ft_strtol.c

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/* ************************************************************************** */
/*                                                                            */
/*                                                        :::      ::::::::   */
/*   ft_strtol.c                                        :+:      :+:    :+:   */
/*                                                    +:+ +:+         +:+     */
/*   By: kfujita <kfujita@student.42tokyo.jp>       +#+  +:+       +#+        */
/*                                                +#+#+#+#+#+   +#+           */
/*   Created: 2022/04/23 22:28:22 by kfujita           #+#    #+#             */
/*   Updated: 2022/04/25 23:30:03 by kfujita          ###   ########.fr       */
/*                                                                            */
/* ************************************************************************** */
 
#include <limits.h>
#include "ft_string.h"
 
static int  get_36based_value(char c)
{
    if ('0' <= c && c <= '9')
        return (c - '0');
    else if ('a' <= c && c <= 'z')
        return (c - 'a' + 10);
    else if ('A' <= c && c <= 'Z')
        return (c - 'A' + 10);
    else
        return (-1);
}
 
static int  set_value(char c, long *p_value, int sign, int base)
{
    int     num_value;
    long    value_tmp;
 
    num_value = get_36based_value(c);
    if (num_value < 0 || base <= num_value)
        return (0 == 1);
    num_value *= sign;
    value_tmp = (*p_value) * base;
    if (sign > 0 && (((LONG_MAX / base) < *p_value)
            || ((LONG_MAX - value_tmp) < num_value)))
        *p_value = LONG_MAX;
    else if (sign < 0 && (((LONG_MIN / base) > *p_value)
            || ((LONG_MIN - value_tmp) > num_value)))
        *p_value = LONG_MIN;
    else
    {
        *p_value = value_tmp + num_value;
        return (0 == 0);
    }
    return (0 == 1);
}
 
static int  get_base(const char **p_str, const int base)
{
    if (base != 0)
        return (base);
    if ((*p_str)[0] == '0')
    {
        if ((*p_str)[1] == 'x')
        {
            (*p_str)++;
            return (16);
        }
        else
            return (8);
    }
    return (10);
}
 
long    ft_strtol(const char *str, char **endptr, int base)
{
    long    sign;
    long    value;
 
    sign = 1;
    value = 0;
    if (endptr != NULL)
        *endptr = (char *)str;
    if (!((2 <= base && base <= 36) || base == 0))
        return (0);
    while (((9 <= *str && *str <= 13) || *str == ' ') && *str != '\0')
        str++;
    if (*str == '-')
        sign = -1;
    else if (*str != '+' && !(('a' <= *str && *str <= 'z')
            || ('A' <= *str && *str <= 'Z') || ('0' <= *str && *str <= '9')))
        return (0);
    if (*str == '+' || *str == '-')
        str++;
    base = get_base(&str, base);
    while (set_value(*str, &value, sign, base))
        str++;
    if (endptr != NULL)
        *endptr = (char *)str;
    return (value);
}