Re: What is the use of pointer "cap_file_" in QtShark

[Guy Harris <guy () alum mit edu>]

On May 22, 2013, at 10:21 AM, Richard Turner <turner () yiran org> wrote:

> In Wireshark/ui/qt/main_window.h there is a private member variable defined as:
>
> capture_file *cap_file_;
>
> I think it's a pointer to the global variable "cfile"

Currently, yes.

We make no claim that Wireshark will, forever, have only one main window and only one capture file open, so it should 
not be treated as if it is, inherently, just a pointer to cfile.

> (defined in tshark.c).

Yes, it's defined there, but tshark.c, as the name suggests, is not linked into Wireshark, it's linked into TShark; the 
cfile in QtShark is defined in ui/qt/main.cpp (and in GTKShark is defined in ui/gtk/main.c).

> Is it true that we keep this pointer only to verify the validity of cfile (we set cap_file_ to NULL when the capture 
> file is closed)?

No, we keep it around to make the code cleaner (and a tiny bit easier to make into something that behaves like a Real 
OS X Application, in which one process handles all open files and captures; "tiny bit" because that's about .001% of 
the work involved - the *big* work is to get rid of, for example, global variables in libwireshark and plugin 
dissectors).

"Global variables considered harmful".
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