1#include <stdlib.h>
 2#include <ctype.h>
 3
 4long atol(const char *s)
 5{
 6	long n=0;
 7	int neg=0;
 8	while (isspace(*s)) s++;
 9	switch (*s) {
10	case '-': neg=1;
11	case '+': s++;
12	}
13	/* Compute n as a negative number to avoid overflow on LONG_MIN */
14	while (isdigit(*s))
15		n = 10*n - (*s++ - '0');
16	return neg ? n : -n;
17}