N3 disassembler

n3-disassemble.py

# useful to disassemble an invocation script - won't work to
# disassemble an entire NEF because it will stop at the first RET

from neo3 import contracts, vm
import base64


class Disassembler(contracts.ApplicationEngine):
    def pre_execute_instruction(self) -> None:
        ins = self.current_context.current_instruction()
        if ins.opcode != vm.OpCode.SYSCALL:
            print(ins.opcode, ins.operand.hex())

    def on_syscall(self, method_id: int):
        descriptor = self.interop.InteropService.get_descriptor(method_id)
        if descriptor is None:
            print(f"SYSCALL - invalid method id -> {method_id}")
        else:
            print(f"SYSCALL {descriptor.method}")


if __name__ == "__main__":
    script = base64.b64decode(
        b'FQwhAjmjdDZlL0GzuALKRMvLfWXTqguIyaA4AkO9vhqqXLNbDCECSG/RVwLESQomcDESpcwdCSP9aXozQGvVocAOABOwmnAMIQKq7DhHD2qtAELG6HfP2Ah9Jnaw9Rb93TYoAbm9OTY5ngwhA7IJ/U9TpxcOpERODLCmu2pTwr0BaSaYnPhfmw+6F6cMDCEDuNnVdx2PUTqghpucyNUJhkA7eMbaNokGOMPUalrc4EoMIQLKDidpe5wkj28W4IX9AGHib0TahbWO6DXBEMql7DulVAwhA9nosWvZsi0zRdbUzeMb4cPh0WFTLj0MzsuV7OLrWDNuF0Ge0Nw6')
    engine = Disassembler(contracts.TriggerType.APPLICATION, None, None, 99999)
    engine.load_script(vm.Script(script))
    engine.execute()