PureBasic

Compress and Decompress Base64

See more Compression Examples

This example demonstrates how to compress and decompress binary data using the Chilkat.Compression class with the BinData object.

The input data is provided as a Base64-encoded string. It is first decoded into raw bytes and loaded into a BinData object. The example then compresses the data in-place using the deflate algorithm. Because compressed data is binary, it is re-encoded to Base64 for easy display and transport.

To verify correctness, the example performs the reverse operation: it decodes the compressed Base64 back to bytes, decompresses the data, and encodes the result to Base64 again. The final Base64 output is compared with the original input to confirm that the compression and decompression process preserved the data exactly.

This example highlights:

• Using BinData to hold and transform binary data
• In-place compression and decompression with CompressBd and DecompressBd
• Converting between binary data and Base64 for display or transmission
• Verifying round-trip integrity after compression and decompression

PureBasic

IncludeFile "CkBinData.pb"
IncludeFile "CkCompression.pb"

Procedure ChilkatExample()

    success.i = 0

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

    ; This is the original data, encoded as base64.
    ; It decodes to plain text containing several repeated lines.
    originalBase64.s = "VGhlIHF1aWNrIGJyb3duIGZveCBqdW1wZWQgb3ZlciB0aGUgbGF6eSBkb2cuDQpUaGUgcXVpY2sgYnJvd24gZm94IGp1bXBlZCBvdmVyIHRoZSBsYXp5IGRvZy4NClRoZSBxdWljayBicm93biBmb3gganVtcGVkIG92ZXIgdGhlIGxhenkgZG9nLg0KVGhlIHF1aWNrIGJyb3duIGZveCBqdW1wZWQgb3ZlciB0aGUgbGF6eSBkb2cuDQpUaGUgcXVpY2sgYnJvd24gZm94IGp1bXBlZCBvdmVyIHRoZSBsYXp5IGRvZy4NCg0K"

    compress.i = CkCompression::ckCreate()
    If compress.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkCompression::setCkAlgorithm(compress, "deflate")

    ; Load the original base64 data into a BinData object.
    ; AppendEncoded decodes the base64 and stores the decoded bytes in binData.
    binData.i = CkBinData::ckCreate()
    If binData.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    success = CkBinData::ckAppendEncoded(binData,originalBase64,"base64")
    If success = 0
        Debug "Failed to decode the original base64 data."
        CkCompression::ckDispose(compress)
        CkBinData::ckDispose(binData)
        ProcedureReturn
    EndIf

    ; Compress the bytes contained in binData.
    ; CompressBd modifies binData in-place, replacing the original bytes
    ; with the compressed bytes.
    success = CkCompression::ckCompressBd(compress,binData)
    If success = 0
        Debug CkCompression::ckLastErrorText(compress)
        CkCompression::ckDispose(compress)
        CkBinData::ckDispose(binData)
        ProcedureReturn
    EndIf

    ; Show the compressed result as base64 so it can be printed as text.
    compressedBase64.s = CkBinData::ckGetEncoded(binData,"base64")

    Debug "Compressed data, base64 encoded:"
    Debug compressedBase64

    ; Expected compressed base64:
    ; C8lIVSgszUzOVkgqyi/PU0jLr1DIKs0tSE1RyC9LLVIoAcrnJFZVKqTkp+vxcoUMYeW8XAA=

    ; --------------------------------------------------------------------
    ; Decompress the data to verify that we get back the original bytes.
    ; --------------------------------------------------------------------

    ; Start with a fresh BinData object containing the compressed bytes.
    ; The compressed data is currently represented as base64 text, so decode it
    ; back to bytes before calling DecompressBd.
    success = CkBinData::ckClear(binData)
    success = CkBinData::ckAppendEncoded(binData,compressedBase64,"base64")
    If success = 0
        Debug "Failed to decode the compressed base64 data."
        CkCompression::ckDispose(compress)
        CkBinData::ckDispose(binData)
        ProcedureReturn
    EndIf

    ; DecompressBd also modifies binData in-place, replacing the compressed bytes
    ; with the decompressed bytes.
    success = CkCompression::ckDecompressBd(compress,binData)
    If success = 0
        Debug CkCompression::ckLastErrorText(compress)
        CkCompression::ckDispose(compress)
        CkBinData::ckDispose(binData)
        ProcedureReturn
    EndIf

    ; Encode the decompressed bytes as base64 so we can compare them with the
    ; original base64 input.
    decompressedBase64.s = CkBinData::ckGetEncoded(binData,"base64")

    Debug "Decompressed data, base64 encoded:"
    Debug decompressedBase64

    ; The decompressed base64 should match the original base64 input.
    If decompressedBase64 = originalBase64
        Debug "Success. The decompressed data matches the original data."
    Else
        Debug "Failure. The decompressed data does not match the original data."
    EndIf



    CkCompression::ckDispose(compress)
    CkBinData::ckDispose(binData)


    ProcedureReturn
EndProcedure