Source: Real-Time Innovations ( Gerardo Pardo-Castellote)
Section 188.8.131.52 (SequenceNumberSet)
A valid SequenceNumberSet must satisfy the following conditions:
• bitmapBase >= 1
• 0 < numBits <= 256
• there are M=(numBits+31)/32 longs containing the pertinent bits
This is seems like an error in how the spec is worded.
What it was trying to say is that for the bitset to represent a set f bits then it must be that 0 < numBits <= 256
However the case with numBits=0 is still valid. It represents an empty set, but the bitmapBase still carries information since. This is use by the ACKNAK sub-message to acknowledges al sequence numbers less or equal to bitmapBase without Nacking anything.
Reported: DDSI-RTPS 2.2 — Wed, 30 Mar 2016 20:21 GMT
Updated: Sat, 23 Dec 2017 22:54 GMT