(Visual FoxPro) 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 ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

LOCAL lnSuccess
LOCAL loZip
LOCAL loEntry

lnSuccess = 0

loZip = CreateObject('Chilkat.Zip')

* ------------------------------------------------------------
* Open an existing ZIP archive.
lnSuccess = loZip.OpenZip("c:/temp/notes.zip")
IF (lnSuccess = 0) THEN
    ? loZip.LastErrorText
    RELEASE loZip
    CANCEL
ENDIF

* Locate a text file entry within the ZIP archive.
loEntry = CreateObject('Chilkat.ZipEntry')

lnSuccess = loZip.EntryOf("notes/readme.txt",loEntry)

IF (lnSuccess <> 0) THEN

    * --------------------------------------------------------
    * At this point, the entry is a mapped entry because it
    * originates from an opened ZIP archive.
    * 
    *     EntryType = 0
    * 
    ? "Initial EntryType = " + STR(loEntry.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
    * 
    lnSuccess = loEntry.AppendString(CHR(13) + CHR(10) + "Additional notes added later.","utf-8")

    IF (lnSuccess = 0) THEN
        ? loZip.LastErrorText
        RELEASE loZip
        RELEASE loEntry
        CANCEL
    ENDIF

    ? "EntryType after AppendString = " + STR(loEntry.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.
    * 
    loZip.FileName = "qa_output/updatedExample.zip"

    * Rewrite the ZIP archive.
    * 
    * The modified in-memory entry is compressed and written
    * into the new ZIP archive.
    * 
    lnSuccess = loZip.WriteZip()
    IF (lnSuccess = 0) THEN
        ? loZip.LastErrorText
        RELEASE loZip
        RELEASE loEntry
        CANCEL
    ENDIF

    * After rewriting the ZIP archive, the entry again becomes
    * a mapped entry:
    * 
    *     EntryType = 0
    * 
    ? "EntryType after WriteZip = " + STR(loEntry.EntryType)
ENDIF

loZip.CloseZip()

? "ZIP entry updated successfully."

RELEASE loZip
RELEASE loEntry