On Sun, May 31, 2009 at 10:41 PM, Sébastien Tandel <sebastien-V68y5HPEe52zQB+pC5nmwQ@public.gmane.org
> Hi Stig,
> First, I have to admit that I'm not really aware of the details of the
> defined LUA API. But as a rule of thumb, I tried to be close as possible to
> what exists in the C API (not LUA).
> Here is an informal description of what rules I tried to follow to create
> this API :
> 1) create objects as close as possible to the ones known in libwireshark
> There are three "obvious" objects until now : Dissector, Tree, TVB.
> 2) method name of each object as close as possible as the ones defined in
> libwireshark. I however modify the name because as C is not object, most of
> the time, a function includes in its name the conceptual "object" name
> related to it. This way, it avoids redundance in python API. For example :
> "proto_tree_add_item" is one method of the "tree" object in the C API. in
> the python API, the Tree class defines a "add_item" method. With the same
> idea for "tvb_get_ntohl", the method is defined in the TVB class with the
> name "get_ntohl".
> 3) formal parameters of functions :
> a) first parameter is in general the "C object" and it does not make any
> sense to include it for the method defined in a python object. (in fact, in
> python it appears in the definition and "disappears" when called)
> b) it might happen that some other parameters are always defined in the
> formal parameters of the C API but are not manipulated by the user and might
> be included automatically by the python API. For these ones, they also
> disappear from the formal parameters list of the python API.
> c) if the parameter takes most of the time one value but sometimes can
> take another value, it is defined as an optional parameter.
> d) if the parameter is totally or partially managed by the python API, it
> is defined as an optional parameter.
> a good example is Tree.add_item(self, field, offset=0, length=-1,
> little_endian=False, adv=True)
> the C API counterpart is : proto_tree_add_item(proto_tree, hfindex, tvb,
> start, length, little_endian)
> - As of rule a), proto_tree is in fact the Tree object => disappear from
> the formal parameter list
> - As of rule b), tvb is not directly manipulated by the user and
> therefore disappear from the formal parameter list
> - As of rule c), little_endian has two possible value False or True. It
> becomes an optional parameter with the default value set to False.
> - As of rule d), "offset" is totally managed by the API with the help of
> the last *added* parameter which indicates whether offset should be
> incremented or not. This last parameter is itself an optional parameter with
> a value of True ("offset" is incremented by "length"). Though, offset is
> totally managed by the python API, it is possible to increment manually the
> There is already two notable exceptions to what I described here above.
> There exists two others objects (register_info and Subtrees). It is likely
> that in the future this list of objects will increase because they've
> initially have been created because of a "ctypes" (python module)
> At the end, they almost serve only as a special dictionary of elements.
> For these objects, I used a so interesting feature of python, definition of
> dynamic attributes.You have a first step in which you add items in this
> "dictionary" (hf_register_info fields and trees). When you have to refer to
> one of these while dissecting, you can refer to them as if they were
> attributes of the related object.
> For example, let's say "hf" is a register_info object, you can add something
> to it by doing :
> hf.add("Imaginary Protocol Length", "imaginary.length", FT_UINT8) => Not
> that you have a lot of optional parameters in here!
> and you can refer to this field while dissecting with
> the name of the attribute is the second parameter passed with every '.'
> changed to '_'
> That's all for now .. I'll add this mail to the wiki documentation.
> Of course, I'll enjoy any comments (from you or anyone else) to improve the
> python API whatever it be following the LUA API or not. :)
> Sebastien Tandel
> 2009/5/31 Stig Bjørlykke <stig.bjorlykke-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
>> Do you use the same naming scheme in the Python bindings as we use in
>> I think we should have the same names for equal functionality in both
>> Python and Lua.
>> Stig Bjørlykke
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