(MFC) Decompress Large Binary File in Blocks

Decompresses a large binary file in blocks. This example uses BeginDecompressBytes, MoreDecompressBytes, and EndDecompressBytes.

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

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

void ChilkatSample(void)
    {
    CkString strOut;

    // 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

    bool success = facSrc.OpenForRead("qa_data/bmp/compressedBmp.dat");
    if (success != true) {
        strOut.append(facSrc.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        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("qa_output/decompressed.bmp");
    if (success != true) {
        strOut.append(facDest.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

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

    CkByteData decompressedBytes;
    CkByteData compressedBytes;

    int i = 0;
    while (i < numBlocks) {
        success = facSrc.ReadBlock(i,blockSize,compressedBytes);
        if (i == 0) {
            success = compress.BeginDecompressBytes(compressedBytes,decompressedBytes);
        }
        else {
            success = compress.MoreDecompressBytes(compressedBytes,decompressedBytes);
        }

        facDest.FileWrite(decompressedBytes);

        i = i + 1;
    }

    // At the very end, flush any remaining decompressed bytes, if any.
    success = compress.EndDecompressBytes(decompressedBytes);
    facDest.FileWrite(decompressedBytes);

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

    strOut.append("Finished decompressing file.");
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }