『C++』Temp_2018_12_26_02

 #include <iostream>
 #include <string>
 #include <stdio.h>
 #include <stdlib.h>
 using namespace std;

 struct Person
 {
     int age;
     int id;
 };

 template <class T> T myRead(void * memory)
 {
     char buffer[sizeof(T)];
     memcpy(buffer, memory, sizeof(T));
     T temp = *((T *)buffer);  // 调用 Person 拷贝构造
     return temp;
 }

 template <class T> T myRead2(void * memory)
 {
     T temp;
     memcpy(&temp, memory, sizeof(T));
     return temp;
 }

 template <class T> T* myRead3(void * memory, int offset)
 {
     T* temp = new T;
     memcpy(temp, (char*)memory+offset, sizeof(T));
     return temp; //返回指针, 有内存泄漏风险
 }

 template <class T> void myRead4(void * memory, int offset, T* data)
 {
     memcpy(data, (char*)memory+offset, sizeof(T));
 }

 template <class T> T* myRead5(void * memory, int offset)
 {
     T* t = (T*)((char*)memory+offset);
     return t;
 }

 int main()
 {
     char bytes[] = "\x05\x00\x00\x00\x0A\x00\x00\x00\x06\x00\x00\x00\x0C\x00\x00\x00";
     Person p = myRead<Person>(bytes);  // 调用 Person 拷贝构造
     printf("age = %d, id = %d\n", p.age, p.id);

     Person p2 = myRead2<Person>(bytes);  // 调用 Person 拷贝构造
     printf("age = %d, id = %d\n", p2.age, p2.id);

     Person* p3 = myRead3<Person>(bytes, );
     printf("age = %d, id = %d\n", p3->age, p3->id);

     Person* p4 = new Person;
     myRead4<Person>(bytes, , p4);
     printf("age = %d, id = %d\n", p4->age, p4->id);

     //这个会崩溃
     //Person* p5 = NULL;
     //myRead4<Person>(bytes, 7, p5);
     //printf("age = %d, id = %d\n", p5->age, p5->id);

     Person* p6 = myRead5<Person>(bytes, );
     printf("age = %d, id = %d\n", p6->age, p6->id);

     cin.get();
     return ;
 }

执行结果

 age = , id =
 age = , id =
 age = , id =
 age = , id =
 //程序崩溃
 age = , id =