Range requests is the ability in HTTP to request a part of a document based on one or more ranges. This can be used in scenarios where the client wants to recover from interrupted data transfers as a result of canceled requests or dropped connections. It can also be used in scenarios where a client requests only a subset of a larger representation, such as a single segment of a very large document for special processing. Ranges specify a start and an end given a unit. The unit can be anything but by far the most common is \u201cbytes\u201d. An example of a range request asking for the first 10 bytes is as follows:<\/p>\n
GET \/api\/range HTTP\/1.1 An example asking for the first and last byte contains two ranges separated by comma as follows:<\/p>\n GET \/api\/range HTTP\/1.1 In this example the resource which we are doing range requests over contains the 26 letters of the English alphabet:<\/p>\n HTTP\/1.1 200 OK abcdefghijklmnopqrstuvwxyz<\/font><\/p>\n The response to a byte range request is a 206 (Partial Content) response. If only one range was requested then the response looks similar to a 200 (OK) response with the exception that it has a Content-Range header field indicating the range and the total length of the document:<\/p>\n HTTP\/1.1 206 Partial Content <\/font>abcdefghij<\/font><\/p>\n Note that the Content-Length header indicates the bytes actually in the response and not the total size of the document requested. <\/p>\n If more than one ranges were requested then the response has the media type \u201cmultipart\/byteranges\u201d with a body part for each range:<\/p>\n HTTP\/1.1 206 Partial Content –57c2656a-9716-4ea0-9d3b-2f76cbac4885 a z Range requests that don\u2019t overlap with the extent of the resource result in a 416 (Requested Range Not Satisfiable) with a Content-Range header indicating the current extent of the resource.<\/p>\n HTTP\/1.1 416 Requested Range Not Satisfiable In addition to using ranges as described above, range requests can be made conditional using an If-Range header field meaning \u201csend me the following range but only if the ETag matches; otherwise send me the whole response.\u201d<\/p>\n With the addition of the ByteRangeStreamContent<\/a> class to ASP.NET Web API (available in latest nightly build, not RTM<\/a>), it is now simpler to support byte range requests. The ByteRangeStreamContent class can also be used in scenarios supporting conditional If-Range requests although we don\u2019t show this scenario in this blog.<\/p>\n The ByteRangeStreamContent is very similar to the already existing StreamContent<\/a> in that it provides a view over a stream. ByteRangeStreamContent requires the stream to be seekable in order to provide one or more ranges over it. Common examples of seekable streams are FileStreams<\/a> and MemoryStreams<\/a>. In this blog we show an example using a MemoryStream but a FileStream or other seekable stream would work just as well.<\/p>\n Below is the sample controller. It is part of the ASP.NET Web API samples<\/a> where the entire sample project is available in our git repository<\/a>.<\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/p>\n <\/div>\n<\/div>\n <\/p>\n The first thing to check is if the incoming request is a range request. If it is then we create a ByteRangeStreamContent and return that. Otherwise we create a StreamContent and return that. The ByteRangeStreamContent throws an InvalidByteRangeException is no overlapping ranges are found so we catch that and create a 416 (Requested Range Not Satisfiable) response.<\/p>\n Running the sample creates a set of range requests. We write the corresponding responses to the console as follows:<\/p>\n Full Content without ranges: ‘abcdefghijklmnopqrstuvwxyz’ <\/p>\n Range ‘bytes=0-0’ requesting the first byte: ‘a’ <\/p>\n Range ‘bytes=-1’ requesting the last byte: ‘z’ <\/p>\n Range ‘bytes=4-‘ requesting byte 4 and up: ‘efghijklmnopqrstuvwxyz’ <\/p>\n Range ‘bytes=0-0, -1’ requesting first and last byte: <\/p>\n –04214a40-a998-4b9e-a564-c21955bd36db <\/p>\n Content-Type: text\/plain <\/p>\n Content-Range: bytes 0-0\/26 <\/p>\n a <\/p>\n –04214a40-a998-4b9e-a564-c21955bd36db <\/p>\n Content-Type: text\/plain <\/p>\n Content-Range: bytes 25-25\/26 <\/p>\n z <\/p>\n –04214a40-a998-4b9e-a564-c21955bd36db– <\/p>\n Range ‘bytes=0-0, 12-15, -1’ requesting first, mid four, and last byte: <\/p>\n –b1d1d766-c424-49cb-9843-dd741be35f4c <\/p>\n Content-Type: text\/plain <\/p>\n Content-Range: bytes 0-0\/26 <\/p>\n a <\/p>\n –b1d1d766-c424-49cb-9843-dd741be35f4c <\/p>\n Content-Type: text\/plain <\/p>\n Content-Range: bytes 12-15\/26 <\/p>\n mnop <\/p>\n –b1d1d766-c424-49cb-9843-dd741be35f4c <\/p>\n Content-Type: text\/plain <\/p>\n Content-Range: bytes 25-25\/26 <\/p>\n z <\/p>\n –b1d1d766-c424-49cb-9843-dd741be35f4c– <\/p>\n Range ‘bytes=100-‘ resulted in status code ‘RequestedRangeNotSatisfiable’ with <\/p>\n Content-Range header ‘bytes *\/26’<\/font><\/p>\n Have fun!