(PureBasic) Streaming Decrypt HTTP Response

If the an encrypted file was previously uploaded, this example demonstrates how to download and decrypt in a streaming way.

Chilkat PureBasic Module Download Chilkat PureBasic Module

IncludeFile "CkTask.pb"
IncludeFile "CkRest.pb"
IncludeFile "CkStream.pb"
IncludeFile "CkCrypt2.pb"

Procedure ChilkatExample()

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

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

    bTls.i = 1
    port.i = 443
    bAutoReconnect.i = 1
    success.i = CkRest::ckConnect(rest,"chilkatdownload.com",port,bTls,bAutoReconnect)

    ; Send the request to download a file.
    success = CkRest::ckSendReqNoBody(rest,"GET","/9.5.0.83/chilkat-9.5.0-python-3.8-x64.zip")
    If success <> 1
        Debug CkRest::ckLastErrorText(rest)
        CkRest::ckDispose(rest)
        ProcedureReturn
    EndIf

    ; Read the response header.
    responseStatusCode.i = CkRest::ckReadResponseHeader(rest)
    If responseStatusCode < 0
        Debug CkRest::ckLastErrorText(rest)
        CkRest::ckDispose(rest)
        ProcedureReturn
    EndIf

    Debug "Response status code = " + Str(responseStatusCode)

    ; We expect a 200 response status if the JPG data is coming.
    ; Otherwise, we'll get a string response body with an error message(or no response body).
    If responseStatusCode <> 200
        errResponse.s = CkRest::ckReadRespBodyString(rest)
        If CkRest::ckLastMethodSuccess(rest) <> 1
            Debug CkRest::ckLastErrorText(rest)
        Else
            Debug errResponse
        EndIf

        CkRest::ckDispose(rest)
        ProcedureReturn
    EndIf

    ; Create an object for decrypting.
    ; This example will use "none" for the encryption algorithm, which means it's just a pass-through.
    ; Typically you would set the decrypt properties, such as secret key, IV, key length, padding scheme, cipher mode..
    crypt.i = CkCrypt2::ckCreate()
    If crypt.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    CkCrypt2::setCkCryptAlgorithm(crypt, "none")

    ; The following settings are ignored in this test because our CryptAlgorithm is "none".
    ; However, if you were truly decrypting, you might set CryptAlgorithm = "aes".
    CkCrypt2::setCkCipherMode(crypt, "cbc")
    CkCrypt2::setCkKeyLength(crypt, 128)
    CkCrypt2::ckSetEncodedKey(crypt,"000102030405060708090A0B0C0D0E0F","hex")
    CkCrypt2::ckSetEncodedIV(crypt,"000102030405060708090A0B0C0D0E0F","hex")

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

    ; The decryptStream's source will be the receiveStream.
    decryptStream.i = CkStream::ckCreate()
    If decryptStream.i = 0
        Debug "Failed to create object."
        ProcedureReturn
    EndIf

    ; The decrypt stream's sink will be a file.
    CkStream::setCkSinkFile(decryptStream, "qa_output/chilkat-9.5.0-python-3.8-x64.zip")
    CkStream::ckSetSourceStream(decryptStream,receiveStream)

    ; Create and run a background async task to decrypt incoming data and write to a file.
    decryptStreamTask.i = CkCrypt2::ckDecryptStreamAsync(crypt,decryptStream)
    success = CkTask::ckRun(decryptStreamTask)

    success = CkRest::ckReadRespBodyStream(rest,receiveStream,1)
    If success <> 1
        Debug CkRest::ckLastErrorText(rest)
        CkRest::ckDispose(rest)
        CkCrypt2::ckDispose(crypt)
        CkStream::ckDispose(receiveStream)
        CkStream::ckDispose(decryptStream)
        ProcedureReturn
    EndIf

    Debug "Successfully received the .zip file."


    CkRest::ckDispose(rest)
    CkCrypt2::ckDispose(crypt)
    CkStream::ckDispose(receiveStream)
    CkStream::ckDispose(decryptStream)


    ProcedureReturn
EndProcedure