---
layout: docs
title: preprocess
id: class.Facebook.HackCodegen.SignedSourceBase.preprocess
docid: class.Facebook.HackCodegen.SignedSourceBase.preprocess
permalink: /docs/reference/class.Facebook.HackCodegen.SignedSourceBase.preprocess/
---
# Facebook\\HackCodegen\\SignedSourceBase::preprocess()




Override this method to process the file data before signing a file
or before checking the signature




``` Hack
protected static function preprocess(
  string $file_data,
): string;
```




## Parameters




+ ` string $file_data `




## Returns




* ` string `