Subversion Repositories planix.SVN

#include <u.h>
#include <libc.h>

#define ULONG_MAX       4294967295UL

ulong
strtoul(char *nptr, char **endptr, int base)
{
        char *p;
        ulong n, nn, m;
        int c, ovfl, neg, v, ndig;

        p = nptr;
        neg = 0;
        n = 0;
        ndig = 0;
        ovfl = 0;

        /*
         * White space
         */
        for(;;p++){
                switch(*p){
                case ' ':
                case '\t':
                case '\n':
                case '\f':
                case '\r':
                case '\v':
                        continue;
                }
                break;
        }

        /*
         * Sign
         */
        if(*p=='-' || *p=='+')
                if(*p++ == '-')
                        neg = 1;

        /*
         * Base
         */
        if(base==0){
                if(*p != '0')
                        base = 10;
                else{
                        base = 8;
                        if(p[1]=='x' || p[1]=='X')
                                base = 16;
                }
        }
        if(base<2 || 36<base)
                goto Return;
        if(base==16 && *p=='0'){
                if(p[1]=='x' || p[1]=='X')
                        if(('0' <= p[2] && p[2] <= '9')
                         ||('a' <= p[2] && p[2] <= 'f')
                         ||('A' <= p[2] && p[2] <= 'F'))
                                p += 2;
        }
        /*
         * Non-empty sequence of digits
         */
        n = 0;
        m = ULONG_MAX/base;
        for(;; p++,ndig++){
                c = *p;
                v = base;
                if('0'<=c && c<='9')
                        v = c - '0';
                else if('a'<=c && c<='z')
                        v = c - 'a' + 10;
                else if('A'<=c && c<='Z')
                        v = c - 'A' + 10;
                if(v >= base)
                        break;
                if(n > m)
                        ovfl = 1;
                nn = n*base + v;
                if(nn < n)
                        ovfl = 1;
                n = nn;
        }

    Return:
        if(ndig == 0)
                p = nptr;
        if(endptr)
                *endptr = p;
        if(ovfl)
                return ULONG_MAX;
        if(neg)
                return -n;
        return n;
}