(Node.js) Retrieve Metadata from Gzip Data in Memory (BinData)

This example demonstrates how to use the GetGzipInfoBd method to retrieve metadata from Gzip data stored in memory within a BinData object.

The Gzip data is first loaded into the BinData instance. The GetGzipInfoBd method then extracts any available metadata from the Gzip header, including the embedded filename, comment, and optional extra data.

The metadata is returned in a JsonObject. Because these fields are optional, the example checks for the existence of each JSON member using HasMember before retrieving its value.

Note: This example requires Chilkat v11.5.0 or greater.

Install Chilkat for Node.js and Electron using npm at Chilkat npm packages for Node.js Chilkat npm packages for Electron on Windows, Linux, MacOS

var os = require('os');
if (os.platform() == 'win32') {  
  var chilkat = require('@chilkat/ck-node23-win64'); 
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node23-linux-arm');
    } else if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node23-linux-arm64');
    } else {
        var chilkat = require('@chilkat/ck-node23-linux-x64');
    }
} else if (os.platform() == 'darwin') {
  var chilkat = require('@chilkat/ck-node23-mac-universal');
}

function chilkatExample() {

    var success = false;

    // This example demonstrates how to retrieve metadata from Gzip data
    // stored in a BinData object.

    var gzip = new chilkat.Gzip();
    var bd = new chilkat.BinData();
    var json = new chilkat.JsonObject();

    // Load a Gzip file into BinData:
    success = bd.LoadFile("example.txt.gz");
    if (success == false) {
        console.log(bd.LastErrorText);
        return;
    }

    // Get the metadata information from the in-memory Gzip data:
    success = gzip.GetGzipInfoBd(bd,json);
    if (success == false) {
        console.log(gzip.LastErrorText);
        return;
    }

    // Output the JSON containing metadata:
    console.log("Gzip metadata JSON:");
    console.log(json.Emit());

    // Access individual fields only if they exist:

    if (json.HasMember("filename") == true) {
        var filename = json.StringOf("filename");
        console.log("Filename: " + filename);
    }

    if (json.HasMember("comment") == true) {
        var comment = json.StringOf("comment");
        console.log("Comment: " + comment);
    }

    if (json.HasMember("extraData") == true) {
        var extraData = json.StringOf("extraData");
        console.log("ExtraData (Base64): " + extraData);
    }


}

chilkatExample();