(DataFlex) Download File (Stream to Local Filesystem)

This example demonstrates how to download the content of a file from Google Drive. The file is streamed to the local filesystem.

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

Use ChilkatAx-win32.pkg

Procedure Test
    Boolean iSuccess
    Variant vGAuth
    Handle hoGAuth
    Handle hoRest
    Boolean iBAutoReconnect
    Handle hoGdCache
    String sFileId
    Handle hoSbPath
    Variant vFileStream
    Handle hoFileStream
    String sJsonResponse
    String sTemp1
    Integer iTemp1
    Boolean bTemp1

    Move True To iSuccess

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

    // This example uses a previously obtained access token having permission for the 
    // Google Drive scope.

    Get Create (RefClass(cComChilkatAuthGoogle)) To hoGAuth
    If (Not(IsComObjectCreated(hoGAuth))) Begin
        Send CreateComObject of hoGAuth
    End
    Set ComAccessToken Of hoGAuth To "GOOGLE_DRIVE_ACCESS_TOKEN"

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

    // Connect using TLS.
    // A single REST object, once connected, can be used for many Google Drive REST API calls.
    // The auto-reconnect indicates that if the already-established HTTPS connection is closed,
    // then it will be automatically re-established as needed.
    Move True To iBAutoReconnect
    Get ComConnect Of hoRest "www.googleapis.com" 443 True iBAutoReconnect To iSuccess

    // Provide the authentication credentials (i.e. the access token)
    Get pvComObject of hoGAuth to vGAuth
    Get ComSetAuthGoogle Of hoRest vGAuth To iSuccess

    // ------------------------------------------------------------------------------
    // To download a file, we must know the file ID.
    // In a previous example (see Build Local Metadata Cache
    // we built a local cache to make it easy to lookup file IDs given a file path.
    // Let's say we want to download "testFolder/abc/123/penguins.jpg".
    // First we lookup the fileId in the cache.  With the fileId, we can download the file.
    Get Create (RefClass(cComChilkatCache)) To hoGdCache
    If (Not(IsComObjectCreated(hoGdCache))) Begin
        Send CreateComObject of hoGdCache
    End
    Set ComLevel Of hoGdCache To 0
    Send ComAddRoot To hoGdCache "C:/ckCache/googleDrive"

    Get ComFetchText Of hoGdCache "testFolder/abc/123/penguins.jpg" To sFileId
    Get ComLastMethodSuccess Of hoGdCache To bTemp1
    If (bTemp1 <> True) Begin
        Showln "Filepath not found in cache."
        Procedure_Return
    End

    // We need to send a GET request like this:
    // GET https://www.googleapis.com/drive/v3/files/fileId?alt=media
    // The fileId is part of the path.
    Get Create (RefClass(cComChilkatStringBuilder)) To hoSbPath
    If (Not(IsComObjectCreated(hoSbPath))) Begin
        Send CreateComObject of hoSbPath
    End
    Get ComAppend Of hoSbPath "/drive/v3/files/" To iSuccess
    Get ComAppend Of hoSbPath sFileId To iSuccess
    Get ComAddQueryParam Of hoRest "alt" "media" To iSuccess

    // Create a stream object with a SinkFile set to the path where the downloaded file will go.
    Get Create (RefClass(cComChilkatStream)) To hoFileStream
    If (Not(IsComObjectCreated(hoFileStream))) Begin
        Send CreateComObject of hoFileStream
    End
    Set ComSinkFile Of hoFileStream To "qa_output/penguins.jpg"
    // Indicate that the response body should stream directly to fileStream,
    // but only if the response status is 200.  
    Get pvComObject of hoFileStream to vFileStream
    Get ComSetResponseBodyStream Of hoRest 200 True vFileStream To iSuccess

    // Download the file, streaming the content to the SinkFile.
    Get ComGetAsString Of hoSbPath To sTemp1
    Get ComFullRequestNoBody Of hoRest "GET" sTemp1 To sJsonResponse
    Get ComLastMethodSuccess Of hoRest To bTemp1
    If (bTemp1 <> True) Begin
        Get ComLastErrorText Of hoRest To sTemp1
        Showln sTemp1
        Procedure_Return
    End

    // A successful response will have a status code equal to 200.
    Get ComResponseStatusCode Of hoRest To iTemp1
    If (iTemp1 <> 200) Begin
        Get ComResponseStatusCode Of hoRest To iTemp1
        Showln "response status code = " iTemp1
        Get ComResponseStatusText Of hoRest To sTemp1
        Showln "response status text = " sTemp1
        Get ComResponseHeader Of hoRest To sTemp1
        Showln "response header: " sTemp1
        Procedure_Return
    End

    Showln "File downloaded."


End_Procedure