(Go) Understanding ZIP Entry Types and the ZIP Object Lifecycle

See more Zip Examples

This example demonstrates how the Chilkat.Zip object manages entries before and after a ZIP archive is written.

The example shows:

• How file references are added from the local filesystem using AppendFilesEx
• How in-memory entries are added using AddString
• How ZIP entry types change as the ZIP archive progresses from an in-memory staging object to an actual written .zip file
• How additional entries can continue to be added even after the ZIP archive has already been written

The example also demonstrates the meaning of the different ZipEntry.EntryType values:

• 1 — File references in the local filesystem that have not yet been processed
• 2 — In-memory data entries
• 0 — Entries mapped to an existing open ZIP archive

This example is useful for understanding how the Chilkat.Zip class internally stages entries prior to writing the final ZIP archive.

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

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    success := false

    success = false

    zip := chilkat.NewZip()

    zipPath := "c:/temp/out.zip"

    // Start a new Zip object and set the output path.
    // This does not create the .zip file yet.  It only initializes the Zip object
    // and records the filename to be used later when WriteZip is called.
    zip.NewZip(zipPath)

    // Add references to files in the local filesystem.
    // AppendFilesEx does not read, compress, or store the file contents at this point.
    // It only adds file references to the Zip object.  The referenced files are
    // read and compressed later, when WriteZip is called.
    recurse := true
    saveExtraPath := false
    archiveOnly := false
    includeHidden := true
    includeSystem := false
    success = zip.AppendFilesEx("c:/temp/files_to_zip",recurse,saveExtraPath,archiveOnly,includeHidden,includeSystem)
    if success == false {
        fmt.Println(zip.LastErrorText())
        zip.DisposeZip()
        return
    }

    // We can inspect the entries that have been added to the Zip object.
    // At this stage, the entries are still references to files in the local filesystem.
    entry := chilkat.NewZipEntry()
    count := zip.NumEntries()
    i := 0
    for i < count {
        zip.EntryAt(i,entry)
        fmt.Println(entry.FileName(), " entryType = ", entry.EntryType())
        i = i + 1
    }

    fmt.Println("----")

    // Sample output for the above loop:
    // 
    // hamlet.xml entryType = 1
    // hello.pdf entryType = 1
    // ...
    // ...
    // 
    // entryType = 1 means "File Entry".
    // A File Entry is a reference to a file in the local filesystem.
    // The file data has not yet been read into the Zip object.
    // 
    // Possible entryType values:
    // 
    // 0 - Mapped Entry:
    //     An entry that already exists in an open .zip file.
    // 
    // 1 - File Entry:
    //     A file in the local filesystem that has been referenced, but not yet
    //     read or compressed.  These entries are added by methods such as
    //     AppendFiles, AppendFilesEx, and AddFile.
    // 
    // 2 - Data Entry:
    //     An entry containing uncompressed data already held in memory.
    //     These entries are added by methods such as AddData, AddString,
    //     AddSb, AddBd, and AddEncoded.
    // 
    // 3 - Null Entry:
    //     An entry that no longer exists in the .zip.
    // 
    // 4 - New Directory Entry:
    //     A directory entry added by calling AddEmpty.

    // Additional entries can still be added before the .zip is written.
    // This entry is created from an in-memory string, so it is a Data Entry
    // rather than a File Entry.
    zip.AddString("helloWorld.txt","Hello World","utf-8")

    // Inspect the Zip object again before writing.
    // The file references are still entryType = 1.
    // The in-memory string entry is entryType = 2.
    count = zip.NumEntries()
    i = 0
    for i < count {
        zip.EntryAt(i,entry)
        fmt.Println(entry.FileName(), " entryType = ", entry.EntryType())
        i = i + 1
    }

    fmt.Println("----")

    // Sample output:
    // 
    // hamlet.xml entryType = 1
    // hello.pdf entryType = 1
    // ...
    // ...
    // helloWorld.txt entryType = 2
    // 
    // helloWorld.txt has entryType = 2 because its contents came from memory.
    // It is not a reference to a file in the local filesystem.

    // ----------------------------------------------------------------------------
    // Write the Zip object to the .zip file.
    // 
    // During this call, Chilkat reads the referenced files from the local filesystem,
    // compresses the data as needed, and writes the final .zip archive.
    zip.SetFileName(zipPath)
    success = zip.WriteZip()
    if success == false {
        fmt.Println(zip.LastErrorText())
        zip.DisposeZip()
        entry.DisposeZipEntry()
        return
    }

    // After WriteZip returns successfully, the .zip file is written and remains
    // open in the Zip object.  The entries now correspond to entries in the
    // currently open .zip archive.
    count = zip.NumEntries()
    i = 0
    for i < count {
        zip.EntryAt(i,entry)
        fmt.Println(entry.FileName(), " entryType = ", entry.EntryType())
        i = i + 1
    }

    fmt.Println("----")

    // Sample output:
    // 
    // hamlet.xml entryType = 0
    // hello.pdf entryType = 0
    // ...
    // ...
    // helloWorld.txt entryType = 0
    // 
    // entryType = 0 means "Mapped Entry".
    // A Mapped Entry is an entry that exists in an open .zip file.

    // ----------------------------------------------------------------------------
    // The .zip remains open after WriteZip, so additional entries can still be added.
    // 
    // This adds another in-memory string entry to the currently open Zip object.
    zip.AddString("helloWorld2.txt","Hello World 2","utf-8")

    // Write the .zip again to include the newly added entry.
    success = zip.WriteZip()
    if success == false {
        fmt.Println(zip.LastErrorText())
        zip.DisposeZip()
        entry.DisposeZipEntry()
        return
    }

    // Inspect the entries one final time.
    // After the second WriteZip, the new entry is also mapped to the open .zip file.
    count = zip.NumEntries()
    i = 0
    for i < count {
        zip.EntryAt(i,entry)
        fmt.Println(entry.FileName(), " entryType = ", entry.EntryType())
        i = i + 1
    }

    fmt.Println("----")

    // Sample output:
    // 
    // hamlet.xml entryType = 0
    // hello.pdf entryType = 0
    // ...
    // ...
    // helloWorld.txt entryType = 0
    // helloWorld2.txt entryType = 0

    // Close the open .zip archive and clear the Zip object.
    zip.CloseZip()

    fmt.Println("Success")

    zip.DisposeZip()
    entry.DisposeZipEntry()