Can I ungzip files in Google Drive with apps script? - google-apps-script

Question

This is a follow-up to this thread.
I am trying to use the code provided by #July.Tech there, but I keep getting unknown compression method error or incorrect header check error. The error came up when either of two different gzip methods were used to create the compressed file, so I would think the file is correctly gzipped.
Any suggestions? (My input file is gzipped so I cannot use Utilities.unzip().)
Here is the entire code:
reports_folder_id = 'xxxxx'; //id of folder where gzipped csv reports are saved
report_name = 'xxxxxx.gz'; // name of gzipped CSV file
function importData() {
var fSource = DriveApp.getFolderById(reports_folder_id);
var fi = fSource.getFilesByName(report_name); // latest report file
eval(UrlFetchApp.fetch('https://cdn.rawgit.com/nodeca/pako/master/dist/pako.js').getContentText());
if ( fi.hasNext() ) { // proceed if report_name file exists in the reports folder
var file = fi.next();
var charData = file.getBlob().getDataAsString(); // same error if .getBytes() is used
var binData = [];
for (var i = 0; i < charData.length; i++) {
binData.push(charData[i] < 0 ? charData[i] + 256 : charData[i]);
}
var data = pako.ungzip(binData); // I get same error for pako.inflate(binData);
var decoded = '';
for (var i = 0; i < data.length; i++) {
decoded += String.fromCharCode(data[i]);
}
}
}
If no suggestion for fixing the above, any ideas on how to ungzip a gDrive file programatically?
Thanks.

Answer 1

As of January 19, 2018 (see release notes) Apps Script now supports gzip compression accessible using the following Utilities methods:
gzip(blob)
ungzip(blob)

Answer 2

Running the supplied example code indeed results in unknown compression method error in my environment as well.
Try changing
var charData = file.getBlob().getDataAsString(); // same error if .getBytes() is used
To
var charData = file.getBlob().getBytes();
So that is
function myFunction() {
reports_folder_id = '<FOLDER_ID>';
report_name = 'zip3.csv.gz'; // name of gzipped CSV file
var fSource = DriveApp.getFolderById(reports_folder_id);
var fi = fSource.getFilesByName(report_name);
eval(UrlFetchApp.fetch('https://cdn.rawgit.com/nodeca/pako/master/dist/pako.js').getContentText());
if ( fi.hasNext() ) {
var file = fi.next();
var blobData = file.getBlob();
var charData = blobData.getBytes();
var binData = [];
for (var i = 0; i < charData.length; i++) {
binData.push(charData[i] < 0 ? charData[i] + 256 : charData[i]);
}
var data = pako.inflate(binData);
var decoded = '';
for (var i = 0; i < data.length; i++) {
decoded += String.fromCharCode(data[i]);
}
Logger.log(decoded);
}
}
Try running this script on a subset of your original "GlicemiaMisurazioni.csv.gz" file: https://drive.google.com/file/d/0B8geUNXmd4J2YzJoemFLMnBTbVU/view?usp=sharing
(I truncated the original csv to 32 rows to speed up execution for the sake of test – the original takes way too long to run)
Checking the logs shows that the uncompressing worked:
4;02/07/2017 03.00.30;;;158.0;158.0;1;0M0000UMQ5D;;;0;;
4;02/07/2017 02.59.30;;;158.0;158.0;1;0M0000UMQ5D;;;0;;
4;02/07/2017 02.58.30;;;159.0;159.0;1;0M0000UMQ5D;;;0;;
4;02/07/2017 02.57.30;;;159.0;159.0;1;0M0000UMQ5D;;;0;;
4;02/07/2017 02.56.30;;;158.0;158.0;1;0M0000UMQ5D;;;0;;
4;02/07/2017 02.56.00;;;;;0;;0.4;Novorapid ;0;Left flank;Test

Answer 3

You need to find out if pako supports gzip compression. If not, you should look for another compression package that supports gzip.