ft_atoi.c

/* ************************************************************************** */
/*                                                                            */
/*                                                        :::      ::::::::   */
/*   ft_atoi.c                                          :+:      :+:    :+:   */
/*                                                    +:+ +:+         +:+     */
/*   By: juchoi <juchoi@student.42seoul.kr>         +#+  +:+       +#+        */
/*                                                +#+#+#+#+#+   +#+           */
/*   Created: 2021/01/21 20:27:21 by juchoi            #+#    #+#             */
/*   Updated: 2021/01/21 20:27:25 by juchoi           ###   ########.fr       */
/*                                                                            */
/* ************************************************************************** */

#include "libft.h"

static int		is_space(char c)
{
	if (c == ' ' || c == '\n' || c == '\t' ||
			c == '\v' || c == '\f' || c == '\r')
		return (1);
	return (0);
}

int				ft_atoi(const char *str)
{
	int			i;
	int			sign;
	long long	num;

	i = 0;
	num = 0;
	sign = 1;
	while (str[i] != '\0' && is_space(str[i]))
		i++;
	if (str[i] == '-' || str[i] == '+')
	{
		if (str[i] == '-')
			sign *= -1;
		i++;
	}
	while (str[i] != '\0' && str[i] >= '0' && str[i] <= '9')
	{
		if (num * sign > 2147483647)
			return (-1);
		if (num * sign < -2147483648)
			return (0);
		num = (num * 10) + (str[i] - '0');
		i++;
	}
	return (sign * num);
}