ngspice/src/frontend/parser/numparse.c

/**********
Copyright 1990 Regents of the University of California.  All rights reserved.
Author: 1985 Wayne A. Christopher, U. C. Berkeley CAD Group
**********/

/* This routine parses a number.  */

#include <config.h>
#include <ngspice.h>
#include <bool.h>
#include "ftedefs.h"
#include "numparse.h"


static double
power10(double num)   /* Chris Inbody */
{
    double d = 1.0;

    while (num-- > 0)
        d *= 10.0;
    return (d);
}


bool ft_strictnumparse = FALSE;

/* Parse a number. This will handle things like 10M, etc... If the number
 * must not end before the end of the string, then whole is TRUE.
 * If whole is FALSE and there is more left to the number, the argument
 * is advanced to the end of the word. Returns NULL
 * if no number can be found or if there are trailing characters when
 * whole is TRUE.
 *
 * If ft_strictnumparse is TRUE, and whole is FALSE, the first of the
 * trailing characters must be a '_'.  */
double *
ft_numparse(char **s, bool whole)
{
    double mant = 0.0;
    int sign = 1, exsign = 1, p;
    double expo = 0.0;
    static double num;
    char *string = *s;

    /* See if the number begins with + or -. */
    if (*string == '+')
        string++;
    else if (*string == '-') {
        string++;
        sign = -1;
    }

    /* We don't want to recognise "P" as 0P, or .P as 0.0P... */
    if ((!isdigit(*string) && *string != '.') ||
            ((*string == '.') && !isdigit(string[1])))
        return (NULL);

    /* Now accumulate a number. Note ascii dependencies here... */
    while (isdigit(*string))
        mant = mant * 10.0 + (*string++ - '0');
    
    /* Now maybe a decimal point. */
    if (*string == '.') {
        string++;
        p = 1;
        while (isdigit(*string))
            mant += (*string++ - '0') / power10(p++);
    }

    /* Now look for the scale factor or the exponent (can't have both). */
    switch (*string) {
        case 'e':
        case 'E':
            /* Parse another number. */
            string++;
            if (*string == '+') {
                exsign = 1;
                string++;
            } else if (*string == '-') {
                exsign = -1;
                string++;
            }
            while(isdigit(*string))
                expo = expo * 10.0 + (*string++ - '0');
            if (*string == '.') {
                string++;
                p = 1;
                while (isdigit(*string))
                    expo += (*string++ - '0') / power10(p++);
            }
            expo *= exsign;
            break;
        case 't':
        case 'T':
            expo = 12.0;
            string++;
            break;
        case 'g':
        case 'G':
            expo = 9.0;
            string++;
            break;
        case 'k':
        case 'K':
            expo = 3.0;
            string++;
            break;
        case 'u':
        case 'U':
            expo = -6.0;
            string++;
            break;
        case 'n':
        case 'N':
            expo = -9.0;
            string++;
            break;
        case 'p':
        case 'P':
            expo = -12.0;
            string++;
            break;
        case 'f':
        case 'F':
            expo = -15.0;
            string++;
            break;
        case 'm':
        case 'M':
            /* Can be either m, mil, or meg. */
            if (string[1] && string[2] && 
                ((string[1] == 'e') || (string[1] == 'E')) &&
                ((string[2] == 'g') || (string[2] == 'G'))) {
                expo = 6.0;
                string += 3;
            } else if (string[1] && string[2] && 
                ((string[1] == 'i') || (string[1] == 'I')) &&
                ((string[2] == 'l') || (string[2] == 'L'))) {
                expo = -6.0;
                mant *= 25.4;
                string += 3;
            } else {
                expo = -3.0;
                string++;
            }
            break;
    }

    if (whole && *string != '\0') {
        return (NULL);
    } else if (ft_strictnumparse && *string && isdigit(string[-1])) {
        if (*string == '_')
            while (isalpha(*string) || (*string == '_'))
                string++;
        else
            return (NULL);
    } else {
        while (isalpha(*string) || (*string == '_'))
            string++;
    }
    *s = string;
    num = sign * mant * pow(10.0, expo);
    if (ft_parsedb)
        fprintf(cp_err, "numparse: got %e, left = %s\n", num, *s);
    return (&num);
}