VBScript

Compressing StringBuilder Data Using CompressSb (Single Call and Chunked)

See more Compression Examples

This example demonstrates how to compress text stored in a StringBuilder using the CompressSb method in two ways:

1. Single-call compression, where the entire input is compressed in one operation.
2. Chunked compression, where the input is split into multiple parts and processed sequentially using the FirstChunk and LastChunk properties.

The example shows how compressed output is appended to a BinData object, and how the result can be verified by decompressing back to the original text. This is useful for both simple use cases and scenarios where data is processed incrementally (such as streaming or large inputs).

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Key Points

• CompressSb converts text to bytes using the Charset property (UTF-8 recommended).
• Compressed data is appended to a BinData object.
• When both FirstChunk and LastChunk are true, compression is done in a single call.
• For chunked processing:
  • First chunk → FirstChunk = true, LastChunk = false
  • Middle chunks → both false
  • Final chunk → LastChunk = true
• Chunked compression is useful when processing data incrementally.

VBScript

Dim fso, outFile
Set fso = CreateObject("Scripting.FileSystemObject")
'Create a Unicode (utf-16) output text file.
Set outFile = fso.CreateTextFile("output.txt", True, True)

success = 0

' This example assumes the Chilkat API has already been unlocked.
' See Global Unlock Sample for sample code.

set compress = CreateObject("Chilkat.Compression")
compress.Algorithm = "zlib"

' ================================================================
' 1) Single-call compression (entire data in one call)
' ================================================================

set sb = CreateObject("Chilkat.StringBuilder")
success = sb.Append("The quick brown fox jumps over the lazy dog. ")
success = sb.Append("This is a simple example using CompressSb.")

set bdCompressed = CreateObject("Chilkat.BinData")

' When both FirstChunk and LastChunk are true (the defaults),
' the entire compression happens in a single call.
compress.FirstChunk = 1
compress.LastChunk = 1

success = compress.CompressSb(sb,bdCompressed)
If (success = 0) Then
    outFile.WriteLine(compress.LastErrorText)
    WScript.Quit
End If

compressedBase64 = bdCompressed.GetEncoded("base64")

outFile.WriteLine("Single-call compressed (base64):")
outFile.WriteLine(compressedBase64)

' ================================================================
' 2) Chunked compression using FirstChunk / LastChunk
' ================================================================

set bdChunkedOut = CreateObject("Chilkat.BinData")

' First chunk
compress.FirstChunk = 1
compress.LastChunk = 0

set sbPart = CreateObject("Chilkat.StringBuilder")
success = sbPart.Append("The quick brown fox ")

success = compress.CompressSb(sbPart,bdChunkedOut)
If (success = 0) Then
    outFile.WriteLine(compress.LastErrorText)
    WScript.Quit
End If

' Middle chunk
compress.FirstChunk = 0
compress.LastChunk = 0

sbPart.Clear 
success = sbPart.Append("jumps over the lazy dog. ")

success = compress.CompressSb(sbPart,bdChunkedOut)
If (success = 0) Then
    outFile.WriteLine(compress.LastErrorText)
    WScript.Quit
End If

' Final chunk
compress.FirstChunk = 0
compress.LastChunk = 1

sbPart.Clear 
success = sbPart.Append("This is a chunked CompressSb example.")

success = compress.CompressSb(sbPart,bdChunkedOut)
If (success = 0) Then
    outFile.WriteLine(compress.LastErrorText)
    WScript.Quit
End If

chunkedBase64 = bdChunkedOut.GetEncoded("base64")

outFile.WriteLine("Chunked compressed (base64):")
outFile.WriteLine(chunkedBase64)

' ================================================================
' 3) Decompress to verify correctness
' ================================================================

set sbDecompressed = CreateObject("Chilkat.StringBuilder")

' Decompress in a single call (entire data already assembled)
compress.FirstChunk = 1
compress.LastChunk = 1

success = compress.DecompressSb(bdChunkedOut,sbDecompressed)
If (success = 0) Then
    outFile.WriteLine(compress.LastErrorText)
    WScript.Quit
End If

outFile.WriteLine("Decompressed text:")
outFile.WriteLine(sbDecompressed.GetAsString())

outFile.Close