[Anima-signaling] GRASP API issue 2: Passing the (CBOR) value of an objective

Brian E Carpenter <brian.e.carpenter@gmail.com> Sun, 08 January 2017 01:16 UTC

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To: Anima signaling DT <anima-signaling@ietf.org>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
Organization: University of Auckland
Message-ID: <93f5edf8-c9e2-3319-eeba-aebc513992d2@gmail.com>
Date: Sun, 8 Jan 2017 14:16:32 +1300
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Cc: draft-liu-anima-grasp-api@ietf.org
Subject: [Anima-signaling] GRASP API issue 2: Passing the (CBOR) value of an objective
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How should the API represent the 'value' part of a GRASP Objective
in a non-OO language?

In an OO language there will be a natural way to represent the value
of an objective: for example, in Python, any valid Python object
that the CBOR library can handle.

In a traditional language such as C, it's not so clear. For example, this doesn't
quite work:

typedef struct {
    gstring name;
    bool neg;
    bool dry;
    bool synch;
    int loop_count;
    void * value;    // user has to cast this pointer appropriately and do own malloc()
    } objective;

This doesn't work because the GRASP implementation won't know how
to CBORise whatever ends up in the 'value' parameter.

Is this already a solved problem in CBORland? For example, should we expect
the ASA to pass an already CBORised byte string?

Regards
   Brian