Compress Large Binary File in Blocks

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var success = false;

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

var facSrc = new CkFileAccess();
var facDest = new CkFileAccess();

//  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 CkCompression();
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.");