DataFlex

Example: Hash Text in Chunks

Shows how to generate a final hash, like SHA-256, for a large text by processing it in chunks. DataFlex

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Handle hoCrypt
    Variant vBd
    Handle hoBd
    String s
    Integer i
    String sEncodedHash

    Move False To iSuccess

    Get Create (RefClass(cComChilkatCrypt2)) To hoCrypt
    If (Not(IsComObjectCreated(hoCrypt))) Begin
        Send CreateComObject of hoCrypt
    End
    Set ComHashAlgorithm Of hoCrypt To "sha256"
    Set ComCharset Of hoCrypt To "utf-8"

    Get Create (RefClass(cComChilkatBinData)) To hoBd
    If (Not(IsComObjectCreated(hoBd))) Begin
        Send CreateComObject of hoBd
    End

    Move "The quick brown fox jumped over the lazy dog." + (character(13)) + (character(10)) To s

    // Accumulate the text in a StringBuilder.  We'll demonstrate hashing the text in chunks,
    // and then also hashing the entire text at once to show the results are the same.

    Get ComAppendString Of hoBd s "utf-8" To iSuccess
    Get ComHashBeginString Of hoCrypt s To iSuccess

    Move 0 To i
    While (i < 200)
        Get ComAppendString Of hoBd s "utf-8" To iSuccess
        Get ComHashMoreString Of hoCrypt s To iSuccess
        Move (i + 1) To i
    Loop

    // Get the hash in base64 format.
    Set ComEncodingMode Of hoCrypt To "base64"

    Get ComHashFinalENC Of hoCrypt To sEncodedHash
    Showln "Hash computed in chunks: " sEncodedHash

    // Let's alternatively compute the hash of the entire amount of data at once,
    // to show the hash computation is the same:
    Get pvComObject of hoBd to vBd
    Get ComHashBdENC Of hoCrypt vBd To sEncodedHash
    Showln "Hash computed in 1 step: " sEncodedHash

    // Output:

    // Hash computed in chunks: unwkVff61k40roRIJizaknreScHaL6frWe37kydXbZQ=
    // Hash computed in 1 step: unwkVff61k40roRIJizaknreScHaL6frWe37kydXbZQ=


End_Procedure