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(Visual Basic 6.0) REST Asynchronous Streaming Upload Simplified
This is example is simplified in that it calls FullRequestStreamAsync instead of making calls to SendReqStreamBodyAsync, ReadResponseHeader, and ReadRespBodyStr.
It demonstrates how to create and write to a stream that feeds an asynchronous upload to cloud storage. This particular example demonstrates an upload to the Azure Cloud Storage service. The same concepts apply to S3, Google Cloud, and Google Drive.
' This example requires the Chilkat API to have been previously unlocked. ' See Global Unlock Sample for sample code. Dim rest As New ChilkatRest ' Connect to the Azure Storage Blob Service Dim bTls As Long bTls = 1 Dim port As Long port = 443 Dim bAutoReconnect As Long bAutoReconnect = 1 ' In this example, the storage account name is "chilkat". Dim success As Long success = rest.Connect("chilkat.blob.core.windows.net",port,bTls,bAutoReconnect) If (success <> 1) Then Debug.Print rest.LastErrorText Exit Sub End If ' Provide Azure Cloud credentials for the REST call. Dim azAuth As New ChilkatAuthAzureStorage azAuth.AccessKey = "AZURE_ACCESS_KEY" ' The account name used here should match the 1st part of the domain passed in the call to Connect (above). azAuth.Account = "chilkat" azAuth.Scheme = "SharedKey" azAuth.Service = "Blob" ' This causes the "x-ms-version: 2021-08-06" header to be automatically added. azAuth.XMsVersion = "2021-08-06" success = rest.SetAuthAzureStorage(azAuth) ' Set some request headers. success = rest.AddHeader("x-ms-blob-content-disposition","attachment; filename=""thisIsATest.txt""") success = rest.AddHeader("x-ms-blob-type","BlockBlob") success = rest.AddHeader("x-ms-meta-m1","v1") success = rest.AddHeader("x-ms-meta-m2","v2") ' Note: The application does not need to explicitly set the following ' headers: x-ms-date, Authorization, and Content-Length. These headers ' are automatically set by Chilkat. Dim sendStream As New ChilkatStream ' Create a background thread task to upload from the stream ' The name of the Azure storage container is "test". ' After the background task is started and running in a background thread, ' the foreground thread will write 100 text lines of "this is a test\r\n" to the ' stream. Dim uploadTask As ChilkatTask Set uploadTask = rest.FullRequestStreamAsync("PUT","/test/thisIsATest.txt",sendStream) ' Start the task. success = uploadTask.Run() ' The application can write to the stream, and close the stream ' when finished. Whatever is written to the stream uploaded to the remote file. Dim i As Long For i = 1 To 100 success = sendStream.WriteString("This is a test" & vbCrLf) If (success <> 1) Then success = uploadTask.Cancel() Debug.Print "Failed to write to sendStream." Exit Sub End If Next ' Close the stream to indicate no more data will be sent. success = sendStream.WriteClose() ' Make sure the uploadTask has finished. ' It is likely that task is already finished.. ' Wait a max of 5 seconds.. success = uploadTask.Wait(5000) ' FullRequestStreamAsync both sent the request and received the response. ' Check to see if the task finished properly. If (uploadTask.StatusInt <> 7) Then Debug.Print "Task did not end in the finished state." Debug.Print "Task status: " & uploadTask.Status Exit Sub End If ' Check to see if the call to FullRequestStream in the background thread pool succeeded. If (uploadTask.TaskSuccess <> 1) Then ' Show what would've been the LastErrorText had FullRequestStream been called synchronously Debug.Print uploadTask.ResultErrorText Exit Sub End If Dim responseStatusCode As Long responseStatusCode = rest.ResponseStatusCode ' When successful, the Azure Storage service will respond with a 201 response code, ' with an empty body. Therefore, in the success condition, the responseStr is empty. If (responseStatusCode = 201) Then Debug.Print "File uploaded." Else ' It failed, so examine the response body, if one was returned: ' Given that FullRequestStream returns a string, the return value is obtained via GetResultString. Dim responseBodyStr As String responseBodyStr = uploadTask.GetResultString() Debug.Print "response body (if any): " & responseBodyStr ' Examine the request/response to see what happened. Debug.Print "response status code = " & rest.ResponseStatusCode Debug.Print "response status text = " & rest.ResponseStatusText Debug.Print "response header: " & rest.ResponseHeader Debug.Print "---" Debug.Print "LastRequestStartLine: " & rest.LastRequestStartLine Debug.Print "LastRequestHeader: " & rest.LastRequestHeader End If
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