ft_atoi.c

/* ************************************************************************** */
/*                                                                            */
/*                                                        :::      ::::::::   */
/*   ft_atoi.c                                          :+:      :+:    :+:   */
/*                                                    +:+ +:+         +:+     */
/*   By: edebi <edebi@student.42.fr>                +#+  +:+       +#+        */
/*                                                +#+#+#+#+#+   +#+           */
/*   Created: 2020/09/14 19:45:54 by edebi             #+#    #+#             */
/*   Updated: 2020/11/03 16:24:43 by edebi            ###   ########.fr       */
/*                                                                            */
/* ************************************************************************** */

#include "libft.h"

int	ft_atoi(char *str)
{
	int					i;
	int					sign;
	unsigned long long	res;

	res = 0;
	sign = 1;
	i = 0;
	while (str[i] == '\t' || str[i] == '\n' || str[i] == '\v' || str[i] == '\f'
			|| str[i] == '\r' || str[i] == ' ')
		i++;
	if (str[i] == '-' || str[i] == '+')
	{
		if (str[i] == '-')
			sign *= -1;
		i++;
	}
	while (str[i] > 47 && str[i] < 58)
	{
		res = (res * 10) + (str[i] - 48);
		i++;
	}
	if (i > 19 || res >= 9223372036854775808ULL)
		return (sign == 1 ? -1 : 0);
	return (res * sign);
}