# Using TransferManager for Amazon S3 operations
<a name="examples-s3-transfermanager"></a>

You can use the AWS SDK for C\$1\$1 `TransferManager` class to reliably transfer files from the local environment to Amazon S3 and to copy objects from one Amazon S3 location to another. `TransferManager` can get the progress of a transfer and pause or resume uploads and downloads.

**Note**  
To avoid being charged for incomplete or partial uploads, we recommend that you enable the [AbortIncompleteMultipartUpload](https://docs.aws.amazon.com/AmazonS3/latest/userguide/mpu-abort-incomplete-mpu-lifecycle-config.html) lifecycle rule on your Amazon S3 buckets.  
This rule directs Amazon S3 to abort multipart uploads that don’t complete within a specified number of days after being initiated. When the set time limit is exceeded, Amazon S3 aborts the upload and then deletes the incomplete upload data.   
For more information, see [Setting lifecycle configuration on a bucket](https://docs.aws.amazon.com/AmazonS3/latest/userguide/how-to-set-lifecycle-configuration-intro.html) in the Amazon S3 User Guide.

## Prerequisites
<a name="codeExamplePrereq"></a>

Before you begin, we recommend you read [Getting started using the AWS SDK for C\$1\$1](getting-started.md). 

Download the example code and build the solution as described in [Getting started on code examples](getting-started-code-examples.md). 

To run the examples, the user profile your code uses to make the requests must have proper permissions in AWS (for the service and the action). For more information, see [Providing AWS credentials](credentials.md).

## Upload and download of object using `TransferManager`
<a name="stream"></a>

This example demonstrates how [https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-transfer/html/class_aws_1_1_transfer_1_1_transfer_manager.html](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-transfer/html/class_aws_1_1_transfer_1_1_transfer_manager.html) transfers large object in memory. `UploadFile` and `DownloadFile` methods are both called asynchronously and return a `TransferHandle` to manage the status of your request. If the object uploaded is larger than `bufferSize` then a multipart upload will be performed. The `bufferSize` defaults to 5MB, but this can be configured via [https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-transfer/html/struct_aws_1_1_transfer_1_1_transfer_manager_configuration.html](https://docs.aws.amazon.com/sdk-for-cpp/latest/api/aws-cpp-sdk-transfer/html/struct_aws_1_1_transfer_1_1_transfer_manager_configuration.html). 

```
        auto s3_client = Aws::MakeShared<Aws::S3::S3Client>("S3Client");
        auto executor = Aws::MakeShared<Aws::Utils::Threading::PooledThreadExecutor>("executor", 25);
        Aws::Transfer::TransferManagerConfiguration transfer_config(executor.get());
        transfer_config.s3Client = s3_client;

        // Create buffer to hold data received by the data stream.
        Aws::Utils::Array<unsigned char> buffer(BUFFER_SIZE);

        // The local variable 'streamBuffer' is captured by reference in a lambda.
        // It must persist until all downloading by the 'transfer_manager' is complete.
        Stream::PreallocatedStreamBuf streamBuffer(buffer.GetUnderlyingData(), buffer.GetLength());

        auto transfer_manager = Aws::Transfer::TransferManager::Create(transfer_config);

        auto uploadHandle = transfer_manager->UploadFile(LOCAL_FILE, BUCKET, KEY, "text/plain", Aws::Map<Aws::String, Aws::String>());
        uploadHandle->WaitUntilFinished();
        bool success = uploadHandle->GetStatus() == Transfer::TransferStatus::COMPLETED; 
      
        if (!success)
        {
            auto err = uploadHandle->GetLastError();           
            std::cout << "File upload failed:  "<< err.GetMessage() << std::endl;
        }
        else
        {
            std::cout << "File upload finished." << std::endl;

            auto downloadHandle = transfer_manager->DownloadFile(BUCKET,
                KEY,
                [&]() { //Define a lambda expression for the callback method parameter to stream back the data.
                    return Aws::New<MyUnderlyingStream>("TestTag", &streamBuffer);
                });
            downloadHandle->WaitUntilFinished();// Block calling thread until download is complete.
            auto downStat = downloadHandle->GetStatus();
            if (downStat != Transfer::TransferStatus::COMPLETED)
            {
                auto err = downloadHandle->GetLastError();
                std::cout << "File download failed:  " << err.GetMessage() << std::endl;
            }
            std::cout << "File download to memory finished."  << std::endl;
```

See the [complete example](https://github.com/awsdocs/aws-doc-sdk-examples/tree/main/cpp/example_code/transfer-manager/transferOnStream.cpp) on Github.