ack/lang/cem/libcc.ansi/stdlib/strtol.c

/*
 * (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
 * See the copyright notice in the ACK home directory, in the file "Copyright".
 */
/* $Id$ */

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

static unsigned long
string2long(register const char* nptr, char** endptr,
    int base, int is_signed);

long int
strtol(register const char* nptr, char** endptr, int base)
{
	return (signed long)string2long(nptr, endptr, base, 1);
}

unsigned long int
strtoul(register const char* nptr, char** endptr, int base)
{
	return (unsigned long)string2long(nptr, endptr, base, 0);
}

static unsigned long
string2long(register const char* nptr, char** const endptr,
    int base, int is_signed)
{
	register unsigned int v;
	register unsigned long val = 0;
	register int c;
	int ovfl = 0, sign = 1;
	const char *startnptr = nptr, *nrstart;

	if (endptr)
		*endptr = (char*)nptr;
	while (isspace(*nptr))
		nptr++;
	c = *nptr;

	if (c == '-' || c == '+')
	{
		if (c == '-')
			sign = -1;
		nptr++;
	}
	nrstart = nptr; /* start of the number */

	/* When base is 0, the syntax determines the actual base */
	if (base == 0)
		if (*nptr == '0')
			if (*++nptr == 'x' || *nptr == 'X')
			{
				base = 16;
				nptr++;
			}
			else
				base = 8;
		else
			base = 10;
	else if (base == 16 && *nptr == '0' && (*++nptr == 'x' || *nptr == 'X'))
		nptr++;

	while (isdigit(c = *nptr) || isalpha(c))
	{
		if (!ovfl)
		{
			if (isalpha(c))
				v = 10 + (isupper(c) ? c - 'A' : c - 'a');
			else
				v = c - '0';
			if (v >= base)
				break;
			if (val > (ULONG_MAX - v) / base)
				++ovfl;
			else
				val = (val * base) + v;
		}
		nptr++;
	}
	if (endptr)
	{
		if (nrstart == nptr)
			*endptr = (char*)startnptr;
		else
			*endptr = (char*)nptr;
	}

	if (!ovfl)
	{
		/* Overflow is only possible when converting a signed long.
		 * The "-(LONG_MIN+1)+(unsigned long) 1" construction is there
		 * to prevent overflow warnings on -LONG_MIN.
		 */
		if (is_signed
		    && ((sign < 0 && val > -(LONG_MIN + 1) + (unsigned long)1)
		           || (sign > 0 && val > LONG_MAX)))
			ovfl++;
	}

	if (ovfl)
	{
		errno = ERANGE;
		if (is_signed)
			if (sign < 0)
				return LONG_MIN;
			else
				return LONG_MAX;
		else
			return ULONG_MAX;
	}
	return (sign * val);
}