(VB.NET) Compressing StringBuilder Data Using CompressSb (Single Call and Chunked)

See more Compression Examples

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).

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.

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Dim success As Boolean = False

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

Dim compress As New Chilkat.Compression
compress.Algorithm = "zlib"

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

Dim sb As New Chilkat.StringBuilder
sb.Append("The quick brown fox jumps over the lazy dog. ")
sb.Append("This is a simple example using CompressSb.")

Dim bdCompressed As New Chilkat.BinData

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

success = compress.CompressSb(sb,bdCompressed)
If (success = False) Then
    Debug.WriteLine(compress.LastErrorText)
    Exit Sub
End If


Dim compressedBase64 As String = bdCompressed.GetEncoded("base64")

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

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

Dim bdChunkedOut As New Chilkat.BinData

' First chunk
compress.FirstChunk = True
compress.LastChunk = False

Dim sbPart As New Chilkat.StringBuilder
sbPart.Append("The quick brown fox ")

success = compress.CompressSb(sbPart,bdChunkedOut)
If (success = False) Then
    Debug.WriteLine(compress.LastErrorText)
    Exit Sub
End If


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

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

success = compress.CompressSb(sbPart,bdChunkedOut)
If (success = False) Then
    Debug.WriteLine(compress.LastErrorText)
    Exit Sub
End If


' Final chunk
compress.FirstChunk = False
compress.LastChunk = True

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

success = compress.CompressSb(sbPart,bdChunkedOut)
If (success = False) Then
    Debug.WriteLine(compress.LastErrorText)
    Exit Sub
End If


Dim chunkedBase64 As String = bdChunkedOut.GetEncoded("base64")

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

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

Dim sbDecompressed As New Chilkat.StringBuilder

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

success = compress.DecompressSb(bdChunkedOut,sbDecompressed)
If (success = False) Then
    Debug.WriteLine(compress.LastErrorText)
    Exit Sub
End If


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