tanaikech / unzipgs

This is a GAS library for unzipping a Zip file protected by a password using Google Apps Script.

UnzipGs

Overview

This is a GAS library for unzipping a Zip file protected by a password using Google Apps Script.

Description

Recently, I had a situation that it is required to unzip a Zip file protected with the password. But unfortunately, in the current stage, the method of Utilities.unzip() cannot unzip such protected files. So when I had been looking for the other workarounds, I found zlib.js. Especially, it's unzip.min.js. This is created for Javascript. So when I used this using Google Apps Script, it was found that it didn't work for Google Apps Script. So I prepared a wrapper script for running it with Google Apps Script. And when I created the wrapper script, I thought that under the current stage, if the protected Zip file can be unzipped, this will be useful for other users. So I created this as a GAS library.

Library's project key

1yeBx1bM_6T-Tt2S3e-wxSgphR2QdhM7r0YRYAUTXzDkbRIrvJdHNZT0R

How to install

• Open Script Editor. And please operate follows by click.
• -> Resource
• -> Library
• -> Input Script ID to text box. Script ID is 1yeBx1bM_6T-Tt2S3e-wxSgphR2QdhM7r0YRYAUTXzDkbRIrvJdHNZT0R.
• -> Add library
• -> Please select latest version
• -> Developer mode ON (If you don't want to use latest version, please select others.)
• -> Identifier is "UnzipGs". This is set under the default.

If you want to read about Libraries, please check this..

About scopes

This library uses no scopes.

Methods

In the current stage, there are 2 methods.

1. unzip(blob, object)

2. getFilenames(blob, object)

1. unzip(blob, object)

This method unzips a Zip file. blob is the file blob of the Zip file. The protected Zip file can be unzipped by setting the password to object. The response value is []blob including the file blobs.

If password is not included in object, the zip file is decompressed using Utilities.unzip().

Sample script

function sample() {
  var id = "###"; // File ID of Zip file.
  var pass = "###"; // Password.

  var blob = DriveApp.getFileById(id).getBlob();
  var res = UnzipGs.unzip(blob, { password: pass }); // or UnzipGs.unzip(blob);
  res.forEach(function(e) {
    Logger.log(
      "filename: %s, mimeType: %s, size: %s",
      e.getName(),
      e.getContentType(),
      e.getBytes().length
    );
  });
}

2. getFilenames(blob, object)

This method retrieves the filenames in the Zip file. There are no methods for retrieving the filenames from the Zip file in Google Apps Script. So I added this. This also uses zlib.js.

Sample script

function sample() {
  var id = "###"; // File ID of Zip file.
  var pass = "###"; // Password.

  var blob = DriveApp.getFileById(id).getBlob();
  var res = UnzipGs.getFilenames(blob, { password: pass }); // or UnzipGs.getFilenames(blob);
  Logger.log(res);
}

Process cost

About the process cost for decompressing, the cost of UnzipGs.unzip() is much higher than that of Utilities.unzip().

• For example, in my environment, when a protected Zip file with the size of 1 MB is unzipped using this library, the process time was about 60 seconds to 90 seconds.

• On the other hand, when Utilities.unzip() is used for the same file without the password, the process time was about 1 second.

IMPORTANT

• When this library is used, please be careful the file size of the Zip file and unzipped files. Because the maximum size of blob which can be used for Google Apps Script is 50 MB (52,428,800 bytes).

• But, when the Zip file is unzipped without using Utilities.unzip() by Google Apps Script, the process cost becomes very high. So I think that the practical size will be required to become smaller.

• By this situation, unfortunately, I couldn't implement the method for zipping.

• The reason of this issue is due to the process of Google Apps Script. For example, if v8 engine can be used with Google Apps Script in the future, this situation will be changed. I would like to expect this.

• Or Google might also update Utilities.unzip() by including the method for decompressing the protected Zip file in the future.

Acknowledgement

• Imaya Yuta: He is the author of zlib.js.
  • This library (UnzipGs) uses unzip.min.js of zlib.js. So this library is a wrapper script for running unzip.min.js, which is for Javascript, with Google Apps Script.

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Licence

MIT

Author

Tanaike

If you have any questions and commissions for me, feel free to contact me.

Update History

• v1.0.0 (July 26, 2019)

  1. Initial release.

• v1.0.1 (April 22, 2021)

  1. A bug was removed. Ref

Testing

• September 16, 2020: When I used a sample zip file with the password, I could confirm that the script worked. But, unfortunately, it seems that unzip.min.js cannot be used with v8 runtime. So when this library is used, please disable V8 runtime at the script editor.

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