strutil.c

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#include <ctype.h>
#include <math.h>
#include "strutil.h"

int EatWhitespace(const char **StrPtr)
{
    const char *Str = *StrPtr;

    while(isspace(*Str))
        Str++;

    *StrPtr = Str;
    return (*Str != '\0');
}


int ParseNumber(double *Number, const char **StrPtr, int FloatAllowed)
{
    const char *Str = *StrPtr;
    double Accum = 0, Div = 1, Exponent = 0;
    int Sign = 1, ExponentSign = 1;
    char c;


    /* Eat leading whitespace */
    if(!EatWhitespace(&Str))
        return 0;

    if(*Str == '-')        /* Read sign */
    {
        Sign = -1;
        Str++;
    }
    else if(*Str == '+')
        Str++;

    /* Read one or more digits appearing left of the decimal point */
    if(isdigit(c = *Str))
        Accum = c - '0';
    else
        return 0;               /* First character is not a digit */

    while(isdigit(c = *(++Str)))
        Accum = 10*Accum + (c - '0');

    if(c == '.')                /* There is a decimal point */
    {
        if(!FloatAllowed)
            return 0;

        /* Read zero or more digits appearing right of the decimal point */
        while(isdigit(c = *(++Str)))
        {
            Div *= 10;
            Accum += (c - '0')/Div;
        }
    }

    if(c == 'e' || c == 'E')    /* There is an exponent */
    {
        if(!FloatAllowed)
            return 0;

        Str++;

        if(*Str == '-')      /* Read exponent sign */
        {
            ExponentSign = -1;
            Str++;
        }
        else if(*Str == '+')
            Str++;

        /* Read digits in the exponent */
        if(isdigit(c = *Str))
        {
            Exponent = c - '0';

            while(isdigit(c = *(++Str)))
                Exponent = 10*Exponent + (c - '0');

            Exponent *= ExponentSign;
            Accum = Accum * pow(10, Exponent);
        }
        else
            return 0;
    }

    *Number = Sign*Accum;
    *StrPtr = Str;
    return 1;
}