Prevent plugin from deleting important directories

To answer my own question here is what I’ve found for the sake of keeping questions answered. What this does is copying the important directory before upgrade and recovering it after upgrade:

function my_dir_copy($source, $dest)
{
    if (is_link($source)) {
        return symlink(readlink($source), $dest);
    }
    if (is_file($source)) {
        return copy($source, $dest);
    }
    if (!is_dir($dest)) {
        mkdir($dest);
    }
    $dir = dir($source);
    while (false !== $entry = $dir->read()) {
        if ($entry == '.' || $entry == '..') {
            continue;
        }
        my_dir_copy("$source/$entry", "$dest/$entry");
    }

    $dir->close();
    return true;
}


function my_dir_rmdirr($dirname)
{

    if (!file_exists($dirname)) {
        return false;
    }


    if (is_file($dirname)) {
        return unlink($dirname);
    }


    $dir = dir($dirname);
    while (false !== $entry = $dir->read()) {

        if ($entry == ‘.’ || $entry == ‘..’) {
        continue;
        }
        rmdirr(“$dirname/$entry”);
    }


    $dir->close();
    return rmdir($dirname);
}


function my_dir_backup()
{
        $to = dirname(__FILE__)."/../igr_backup/";
        $from = dirname(__FILE__)."/whatever_directory_you_preserve/";
        my_dir_copy($from, $to);
}
function my_dir_recover()
{
        $from = dirname(__FILE__)."/../igr_backup/";
        $to = dirname(__FILE__)."/whatever_directory_you_preserve/";
        my_dir_copy($from, $to);
        if (is_dir($from)) {
                my_dir_rmdirr($from);
        }
}
add_filter('upgrader_pre_install', 'my_dir_backup', 10, 2);
add_filter('upgrader_post_install', 'my_dir_recover', 10, 2);