Ethereal-dev: RE: [Ethereal-dev] [RFC] specially mark protocol fields "generate d" byEthereal?
|From: Ulf Lamping
|
|> Olivier Biot schrieb:
|>
|> Also note that fields may have the hidden flag and the
|generated flag on at
|> the same time.
|
|Of course this should be a flag or'ed to the "normal" FT_
|field, FTF_HIDDEN and FTF_GENERATED (usually, if hidden is
|used, generated will also be used), so for example:
|
|#define FTF_HIDDEN 0x8000
|#define FTF_GENERATED 0x4000
|
|>
|> |So the hf_register_info entry could look, like: FT_FRAMENUM |
|> |FT_GENERATED, or we could provide another set of field registration
|> |functions, like: proto_tree_add_uint_generated()
|>
|> Here we need to be careful as today the FT_* are an enum
|which may be just
|> one single 8-bit byte.
|
|an enum is an int (ANSI C), and an int is an all of our
|platforms 32bit AFAIK, so no problem here.
AFAIK int used to be the most common integer type available on a platform;
it is only guaranteed to be at least 16 bit wide. We must also take care of
unwanted sign extension. Maybe restricting to the 15 least significant bits
is the safest. In that case, I'd suggest 0x4000 and 0x2000 to be used.
Extracting the field type from the int should be done with a preprocessor
macro for efficiency reasons, like:
#define FTYPE(x) ((x) & 0x00FF)
#define FT_IS_GENERATED(x) ((x) & FTF_GENERATED)
#define FT_IS_HIDDEN(x) ((x) & FTF_HIDDEN)
All the switch(), if and g_assert() calls need then to use the correct value
(FTYPE(x) instead of x).
|
|>
|> We however still have some spare room in the HFILL macro to
|accommodate a
|> bitfield without requiring us to edit all dissectors. We
|could even write
|> HFILL for default, HFILL_HIDDEN for hidden, HFILL_GENERATED
|for generated
|> and HFILL_GENERATED_HIDDEN for hidden generated fields, but there are
|> certainly other worthwile approaches.
|
|As described above, or'ing to the FT_ fields should be ok for
|the reasons described above.
Unless someone objects to this by arguing about the maintainability of the
code? Mmh... They would already have done so, I think :)
|> |Anyone an idea of how much effort that would be?
|>
|> Add the basic framework to the field registration: minimal.
|> Add the field rendering changes: minimal, mainly GTK+.
|
|As I know GTK now, both agreed.
|
|> Review the dissectors: potentially huge, but not required
|for technically
|> running Ethereal.
|
|Fortunately, we can make the changes step by step.
And that means we can give it a start very quickly!
Regards,
Olivier
