(Xojo Plugin) 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.

Chilkat Xojo Plugin Download Xojo Plugin for Windows, Linux, Mac OS X, and ARM, ARM64

Dim success As Boolean
success = False

Dim zip As New Chilkat.Zip

// ------------------------------------------------------------
// Open an existing ZIP archive.
success = zip.OpenZip("c:/temp/notes.zip")
If (success = False) Then
    System.DebugLog(zip.LastErrorText)
    Return
End If

// Locate a text file entry within the ZIP archive.
Dim entry As New Chilkat.ZipEntry

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

If (success <> False) Then

    // --------------------------------------------------------
    // At this point, the entry is a mapped entry because it
    // originates from an opened ZIP archive.
    // 
    //     EntryType = 0
    // 
    System.DebugLog("Initial EntryType = " + Str(entry.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(EndOfLine.Windows + "Additional notes added later.","utf-8")

    If (success = False) Then
        System.DebugLog(zip.LastErrorText)
        Return
    End If

    System.DebugLog("EntryType after AppendString = " + Str(entry.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.FileName = "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) Then
        System.DebugLog(zip.LastErrorText)
        Return
    End If

    // After rewriting the ZIP archive, the entry again becomes
    // a mapped entry:
    // 
    //     EntryType = 0
    // 
    System.DebugLog("EntryType after WriteZip = " + Str(entry.EntryType))
End If

zip.CloseZip 

System.DebugLog("ZIP entry updated successfully.")