c++ - 将对象转换为 char，然后转换为 "uncasting it back"

Question

如果你有对象

struct Packet P;

由

组成

struct Packet {
    struct Packet_header header;
    unsigned char data[MAXIMUM_BUFFER_LENGTH];
};

标题由

组成

struct Packet_header {
    unsigned int checksum;
    unsigned int seq;
    unsigned int ack;
    unsigned int data_length;
};

如果我尝试抛出数据包

(unsigned char*) &P

有没有办法让我“uncast”回去得到我原来的数据包 P？

Answer 1

最简单的方法是使用 reinterpret_cast<Packet>(*(reinterpret_cast<Packet*>(pUC))) , 其中pUC是 unsigned char* .

正确的方法是在Packet_header ，一个转换构造函数和一个转换运算符(或类似转换的方法):

struct Packet_header {
    Packet_header(unsigned char*);  //construct object form unsigned char*
    operator unsigned char*();      //cast it back
    const unsigned char* getUC();   //or get an unsigned char*

    unsigned int checksum;
    unsigned int seq;
    unsigned int ack;
    unsigned int data_length;
};