<\/p>\n Henrik<\/p>\n","protected":false},"excerpt":{"rendered":" Range requests is the ability in HTTP to request a part of a document based on one or more ranges. This can be used in scenarios where the client wants to recover from interrupted data transfers as a result of canceled requests or dropped connections. It can also be used in scenarios where a client […]<\/p>\n","protected":false},"author":403,"featured_media":58792,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"_acf_changed":false,"footnotes":""},"categories":[197],"tags":[31,34,7420,80],"class_list":["post-1994","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-aspnet","tag-asp-net","tag-asp-net-web-api","tag-codepl","tag-httpclient"],"acf":[],"blog_post_summary":" Range requests is the ability in HTTP to request a part of a document based on one or more ranges. This can be used in scenarios where the client wants to recover from interrupted data transfers as a result of canceled requests or dropped connections. It can also be used in scenarios where a client […]<\/p>\n","_links":{"self":[{"href":"https:\/\/devblogs.microsoft.com\/dotnet\/wp-json\/wp\/v2\/posts\/1994","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/devblogs.microsoft.com\/dotnet\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/devblogs.microsoft.com\/dotnet\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/dotnet\/wp-json\/wp\/v2\/users\/403"}],"replies":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/dotnet\/wp-json\/wp\/v2\/comments?post=1994"}],"version-history":[{"count":0,"href":"https:\/\/devblogs.microsoft.com\/dotnet\/wp-json\/wp\/v2\/posts\/1994\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/dotnet\/wp-json\/wp\/v2\/media\/58792"}],"wp:attachment":[{"href":"https:\/\/devblogs.microsoft.com\/dotnet\/wp-json\/wp\/v2\/media?parent=1994"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/dotnet\/wp-json\/wp\/v2\/categories?post=1994"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/devblogs.microsoft.com\/dotnet\/wp-json\/wp\/v2\/tags?post=1994"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}
Host: localhost:50231
Range : bytes=0-9<\/font><\/p>\n
Host: localhost:50231
Range : bytes=0-0, -1<\/font> <\/p>\n
Content-Length: 26
Content-Type: text\/plain <\/p>\n
Content-Length: 10
Content-Type: text\/plain
<\/font>Content-Range: bytes 0-9\/26 <\/p>\n
Content-Length: 244
Content-Type: multipart\/byteranges; boundary="57c2656a-9716-4ea0-9d3b-2f76cbac4885"<\/font><\/p>\n
Content-Type: text\/plain
Content-Range: bytes 0-0\/26 <\/p>\n
–57c2656a-9716-4ea0-9d3b-2f76cbac4885
Content-Type: text\/plain
Content-Range: bytes 25-25\/26 <\/p>\n
–57c2656a-9716-4ea0-9d3b-2f76cbac4885–<\/font> <\/p>\n
Content-Range: bytes *\/26<\/font><\/p>\nThe Range Controller<\/h2>\n
1:<\/span> public class RangeController : ApiController<\/pre>\n 2:<\/span> {<\/pre>\n 3:<\/span> \/\/ Sample content used to demonstrate range requests<\/pre>\n 4:<\/span> private static readonly byte[] _content = Encoding.UTF8.GetBytes("abcdefghijklmnopqrstuvwxyz");<\/pre>\n 5:<\/span> <\/pre>\n 6:<\/span> \/\/ Content type for our body<\/pre>\n 7:<\/span> private static readonly MediaTypeHeaderValue _mediaType = MediaTypeHeaderValue.Parse("text\/plain");<\/pre>\n 8:<\/span> <\/pre>\n 9:<\/span> public HttpResponseMessage Get()<\/pre>\n 10:<\/span> {<\/pre>\n 11:<\/span> \/\/ A MemoryStream is seekable allowing us to do ranges over it. Same goes for FileStream.<\/pre>\n 12:<\/span> MemoryStream memStream = new MemoryStream(_content);<\/pre>\n 13:<\/span> <\/pre>\n 14:<\/span> \/\/ Check to see if this is a range request (i.e. contains a Range header field)<\/pre>\n 15:<\/span> \/\/ Range requests can also be made conditional using the If-Range header field. This can be <\/pre>\n 16:<\/span> \/\/ used to generate a request which says: send me the range if the content hasn't changed; <\/pre>\n 17:<\/span> \/\/ otherwise send me the whole thing.<\/pre>\n 18:<\/span> if (Request.Headers.Range != null)<\/pre>\n 19:<\/span> {<\/pre>\n 20:<\/span> try<\/pre>\n 21:<\/span> {<\/pre>\n 22:<\/span> HttpResponseMessage partialResponse = Request.CreateResponse(HttpStatusCode.PartialContent);<\/pre>\n 23:<\/span> partialResponse.Content = new ByteRangeStreamContent(memStream, Request.Headers.Range, _mediaType);<\/pre>\n 24:<\/span> return partialResponse;<\/pre>\n 25:<\/span> }<\/pre>\n 26:<\/span> catch (InvalidByteRangeException invalidByteRangeException)<\/pre>\n 27:<\/span> {<\/pre>\n 28:<\/span> return Request.CreateErrorResponse(invalidByteRangeException);<\/pre>\n 29:<\/span> }<\/pre>\n 30:<\/span> }<\/pre>\n 31:<\/span> else<\/pre>\n 32:<\/span> {<\/pre>\n 33:<\/span> \/\/ If it is not a range request we just send the whole thing as normal<\/pre>\n 34:<\/span> HttpResponseMessage fullResponse = Request.CreateResponse(HttpStatusCode.OK);<\/pre>\n 35:<\/span> fullResponse.Content = new StreamContent(memStream);<\/pre>\n 36:<\/span> fullResponse.Content.Headers.ContentType = _mediaType;<\/pre>\n 37:<\/span> return fullResponse;<\/pre>\n 38:<\/span> }<\/pre>\n 39:<\/span> }<\/pre>\n 40:<\/span> }<\/pre>\nTrying It Out<\/h2>\n