(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 <C_CkAuthGoogle.h>
#include <C_CkRest.h>
#include <C_CkCache.h>
#include <C_CkStringBuilder.h>
#include <C_CkStream.h>

void ChilkatSample(void)
    {
    BOOL success;
    HCkAuthGoogle gAuth;
    HCkRest rest;
    BOOL bAutoReconnect;
    HCkCache gdCache;
    const char *fileId;
    HCkStringBuilder sbPath;
    HCkStream fileStream;
    const char *jsonResponse;

    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.

    gAuth = CkAuthGoogle_Create();
    CkAuthGoogle_putAccessToken(gAuth,"GOOGLE_DRIVE_ACCESS_TOKEN");

    rest = CkRest_Create();

    // 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.
    bAutoReconnect = TRUE;
    success = CkRest_Connect(rest,"www.googleapis.com",443,TRUE,bAutoReconnect);

    // Provide the authentication credentials (i.e. the access token)
    CkRest_SetAuthGoogle(rest,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.
    gdCache = CkCache_Create();
    CkCache_putLevel(gdCache,0);
    CkCache_AddRoot(gdCache,"C:/ckCache/googleDrive");

    fileId = CkCache_fetchText(gdCache,"testFolder/abc/123/penguins.jpg");
    if (CkCache_getLastMethodSuccess(gdCache) != TRUE) {
        printf("Filepath not found in cache.\n");
        CkAuthGoogle_Dispose(gAuth);
        CkRest_Dispose(rest);
        CkCache_Dispose(gdCache);
        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.
    sbPath = CkStringBuilder_Create();
    CkStringBuilder_Append(sbPath,"/drive/v3/files/");
    CkStringBuilder_Append(sbPath,fileId);
    CkRest_AddQueryParam(rest,"alt","media");

    // Create a stream object with a SinkFile set to the path where the downloaded file will go.
    fileStream = CkStream_Create();
    CkStream_putSinkFile(fileStream,"qa_output/penguins.jpg");
    // Indicate that the response body should stream directly to fileStream,
    // but only if the response status is 200.  
    CkRest_SetResponseBodyStream(rest,200,TRUE,fileStream);

    // Download the file, streaming the content to the SinkFile.
    jsonResponse = CkRest_fullRequestNoBody(rest,"GET",CkStringBuilder_getAsString(sbPath));
    if (CkRest_getLastMethodSuccess(rest) != TRUE) {
        printf("%s\n",CkRest_lastErrorText(rest));
        CkAuthGoogle_Dispose(gAuth);
        CkRest_Dispose(rest);
        CkCache_Dispose(gdCache);
        CkStringBuilder_Dispose(sbPath);
        CkStream_Dispose(fileStream);
        return;
    }

    // A successful response will have a status code equal to 200.
    if (CkRest_getResponseStatusCode(rest) != 200) {
        printf("response status code = %d\n",CkRest_getResponseStatusCode(rest));
        printf("response status text = %s\n",CkRest_responseStatusText(rest));
        printf("response header: %s\n",CkRest_responseHeader(rest));
        CkAuthGoogle_Dispose(gAuth);
        CkRest_Dispose(rest);
        CkCache_Dispose(gdCache);
        CkStringBuilder_Dispose(sbPath);
        CkStream_Dispose(fileStream);
        return;
    }

    printf("File downloaded.\n");


    CkAuthGoogle_Dispose(gAuth);
    CkRest_Dispose(rest);
    CkCache_Dispose(gdCache);
    CkStringBuilder_Dispose(sbPath);
    CkStream_Dispose(fileStream);

    }