Length translation between tagged streams and PDUs

[jacobagilbert]

It appears the length of PDUs is in bytes and tagged streams are in samples. This creates issues when sending non-byte pdu data over networks. I don't know if this is the proper way to fix this, but it seems to resolve the issue. See my post here for an example: http://lists.gnu.org/archive/html/discuss-gnuradio/2016-02/msg00045.html

[jmcorgan]

The flowgraph in the email is pretty clear about the bug. I'm looking into this.

[jmcorgan]

The problem is in:

https://github.com/gnuradio/gnuradio/blob/master/gr-blocks/lib/socket_pdu_impl.cc#L196

Here, 'len' is assigned the return value from pmt::length(), which is in items, while everywhere after that it is treated as bytes. So the PDU is 512 items of floats, but only 512 bytes are written to the socket.

On the receiving end, the 512 bytes are pulled into a buffer of the appropriate length for 512 floats, but anything after that is garbage.

The fix in this PR is not the correct one; I'll open a new PR and reference this one.

[jmcorgan]

Also, it appears we have an identical bug in pmt::print(), so it only displays the first 512 bytes of the PDU.

[jacobagilbert]

Ok - thanks or figuring that out Jonathan. I wasn't sure where a fix should go but felt bad pointing out an issue with no suggestions.

It also appears that the UDP send function (https://github.com/gnuradio/gnuradio/blob/master/gr-blocks/lib/socket_pdu_impl.cc#L211) does the same thing, and the TCP server-side send function (https://github.com/gnuradio/gnuradio/blob/master/gr-blocks/lib/socket_pdu_impl.cc#L176) also has the same issue however the offending function is actually located at (https://github.com/gnuradio/gnuradio/blob/master/gr-blocks/lib/tcp_connection.cc#L54).