Storing hardcoded calldata in a Solidity contract

Question

I've been trying to store a hardcoded call in a contract, but I'm getting confused on the encoding.

Let's say I have the following bytes:

0x9461d6f7000000000000000000000000000000000000000000000000000000000000000a796f000000000000000000000000000000000000000000000000000000000000

This translates to calling function testData(uint256 testVar, bytes32 otherVar) with 10 & "yo".

If I store this as a bytes like so:

bytes public hardcodedCallData = "0x9461d6f7000000000000000000000000000000000000000000000000000000000000000a796f000000000000000000000000000000000000000000000000000000000000";

And then do a address.call(hardcodedCallData), it does not work. The fallback function is triggered instead, assuming that it is malformed. When storing it as such, it seems it decodes to bytes that look different.

I seem to have a misunderstanding on encoding here somewhere. Given calldata, how do I store it as bytes as hardcoded, so I can do the above?

I tried variations (playing with strings for example), but not able to figure this out.

Answer 1

The issue is that when you use a string literal like

bytes public hardcodedCallData = "0x9461d6f7000000000000000000000000000000000000000000000000000000000000000a796f000000000000000000000000000000000000000000000000000000000000";

Solidity interprets the string as ASCII. In fact, if you do

"307839343631643666373030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030306137393666303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030303030"
.decode('hex').encode("ascii")

in Python, you'll see that this is the ASCII encoding of your intended hex value.

What you should be using is

bytes public hardcodedCallData = hex"9461d6f7000000000000000000000000000000000000000000000000000000000000000a796f000000000000000000000000000000000000000000000000000000000000";

See http://solidity.readthedocs.io/en/develop/types.html?highlight=hex#hexadecimal-literals