(MFC) 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.

Chilkat C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

#include <CkRest.h>
#include <CkAuthAzureStorage.h>
#include <CkStream.h>
#include <CkTask.h>

void ChilkatSample(void)
    {
    CkString strOut;

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

    CkRest rest;

    // Connect to the Azure Storage Blob Service
    bool bTls = true;
    int port = 443;
    bool bAutoReconnect = true;
    // In this example, the storage account name is "chilkat".
    bool success = rest.Connect("chilkat.blob.core.windows.net",port,bTls,bAutoReconnect);
    if (success != true) {
        strOut.append(rest.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Provide Azure Cloud credentials for the REST call.
    CkAuthAzureStorage azAuth;
    azAuth.put_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.put_Account("chilkat");
    azAuth.put_Scheme("SharedKey");
    azAuth.put_Service("Blob");
    // This causes the "x-ms-version: 2020-08-04" header to be automatically added.
    azAuth.put_XMsVersion("2020-08-04");
    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.

    CkStream sendStream;

    // 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.
    CkTask *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.
    int i;
    for (i = 1; i <= 100; i++) {
        success = sendStream.WriteString("This is a test\r\n");
        if (success != true) {
            success = uploadTask->Cancel();
            delete uploadTask;
            strOut.append("Failed to write to sendStream.");
            strOut.append("\r\n");
            SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
            return;
        }

    }

    // 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->get_StatusInt() != 7) {
        strOut.append("Task did not end in the finished state.");
        strOut.append("\r\n");
        strOut.append("Task status: ");
        strOut.append(uploadTask->status());
        strOut.append("\r\n");
        delete uploadTask;
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Check to see if the call to FullRequestStream in the background thread pool succeeded.
    if (uploadTask->get_TaskSuccess() != true) {
        // Show what would've been the LastErrorText had FullRequestStream been called synchronously
        strOut.append(uploadTask->resultErrorText());
        strOut.append("\r\n");
        delete uploadTask;
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    int responseStatusCode = rest.get_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) {
        strOut.append("File uploaded.");
        strOut.append("\r\n");
    }
    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.
        const char *responseBodyStr = uploadTask->getResultString();
        strOut.append("response body (if any): ");
        strOut.append(responseBodyStr);
        strOut.append("\r\n");

        // Examine the request/response to see what happened.
        strOut.append("response status code = ");
        strOut.appendInt(rest.get_ResponseStatusCode());
        strOut.append("\r\n");
        strOut.append("response status text = ");
        strOut.append(rest.responseStatusText());
        strOut.append("\r\n");
        strOut.append("response header: ");
        strOut.append(rest.responseHeader());
        strOut.append("\r\n");
        strOut.append("---");
        strOut.append("\r\n");
        strOut.append("LastRequestStartLine: ");
        strOut.append(rest.lastRequestStartLine());
        strOut.append("\r\n");
        strOut.append("LastRequestHeader: ");
        strOut.append(rest.lastRequestHeader());
        strOut.append("\r\n");
    }



    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }