char	*ft_strstr(const char *str, const char *sub)
{
	int i;
	int pos;
	int len;

	i = 0;
	pos = 0;
	len = 0;
	while (sub[len] != '\0')
		len++;
	if (len == 0)
		return ((char *)str);
	while (str[i])
	{
		pos = 0;
		while (sub[pos] == str[i + pos])
		{
			if (pos == len - 1)
				return ((char *)str + i);
			pos++;
		}
		i++;
	}
	return (NULL);
}