I'm another of what seem to be legions of people trying to interface
with OS stores that keep void * in c/c++. My particular one is Windows
TLSData, but for my example I don't need any Windows code, just D.
// this based on code I snagged from this group
// DMD 2.059 Win 7 Home Premium 64 bit.
import std.stdio: writeln;
struct MyStruct {
string structName;
public string toString() {
return structName;
}
void* opCast() {
return &this;
}
}
class MyObject {
string oname;
this(string who) {
oname = who;
}
public string toString() {
return oname;
}
void* opCast() {
return &this;
}
}
void main() {
MyStruct test = MyStruct("Example struct");
MyStruct test2;
void* temp1 = cast(void*)test;
void* temp2 = &test;
assert(temp1 == temp2);
writeln(*cast(MyStruct*)temp1);
test2 = *cast(MyStruct*)temp1;
writeln(test2);
auto o1 = new MyObject("Ok");
MyObject o2;
temp1 = cast(void*)o1;
temp2 = &o1;
//assert(temp1 == temp2); // this is true for struct,
// why not object?
writeln(*cast(MyObject*)temp1);
o2 = *cast(MyObject*)temp1;
writeln(o2);
}
Structs seem to go both directions just fine, although something
prettier than *cast(MyStruct*) would be nice for the return trip.
Objects seem to require a dedicated opCast and from my ng spelunking it
appears opCast is frowned upon.
How would I do the to void* w/o opCast and is there a prettier way than
*cast(MyThing*) to get back the original "thing" from a void *?
If I get prettier code I'll post it to the FAQ on the Wiki so that you
gurus can quit dealing with the question so often.
