(Unicode C++) 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.

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#include <CkAuthGoogleW.h>
#include <CkRestW.h>
#include <CkCacheW.h>
#include <CkStringBuilderW.h>
#include <CkStreamW.h>

void ChilkatSample(void)
    {
    bool success = true;

    // 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.

    CkAuthGoogleW gAuth;
    gAuth.put_AccessToken(L"GOOGLE_DRIVE_ACCESS_TOKEN");

    CkRestW rest;

    // 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.
    bool bAutoReconnect = true;
    success = rest.Connect(L"www.googleapis.com",443,true,bAutoReconnect);

    // Provide the authentication credentials (i.e. the access token)
    rest.SetAuthGoogle(gAuth);

    // ------------------------------------------------------------------------------
    // 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.
    CkCacheW gdCache;
    gdCache.put_Level(0);
    gdCache.AddRoot(L"C:/ckCache/googleDrive");

    const wchar_t *fileId = gdCache.fetchText(L"testFolder/abc/123/penguins.jpg");
    if (gdCache.get_LastMethodSuccess() != true) {
        wprintf(L"Filepath not found in cache.\n");
        return;
    }

    // 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.
    CkStringBuilderW sbPath;
    sbPath.Append(L"/drive/v3/files/");
    sbPath.Append(fileId);
    rest.AddQueryParam(L"alt",L"media");

    // Create a stream object with a SinkFile set to the path where the downloaded file will go.
    CkStreamW fileStream;
    fileStream.put_SinkFile(L"qa_output/penguins.jpg");
    // Indicate that the response body should stream directly to fileStream,
    // but only if the response status is 200.  
    rest.SetResponseBodyStream(200,true,fileStream);

    // Download the file, streaming the content to the SinkFile.
    const wchar_t *jsonResponse = rest.fullRequestNoBody(L"GET",sbPath.getAsString());
    if (rest.get_LastMethodSuccess() != true) {
        wprintf(L"%s\n",rest.lastErrorText());
        return;
    }

    // A successful response will have a status code equal to 200.
    if (rest.get_ResponseStatusCode() != 200) {
        wprintf(L"response status code = %d\n",rest.get_ResponseStatusCode());
        wprintf(L"response status text = %s\n",rest.responseStatusText());
        wprintf(L"response header: %s\n",rest.responseHeader());
        return;
    }

    wprintf(L"File downloaded.\n");
    }