public static Freezable newFreezable(int id) {
Freezable f = GOLD[id];
if (f == null) {
try {
GOLD[id] = f = (Freezable) Class.forName(TypeMapGen.CLAZZES[id]).newInstance();
} catch (Exception e) {
throw Log.errRTExcept(e);
}
}
return f.newInstance();
}
/**
* Checks that this Freezable object can be mutated from the given {@link Environment}.
*
* @param object a Freezable object that we check is still mutable.
* @param env the {@link Environment} attempting the mutation.
* @throws MutabilityException when the object was frozen already, or is from another context.
*/
public static void checkMutable(Freezable object, Environment env) throws MutabilityException {
if (!object.mutability().isMutable()) {
throw new MutabilityException("trying to mutate a frozen object");
}
// Consider an {@link Environment} e1, in which is created {@link UserDefinedFunction} f1,
// that closes over some variable v1 bound to list l1. If somehow, via the magic of callbacks,
// f1 or l1 is passed as argument to some function f2 evaluated in {@link environment} e2
// while e1 is be mutable, e2, being a different {@link Environment}, should not be
// allowed to mutate objects from e1. It's a bug, that shouldn't happen in our current code
// base, so we throw an AssertionError. If in the future such situations are allowed to happen,
// then we should throw a MutabilityException instead.
if (!object.mutability().equals(env.mutability())) {
throw new AssertionError("trying to mutate an object from a different context");
}
}
public static void main(String[] args) {
// Shared freezable object
final F<ObjectInterface> freezableObj = Freezable.of(new MyObject(0));
System.out.println("We create a shared object: " + freezableObj);
// Create refs to freezableObj
R<ObjectInterface> r1 = R.createRef(freezableObj);
R<ObjectInterface> r2 = R.createRef(freezableObj);
System.out.println("Initial configuration");
System.out.println("R1 " + r1);
System.out.println("R2 " + r2);
// One of them changes the value
System.out.println("R2 changes the value of the instance to 5");
r2.instance().setValue(5);
// Now, we freeze ref2. Ref2 will keep the original reference.
r1.freeze();
System.out.println("R1 calls freeze()");
System.out.println("R1 " + r1);
System.out.println("R2 " + r2);
// Ref1 changes the content. Since Ref2 has frozen the instance, Ref1 obtains a copy.
// r1.get().instance() returns a proxied interface of the object. Method setValue
// is intercepted. Since freezableObj is frozen, a new copy is generated and assigned
// to r1.
System.out.println("R2 modify the value to 1 and obtains a new copy");
r2.instance().setValue(1);
// Now r2 has a different copy
System.out.println("R1 " + r1);
System.out.println("R2 " + r2);
System.out.println("We create R3 with the first instance (still locked)");
R<ObjectInterface> r3 = new R<>(freezableObj);
System.out.println("R3 " + r3);
System.out.println("R2 has freedom to change its own copy");
r2.instance().setValue(100);
System.out.println("R1 " + r1);
System.out.println("R2 " + r2);
System.out.println("R3 " + r3);
System.out.println("R3 changes its copy");
r3.instance().setValue(200);
System.out.println("R1 " + r1);
System.out.println("R2 " + r2);
System.out.println("R3 " + r3);
}
// Also, allow auto-serialization
public static void put(Key key, Freezable fr) {
if (fr == null) UKV.put(key, null);
else UKV.put(key, new Value(key, fr.write(new AutoBuffer()).buf()));
}