strtol.c

最新Minix3源码

/*
 * (c) copyright 1987 by the Vrije Universiteit, Amsterdam, The Netherlands.
 * See the copyright notice in the ACK home directory, in the file "Copyright".
 */
/* $Header: strtol.c,v 1.4 90/05/11 15:22:19 eck Exp $ */

#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);
}

#define between(a, c, z)  ((unsigned) ((c) - (a)) <= (unsigned) ((z) - (a)))

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++;

	for (;;) {
		c = *nptr;
		if (between('0', c, '9')) {
			v = c - '0';
		} else
		if (between('a', c, 'z')) {
			v = c - 'a' + 0xa;
		} else
		if (between('A', c, 'Z')) {
			v = c - 'A' + 0xA;
		} else {
			break;
		}
		if (v >= base) break;
		if (val > (ULONG_MAX - v) / base) ovfl++;
		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. */
		if (is_signed
		    && (   (sign < 0 && val > -(unsigned long)LONG_MIN)
			|| (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 (long) sign * val;
}