Visual FoxPro

Append Text Data to an Existing ZIP Entry Using ZipEntry.AppendString

See more Zip Examples

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.

Visual FoxPro

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