cpython/Python/mystrtoul.c

/***********************************************************
Copyright 1991, 1992, 1993 by Stichting Mathematisch Centrum,
Amsterdam, The Netherlands.

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******************************************************************/

/*
**	strtoul
**		This is a general purpose routine for converting
**		an ascii string to an integer in an arbitrary base.
**		Leading white space is ignored.  If 'base' is zero
**		it looks for a leading 0, 0x or 0X to tell which
**		base.  If these are absent it defaults to 10.
**		Base must be 0 or between 2 and 36 (inclusive).
**		If 'ptr' is non-NULL it will contain a pointer to
**		the end of the scan.
**		Errors due to bad pointers will probably result in
**		exceptions - we don't check for them.
*/

#include <ctype.h>
#include <errno.h>

unsigned long
strtoul(str, ptr, base)
register char *	str;
char **		ptr;
int		base;
{
    register unsigned long	result;	/* return value of the function */
    register int		c;	/* current input character */
    register unsigned long	temp;	/* used in overflow testing */
    int				ovf;	/* true if overflow occurred */

    result = 0;
    ovf = 0;

/* catch silly bases */
    if (base != 0 && (base < 2 || base > 36))
    {
	if (ptr)
	    *ptr = str;
	return 0;
    }

/* skip leading white space */
    while (*str && isspace(*str))
	str++;

/* check for leading 0 or 0x for auto-base or base 16 */
    switch (base)
    {
    case 0:		/* look for leading 0, 0x or 0X */
	if (*str == '0')
	{
	    str++;
	    if (*str == 'x' || *str == 'X')
	    {
		str++;
		base = 16;
	    }
	    else
		base = 8;
	}
	else
	    base = 10;
	break;

    case 16:	/* skip leading 0x or 0X */
	if (*str == '0' && (*(str+1) == 'x' || *(str+1) == 'X'))
	    str += 2;
	break;
    }

/* do the conversion */
    while (c = *str)
    {
	if (isdigit(c) && c - '0' < base)
	    c -= '0';
	else
	{
	    if (isupper(c))
		c = tolower(c);
	    if (c >= 'a' && c <= 'z')
		c -= 'a' - 10;
	    else	/* non-"digit" character */
		break;
	    if (c >= base)	/* non-"digit" character */
		break;
	}
	temp = result;
	result = result * base + c;
	if ((result - c) / base != temp)	/* overflow */
	    ovf = 1;
	str++;
    }

/* set pointer to point to the last character scanned */
    if (ptr)
	*ptr = str;
    if (ovf)
    {
	result = ~0;
	errno = ERANGE;
    }
    return result;
}

long
strtol(str, ptr, base)
char *	str;
char ** ptr;
int	base;
{
	long result;
	char sign;
	
	while (*str && isspace(*str))
		str++;
	
	sign = *str;
	if (sign == '+' || sign == '-')
		str++;
	
	result = (long) strtoul(str, ptr, base);
	
	/* Signal overflow if the result appears negative,
	   except for the largest negative integer */
	if (result < 0 && !(sign == '-' && result == -result)) {
		errno = ERANGE;
		result = 0x7fffffff;
	}
	
	if (sign == '-')
		result = -result;
	
	return result;
}