ft_atoi.c

/* ************************************************************************** */
/*                                                                            */
/*                                                        :::      ::::::::   */
/*   ft_atoi.c                                          :+:      :+:    :+:   */
/*                                                    +:+ +:+         +:+     */
/*   By: ide-spir <marvin@42.fr>                    +#+  +:+       +#+        */
/*                                                +#+#+#+#+#+   +#+           */
/*   Created: 2022/01/04 16:22:57 by ide-spir          #+#    #+#             */
/*   Updated: 2022/01/19 17:16:18 by ide-spir         ###   ########.fr       */
/*                                                                            */
/* ************************************************************************** */

#include "libft.h"

static int	check_char(const char *str, int *sign)
{
	int	i;

	i = 0;
	while (str[i] == ' ' || (str[i] >= '\t' && str[i] <= '\r'))
		i++;
	if (str[i] == '-' || str[i] == '+')
	{
		if (str[i] == '-')
			*sign = -1;
		i++;
	}
	return (i);
}

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

	sign = 1;
	res = 0;
	i = 0;
	i = check_char(str, &sign);
	while (str[i] >= '0' && str[i] <= '9')
	{
		res = res * 10 + str[i] - '0';
		if (res > 9223372036854775807)
		{
			if (sign == -1)
				return (0);
			return (-1);
		}
		i++;
	}
	return (res * sign);
}