# -*- coding: utf-8 -*-
'''
 * @Author       : zoufuzhou
 * @Date         : 2024-08-23 16:34:37
 * @Description  : Memory map header structure
 * @LastEditTime : 2024-08-26 16:34:37
'''

import struct


class Head:

    __format_string = 'III'

    # 使用 __slots__ 来优化内存使用
    __slots__ = ('maxsize', 'size', 'next')

    def __init__(self: 'Head', maxsize: int, size: int, next: int):
        self.maxsize = maxsize
        self.size = size
        self.next = next

    def length(self) -> int:
        """返回打包后的字节长度。"""
        return struct.calcsize(self.__format_string)

    def pack(self) -> bytes:
        """将属性打包为字节数据。"""
        return struct.pack(self.__format_string, self.maxsize, self.size, self.next)

    def unpack(self, data: bytes) -> None:
        """从字节数据解包到属性中。"""
        # print("|Head|unpack|self.maxsize:"+str(self.maxsize)+", self.size:"+str(self.size)+
        #       ", self.next:"+str(self.next)+",self.__format_string:"+self.__format_string
        #       +",self.length():"+str(self.length())+",datalen:"+str(len(data)))
        if len(data) != self.length():
            raise ValueError(
                f"数据长度不匹配: 期望 {self.length()}, 实际 {len(data)}.")
        self.maxsize, self.size, self.next = struct.unpack(
            self.__format_string, data)
        # print("|Head|unpack|self.maxsize:"+str(self.maxsize)+", self.size:"+str(self.size)+", self.next:"+str(self.next)+",self.__format_string:"+self.__format_string)

    def __str__(self) -> str:
        return f"maxsize: {self.maxsize}, size: {self.size}, next: {self.next}"

    def __repr__(self) -> str:
        return self.__str__()