大小端序和系统

大小端续

分析

unsigned int value = 0x12345678；
用unsigned char buf[4]表示value；
大端【地址相反】：
栈底
buf[3]：78
buf[2]：56
buf[1]：34
buf[0]：12
栈顶
小端序：
栈底
buf[3]：12
buf[2]：34
buf[1]：56
buf[0]：78
栈顶

地址	Big-Endian	Little-Endian
0x01000000	0x12	0x78
0x01000001	0x34	0x56
0x01000002	0x78	0x34
0x01000003	0x78	0x12

转换代码

#include 
using namespace std;
template 
T Convert(T input)
{
    return input;
}
template <>
unsigned int Convert(unsigned int input)
{
    input = (input & 0xff000000) >> 24 | 
        (input & 0x000000ff) << 24 | 
        (input & 0x00ff0000) >> 8 | 
        (input & 0x0000ff00) << 8;
    return input;
}

template <>
unsigned short Convert(unsigned short input)
{
    input = (input & 0xff00) >> 8 | 
        (input & 0x00ff) << 8;
    return input;
}

bool IsLittleEndian()
{
    union test
    {
        uint32_t i;
        char c;
    };
    test temp;
    temp.i = 0x01020304;
    return (temp.c == 4);
}
bool IsBigEndian()
{
    uint32_t tempInt = 0x01020304;
    unsigned char* tempChar = (unsigned char*)&tempInt;
    return (*tempChar == 1);
}
int main(int argc, char* argv[])
{
    unsigned int input = 0x12345678;
    printf("before %x\n", input);
    printf("after %x\n", Convert(input));
    unsigned short input2 = 0x1234;
    printf("before %x\n", input2);
    printf("after %x\n", Convert(input2));
    printf("Is little endian %d.\n", int(IsLittleEndian()));
    printf("Is big endian %d.\n", int(IsBigEndian()));
    return 0;
}

输出结果：

before 12345678
after 78563412
before 1234
after 3412
Is little endian 1.
Is big endian 0.

参考：

• https://blog.csdn.net/SwordArcher/article/details/82417429

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