判断IP、MAC地址是否符合规范

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <ctype.h>

int is_valid_ip(const char *ip)
{
if (ip == NULL || strlen(ip) < 7)
{
return -1;
}

int len = strlen(ip);
const char *start = ip;
const char *end = ip + len - 1;
int ret = 0;
int dot_count = 0;
int cur_val = 0;
int val = -1;

while (end > start && isspace(*end))
{
--end;
}

while (start < end && isspace(*start))
{
++start;
}

if (start >= end || isdigit(*start) == 0 || isdigit(*end) == 0)
{
return -1;
}

while (start <= end)
{
while (start <= end && '0' <= *start && *start <= '9')
{
cur_val = 10 * cur_val + (*start - '0');
if (cur_val < 0 || cur_val > 255)
{
ret = -1;
break;
}

val = cur_val;
++start;
}

if (start <= end)
{
if (*start == '.' && val != -1)
{
++start;
++dot_count;
cur_val = 0;
val = -1;
}
else
{
ret = -1;
break;
}
}
else
{
break;
}
}

if (ret == 0 && dot_count != 3)
{
ret = -1;
}

return ret;
}

int is_valid_mac(const char *mac)
{
if (mac == NULL || strlen(mac) < 17)
{
return -1;
}

int len = strlen(mac);
int ret = 0;
int num_count = 0;
int colon_count = 0;
const char *start = mac;
const char *end = mac + len - 1;

while (end > start && isspace(*end))
{
--end;
}

while (start < end && isspace(*start))
{
++start;
}

if ((end - start) != 16 || isxdigit(*start) == 0 || isxdigit(*end) == 0)
{
return -1;
}

while (start <= end)
{
while (start <= end && isxdigit(*start))
{
++start;
if (++num_count > 2)
{
ret = -1;
break;
}
}

if (start <= end )
{
if (*start == ':' && num_count == 2)
{
++colon_count;
num_count = 0;
++start;
}
else
{
ret = -1;
break;
}
}
else
{
break;
}
}

if (ret == 0 && colon_count != 5)
{
ret = -1;
}

return ret;
}

void demo()
{
int ret;
const char *ip = "192.168.1.1";

ret = is_valid_ip(ip);
if (ret == 0)
{
printf("%s is a valid ip!\n", ip);
}
else
{
printf("%s is an invalid ip!\n", ip);
}

ip = "192.256.1.1  ";
ret = is_valid_ip(ip);
if (ret == 0)
{
printf("%s is a valid ip!\n", ip);
}
else
{
printf("%s is an invalid ip!\n", ip);
}

const char *mac = "11:22:33:44:55:66";
ret = is_valid_mac(mac);
if (ret == 0)
{
printf("%s is a valid MAC address!\n", mac);
}
else
{
printf("%s is an invalid MAC address!\n", mac);
}

mac = "11:22:33:44:  :66";
ret = is_valid_mac(mac);
if (ret == 0)
{
printf("%s is a valid MAC address!\n", mac);
}
else
{
printf("%s is an invalid MAC address!\n", mac);
}
}

int main()
{
demo();

return 0;
}