The file is overwritten when uploading a file with the same name

Please help somehow

EC site to create a "ubercart_marketplace" are using to upload the file.

If there are files with the same name in upload folder, the file will be overwritten without being renamed.

"mp_file.module" I think you have not worked well in the following code.

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function mp_file_mp_file_name($dir, $file_name, $file_name_ext, $node_id, $title ,$new_name_hook ) {
$node_sanitized_title = preg_replace('/[^0-9a-z\.\_\-]/i', '', $title);

$new_file_name = $node_id . "_" . $file_name . "." . $file_name_ext;

// We could now return $new_file_name but first let's rename it if this file name already exists.
// NB: $file_name also has a counter in it for files in the temp directory
$i_file = 0;
while (file_exists($dir . $new_file_name)) {
$i_file++;
$new_file_name = $node_id . "_" . $file_name . "_" . sprintf('%03d', $i_file) . "." . $file_name_ext;
}

return $new_file_name;
}
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If the file already existed with the same name, to rename the file? How can I.

Has created a website to sell digital content, and products will be replaced by sliding the file is overwritten. We think a very big problem.

Please tell us.
Thank you.