swrap2 method
Binds a cwraped C function taking 2 arguments that returns a struct
via the WASM structure-return (sret) convention.
The first parameter is the caller-allocated pointer the struct is
written into, followed by the function's real arguments. Always
returns void, read the result back out of the pointer you passed in.
Implementation
WF3<void> swrap2(String name) {
final f = _ws(name, 2);
return (a1, a2, a3) => f.run([a1, a2, a3]);
}