Subversion Repositories planix.SVN

#include <math.h>
#include <errno.h>

/*
 * bug: should detect overflow, set errno = ERANGE, and return +/- HUGE_VAL
 */
double
strtod(const char *cp, char **endptr)
{
        double num, dem;
        extern double pow10(int);
        int neg, eneg, dig, predig, exp, c;
        const char *p;

        p = cp;
        num = 0;
        neg = 0;
        dig = 0;
        predig = 0;
        exp = 0;
        eneg = 0;

        c = *p++;
        while(c == ' ' || c == '\t' || c == '\n' || c == '\f' || c == '\v' || c == '\r')
                c = *p++;
        if(c == '-' || c == '+'){
                if(c == '-')
                        neg = 1;
                c = *p++;
        }
        while(c >= '0' && c <= '9'){
                num = num*10 + c-'0';
                predig++;
                c = *p++;
        }
        if(c == '.')
                c = *p++;
        while(c >= '0' && c <= '9'){
                num = num*10 + c-'0';
                dig++;
                c = *p++;
        }
        if(dig+predig == 0){
                if(endptr)
                        *endptr = (char *)cp;
                return 0.0;
        }
        if(c == 'e' || c == 'E'){
                c = *p++;
                if(c == '-' || c == '+'){
                        if(c == '-'){
                                dig = -dig;
                                eneg = 1;
                        }
                        c = *p++;
                }
                while(c >= '0' && c <= '9'){
                        exp = exp*10 + c-'0';
                        c = *p++;
                }
        }
        exp -= dig;
        if(exp < 0){
                exp = -exp;
                eneg = !eneg;
        }
        dem = pow10(exp);
        if(dem==HUGE_VAL)
                num = eneg? 0.0 : HUGE_VAL;
        else if(dem==0)
                num = eneg? HUGE_VAL : 0.0;
        else if(eneg)
                num /= dem;
        else
                num *= dem;
        if(neg)
                num = -num;
        if(endptr){
                *endptr = (char *)--p;
                /*
                 * Fix cases like 2.3e+
                 */
                while(p > cp){
                        c = *--p;
                        if(c!='-' && c!='+' && c!='e' && c!='E')
                                break;
                        (*endptr)--;
                }
        }
        return num;
}