Allow call from native contract

[erikzhang]

Close #1699

[erikzhang]

@doubiliu

[doubiliu]

@erikzhang Got it. I will test it as soon as possible

[doubiliu]

Well,I have done some test.
Unfortunately, it seems that the call still fails.
Test example:

  [ContractMethod(0_01000000,CallFlags.All)]
        public bool InvokeCallBackMethod(ApplicationEngine engine)
        {
            Console.WriteLine("InvokeCallBackMethod");
            Action callBack = new Action(Refund);
            engine.CallFromNativeContract(callBack , NativeContract.Oracle.Hash, "f1", new Array() { UInt160.Zero.ToArray() });
            return false;
        }

        [ContractMethod(0_01000000, CallFlags.All)]
        public bool f1(ApplicationEngine engine,Array array)
        {
            Console.WriteLine("执行f1");
            return true;
        }

        [ContractMethod(0_01000000, CallFlags.All)]
        public void Refund()
        {
            Console.WriteLine("Refund");
        }

We found the following problems:

1. The first function return value can only be set to void type, otherwise there will still be occupation problems
2. When the called function is a native contract method, it will cause an exception due to the lack of a Ret operation.

[erikzhang]

The first function return value can only be set to void type, otherwise there will still be occupation problems

Yes. That's why I created two methods.

[erikzhang]

When the called function is a native contract method, it will cause an exception due to the lack of a Ret operation.

Native contracts have a RET opcode at the end of script implicitly too, just like the other contracts.

[doubiliu]

Has tested.At present, the native contract can already call other contracts. @erikzhang

[erikzhang]

Has tested.At present, the native contract can already call other contracts.

Did you test the case that it calls to another native contract?

[doubiliu]

YES. But I found that there are limits on the return value type of the contract. If the return value of the contract method is of type bool, it will perform an error.But currently this does not affect my use.

[erikzhang]

If the return value of the contract method is of type bool, it will perform an error.

Fixed.

[doubiliu]

@erikzhang There is still a problem, the method name is occupied.

@erikzhang

[erikzhang]

Because you call a method with null?

[Tommo-L]

Because you call a method with null?

@doubiliu has called CallFromNativeContract twice in a row. Maybe we shouldn't do that.

[erikzhang]

No, you shouldn't. Is there any other problem?

[doubiliu]

If we invoke extra function once ,it is ok.

[erikzhang]

Go?