内存中存储多字节有两种方法,即小端字节序和大端字节序,Ubuntu10.04是小端字节序,网际协议所用的字节序为大端字节序
内存地址增长方向: 低序字节->高序字节 小端字节序
高序字节->低序字节 大端字节序
主机和网络字节序转换函数在头文件<netinet/in.h>中,函数分别为:
uint16_t htons(uint16_t)
uint32_t htonl(uint32_t)
uint16_t ntohs(uint16_t)
uint32_t ntohl(uint32_t)
命名规则为: h-host,n-network,s-short,l-long, to 即变换到
测试程序为 byteorder_convert_fun1.cpp:
#include <iostream>
#include <iomanip>
#include <netinet/in.h>
using std::cin;
using std::cout;
using std::endl;
using std::hex;
typedefunsigned short int uint16_t;
typedef unsigned int uint32_t;
int main(int argc, char **argv)
{
uint16_t c1,d1;
uint32_t c2,d2;
c1 = 0x1A2B;
c2 = 0x1A2B3C4D;
cout<<hex<<c1<<'\t'<<"htons(c1) = "<<htons(c1)<<endl;
cout<<hex<<c2<<'\t'<<"htonl(c2) = "<<htonl(c2)<<endl;
d1 = 0x3E4F;
d2 = 0x3E4F5A6B;
cout<<hex<<d1<<'\t'<<"ntohs(d1) = "<<ntohs(d1)<<endl;
cout<<hex<<c2<<'\t'<<"ntohl(d2) = "<<ntohl(d2)<<endl;
return 0;
}
root@gujinjin-desktop:/home/gujinjin/Socket# ./byteorder_convert_fun1
1a2b htons(c1) = 2b1a
1a2b3c4d htonl(c2) = 4d3c2b1a
3e4f ntohs(d1) = 4f3e
3e4f5a6b ntohl(d2) = 6b5a4f3e
说明:
程序中用typedef 重新定义了 uint16_t 和 uint32_t, 也可以不用定义直接包含头文件 <sys/types.h>