V6/usr/source/s4/atoi.c

atoi(ap)
char *ap;
{
	register n, c;
	register char *p;
	int f;

	p = ap;
	n = 0;
	f = 0;
loop:
	while(*p == ' ' || *p == '	')
		p++;
	if(*p == '-') {
		f++;
		p++;
		goto loop;
	}
	while(*p >= '0' && *p <= '9')
		n = n*10 + *p++ - '0';
	if(f)
		n = -n;
	return(n);
}