(MFC) 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 C/C++ Library Downloads MS Visual C/C++ Libs

See Also: Using MFC CString in Chilkat

#include <CkRest.h>
#include <CkAuthAws.h>
#include <CkStream.h>
#include <CkTask.h>
#include <CkByteData.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 Amazon AWS REST server.
    bool bTls = true;
    int port = 443;
    bool bAutoReconnect = true;
    bool success = rest.Connect("s3.amazonaws.com",port,bTls,bAutoReconnect);

    // ----------------------------------------------------------------------------
    // 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.
    CkAuthAws authAws;
    authAws.put_AccessKey("AWS_ACCESS_KEY");
    authAws.put_SecretKey("AWS_SECRET_KEY");
    authAws.put_ServiceName("s3");
    success = rest.SetAuthAws(authAws);

    // Set the bucket name via the HOST header.
    // In this case, the bucket name is "chilkat100".
    rest.put_Host("chilkat100.s3.amazonaws.com");

    // Send the request to download the JPG.
    success = rest.SendReqNoBody("GET","/starfish.jpg");
    if (success != true) {
        strOut.append(rest.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // Read the response header.
    int responseStatusCode = rest.ReadResponseHeader();
    if (responseStatusCode < 0) {
        strOut.append(rest.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    strOut.append("Response status code = ");
    strOut.appendInt(responseStatusCode);
    strOut.append("\r\n");

    // 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) {
        const char *errResponse = rest.readRespBodyString();
        if (rest.get_LastMethodSuccess() != true) {
            strOut.append(rest.lastErrorText());
            strOut.append("\r\n");
        }
        else {
            strOut.append(errResponse);
            strOut.append("\r\n");
        }

        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    CkStream bodyStream;
    // Set a 10 second read timeout for the stream. 
    // (Give up if no data arrives within 10 seconds after calling a read method.)
    bodyStream.put_ReadTimeoutMs(10000);

    // Create a background thread task to read the response body (which feeds
    // it to the bodyStream object.)
    CkTask *readResponseBodyTask = rest.ReadRespBodyStreamAsync(bodyStream,true);

    // Start the task. 
    success = readResponseBodyTask->Run();

    // The application can now read the bodyStream...
    CkByteData nextChunk;
    while ((bodyStream.get_EndOfStream() != 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)
        success = bodyStream.ReadBytes(nextChunk);
        if (success != true) {
            strOut.append("Failed to receive more response data.");
            strOut.append("\r\n");
            // Make sure the background task is aborted/cancelled.
            success = readResponseBodyTask->Cancel();
            delete readResponseBodyTask;
            SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
            return;
        }

        // OK.. the app has the next chunk of the body, and may do whatever it wishes with it...
        // See the CkByteData online reference documentation for 
        // information about accessing and manipulating the byte data.

    }

    delete readResponseBodyTask;

    strOut.append("Successfully received the entire response body.");
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }