Memory/Pointer simulation in Python

main.py

from abc import ABC, abstractmethod
from dataclasses import dataclass
from typing import Literal, Any

BYTEORDER: Literal["little", "big"] = "big"


class Type(ABC):
    @abstractmethod
    def load(self, offset, memory):
        pass

    @abstractmethod
    def store(self, value, offset, memory):
        pass


class U64(Type):
    def load(self, offset, memory):
        return memory.get_int(offset)

    def store(self, value, offset, memory):
        assert isinstance(value, int)
        assert 0 <= value < 2**64
        return memory.set_int(offset, value)


class U64List(Type):
    def load(self, offset, memory):
        car = memory.get_int(offset)
        cdr = memory.get_int(offset + 8)
        return (car, Pointer(cdr, self, memory))

    def store(self, value, offset, memory):
        assert isinstance(value, tuple)
        assert len(value) == 2
        assert isinstance(value[0], int)
        assert isinstance(value[1], Pointer)
        memory.set_int(offset, value[0])
        memory.set_int(offset + 8, value[1].address)


class Memory(bytearray):
    def __init__(self, n_bytes):
        super().__init__(b"\x00" * n_bytes)

    def set_int(self, offset, value: int, n_bytes=8):
        self.set_bytes(offset, value.to_bytes(n_bytes, BYTEORDER))

    def get_int(self, offset, n_bytes=8) -> int:
        return int.from_bytes(self.get_bytes(offset, n_bytes), BYTEORDER)

    def set_bytes(self, offset, data):
        self[offset : offset + len(data)] = data

    def get_bytes(self, offset, length) -> bytes:
        return self[offset : offset + length]


@dataclass
class Pointer:
    address: int
    type: Type
    mem: Memory

    def read(self) -> Any:
        return self.type.load(self.address, self.mem)

    def write(self, value: Any):
        return self.type.store(value, self.address, self.mem)


mem = Memory(50)

nil = Pointer(0, U64List(), mem)

p1 = Pointer(1, U64List(), mem)
p1.write((10, nil))

p2 = Pointer(17, U64List(), mem)
p2.write((20, p1))

print(mem)

print(p2.read())
print(p1.read())