Parse IP address

parse_ip.c

#include <windows.h>
#include <stdio.h>
#include <stdlib.h>

typedef unsigned char u_char;
typedef unsigned char uchar;
typedef unsigned long u_long;
typedef unsigned long ip_addr;
typedef unsigned short ushort;

char * parse_ipad(ip_addr * ipout,   /* pointer to IP address to set */
           unsigned * sbits,          /* default subnet bit number */
           char * stringin)           /* buffer with ascii to parse */
{
    char * cp;
    int dots = 0;   /* periods imbedded in input string */
    int number;
    union   {
        u_char c[4];
        u_long l;
    } retval;
    char * toobig = "each number must be less than 255";

    cp = stringin;
    while (*cp) {
        if (*cp > '9' || *cp < '.' || *cp == '/')
            return("all chars must be digits (0-9) or dots (.)");
        if (*cp == '.')dots++;
        cp++;
    }

    //if( dots < 1 || dots > 3 )
    if ( dots != 3 )
        return("string must contain 1 - 3 dots (.)");

    cp = stringin;
    if ((number = atoi(cp)) > 255)  /* set net number */
        return(toobig);

    retval.c[0] = (u_char)number;

    while (*cp != '.')cp++;  /* find dot (end of number) */
    cp++;            /* point past dot */

    if (dots == 1 || dots == 2) retval.c[1] = 0;
    else {
        number = atoi(cp);
        while (*cp != '.')cp++;  /* find dot (end of number) */
        cp++;            /* point past dot */
        if (number > 255) return(toobig);
        retval.c[1] = (u_char)number;
    }

    if (dots == 1) retval.c[2] = 0;
    else {
        number = atoi(cp);
        while (*cp != '.')cp++;  /* find dot (end of number) */
        cp++;            /* point past dot */
        if (number > 255) return(toobig);
        retval.c[2] = (u_char)number;
    }

    if ((number = atoi(cp)) > 255)
        return(toobig);
    retval.c[3] = (u_char)number;

    if (retval.c[0] < 128) *sbits = 8;
    else if (retval.c[0] < 192) *sbits = 16;
    else *sbits = 24;

    *ipout = retval.l;      /* everything went OK, return number */
    return(NULL);         /* return OK code (no error string) */
}

int parse_ip_address(uchar* ip_str, uchar * ip_addr)
{
    uchar j;
    uchar ch;
    ushort val;
    uchar number_flag;

    /* skip spaces */
    while (*ip_str == ' ') {
        ip_str++;
    }

    for (j = 0; j < 4; j++) {
        number_flag = FALSE;
        val = 0;
        while (TRUE) {
            ch = *ip_str;

            if (!(ch >= '0' && ch <= '9')) {
                break;
            }
            number_flag = TRUE;
            ip_str++;
            val = (val * 10) + (ch - '0');
            if (val > 255) {
                return FALSE;
            }
        }
        ip_addr[j] = val;

        if (j < 3) {
            ch = *ip_str++;
            if (ch != '.') {
                return FALSE;
            }
        }
    }

    if ((j != 4) || !number_flag) {
        return FALSE;
    }

    return TRUE;
}

int main(int argc, char** argv)
{
    union {
        u_char c[4];
        u_long l;
    } tmp;
    
    char szIp[] = "192.168.16.255";
    ip_addr ip;
    unsigned sbits = 0 ;

    parse_ipad(&ip, &sbits, szIp);
    printf("%08X\n", ip);

    memcpy(&tmp, &ip, 4);
    char szbuf[64];
    memset(szbuf, 0, sizeof(szbuf));
    sprintf(szbuf, "%d.%d.%d.%d", tmp.c[0], tmp.c[1], tmp.c[2], tmp.c[3]);
    printf("%s\n", szbuf);
    
    ip = 0;
    parse_ip_address(szIp, (char*)&ip);
    memcpy(&tmp, &ip, 4);
    char szbuf[64];
    memset(szbuf, 0, sizeof(szbuf));
    sprintf(szbuf, "%d.%d.%d.%d", tmp.c[0], tmp.c[1], tmp.c[2], tmp.c[3]);
    printf("%s\n", szbuf);
}