(Visual Basic 6.0) Compress and Decompress Hex String

Imagine we have data represented as a hex string. This example demonstrates how to decode, compress, and re-encode to a smaller hex string representing the compressed data. An even better choice is to re-encode to a more compact encoding such as base64.

Note: This example requires Chilkat v9.5.0.66 or greater.

Chilkat ActiveX Downloads ActiveX for 32-bit and 64-bit Windows

' This example assumes the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.

Dim success As Long

Dim strHex As String
strHex = "54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A0D0A"

Dim compress As New ChilkatCompression
compress.Algorithm = "deflate"

Dim binDat As New ChilkatBinData
' Load the hex string into a BinData object.
' This decodes the hexidecimal. The decoded bytes will be contained in the BinData.
success = binDat.AppendEncoded(strHex,"hex")

' Compress the BinData.
success = compress.CompressBd(binDat)

' Get the compressed data in hex format:
Dim compressedHex As String
compressedHex = binDat.GetEncoded("hex")
Debug.Print "compressed hex:"
Debug.Print compressedHex

' The compressed hex is: 0BC94855282CCD4CCE56482ACA2FCF5348CBAF50C82ACD2D484D51C82F4B2D522801CAE72456552AA4E4A7EBF172850C61E5BC5C00

' Even better, get the compressed data in base64 format:
' (base64url and modbase64 are other valid choices...)
Dim compressedBase64 As String
compressedBase64 = binDat.GetEncoded("base64")
Debug.Print "compressed base64:"
Debug.Print compressedBase64

' The compressed base64 is: C8lIVSgszUzOVkgqyi/PU0jLr1DIKs0tSE1RyC9LLVIoAcrnJFZVKqTkp+vxcoUMYeW8XAA=

' Now decompress:
success = binDat.Clear()
success = binDat.AppendEncoded(compressedHex,"hex")
success = compress.DecompressBd(binDat)

Dim decompressedHex As String
decompressedHex = binDat.GetEncoded("hex")
Debug.Print "decompressed hex:"
Debug.Print decompressedHex

' The output is the original hex string:
' 54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A54686520717569636B2062726F776E20666F78206A756D706564206F76657220746865206C617A7920646F672E0D0A0D0A