ip整形和字符串转换

#include <iostream>
#include <string>

std::string int2str(int i)
{
    char t[20] = {0};
    sprintf(t, "%d", i);
    return t;
}

std::string ip_int2str(int ip)
{
            std::string ret = "";
            int i = 0;
            while( i < 4 )
            {
                   int a = ( ip >> (i * 8) ) & 0xFF;
                   if( i < 3)
                       ret += int2str(a) + ".";
                   else
                       ret += int2str(a);
                   i ++;
            }

            return ret;
}

int ip_str2int(std::string ip)
{
    int ret = 0;
    char* p = (char*)ip.c_str();
    char* a[4] = {0};
    int b[4] = {0};
    int in = 0;
    while((a[in] = strtok(p, ".")) != NULL)
    {
                   p = NULL;
                   sscanf(a[in], "%d", &b[in]);
                   in++;

    }

    for( int i = 3; i >= 0; --i )
    {
         ret = ret << 8;
         ret += b[i];
    }

    return ret;
}

int main()
{
    printf("0, ip int -> str.\n");
    printf("1, ip str -> int.\n");

    int i = 0 ;
    std::cin >> i;

    if( i == 0 )
    {
        int ip_int = 0;
        while(true)
        {
            std::cout << "input ip_int:";
            std::cin >> ip_int;
            std::string str = ip_int2str(ip_int);
            printf("ip_str:%s\n", str.c_str());
        }

    }else
    {
         std::string ip_str = "";
         while(true)
         {
             std::cout << "input ip_str:";
             std::cin >> ip_str;
             int ip_int = ip_str2int(ip_str);
             printf("ip_int:%d\n", ip_int);
         }

    }

    system("pause");
    return 0;
}