(MFC) Unzip Binary File to Stream

Demonstrates how to unzip a large binary file to a stream to allow the application to process the uncompressed bytes chunk by chunk.

Note: This example requires Chilkat v9.5.0.67 or greater.

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

See Also: Using MFC CString in Chilkat

#include <CkZip.h>
#include <CkZipEntry.h>
#include <CkStream.h>
#include <CkTask.h>
#include <CkFileAccess.h>
#include <CkBinData.h>

void ChilkatSample(void)
    {
    CkString strOut;

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

    CkZip zip;

    // First open a .zip.
    bool success = zip.OpenZip("qa_data/zips/big.zip");
    if (success != true) {
        strOut.append(zip.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Get the entry to be unzipped to a stream..
    CkZipEntry *entry = zip.GetEntryByIndex(0);
    if (zip.get_LastMethodSuccess() != true) {
        strOut.append(zip.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    CkStream dataStream;

    CkTask *unzipTask = entry->UnzipToStreamAsync(dataStream);
    if (entry->get_LastMethodSuccess() != true) {
        strOut.append(entry->lastErrorText());
        strOut.append("\r\n");
        delete entry;
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Start the background unzip thread.
    unzipTask->Run();

    // We'll read the uncompressed data chunk-by-chunk and write to an output file.
    CkFileAccess fac;
    success = fac.OpenForWrite("qa_output/out.dat");
    if (success != true) {
        strOut.append(fac.lastErrorText());
        strOut.append("\r\n");
        delete entry;
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Read the stream.  (this is reading the unzipped file data)
    CkBinData bd;
    while (dataStream.get_EndOfStream() != true) {
        // Get the next chunk of decompressed bytes.
        dataStream.ReadBd(bd);
        // Do something with it..
        // In this simple example, we'll just write to the file.
        fac.FileWriteBd(bd,0,0);
        // Clear for the next read.
        bd.Clear();
    }

    fac.FileClose();

    delete entry;
    delete unzipTask;
    strOut.append("Success.");
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }