C/C++ ip地址与int类型的转换实例详解

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

实现代码

#include

#include

#include

#include

#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;

}

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