/**
* Stores the provided {@code value} to the provided byte {@code buffer} at the specified {@code
* index} using the provided {@code wordSize} in bytes. Note that only integer and short sizes are
* supported.
*
* @param buffer the byte buffer to which the value is stored
* @param wordSize the number of bytes used to store the provided value
* @param index the index to which the value is stored
* @param value the value that is stored assuming it does not require more than the specified
* number of bytes.
*/
private static void storeWordInBuffer(ByteBuffer buffer, int wordSize, int index, int value)
{
index *= wordSize;
if (wordSize == SHORT_NUM_BYTES)
{
buffer.putShort(index, (short)value);
}
else
{
buffer.putInt(index, value);
}
}
/**
* Send an object through the telemetry link.
* @throws IOException
* @param[in] obj Object handle to send
* @param[in] type Transaction type \return Success (true), Failure (false)
*/
private bool transmitSingleObject(UAVObject obj, int type, bool allInstances)
{
int length;
int allInstId = uavConsts.ALL_INSTANCES;
ByteBuffer bbuf = new ByteBuffer(uavConsts.MAX_PACKET_LENGTH);
// Determine data length
if (type == uavConsts.TYPE_OBJ_REQ || type == uavConsts.TYPE_ACK)
{
length = 0;
}
else
{
length = obj.getNumBytes();
}
// Setup type and object id fields
bbuf.put((byte)(uavConsts.SYNC_VAL & 0xff));
bbuf.put((byte)(type & 0xff));
bbuf.putShort((UInt16)(length + 2 /* SYNC, Type */+ 2 /* Size */+ 4 /* ObjID */+ (obj
.isSingleInstance() ? 0 : 2)));
bbuf.putUint32((UInt32)obj.getObjID());
// Setup instance ID if one is required
if (!obj.isSingleInstance())
{
// Check if all instances are requested
if (allInstances)
bbuf.putShort((UInt16)(allInstId & 0xffff));
else
bbuf.putShort((UInt16)(obj.getInstID() & 0xffff));
}
// Check length
if (length >= uavConsts.MAX_PAYLOAD_LENGTH)
return false;
// Copy data (if any)
if (length > 0)
try
{
if (obj.pack(bbuf) == 0)
return false;
}
catch (Exception e)
{
// TODO Auto-generated catch block
Debug.Write(e.Message);
return false;
}
// Calculate checksum
bbuf.put((byte)(CRC.updateCRC(0, bbuf.array(), bbuf.position()) & 0xff));
int packlen = bbuf.position();
bbuf.position(0);
byte[] dst = new byte[packlen];
bbuf.get(dst, 0, packlen);
if (type == uavConsts.TYPE_OBJ_ACK || type == uavConsts.TYPE_OBJ_REQ)
{
// Once we send a UAVTalk packet that requires an ack or object let's set up
// the transaction here
setupTransaction(obj, allInstances, type);
}
ch.write(dst);
// Update stats
++txStats.Objects;
txStats.Bytes += bbuf.position();
txStats.ObjectBytes += length;
// Done
return true;
}
