Add check for EmitterBeam length > 255 to be compliant with DIS 7 spec.

[timpokorny]

DIS 7 Spec (7.6.2 paragraph f.5.i) says that for an emitter beam, if the length of the beam is greater than 255, write it as 0.

I checked that the length for this record isn't being used anywhere in deserialization (we go by the number of records, which is also written to the record in the PDU), so this shouldn't have an advserse impact.

[michaelrfraser]

Hey Tim, I’m still not sure that fix is 100% standard compliant (it looks like it never was). The standard talks about the Beam Data Length field being

• The size of the data field (The BeamData member in our case)
• Measured in 32-bit words

However from what I can see our code is treating it as

• The size of the entire EmitterBeam component
• Measured in bytes (8-bit words)

So line 143 needs to be changed from:

int beamLength = getByteLength();

to

int beamDataLength = beamData.getByteLength() / 4; // Size of the beam data in 32-bit words

[timpokorny]

@michaelrfraser - I concur. I have updated the encoding for both this instance, in EmitterBeam, and for the same problem in EmitterSystem. Updated in commit https://github.com/openlvc/disco/commit/9de56e9b72b7eddcf580f619249cc6d2e4985f0f