Method evaluate

code-ch13/script.py:156–244

(self, z, witness)

        return encode_varint(total) + result

    def evaluate(self, z, witness):
        # create a copy as we may need to add to this list if we have a
        # RedeemScript
        cmds = self.cmds[:]
        stack = []
        altstack = []
        while len(cmds) > 0:
            cmd = cmds.pop(0)
            if type(cmd) == int:
                # do what the opcode says
                operation = OP_CODE_FUNCTIONS[cmd]
                if cmd in (99, 100):
                    # op_if/op_notif require the cmds array
                    if not operation(stack, cmds):
                        LOGGER.info('bad op: {}'.format(OP_CODE_NAMES[cmd]))
                        return False
                elif cmd in (107, 108):
                    # op_toaltstack/op_fromaltstack require the altstack
                    if not operation(stack, altstack):
                        LOGGER.info('bad op: {}'.format(OP_CODE_NAMES[cmd]))
                        return False
                elif cmd in (172, 173, 174, 175):
                    # these are signing operations, they need a sig_hash
                    # to check against
                    if not operation(stack, z):
                        LOGGER.info('bad op: {}'.format(OP_CODE_NAMES[cmd]))
                        return False
                else:
                    if not operation(stack):
                        LOGGER.info('bad op: {}'.format(OP_CODE_NAMES[cmd]))
                        return False
            else:
                # add the cmd to the stack
                stack.append(cmd)
                # p2sh rule. if the next three cmds are:
                # OP_HASH160 <20 byte hash> OP_EQUAL this is the RedeemScript
                # OP_HASH160 == 0xa9 and OP_EQUAL == 0x87
                if len(cmds) == 3 and cmds[0] == 0xa9 \
                    and type(cmds[1]) == bytes and len(cmds[1]) == 20 \
                    and cmds[2] == 0x87:
                    redeem_script = encode_varint(len(cmd)) + cmd
                    # we execute the next three opcodes
                    cmds.pop()
                    h160 = cmds.pop()
                    cmds.pop()
                    if not op_hash160(stack):
                        return False
                    stack.append(h160)
                    if not op_equal(stack):
                        return False
                    # final result should be a 1
                    if not op_verify(stack):
                        LOGGER.info('bad p2sh h160')
                        return False
                    # hashes match! now add the RedeemScript
                    redeem_script = encode_varint(len(cmd)) + cmd
                    stream = BytesIO(redeem_script)
                    cmds.extend(Script.parse(stream).cmds)