C++

Decompress Large Binary File in Blocks

See more Compression Examples

Decompresses a large binary file in blocks. C++

#include <CkFileAccess.h>
#include <CkCompression.h>
#include <CkByteData.h>

void ChilkatSample(void)
    {
    bool success = false;

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

    CkFileAccess facSrc;
    CkFileAccess facDest;

    //  Open a previously compressed file for decompressing.
    //  See Compress Large File in Blocks

    success = facSrc.OpenForRead("c:/temp/qa_output/compressedBmp.dat");
    if (success == false) {
        std::cout << facSrc.lastErrorText() << "\r\n";
        return;
    }

    //  If we compress in 32K chunks, find out how many blocks there will be.
    int blockSize = 32768;
    int numBlocks = facSrc.GetNumBlocks(blockSize);

    //  Open an output file for the decompressed data.
    success = facDest.OpenForWrite("c:/temp/qa_output/decompressed.bmp");
    if (success == false) {
        std::cout << facDest.lastErrorText() << "\r\n";
        return;
    }

    CkCompression compress;
    compress.put_Algorithm("deflate");

    CkByteData decompressedBytes;
    CkByteData compressedBytes;

    //  Assuming numBlocks > 1
    compress.put_FirstChunk(true);
    compress.put_LastChunk(false);

    int i = 0;
    while (i < numBlocks) {
        success = facSrc.ReadBlock(i,blockSize,compressedBytes);

        success = compress.DecompressBytes(compressedBytes,decompressedBytes);
        facDest.FileWrite(decompressedBytes);

        i = i + 1;

        compress.put_FirstChunk(false);
        if (i == (numBlocks - 1)) {
            compress.put_LastChunk(true);
        }

    }

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

    std::cout << "Finished decompressing file." << "\r\n";
    }