Wireshark-dev: Re: [Wireshark-dev] proto.h extension (unit strings)

From: Michael Mann <mmann78@xxxxxxxxxxxx>
Date: Sun, 11 Dec 2016 22:17:11 -0500
I thought this was a good idea, just took a while to get around to it:
https://code.wireshark.org/review/19211
 
 
-----Original Message-----
From: Guy Harris <guy@xxxxxxxxxxxx>
To: Developer support list for Wireshark <wireshark-dev@xxxxxxxxxxxxx>
Sent: Fri, May 8, 2015 3:09 pm
Subject: Re: [Wireshark-dev] proto.h extension


On May 8, 2015, at 7:06 AM, "John Dill" <John.Dill@xxxxxxxxxxxxxxxxx> wrote:

>> Message: 3
>> Date: Thu, 7 May 2015 11:29:22 -0700
>> From: Guy Harris <guy@xxxxxxxxxxxx>
>> To: Developer support list for Wireshark <wireshark-dev@xxxxxxxxxxxxx>
>> Subject: Re: [Wireshark-dev] proto.h extension
>> Message-ID: <CF2E7490-F023-49C2-8383-6C1A1394B4E7@xxxxxxxxxxxx>
>> Content-Type: text/plain; charset=iso-8859-1
>>
>> On May 7, 2015, at 8:13 AM, "John Dill" <John.Dill@xxxxxxxxxxxxxxxxx> wrote:
>>
>>> I have a couple of extensions that I created for the Wireshark baseline
>> that we're using (1.10.x). The diffs to proto.h and proto.c show the code
>> changes to add a couple of features that I've found useful, unit strings
>> and hiding the bits for bitmask header fields.
>>>
>>> http://codepad.org/KTGdEL1t
>>
>> You need more than
>>
>> /* Following constants have to be ORed with a base_display_e when dissector
>> * want to control aspects of the display string for a header_field_info */
>>
>> as a comment there - you need comments explaining what each of those flags actually *does*.
>
> Guy,
>
> Sorry it wasn't clear. Starting from this snippet...
>
> /*
> * BASE_UNIT_STRING - Append a unit string to the numeric value

That one's reasonable; I've thought of a similar option.

> *
> * When active, Wireshark will append a unit string declared as a
> * simple 'char *' for the 'strings' to the numeric value.

You might want to, instead, have it be a structure with a pair of strings, so that if the field has the value 1, you can print the singular rather than the plural, e.g.:

struct unit_names {
char *singular; /* name to use for 1 unit */
char *plural; /* name to use for < 1 or > 1 units */
};

struct unit_names feet {
"foot",
"feet"
};

{
&hf_MFD_State_Data_Slew_Elevation_Ch1,
{
"Slew_Elevation_Ch1",
"ndo.MFD_State_Data.Slew_Elevation_Ch1",
FT_FLOAT,
BASE_NONE | BASE_UNIT_STRING,
&feet,
0x0,
NULL,
HFILL
}
},

(For floating-point numbers, "1 unit" means "*exactly* 1 unit", i.e. an exact floating-point comparison with 1x2^0.)

We could either

1) require that both be non-null

or

2) assume that, if the plural is null, you can pluralize using the standard rules of English.

Does anybody have a preference there?