public async IAsyncEnumerable <GetObjectResponse> MultipartDownloadAsync(string bucketName, string objectKey, Stream output, int bufferSize = 16777216, int numParallelParts = 4, Action <GetObjectRequest>?config = null, [EnumeratorCancellation] CancellationToken token = default)
{
Validator.RequireNotNull(output, nameof(output));
//Use a HEAD request on the object key to determine if the file was originally uploaded with multipart
HeadObjectResponse headResp = await _objectClient.HeadObjectAsync(bucketName, objectKey, req => req.PartNumber = 1, token).ConfigureAwait(false);
Queue <Task <GetObjectResponse> > queue = new Queue <Task <GetObjectResponse> >();
if (headResp.NumberOfParts == null)
{
GetObjectResponse getResp = await _objectClient.GetObjectAsync(bucketName, objectKey, config, token).ConfigureAwait(false);
if (!getResp.IsSuccess)
{
throw new S3RequestException(getResp);
}
await getResp.Content.CopyToAsync(output, 81920, token).ConfigureAwait(false);
yield return(getResp);
}
else
{
int parts = headResp.NumberOfParts.Value;
using (SemaphoreSlim semaphore = new SemaphoreSlim(numParallelParts))
using (Mutex mutex = new Mutex())
{
for (int i = 1; i <= parts; i++)
{
await semaphore.WaitAsync(token).ConfigureAwait(false);
if (token.IsCancellationRequested)
{
yield break;
}
queue.Enqueue(DownloadPartAsync(bucketName, objectKey, output, headResp.ContentLength, i, bufferSize, semaphore, mutex, config, token));
}
while (queue.TryDequeue(out Task <GetObjectResponse>?task))
{
if (token.IsCancellationRequested)
{
yield break;
}
GetObjectResponse response = await task !.ConfigureAwait(false);
yield return(response);
}
}
}
}
public Task <HeadObjectResponse> HeadObjectAsync(string bucketName, string objectKey, Action <HeadObjectRequest>?config = null, CancellationToken token = default)
{
return(_objectClient.HeadObjectAsync(bucketName, objectKey, config, token));
}