Ary Borenszweig wrote:
Tom S escribió:
/** Just a simple hack to have interfaces implemented by structs ...
because I can :P
Tested on DMD 1.039 [win32], GDC (various versions) [linux32] and
codepad.org
Output:
Entering main
Foo.func1 called ; val1 = 3.141590, val2 = Hello, world!
Foo.func2 called ; val1 = 3.141590, val2 = Hello, world!
Foo.func2 called ; val1 = 3.141590, val2 = Hello, world!
Foo.func3 called ; val1 = 3.141590, val2 = Hello, world! ; p1 = 123,
p2 = some parameter
Leaving main
*/
module structIface;
extern (C) int printf(char*, ...);
// ---- evil implementation
char[] structImplementInterface(char[] iface, char[][] funcs) {
char[] res = "private {";
res ~= \n"alias typeof(*this) _iface_"~iface~"_ThisType;";
foreach (func; funcs) {
res ~= \n"static assert (is(typeof(&"~iface~".init."~func~")),
`The interface "~iface~" doesn't declare a '"~func~"'
function, `
`thus struct `~_iface_"~iface~"_ThisType.stringof~` cannot
implement it`);";
res ~= \n"static void _iface_" ~ iface ~ "_func_" ~ func ~ "()
{";
version (GNU) {
res ~= \n\t"asm { naked; sub dword ptr 4[ESP], _iface_" ~
iface ~ "_vtbl.offsetof; jmp " ~ func ~ "; }";
} else {
res ~= \n\t"asm { naked; sub EAX, _iface_" ~ iface ~
"_vtbl.offsetof; jmp " ~ func ~ "; }";
}
res ~= \n"}";
}
res ~= \n ~ iface ~ " as" ~ iface ~ "() {";
res ~= \n\t"return cast("~iface~")cast(void*)&_iface_" ~ iface ~
"_vtbl;";
res ~= \n"}";
res ~= \n"void** _iface_" ~ iface ~ "_vtbl = cast(void**)([";
res ~= \n\t"null"; // for classinfo
foreach (func; funcs) {
res ~= ",\n\tcast(void*)&Foo._iface_" ~ iface ~ "_func_" ~ func;
}
res ~= \n"]).ptr;";
res ~= "}";
return res;
}
// ---- end of the evil implementation
Since a lot of compile stuff is done via strings, I wish you could do
somehing like this in D (like in PHP):
res ~= res ~= "\n\treturn cast(${iface})cast(void*)&_iface_${iface}_vtbl;";
Much nicer and understandable. And I think it's not hard to implement:
when doing semantic for a string like that, parse it and search the
variables in the current scope and upwards (as a usual search). For this
to work, primitives should have a string representation, and if it's a
class or struct, then toString() is invoked.
It's really hard to follow a code like that, with thousands of "~".
And maybe this should only be done for strings enclosed in `, so that
the search is not always done.
Macros are supposed to solve that. D1.0 even has a "macro" keyword, but
so far macros are just vaporware.
