Demos delegatecall in serpent

delegatecall_test.py

import serpent
from ethereum import tester as t

code = '''\
def foo(x, flag):
    with prefix = 0:
        if flag == "double":
            prefix = 0x6ffa1caa*2**248
        else:
            prefix = 0x70cd69ae*2**248
        delegate_calldata = alloc(36)
        out = alloc(32)
        mstore(ref(delegate_calldata), prefix / 2**248)
        prefix *= 2**8
        mstore8(ref(delegate_calldata) + 1, prefix / 2**248)
        prefix *= 2**8
        mstore8(ref(delegate_calldata) + 2, prefix / 2**248)
        prefix *= 2**8
        mstore8(ref(delegate_calldata) + 3, prefix / 2**248)
        mstore(ref(delegate_calldata) + 4, x)
        delegatecall(msg.gas, self, 128, 36, 128 + 36, 32)
        return(out[0])

def double(x):
    return(2*x)

def half(x):
    return(x/2)'''

print serpent.compile_to_lll(code)
s = t.state()
c = s.abi_contract(code)
double = int('double'.encode('hex').ljust(64, '0'), 16)
print c.foo(1, double)