c++ - 字符混淆中的转义序列

Question

我遇到了这个例子 here.

#include <iostream>

int main()
{
    int i = 7;

    char* p = reinterpret_cast<char*>(&i);
    if(p[0] == '\x7') //POINT OF INTEREST
        std::cout << "This system is little-endian\n";
    else
        std::cout << "This system is big-endian\n";
}

我感到困惑的是 if 语句。转义序列在这里如何表现？我得到与 p[0] == '\07' 相同的结果(\x 是十六进制转义序列)。检查 p[0] == '\x7' 如何告诉我系统是小端还是大端？

Answer 1

一个(32位)整数在内存中的布局是；

Big endian:

+-----+-----+-----+-----+
|  0  |  0  |  0  |  7  |
+-----+-----+-----+-----+
   ^ pointer to int points here

Little endian:

+-----+-----+-----+-----+
|  7  |  0  |  0  |  0  |
+-----+-----+-----+-----+
   ^ pointer to int points here

代码基本上做的是读取整数指针指向的第一个char，在小端的情况下是\x0，而大端是\x7.