(DataFlex) REST Read Response with Stream API

Demonstrates how to make a REST call that returns a binary body, and to receive the body through a stream API.

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

Use ChilkatAx-9.5.0-win32.pkg

Procedure Test
    Handle hoRest
    Boolean iBTls
    Integer iPort
    Boolean iBAutoReconnect
    Boolean iSuccess
    Variant vAuthAws
    Handle hoAuthAws
    Integer iResponseStatusCode
    String sErrResponse
    Variant vBodyStream
    Handle hoBodyStream
    Variant vReadResponseBodyTask
    Handle hoReadResponseBodyTask
    Variant hoNextChunk
    String sTemp1
    Boolean bTemp1

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

    Get Create (RefClass(cComChilkatRest)) To hoRest
    If (Not(IsComObjectCreated(hoRest))) Begin
        Send CreateComObject of hoRest
    End

    // Connect to the Amazon AWS REST server.
    Move True To iBTls
    Move 443 To iPort
    Move True To iBAutoReconnect
    Get ComConnect Of hoRest "s3.amazonaws.com" iPort iBTls iBAutoReconnect To iSuccess

    // ----------------------------------------------------------------------------
    // Important: For buckets created in regions outside us-east-1,
    // there are three important changes that need to be made.
    // See Working with S3 Buckets in Non-us-east-1 Regions for the details.
    // ----------------------------------------------------------------------------

    // Provide AWS credentials for the REST call.
    Get Create (RefClass(cComChilkatAuthAws)) To hoAuthAws
    If (Not(IsComObjectCreated(hoAuthAws))) Begin
        Send CreateComObject of hoAuthAws
    End
    Set ComAccessKey Of hoAuthAws To "AWS_ACCESS_KEY"
    Set ComSecretKey Of hoAuthAws To "AWS_SECRET_KEY"
    Set ComServiceName Of hoAuthAws To "s3"
    Get pvComObject of hoAuthAws to vAuthAws
    Get ComSetAuthAws Of hoRest vAuthAws To iSuccess

    // Set the bucket name via the HOST header.
    // In this case, the bucket name is "chilkat100".
    Set ComHost Of hoRest To "chilkat100.s3.amazonaws.com"

    // Send the request to download the JPG.
    Get ComSendReqNoBody Of hoRest "GET" "/starfish.jpg" To iSuccess
    If (iSuccess <> True) Begin
        Get ComLastErrorText Of hoRest To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // Read the response header.
    Get ComReadResponseHeader Of hoRest To iResponseStatusCode
    If (iResponseStatusCode < 0) Begin
        Get ComLastErrorText Of hoRest To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    Showln "Response status code = " iResponseStatusCode

    // 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 (iResponseStatusCode <> 200) Begin
        Get ComReadRespBodyString Of hoRest To sErrResponse
        Get ComLastMethodSuccess Of hoRest To bTemp1
        If (bTemp1 <> True) Begin
            Get ComLastErrorText Of hoRest To sTemp1
            Showln sTemp1
        End
        Else Begin
            Showln sErrResponse
        End

        Procedure_Return
    End

    Get Create (RefClass(cComChilkatStream)) To hoBodyStream
    If (Not(IsComObjectCreated(hoBodyStream))) Begin
        Send CreateComObject of hoBodyStream
    End
    // Set a 10 second read timeout for the stream. 
    // (Give up if no data arrives within 10 seconds after calling a read method.)
    Set ComReadTimeoutMs Of hoBodyStream To 10000

    // Create a background thread task to read the response body (which feeds
    // it to the bodyStream object.)
    Get pvComObject of hoBodyStream to vBodyStream
    Get ComReadRespBodyStreamAsync Of hoRest vBodyStream True To vReadResponseBodyTask
    If (IsComObject(vReadResponseBodyTask)) Begin
        Get Create (RefClass(cComChilkatTask)) To hoReadResponseBodyTask
        Set pvComObject Of hoReadResponseBodyTask To vReadResponseBodyTask
    End

    // Start the task. 
    Get ComRun Of hoReadResponseBodyTask To iSuccess

    // The application can now read the bodyStream...
    While ((ComEndOfStream(hoBodyStream)) <> True)

        // Read the next chunk of bytes (whatever is immediately available,
        // or wait for more data (up to 10 seconds because we set the stream's ReadTimeoutMs property)
        Get ComReadBytes Of hoBodyStream To hoNextChunk
        Get ComLastMethodSuccess Of hoBodyStream To bTemp1
        If (bTemp1 <> True) Begin
            Showln "Failed to receive more response data."
            // Make sure the background task is aborted/cancelled.
            Get ComCancel Of hoReadResponseBodyTask To iSuccess
            Send Destroy of hoReadResponseBodyTask
            Procedure_Return
        End

        // OK.. the app has the next chunk of the body, and may do whatever it wishes with it...
    Loop

    Send Destroy of hoReadResponseBodyTask

    Showln "Successfully received the entire response body."


End_Procedure