cpu大小端测试

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关于cpu大小端中int或short的存放顺序，以及大小端序到网络序的转换

测试如下：

#include <stdio.h>#include <arpa/inet.h>int main(){unsigned int a = 0x12345678;unsigned int b;unsigned char *c;unsigned char *d;b = ntohl(a);c = (unsigned char *)&a;d = (unsigned char *)&b;printf("a = 0x%x, b = 0x%x\n", a, b);printf("c0 = 0x%x, c1 = 0x%x, c2 = 0x%x, c3 = 0x%x\n", c[0],c[1],c[2],c[3]);printf("d0 = 0x%x, d1 = 0x%x, d2 = 0x%x, d3 = 0x%x\n", d[0],d[1],d[2],d[3]);return 0;}

大端mips

a = 0x12345678, b = 0x12345678
c0 = 0x12, c1 = 0x34, c2 = 0x56, c3 =0x78
d0 = 0x12, d1 = 0x34, d2 = 0x56, d3 =0x78

由此，大端的高位在低地址，通过ntohl转换为网络字节序时数据没有变化

小端arm：

a = 0x12345678, b = 0x78563412
c0 = 0x78, c1 = 0x56, c2 = 0x34, c3 = 0x12
d0 = 0x12, d1 = 0x34, d2 = 0x56, d3 = 0x78

由此，小端的高位在低地址，通过ntohl转换为网络字节序时数据高低变换

也就是说，大端的系统上ntoh相关函数是不作处理的

小端的系统htoh相关函数会将高低位变换

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