(Unicode C++) Append Text Data to an Existing ZIP Entry Using ZipEntry.AppendString

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This example demonstrates how to use the ZipEntry.AppendString method to append text data to an existing ZIP entry.

The example opens an existing ZIP archive, locates a text file entry, and appends additional text to the end of the file contents.

An important concept demonstrated by this example is that appending data to a ZIP entry transforms the entry into an in-memory Data Entry (EntryType = 2).

For example:

• If the entry is a mapped entry from an opened ZIP archive (EntryType = 0), the compressed entry is first inflated into memory.
• If the entry is a referenced filesystem file (EntryType = 1), the file contents are first loaded into memory.

The new text is then appended to the uncompressed in-memory data, and the entry becomes a Data Entry.

After the ZIP archive is rewritten, the modified entry again becomes a mapped entry stored within the ZIP archive.

Note: This example requires Chilkat v11.0.0 or greater.

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#include <CkZipW.h>
#include <CkZipEntryW.h>

void ChilkatSample(void)
    {
    bool success = false;

    CkZipW zip;

    // ------------------------------------------------------------
    // Open an existing ZIP archive.
    success = zip.OpenZip(L"c:/temp/notes.zip");
    if (success == false) {
        wprintf(L"%s\n",zip.lastErrorText());
        return;
    }

    // Locate a text file entry within the ZIP archive.
    CkZipEntryW entry;

    success = zip.EntryOf(L"notes/readme.txt",entry);

    if (success != false) {

        // --------------------------------------------------------
        // At this point, the entry is a mapped entry because it
        // originates from an opened ZIP archive.
        // 
        //     EntryType = 0
        // 
        wprintf(L"Initial EntryType = %d\n",entry.get_EntryType());

        // Append additional text to the ZIP entry.
        // 
        // The existing compressed ZIP entry is first inflated
        // into memory. The new text is then appended.
        // 
        // After AppendString is called, the entry becomes
        // an in-memory Data Entry:
        // 
        //     EntryType = 2
        // 
        success = entry.AppendString(L"\r\nAdditional notes added later.",L"utf-8");

        if (success == false) {
            wprintf(L"%s\n",zip.lastErrorText());
            return;
        }

        wprintf(L"EntryType after AppendString = %d\n",entry.get_EntryType());

        // --------------------------------------------------------
        // Write the modified ZIP archive to a different file.
        // 
        // Changing zip.FileName causes the ZIP archive to be
        // written to a new output file rather than overwriting
        // the original ZIP archive.
        // 
        zip.put_FileName(L"qa_output/updatedExample.zip");

        // Rewrite the ZIP archive.
        // 
        // The modified in-memory entry is compressed and written
        // into the new ZIP archive.
        // 
        success = zip.WriteZip();
        if (success == false) {
            wprintf(L"%s\n",zip.lastErrorText());
            return;
        }

        // After rewriting the ZIP archive, the entry again becomes
        // a mapped entry:
        // 
        //     EntryType = 0
        // 
        wprintf(L"EntryType after WriteZip = %d\n",entry.get_EntryType());
    }

    zip.CloseZip();

    wprintf(L"ZIP entry updated successfully.\n");
    }