ft_atol.c

/* ************************************************************************** */
/*                                                                            */
/*                                                        :::      ::::::::   */
/*   ft_atol.c                                          :+:      :+:    :+:   */
/*                                                    +:+ +:+         +:+     */
/*   By: yshimoda <yshimoda@student.42tokyo.jp>     +#+  +:+       +#+        */
/*                                                +#+#+#+#+#+   +#+           */
/*   Created: 2022/10/19 19:14:41 by yshimoda          #+#    #+#             */
/*   Updated: 2022/10/19 19:40:31 by yshimoda         ###   ########.fr       */
/*                                                                            */
/* ************************************************************************** */

#include "libft.h"

static int	ft_check_over(int sign, long ans, char c)
{
	long	tmp;

	tmp = LONG_MAX / 10;
	if (sign == 1)
		c++;
	if (tmp < ans || (tmp == ans && LONG_MAX % 10 + 1 < c - '0'))
		return (1);
	return (0);
}

long	ft_atol(const char *str)
{
	int		sign;
	long	total;

	sign = 1;
	total = 0;
	while (*str == '\t' || *str == '\n' || *str == '\v'
		|| *str == '\f' || *str == '\r' || *str == ' ')
		str++;
	if (*str == '-')
		sign *= -1;
	if (*str == '-' || *str == '+')
		str++;
	while ('0' <= *str && *str <= '9')
	{
		if (sign == 1 && ft_check_over(sign, total, *str))
			return (LONG_MAX);
		if (sign == -1 && ft_check_over(sign, total, *str))
			return (LONG_MIN);
		total = total * 10 + *str - '0';
		str++;
	}
	total *= sign;
	return (total);
}