inet_addr 函數 和 inet_ntoa 函數 自實作

#include <stdio.h>

long change_uint(long a, long b, long c, long d){

    long address = 0;

    address |= d<<24;

    address |= c<<16;

    address |= b<<8;

    address |= a;

    return address;

}

long change_addr(const char *str){

    long a, b, c, d;

    sscanf(str, "%ld.%ld.%ld.%ld", &a, &b, &c, &d);

    return change_uint(a, b, c, d);

}

int main(int argc, char* argv[]){

    long addr;

    addr = change_addr("192.168.0.1");

    printf("%ld\n", addr);

    return 0;

}

#include<stdio.h>

#include<stdlib.h>

#include<string.h>

char *my_inet_ntoa(unsigned long);

char str[30];

int main(int argc,char **argv)

{

unsigned long inaddr=3232235777;

printf("%s\n",my_inet_ntoa(inaddr));

return 0;

}

char *my_inet_ntoa(unsigned long inaddr)

{

    int a[4],i;

    char b[20],c[15],d[10],e[5];

    a[0]=((inaddr & 0xff000000)>>24);

    a[1]=((inaddr & 0x00ff0000)>>16);

    a[2]=((inaddr & 0x0000ff00)>>8);

    a[3]=((inaddr & 0x000000ff)>>0);

//    itoa(a[0],b,10);

    sprintf(b,"%d",a[0]);

    strcat(b,".");

    printf("%c %c %c \n", b[0], b[1], b[2]);

//    itoa(a[1],c,10);

    sprintf(c,"%d",a[1]);

    strcat(c,".");

//    itoa(a[2],d,10);

    sprintf(d,"%d",a[2]);

    strcat(d,".");

//    itoa(a[3],e,10);

    sprintf(e,"%d",a[3]);

    strcat(str,strcat(b,strcat(c,strcat(d,e))));

    return str;

}