[Tinyos-devel] timestamps in seriallisten/sflisten etc.

[David Gay]

Ok, a suggestion:

- Packet sources acquire a timestamp - this means changing the
net.tinyos.packet.PacketSource interface, e.g., add the following
method
    /**
     * Read a packet
     * @param timestamp timestamp[0] is set to the time at which the
packet was received
     * @return The packet read (newly allocated). The format is described
     *   above
     * @exception IOException If the source detected a problem. The source
     *   is automatically closed.
     */
    public byte[] readPacket(long timestamp[]) throws IOException;

The existing readPacket can stay as is, for backwards compatibility
(we could add @deprecated to it at some point)

- Something similar happens for the C, C++, and Python packet
abstractions/interfaces/etc (in a more or less ad-hoc fashion
depending on whether they have a generic packet-source-like concept).

- The serial forwarder protocol is extended to also communicate
timestamps (presumably as 8-byte millisecond timestamps). Note that
the protocol has a version number precisely to allow for extensions,
so use it! (when talking to an old serial forwarder implementation you
can just fill in the timestamp with the local time - better than
nothing)

- If you're so inclined, you can include the ack information in the
serial forwarder protocol (note that it's already in packet sources,
see the return value from writePacket)

- Implementations of packet sources need to fill in timestamps. Here's
the obvious cases:
  * serial and network packet sources: call System.currentTimeMillis()
at the appropriate time (first byte received from network / serial
port?)
  * serial-forwarder packet sources (this essentially means the serial
forwarder, net.tinyos.sf and the C/C++ implementations): forward the
timestamps from the packet sources being forwarded... (note that the
Java serial-forwarder, at least, can forward an arbitrary packet
source)

David