(C++) Get Object MetaData from Google Cloud Storage

Demonstrates how to download a Google Cloud Storage object's metadata.

Chilkat C/C++ Library Downloads
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#include <CkStringBuilder.h>
#include <CkHttp.h>

void ChilkatSample(void)
    {
    // 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..
    CkStringBuilder sbToken;
    sbToken.LoadFile("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]?projection=full"

    CkHttp http;

    http.put_AuthToken(sbToken.getAsString());

    // Construct a URL to download the metadata for the object named "starfish.jpg" located in the "chilkat-ocean" bucket.
    http.SetUrlVar("bucket_name","chilkat-ocean");
    http.SetUrlVar("object_name","starfish.jpg");
    const char *url = "https://www.googleapis.com/storage/v1/b/{$bucket_name}/o/{$object_name}?projection=full";

    // If there is an error response, then we didn't actually download the metadata,
    // but instead we downloaded an error response..
    CkStringBuilder sbMetaData;
    bool success = http.DownloadSb(url,"utf-8",sbMetaData);
    if (success == false) {
        std::cout << http.lastErrorText() << "\r\n";
        return;
    }

    int responseCode = http.get_LastStatus();
    if (responseCode == 401) {
        std::cout << "If invalid credentials, then it is likely the access token expired." << "\r\n";
        std::cout << "Your app should automatically fetch a new access token and re-try." << "\r\n";
    }

    if (responseCode != 200) {
        std::cout << "Error response code = " << responseCode << "\r\n";
        std::cout << "Error:" << "\r\n";
        std::cout << sbMetaData.getAsString() << "\r\n";
        return;
    }

    std::cout << sbMetaData.getAsString() << "\r\n";
    std::cout << "Success." << "\r\n";

    // Sample output:

    // {
    //  "kind": "storage#object",
    //  "id": "chilkat-ocean/starfish.jpg/1502670320090292",
    //  "selfLink": "https://www.googleapis.com/storage/v1/b/chilkat-ocean/o/starfish.jpg",
    //  "name": "starfish.jpg",
    //  "bucket": "chilkat-ocean",
    //  "generation": "1502670320090292",
    //  "metageneration": "1",
    //  "contentType": "image/jpeg",
    //  "timeCreated": "2017-08-14T00:25:20.040Z",
    //  "updated": "2017-08-14T00:25:20.040Z",
    //  "storageClass": "MULTI_REGIONAL",
    //  "timeStorageClassUpdated": "2017-08-14T00:25:20.040Z",
    //  "size": "6229",
    //  "md5Hash": "LpxZ2/JmI2fcl9/dqF2gSA==",
    //  "mediaLink": "https://www.googleapis.com/download/storage/v1/b/chilkat-ocean/o/starfish.jpg?generation=1502670320090292&alt=media",
    //  "acl": [
    //   {
    //    "kind": "storage#objectAccessControl",
    //    "id": "chilkat-ocean/starfish.jpg/1502670320090292/project-owners-933037264567",
    //    "selfLink": "https://www.googleapis.com/storage/v1/b/chilkat-ocean/o/starfish.jpg/acl/project-owners-933037264567",
    //    "bucket": "chilkat-ocean",
    //    "object": "starfish.jpg",
    //    "generation": "1502670320090292",
    //    "entity": "project-owners-933037264567",
    //    "role": "OWNER",
    //    "projectTeam": {
    //     "projectNumber": "933037264567",
    //     "team": "owners"
    //    },
    //    "etag": "CLT5kpW71dUCEAE="
    //   },
    //   {
    //    "kind": "storage#objectAccessControl",
    //    "id": "chilkat-ocean/starfish.jpg/1502670320090292/project-editors-933037264567",
    //    "selfLink": "https://www.googleapis.com/storage/v1/b/chilkat-ocean/o/starfish.jpg/acl/project-editors-933037264567",
    //    "bucket": "chilkat-ocean",
    //    "object": "starfish.jpg",
    //    "generation": "1502670320090292",
    //    "entity": "project-editors-933037264567",
    //    "role": "OWNER",
    //    "projectTeam": {
    //     "projectNumber": "933037264567",
    //     "team": "editors"
    //    },
    //    "etag": "CLT5kpW71dUCEAE="
    //   },
    //   {
    //    "kind": "storage#objectAccessControl",
    //    "id": "chilkat-ocean/starfish.jpg/1502670320090292/project-viewers-933037264567",
    //    "selfLink": "https://www.googleapis.com/storage/v1/b/chilkat-ocean/o/starfish.jpg/acl/project-viewers-933037264567",
    //    "bucket": "chilkat-ocean",
    //    "object": "starfish.jpg",
    //    "generation": "1502670320090292",
    //    "entity": "project-viewers-933037264567",
    //    "role": "READER",
    //    "projectTeam": {
    //     "projectNumber": "933037264567",
    //     "team": "viewers"
    //    },
    //    "etag": "CLT5kpW71dUCEAE="
    //   },
    //   {
    //    "kind": "storage#objectAccessControl",
    //    "id": "chilkat-ocean/starfish.jpg/1502670320090292/user-starfish@chilkat-176611.iam.gserviceaccount.com",
    //    "selfLink": "https://www.googleapis.com/storage/v1/b/chilkat-ocean/o/starfish.jpg/acl/user-starfish@chilkat-176611.iam.gserviceaccount.com",
    //    "bucket": "chilkat-ocean",
    //    "object": "starfish.jpg",
    //    "generation": "1502670320090292",
    //    "entity": "user-starfish@chilkat-176611.iam.gserviceaccount.com",
    //    "role": "OWNER",
    //    "email": "starfish@chilkat-176611.iam.gserviceaccount.com",
    //    "etag": "CLT5kpW71dUCEAE="
    //   }
    //  ],
    //  "owner": {
    //   "entity": "user-starfish@chilkat-176611.iam.gserviceaccount.com"
    //  },
    //  "crc32c": "9RjgwQ==",
    //  "etag": "CLT5kpW71dUCEAE="
    // }
    // 
    }