DataFlex

Compress and Encrypt a Large File (Low and Constant Memory Footprint)

See more Compression Examples

Demonstrates how to compress and encrypt a large file such that the memory footprint remains low and constant.

Note: This example requires Chilkat v9.5.0.99 or greater.

DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoCompress
    Variant vJson
    Handle hoJson
    String sInPath
    String sOutPath
    String sInPath2
    String sOutPath2
    Handle hoCrypt
    String sDecryptedPath
    String sOutPath3
    String sTemp1

    Move False To iSuccess

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

    Get Create (RefClass(cComChilkatCompression)) To hoCompress
    If (Not(IsComObjectCreated(hoCompress))) Begin
        Send CreateComObject of hoCompress
    End
    Set ComAlgorithm Of hoCompress To "deflate"

    // Set encryption params.
    // The possible values are the same as for the corresponding properties in the Chilkat Crypt2 class/object.
    // The encoded IV and Key must be specified as hex.
    Get Create (RefClass(cComChilkatJsonObject)) To hoJson
    If (Not(IsComObjectCreated(hoJson))) Begin
        Send CreateComObject of hoJson
    End
    Get ComUpdateString Of hoJson "cryptAlgorithm" "aes" To iSuccess
    Get ComUpdateString Of hoJson "cipherMode" "cbc" To iSuccess
    Get ComUpdateInt Of hoJson "keyLength" 128 To iSuccess
    Get ComUpdateInt Of hoJson "paddingScheme" 0 To iSuccess
    Get ComUpdateString Of hoJson "encodedIV" "000102030405060708090A0B0C0D0E0F" To iSuccess
    Get ComUpdateString Of hoJson "encodedKey" "000102030405060708090A0B0C0D0E0F" To iSuccess

    // Do file-to-file compression+encryption in a single call.
    Move "qa_data/largeFile.dat" To sInPath
    Move "c:/temp/qa_output/compressed_encrypted.dat" To sOutPath
    Get pvComObject of hoJson to vJson
    Get ComCompressEncryptFile Of hoCompress vJson sInPath sOutPath To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoCompress To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // We can do file-to-file decrypt/decompress like this:
    Move sOutPath To sInPath2
    Move "c:/temp/qa_output/restored.dat" To sOutPath2
    Get pvComObject of hoJson to vJson
    Get ComDecryptDecompressFile Of hoCompress vJson sInPath2 sOutPath2 To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoCompress To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Note: The above decrypt + decompress is the equivalent of doing the same in these two steps:
    Get Create (RefClass(cComChilkatCrypt2)) To hoCrypt
    If (Not(IsComObjectCreated(hoCrypt))) Begin
        Send CreateComObject of hoCrypt
    End
    Set ComCryptAlgorithm Of hoCrypt To "aes"
    Set ComCipherMode Of hoCrypt To "cbc"
    Set ComKeyLength Of hoCrypt To 128
    Set ComPaddingScheme Of hoCrypt To 0
    Send ComSetEncodedIV To hoCrypt "000102030405060708090A0B0C0D0E0F" "hex"
    Send ComSetEncodedKey To hoCrypt "000102030405060708090A0B0C0D0E0F" "hex"

    Move "c:/temp/qa_output/decrypted.dat" To sDecryptedPath
    Get ComCkDecryptFile Of hoCrypt sInPath2 sDecryptedPath To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoCrypt To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Move "c:/temp/qa_output/restored_in_two_steps.dat" To sOutPath3
    Get ComDecompressFile Of hoCompress sDecryptedPath sOutPath3 To iSuccess
    If (iSuccess = False) Begin
        Get ComLastErrorText Of hoCompress To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Showln "Success."


End_Procedure