(Node.js) Unzip One File to a Stream

Demonstrates how to unzip a particular file contained within a .zip archive to a Chilkat stream.

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

var os = require('os');
if (os.platform() == 'win32') {  
    if (os.arch() == 'ia32') {
        var chilkat = require('@chilkat/ck-node21-win-ia32');
    } else {
        var chilkat = require('@chilkat/ck-node21-win64'); 
    }
} else if (os.platform() == 'linux') {
    if (os.arch() == 'arm') {
        var chilkat = require('@chilkat/ck-node21-arm');
    } else if (os.arch() == 'x86') {
        var chilkat = require('@chilkat/ck-node21-linux32');
    } else {
        var chilkat = require('@chilkat/ck-node21-linux64');
    }
} else if (os.platform() == 'darwin') {
    if (os.arch() == 'arm64') {
        var chilkat = require('@chilkat/ck-node21-mac-m1');
    } else {
        var chilkat = require('@chilkat/ck-node21-macosx');
    }
}

function chilkatExample() {

    // This example requires the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    var zip = new chilkat.Zip();

    // First open a .zip.
    var success = zip.OpenZip("qa_data/hamlet.zip");
    if (success !== true) {
        console.log(zip.LastErrorText);
        return;
    }

    // Find the entry to be unzipped to a stream..
    // entry: ZipEntry
    var entry = zip.FirstMatchingEntry("*hamlet.xml");
    if (zip.LastMethodSuccess !== true) {
        console.log(zip.LastErrorText);
        return;
    }

    // There are three ways we can unzip (inflate) to a stream.
    // 
    // 1) Set a sink file on the stream object and call UnzipToStream synchronously.
    //    This unzips to the stream's sink (which is to simply unzip to a file in the filesystem).
    // 
    // 2) Create a stream object and call UnzipToStreamAsync.  This starts the unzip in a background
    //    thread (after Task.Run is called).  Your application can then read the unzipped (inflated) file
    //    directly from the stream.
    // 
    // 3) (not shown in this example) Unzip to a stream object that is the source of something else.
    //    

    // ----------------------------------------------------------------
    // Case 1: Unzip to a file by setting the sink of streamA to a file.
    var streamA = new chilkat.Stream();
    streamA.SinkFile = "qa_output/hamletA.xml";

    success = entry.UnzipToStream(streamA);
    if (success !== true) {
        console.log(entry.LastErrorText);

        return;
    }

    // Close the stream to close the output file.
    success = streamA.WriteClose();

    // ----------------------------------------------------------------
    // Case 2a: Uzip to a stream asynchronously. 
    var streamB = new chilkat.Stream();

    // unzipTask: Task
    var unzipTask = entry.UnzipToStreamAsync(streamB);
    if (entry.LastMethodSuccess !== true) {
        console.log(entry.LastErrorText);

        return;
    }

    // Start the background unzip thread.
    unzipTask.Run();

    // Read the stream.  (this is reading the unzipped file data)
    var sb = new chilkat.StringBuilder();
    while (streamB.EndOfStream !== true) {
        // Each call to ReadSb appends to the contents of sb.
        streamB.ReadSb(sb);
    }

    sb.WriteFile("qa_output/hamletB.xml","utf-8",false);

    console.log("Success.");

    // ----------------------------------------------------------------
    // Case 2b: Uzip to a stream asynchronously and emit output while reading. 
    var streamC = new chilkat.Stream();

    unzipTask = entry.UnzipToStreamAsync(streamC);
    if (entry.LastMethodSuccess !== true) {
        console.log(entry.LastErrorText);

        return;
    }

    unzipTask.Run();

    while (streamC.EndOfStream !== true) {
        var s = streamC.ReadString();
        console.log(s);
    }

    console.log("Success.");

}

chilkatExample();