(MFC) OneDrive -- Streaming REST Download to File

Downloads the contents of a DriveItem directly to a file in the local filesystem using the Chilkat REST class.

Note: This example requires Chilkat v9.5.0.69 or greater.

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

See Also: Using MFC CString in Chilkat

#include <CkRest.h>
#include <CkOAuth2.h>
#include <CkBinData.h>
#include <CkUrl.h>
#include <CkStringBuilder.h>
#include <CkJsonObject.h>
#include <CkStream.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;

    // Use your previously obtained access token here:
    // See the following examples for getting an access token:
    //    Get Microsoft Graph OAuth2 Access Token (Azure AD v2.0 Endpoint).
    //    Get Microsoft Graph OAuth2 Access Token (Azure AD Endpoint).
    //    Refresh Access Token (Azure AD v2.0 Endpoint).
    //    Refresh Access Token (Azure AD Endpoint).

    // First connect to graph.microsoft.com.  If there's a connectivity problem, we'll find out here.
    bool success = rest.Connect("graph.microsoft.com",443,true,true);
    if (success != true) {
        strOut.append(rest.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // (Make sure your token was obtained with the FilesRead or Files.ReadWrite scope.)
    CkOAuth2 oauth2;
    oauth2.put_AccessToken("MICROSOFT_GRAPH_ACCESS_TOKEN");
    rest.SetAuthOAuth2(oauth2);

    // Send the GET request to download the file.
    const char *uriPath = "/v1.0/me/drive/root:/Misc/wildlife/penguins.jpg:/content";
    success = rest.SendReqNoBody("GET",uriPath);
    if (rest.get_LastMethodSuccess() != true) {
        strOut.append(rest.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    // NOTE: This way of doing the HTTP GET (i.e. download) may be more cumbersome, but it 
    // allows for finer control of handling errors.  The connection establishment, the sending of the
    // request, the reading of the response header, and the reading of the response body (i.e. the file data)
    // are handled by separate method calls.  If the response header indicates an error, we can read
    // the response body and treat it differently than if reading the file data.

    // Read the response header.
    int statusCode = rest.ReadResponseHeader();
    strOut.append("Response Status Code = ");
    strOut.appendInt(statusCode);
    strOut.append("\r\n");
    if (statusCode == 302) {
        // This is a redirect.  Read the response body, if any, and then follow the redirect.
        // Usually the response body will be empty for a redirect, but we need to be sure to read
        // the response body just in case it exists.
        CkBinData discard;
        rest.ReadRespBd(discard);
        rest.Disconnect(10);

        // For OneDrive, the redirect URL does not need authorization because the only way
        // to have obtained the direct download URL is from an authenticated request.
        // In fact, if we leave the authentication present, the GET request to the redirect URL will fail.

        // Note: The ClearAuth method is introduced in v9.5.0.69.
        rest.ClearAuth();

        // Follow the redirect URL...
        CkUrl *redirectUrl = rest.RedirectUrl();
        strOut.append("Redirect Host: ");
        strOut.append(redirectUrl->host());
        strOut.append("\r\n");
        strOut.append("Redirect URI Path: ");
        strOut.append(redirectUrl->pathWithQueryParams());
        strOut.append("\r\n");

        success = rest.Connect(redirectUrl->host(),redirectUrl->get_Port(),redirectUrl->get_Ssl(),true);
        if (success != true) {
            strOut.append(rest.lastErrorText());
            strOut.append("\r\n");
            SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
            return;
        }

        // Send the request..
        success = rest.SendReqNoBody("GET",redirectUrl->path());
        delete redirectUrl;
        if (rest.get_LastMethodSuccess() != true) {
            strOut.append(rest.lastErrorText());
            strOut.append("\r\n");
            SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
            return;
        }

        statusCode = rest.ReadResponseHeader();
        strOut.append(rest.lastErrorText());
        strOut.append("\r\n");
        strOut.append("Redirect Response Status Code = ");
        strOut.appendInt(statusCode);
        strOut.append("\r\n");

    }

    if (statusCode >= 300) {

        // Read the error response body.
        CkStringBuilder sbJson;
        success = rest.ReadRespSb(sbJson);
        if (success != true) {
            strOut.append(rest.lastErrorText());
            strOut.append("\r\n");
            SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
            return;
        }

        CkJsonObject jsonErr;
        jsonErr.put_EmitCompact(false);
        jsonErr.LoadSb(sbJson);
        strOut.append(jsonErr.emit());
        strOut.append("\r\n");

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

    // Stream the response body directly to a local file.
    const char *localPath = "qa_output/penguins.jpg";

    CkStream stream;
    stream.put_SinkFile(localPath);

    success = rest.ReadRespBodyStream(stream,true);
    if (success != true) {
        strOut.append(rest.lastErrorText());
        strOut.append("\r\n");
        SetDlgItemText(IDC_EDIT1,strOut.getUnicode());
        return;
    }

    strOut.append("Successfully streamed a OneDrive file to the local filesystem.");
    strOut.append("\r\n");


    SetDlgItemText(IDC_EDIT1,strOut.getUnicode());

    }