(Node.js) Compress Large Binary File in Blocks

Compresses a large binary file in blocks.

Note: This example requires Chilkat v11.0.0 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 assumes the Chilkat API to have been previously unlocked.
    // See Global Unlock Sample for sample code.

    var facSrc = new chilkat.FileAccess();
    var facDest = new chilkat.FileAccess();

    // Open a large binary file for reading.
    success = facSrc.OpenForRead("qa_data/bmp/big.bmp");
    if (success == false) {
        console.log(facSrc.LastErrorText);
        return;
    }

    // If we compress in 64K chunks, find out how many blocks there will be.
    var blockSize = 65536;
    var numBlocks = facSrc.GetNumBlocks(blockSize);

    // Open an output file for the compressed data.
    success = facDest.OpenForWrite("c:/temp/qa_output/compressedBmp.dat");
    if (success == false) {
        console.log(facDest.LastErrorText);
        return;
    }

    var compress = new chilkat.Compression();
    compress.Algorithm = "deflate";

    // Assuming numBlocks > 1
    compress.FirstChunk = true;
    compress.LastChunk = false;

    var i = 0;
    while (i < numBlocks) {
        fileBytes = facSrc.ReadBlock(i,blockSize);
        compressedBytes = compress.CompressBytes(fileBytes);

        facDest.FileWrite(compressedBytes);

        i = i+1;

        compress.FirstChunk = false;
        if (i == (numBlocks - 1)) {
            compress.LastChunk = true;
        }

    }

    facSrc.FileClose();
    facDest.FileClose();

    console.log("Finished compressing file.");

}

chilkatExample();