[Mono-list] Wrapper additions

[Dietmar Maurer]

Paolo Molaro wrote:

> On 09/20/01 Dietmar Maurer wrote:
> > > I think we shouldn't use the string type to pass char* data back and forth
> > > to unix APIs. The problem is: string is supposed to be unicode chars, but
> > > what encoding does that API use? latin1? utf8?
> >
> > UTF8, or the same char set which is used for system calls?
> >
> > > We don't know and the lame
> > > attribute MS added (CHAR_SET_ANSI) is only usable with their APIs.
> > > We should probably use byte[] and have the caller decide the proper encoding.
> > > Comments welcome.
> >
> > I thought its the task of PInvoke to convert from unicode to the system char set
> > and back? Passing a byte[] only moves the problem to another location.
>
> Yes, but hopefully to a location that knows better.
> For example, we may have library A that takes char* strings in latin1
> encoding and a library B (say, Gtk+ 2.0) that takes char* strings in utf8
> encoding. The resulting C# code is:
>
>         [DllImport("A", EntryPoint="afunc"]
>         public unsafe static extern void afunc (string arg);
>
>         [DllImport("B", EntryPoint="bfunc"]
>         public unsafe static extern void bfunc (string arg);
>
> How can the P/Invoke code know when it has to convert a UCS-2 string to
> utf8 or latin1? Even if the Charset argument of DllImport could be changed
> to be more flexible, it still applies to a whole function, not to a single
> argument/return type. What if a function takes two char* arguments, one in
> latin1 and one in utf8?

I this really an issue? Are there situations where we need this?

> Only the caller may know that, unless the DllImport
> attribute spec is changed to take this issues into account and I really hope
> the ECMA folks will consider some solutions for this.
>
> > > opendir () return a pointer and you can't cast it (portably) to
> > > an int. Use gpointer (the same issue is in mono_wrapper_getenv and
> > > mono_wrapper_environ).
> >
> > The problem is in the perl script. Here is a patch:
>
> Oh, thanks!
>
> lupus
>
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