuffer);
Log.d(TAG, "WRITE: " + outputstring);
}
}