Wireshark · Wireshark-dev: [Wireshark-dev] How can I re-use definition of hf[]?

["Tamazov, Artem" <artem.tamazov@xxxxxxxxxxx>]

Hello,

I would like to implement two dissectors which are very similar.
How can I re-use definition of hf[]?  

See sample code below (question is in comments):

==================
...
static int proto_PROTOABBREV_VARIATION_A = -1;
static int proto_PROTOABBREV_VARIATION_B = -1;
static int hf_PROTOABBREV_FIELDABBREV = -1;
static gint ett_PROTOABBREV = -1;

static int dissect_PROTOABBREV_VARIATION_A(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
...
}

static int dissect_PROTOABBREV_VARIATION_B(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree)
{
...
}

void proto_register_PROTOABBREV(void)
{
	static hf_register_info hf[] = {
		{ &hf_PROTOABBREV_FIELDABBREV,
			{ "FIELDNAME",           "PROTOABBREV.FIELDABBREV",
			FIELDTYPE, FIELDBASE, FIELDCONVERT, BITMASK,
			"FIELDDESCR", HFILL }
		}
	};

	static gint *ett[] = {
		&ett_PROTOABBREV
	};

	proto_PROTOABBREV_VARIATION_A = proto_register_protocol("PROTONAME VARIATION A",
	    "PROTOSHORTNAME A", "PROTOABBREVA");
	proto_PROTOABBREV_VARIATION_B = proto_register_protocol("PROTONAME VARIATION B",
	    "PROTOSHORTNAME B", "PROTOABBREVB");

	proto_register_field_array(proto_PROTOABBREV_VARIATION_A, hf, array_length(hf));
	/* 
	 * *QUESTION*:
	 * 	AFAIK double registration of hf[] is wrong, although currently Wireshark
	 *	tolerates this. How to _properly_ re-use hf[] in variation B?
       */	
	proto_register_field_array(proto_PROTOABBREV_VARIATION_B, hf, array_length(hf));
	proto_register_subtree_array(ett, array_length(ett));
}

void
proto_reg_handoff_PROTOABBREV(void)
{
	dissector_handle_t PROTOABBREV_handle;
	PROTOABBREV_handle = new_create_dissector_handle(dissect_PROTOABBREV_VARIATION_A, proto_PROTOABBREV_VARIATION_A);
	dissector_add("PARENT_SUBFIELD", ID_VALUE, PROTOABBREV_handle);
	PROTOABBREV_handle = new_create_dissector_handle(dissect_PROTOABBREV_VARIATION_B, proto_PROTOABBREV_VARIATION_B);
	dissector_add("PARENT_SUBFIELD", ID_VALUE, PROTOABBREV_handle);
}
==================

I see one possible way -- using of C preprocessor capabilities:

==================
...
static int hf_PROTOABBREV_FIELDABBREV_for_A = -1;
static int hf_PROTOABBREV_FIELDABBREV_for_B = -1;
...
#define HF_INITIALIZER_FIELDABBREV(hf_handle)\
		{ &(hf_handle),\
			{ "FIELDNAME",           "PROTOABBREV.FIELDABBREV",\
			FIELDTYPE, FIELDBASE, FIELDCONVERT, BITMASK,\
			"FIELDDESCR", HFILL }\
		}\
	}
...
	static hf_register_info hf_a[] = HF_INITIALIZER_FIELDABBREV(hf_PROTOABBREV_FIELDABBREV_for_A);
	static hf_register_info hf_b[] = HF_INITIALIZER_FIELDABBREV(hf_PROTOABBREV_FIELDABBREV_for_B);
...
	proto_register_field_array(proto_PROTOABBREV_VARIATION_A, hf_a, array_length(hf_a));
	proto_register_field_array(proto_PROTOABBREV_VARIATION_B, hf_b, array_length(hf_b));
...
==================

But this solution is not elegant, I guess.
Any ideas?

Thank you in advance, 
artem// 
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