C/C++ 大小端转换

自写函数实现

#include<iostream>
using namespace std;

unsigned int fun1(unsigned int a)
{
	unsigned int b = 0;
	*(char *)(unsigned int(&b)) = *(char *)(unsigned int(&a) + 3);
	*(char *)(unsigned int(&b) + 1) = *(char *)(unsigned int(&a) + 2);
	*(char *)(unsigned int(&b) + 2) = *(char *)(unsigned int(&a) + 1);
	*(char *)(unsigned int(&b) + 3) = *(char *)(unsigned int(&a));
	cout <<  b << endl;
	cout << 0x44332211 << endl;
    return b;
}

unsigned int fun2(unsigned int a) {
	unsigned int y=0;	
	((char*)&b)[0] = ((char*)&a)[3];
	((char*)&b)[1] = ((char*)&a)[2];
	((char*)&b)[2] = ((char*)&a)[1];
	((char*)&b)[3] = ((char*)&a)[0];

	cout << b << endl;
	cout << 0x44332211 << endl;
    return b;

}
int main()
{
	fun1(0x11223344);
	fun2(0x11223344);
	return 0;
}

思路

以unsigned int类型为例，其变量占用四个字节内存空间，假设a=0x11223344，大端存储