Andrei Alexandrescu wrote:
I seem to recall that
interface dispach in D does a linear search in the interfaces list, so
you may want to repeat your tests with a variable number of interfaces,
and a variable position of the interface being used.
Such numbers are not interesting to me. On average, each class I write
implements one interface. I rarely use inheritance and interfaces in the
same class.
But your information is incorrect. Here's what happens:
object of class A
| vtable
| | classinfo pointer
| | methods...
| fields...
| interface vtable
| | struct Interface*
| | methods
struct Interface
{
ptrdiff_t this_offset;
ClassInfo interfaceInfo;
}
There are two ways to implement interface calls with this paradigm. The
compiler way:
interface I
{
void doStuff(int arg);
}
class A
{
void doStuff(int arg) { writefln("do stuff! %s", arg); }
// this method actually goes into the interface vtable
ReturnType!doStuff __I_doStuff(ParameterTypeTuple!doStuff args)
{
auto iface = cast(Interface*)this.vtable[0];
this = this + iface.this_offset;
return doStuff(args);
}
}
You can also do it with the runtime, but that's a lot harder. It would
be effectively the same code.
