ft_atoi.c

/* ************************************************************************** */
/*                                                                            */
/*                                                        :::      ::::::::   */
/*   ft_atoi.c                                          :+:      :+:    :+:   */
/*                                                    +:+ +:+         +:+     */
/*   By: kyalexan <marvin@42.fr>                    +#+  +:+       +#+        */
/*                                                +#+#+#+#+#+   +#+           */
/*   Created: 2021/11/22 10:26:01 by kyalexan          #+#    #+#             */
/*   Updated: 2021/12/15 12:58:25 by kyalexan         ###   ########.fr       */
/*                                                                            */
/* ************************************************************************** */

#include "libft.h"

static int	ft_isspace(char c)
{
	return (c == ' ' || c == '\n' \
				|| c == '\t' || c == '\v' \
				|| c == '\f' || c == '\r');
}

static void	handle_spaces(const char *nptr, int *i)
{
	while (ft_isspace(nptr[*i]))
		(*i)++;
}

static int	handle_sign(char c, int *i)
{
	int	sign;

	sign = 1;
	if (c == '-')
	{
		sign = -1;
		(*i)++;
	}
	else if (c == '+')
		(*i)++;
	return (sign);
}

static int	ft_strcmp(const char *s1, const char *s2)
{
	int	i;

	i = 0;
	while (s1[i] || s2[i])
	{
		if (s1[i] != s2[i])
			return ((unsigned char)s1[i] - (unsigned char)s2[i]);
		i++;
	}
	return (0);
}

int	ft_atoi(const char *nptr)
{
	int	number;
	int	sign;
	int	i;

	i = 0;
	handle_spaces(nptr, &i);
	sign = handle_sign(nptr[i], &i);
	number = 0;
	if (!ft_strcmp(nptr + i, "0"))
		return (0);
	else if (!ft_strcmp(nptr + i, "2147483647"))
		return (2147483647);
	else if (!ft_strcmp(nptr + i, "2147483648") && sign == -1)
		return (-2147483648);
	while (ft_isdigit(nptr[i]))
	{
		number *= 10;
		number += nptr[i] - '0';
		i++;
	}
	return (number * sign);
}