ft_strnstr.c

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/* ************************************************************************** */
/*                                                                            */
/*                                                        :::      ::::::::   */
/*   ft_strnstr.c                                       :+:      :+:    :+:   */
/*                                                    +:+ +:+         +:+     */
/*   By: tspoof <tspoof@student.hive.fi>            +#+  +:+       +#+        */
/*                                                +#+#+#+#+#+   +#+           */
/*   Created: 2022/11/01 15:17:40 by tspoof            #+#    #+#             */
/*   Updated: 2022/12/08 00:53:31 by tspoof           ###   ########.fr       */
/*                                                                            */
/* ************************************************************************** */
 
#include "libft.h"
 
// First checks if needles first char matches with a char in haystack.
// Then compares needles and haystacks characters one by one
// from that point froward.
char    *ft_strnstr(const char *haystack, const char *needle, size_t len)
{
    size_t      i;
    size_t      j;
    size_t      needle_len;
 
    if (*needle == '\0' || haystack == needle)
        return ((char *)haystack);
    if (len == 0)
        return (NULL);
    needle_len = ft_strlen(needle);
    i = 0;
    while (i < len && haystack[i])
    {
        if (haystack[i] == needle[0])
        {
            j = 0;
            while (needle[j] && haystack[i + j] && haystack[i + j] == needle[j]
                && i + j < len)
                j++;
            if (j == needle_len)
                return ((char *)haystack + i);
        }
        i++;
    }
    return (NULL);
}