Node.js

Compress Large Binary File in Blocks

See more Compression Examples

Compresses a large binary file in blocks. Node.js

NODEJS_PRELUDE

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();