Module coap_message_utils::inmemory_write
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Implementation of coap_message::MutableWritableMessage on a slice of memory
Message is the main struct of this module.
Exceeding the guarantees of MutableWritableMessage, this does allow some out-of-sequence invocations: Even after payload has been written to, options can be added, memmove’ing (right-rotating) the written payload, possibly truncating it out of the buffer. This is needed to accommodate libOSCORE’s requirements (because while libOSCORE can also do without a memmove-ing message, that’d require its use through WritableMessage to adhere to in-OSCORE write sequence conventions, making the whole situation no easier on the coap-message abstraction). Data will only be moved if an option is added after content has been set, so this comes at no runtime cost for those who do not need it. (It may be later turned into a feature. Then, the memmove code would be removed; carrying the latest option number in the WriteState should come at no extra cost due to the struct’s content and alignment).