(Classic ASP) 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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<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body>
<%
success = 0

set zip = Server.CreateObject("Chilkat.Zip")

' ------------------------------------------------------------
' Open an existing ZIP archive.
success = zip.OpenZip("c:/temp/notes.zip")
If (success = 0) Then
    Response.Write "<pre>" & Server.HTMLEncode( zip.LastErrorText) & "</pre>"
    Response.End
End If

' Locate a text file entry within the ZIP archive.
set entry = Server.CreateObject("Chilkat.ZipEntry")

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

If (success <> 0) Then

    ' --------------------------------------------------------
    ' At this point, the entry is a mapped entry because it
    ' originates from an opened ZIP archive.
    ' 
    '     EntryType = 0
    ' 
    Response.Write "<pre>" & Server.HTMLEncode( "Initial EntryType = " & entry.EntryType) & "</pre>"

    ' 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(vbCrLf & "Additional notes added later.","utf-8")

    If (success = 0) Then
        Response.Write "<pre>" & Server.HTMLEncode( zip.LastErrorText) & "</pre>"
        Response.End
    End If

    Response.Write "<pre>" & Server.HTMLEncode( "EntryType after AppendString = " & entry.EntryType) & "</pre>"

    ' --------------------------------------------------------
    ' 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 = 0) Then
        Response.Write "<pre>" & Server.HTMLEncode( zip.LastErrorText) & "</pre>"
        Response.End
    End If

    ' After rewriting the ZIP archive, the entry again becomes
    ' a mapped entry:
    ' 
    '     EntryType = 0
    ' 
    Response.Write "<pre>" & Server.HTMLEncode( "EntryType after WriteZip = " & entry.EntryType) & "</pre>"
End If

zip.CloseZip 

Response.Write "<pre>" & Server.HTMLEncode( "ZIP entry updated successfully.") & "</pre>"

%>
</body>
</html>