Parse a coap message

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I don't know what forum this belongs in but I clicked a link that said to click here for programming questions. So here I am.

CoAP = Constrained Applications Protocol.
RFC 7252[^]

In RFC 7252 Section 3, Figure 7 the third row, bytes 9 ... 16 or maybe more, is the Options field. I am unable to find anything that specifies how long the options field is. I understand that it can change, but unlike the Token field who's length is specified by field TKL, I cannot recognize where the length of the Options is specified.

Yes, I see sections 3.1 and 3.2 but am not able to understand what they are telling me.

When my code needs to send a CoAP message, how do I determine what options can be sent?

What I have tried:

I have tried reading the RFC and have tried chasing down a few links. My searches for a forum for internet protocols did not help me any so I returned to the best place I know.