ft_atoi.c

/* ************************************************************************** */
/*                                                                            */
/*                                                        :::      ::::::::   */
/*   atoi.c                                             :+:      :+:    :+:   */
/*                                                    +:+ +:+         +:+     */
/*   By: dskrypny <marvin@42.fr>                    +#+  +:+       +#+        */
/*                                                +#+#+#+#+#+   +#+           */
/*   Created: 2017/10/31 19:59:24 by dskrypny          #+#    #+#             */
/*   Updated: 2018/05/23 19:08:05 by dskrypny         ###   ########.fr       */
/*                                                                            */
/* ************************************************************************** */

#include "libft.h"

int		ft_atoi(const char *str)
{
	unsigned long	res;
	size_t			i;
	int				flag;

	i = 0;
	flag = 1;
	res = 0;
	while ((str[i] <= '\r' && str[i] >= '\t') || str[i] == ' ')
		i++;
	if (str[i] == '-' || str[i] == '+')
	{
		if (str[i] == '-')
			flag = -1;
		i++;
	}
	while (str[i] && (str[i] <= '9' && str[i] >= '0'))
	{
		res = res * 10 + str[i] - '0';
		if (res > 922337236854775807 && flag == 1)
			return (-1);
		if (res > 922337236854775808 && flag == -1)
			return (0);
		i++;
	}
	return ((int)res * flag);
}