ip地址与int类型的转换

前言

最近看道一个面试题目，大体意思就是将ip地址，例如“192.168.1.116”转换成int类型，同时还能在转换回去

思路

ip地址转int类型，例如ip为“192.168.1.116”,相当于“.“将ip地址分为了4部分，各部分对应的权值为256^3, 256^2, 256, 1,相成即可

int类型转ip地址，思路类似，除以权值即可，但是有部分字符串的操作

代码

#include <stdio.h>  
#include <stdlib.h>  
#include <string.h>  
#include <math.h>  
  
#define LEN 16  
  
typedef unsigned int uint;  
  
/** 
 * 字符串转整形 
 */  
uint ipTint(char *ipstr)  
{  
    if (ipstr == NULL)  return 0;  
  
    char *token;  
    uint i = 3, total = 0, cur;  
  
    token = strtok(ipstr, ".");  
  
    while (token != NULL) {  
        cur = atoi(token);  
        if (cur >= 0 && cur <= 255) {  
            total += cur * pow(256, i);  
        }  
        i --;  
        token = strtok(NULL, ".");  
    }  
  
    return total;  
}  
  
/** 
 * 逆置字符串 
 */  
void swapStr(char *str, int begin, int end)  
{  
    int i, j;  
  
    for (i = begin, j = end; i <= j; i ++, j --) {  
        if (str[i] != str[j]) {  
            str[i] = str[i] ^ str[j];  
            str[j] = str[i] ^ str[j];  
            str[i] = str[i] ^ str[j];  
        }  
    }  
}  
  
/** 
 * 整形转ip字符串 
 */  
char* ipTstr(uint ipint)  
{  
    char *new = (char *)malloc(LEN);  
    memset(new, '\0', LEN);  
    new[0] = '.';  
    char token[4];  
    int bt, ed, len, cur;  
  
    while (ipint) {  
        cur = ipint % 256;  
        sprintf(token, "%d", cur);  
        strcat(new, token);  
        ipint /= 256;  
        if (ipint)  strcat(new, ".");  
    }  
  
    len = strlen(new);  
    swapStr(new, 0, len - 1);  
  
    for (bt = ed = 0; ed < len;) {  
        while (ed < len && new[ed] != '.') {  
            ed ++;  
        }  
        swapStr(new, bt, ed - 1);  
        ed += 1;  
        bt = ed;  
    }  
  
    new[len - 1] = '\0';  
  
    return new;  
}  
  
int main(void)  
{  
    char ipstr[LEN], *new;  
    uint ipint;  
  
    while (scanf("%s", ipstr) != EOF) {  
        ipint = ipTint(ipstr);  
        printf("%u\n", ipint);  
  
        new = ipTstr(ipint);  
        printf("%s\n", new);  
    }  
  
    return 0;  
}

补充：软件开发 , C++ ,