fstream直接访问结构变量

Question

I know how to read and write a complete struct with fstream. But just for curiosity, is there a way to access (read or write) a variable directly? I have never seen somebody doing this.

aStruct * dummyStruct = 0;
int num = 7;

File.seekp(streamPosition, ios::beg);
File.seekp((unsigned long long)&(dummyStruct->aVariable), ios::cur);

File.write(reinterpret_cast<const char*>(&num), sizeof(num));

Has anybody done something like this?

Answer 1

您可以使用offsetof确定变量的偏移位置。

File.seekp(offsetof(aStruct, aVariable), ios::cur);