(C) Download Object from Google Cloud Storage

Demonstrates how to download an object from Google Cloud Storage to a file.

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#include <C_CkStringBuilder.h>
#include <C_CkHttp.h>
#include <C_CkBinData.h>

void ChilkatSample(void)
    {
    HCkStringBuilder sbToken;
    HCkHttp http;
    const char *url;
    HCkBinData fileData;
    BOOL success;
    HCkStringBuilder sbErrorResponse;
    int responseCode;

    // This example 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 
    // scope "https://www.googleapis.com/auth/cloud-platform"

    // In this example, Get Google Cloud Storage OAuth2 Access Token, 
    // the service account access token was saved to a text file.  This example fetches the access token from the file..
    sbToken = CkStringBuilder_Create();
    CkStringBuilder_LoadFile(sbToken,"qa_data/tokens/googleCloudStorageAccessToken.txt","utf-8");

    // Send a GET equivalent to this curl command.

    // curl -X GET \
    //     -H "Authorization: Bearer [OAUTH2_TOKEN]" \
    //     -o "[SAVE_TO_LOCATION]" \
    //     "https://www.googleapis.com/storage/v1/b/[BUCKET_NAME]/o/[OBJECT_NAME]?alt=media"

    http = CkHttp_Create();

    CkHttp_putAuthToken(http,CkStringBuilder_getAsString(sbToken));

    // Construct a URL to download an object named "starfish.jpg" from the "chilkat-ocean" bucket.
    CkHttp_SetUrlVar(http,"bucket_name","chilkat-ocean");
    CkHttp_SetUrlVar(http,"object_name","starfish.jpg");
    url = "https://www.googleapis.com/storage/v1/b/{$bucket_name}/o/{$object_name}?alt=media";

    // If there is an error response, then we didn't actually download the file data,
    // but instead we downloaded an error response..
    fileData = CkBinData_Create();
    success = CkHttp_DownloadBd(http,url,fileData);
    if (success == FALSE) {
        printf("%s\n",CkHttp_lastErrorText(http));
        CkStringBuilder_Dispose(sbToken);
        CkHttp_Dispose(http);
        CkBinData_Dispose(fileData);
        return;
    }

    sbErrorResponse = CkStringBuilder_Create();
    responseCode = CkHttp_getLastStatus(http);
    if (responseCode == 401) {
        printf("If invalid credentials, then it is likely the access token expired.\n");
        printf("Your app should automatically fetch a new access token and re-try.\n");
    }

    if (responseCode != 200) {
        // Get the error response
        CkStringBuilder_AppendBd(sbErrorResponse,fileData,"utf-8",0,0);
        printf("Error response code = %d\n",responseCode);
        printf("Error:\n");
        printf("%s\n",CkStringBuilder_getAsString(sbErrorResponse));
        CkStringBuilder_Dispose(sbToken);
        CkHttp_Dispose(http);
        CkBinData_Dispose(fileData);
        CkStringBuilder_Dispose(sbErrorResponse);
        return;
    }

    printf("Success.\n");

    // Save the downloaded data to a file.
    success = CkBinData_WriteFile(fileData,"qa_output/starfish.jpg");


    CkStringBuilder_Dispose(sbToken);
    CkHttp_Dispose(http);
    CkBinData_Dispose(fileData);
    CkStringBuilder_Dispose(sbErrorResponse);

    }