How to satisfy multiple byte ranges when using PushStreamContent in WebAPI? - asp.net-web-api

Question

I need to use PushStreamContent because of the source of my data (effectively have to concatenate blobs), but I also have to support requests for multiple byte ranges (arbitrary ranges not aligned to the stored blobs). What is not clear to me is if I can use PushStreamContent to generate a multipart/byteranges response, if each range needs to be separated in the response, and if so, how to do it, and how it relates to the chunked transfer encoding which PushStreamContent invokes.

Answer 1

You can do it using MultipartContent like this:
public class MyRangeController : ApiController
{
[HttpGet]
public HttpResponseMessage Get()
{
// Create a multi-part content object for the response; note that per RFC spec, subtype must be "byteranges"
// Note that the content type of the over-all response will be "multipart/byteranges"
// We choose to use a GUID string for the separator; it could be anything suitable.
var multipartContent = new MultipartContent("byteranges", Guid.NewGuid().ToString("D"));
// Create the response object and set its content
var response = new HttpResponseMessage(HttpStatusCode.PartialContent) { Content = multipartContent };
foreach (var rangeItemHeaderValue in Request.Headers.Range.Ranges)
{
// Create PushStreamContent object for our current byte range...
var pushStreamContent = new PushStreamContent((stream1, content, arg3) =>
{
// Write to stream1
stream1.Close();
});
// We need to add certain headers to each part of the response
pushStreamContent.Headers.ContentRange = new ContentRangeHeaderValue(rangeItemHeaderValue.From.Value, rangeItemHeaderValue.To.Value, /* total size of the resource */);
pushStreamContent.Headers.ContentType = new MediaTypeHeaderValue(/* Set a content type for each part of the response */);
// Add the part to the multi-part content response
multipartContent.Add(pushStreamContent);
}
return response;
}
}