Subversion Repositories planix.SVN

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

/*
 * Reads a floating-point number by interpreting successive characters
 * returned by (*f)(vp).  The last call it makes to f terminates the
 * scan, so is not a character in the number.  It may therefore be
 * necessary to back up the input stream up one byte after calling charstod.
 */

#define ADVANCE *s++ = c; if(s>=e) return NaN(); c = (*f)(vp)

double
charstod(int(*f)(void*), void *vp)
{
        char str[400], *s, *e, *start;
        int c;

        s = str;
        e = str + sizeof str - 1;
        c = (*f)(vp);
        while(c == ' ' || c == '\t')
                c = (*f)(vp);
        if(c == '-' || c == '+'){
                ADVANCE;
        }
        start = s;
        while(c >= '0' && c <= '9'){
                ADVANCE;
        }
        if(c == '.'){
                ADVANCE;
                while(c >= '0' && c <= '9'){
                        ADVANCE;
                }
        }
        if(s > start && (c == 'e' || c == 'E')){
                ADVANCE;
                if(c == '-' || c == '+'){
                        ADVANCE;
                }
                while(c >= '0' && c <= '9'){
                        ADVANCE;
                }
        }else if(s == start && (c == 'i' || c == 'I')){
                ADVANCE;
                if(c != 'n' && c != 'N')
                        return NaN();
                ADVANCE;
                if(c != 'f' && c != 'F')
                        return NaN();
                ADVANCE;
                if(c != 'i' && c != 'I')
                        return NaN();
                ADVANCE;
                if(c != 'n' && c != 'N')
                        return NaN();
                ADVANCE;
                if(c != 'i' && c != 'I')
                        return NaN();
                ADVANCE;
                if(c != 't' && c != 'T')
                        return NaN();
                ADVANCE;
                if(c != 'y' && c != 'Y')
                        return NaN();
                ADVANCE;  /* so caller can back up uniformly */
                USED(c);
        }else if(s == str && (c == 'n' || c == 'N')){
                ADVANCE;
                if(c != 'a' && c != 'A')
                        return NaN();
                ADVANCE;
                if(c != 'n' && c != 'N')
                        return NaN();
                ADVANCE;  /* so caller can back up uniformly */
                USED(c);
        }
        *s = 0;
        return strtod(str, &s);
}