Benjamin Valentin 2751708341 nanocoap: add payload helper functions
This adds two functions `coap_payload_add()` and `coap_payload_advance()`.

 - `coap_payload_add()` will add n bytes to the payload buffer and advance
    payload pointer accordingly.

    const char hello[] = "Hello CoAP!";
    coap_payload_add(pkt, hello, sizeof(hello));

 - `coap_payload_advance()` will advance the payload buffer after data
    has been added to it.

    int len = snprintf(pkt->payload, pkt->payload_len, "%s %s!", "Hello", "CoAP");
    coap_payload_advance(pkt, len);

I considered adding an additional parameter to keep track of the total request size
(returned size from coap_opt_finish() incremented by each added payload fragment),
but decided against it to keep consistency with the existing API.
2020-05-01 13:58:22 +02:00
..
2017-12-01 12:55:45 +01:00