range-request-middleware

HTTP range request middleware.

Handles range request and partial response.

Compliant with RFC 9110, 14. Range Requests

Usage

Upon receipt of a range request, if the response satisfies the range requirement, merge it to a partial response.

import { rangeRequest } from "https://deno.land/x/range_request_middleware@$VERSION/mod.ts";
import {
  assert,
  assertEquals,
  assertThrows,
} from "https://deno.land/std/testing/asserts.ts";

const middleware = rangeRequest();
const request = new Request("test:", {
  headers: { range: "bytes=5-9" },
});
const response = await middleware(
  request,
  () => new Response("abcdefghijklmnopqrstuvwxyz"),
);

assertEquals(response.status, 206);
assertEquals(response.headers.get("content-range"), "bytes 5-9/26");
assertEquals(response.headers.get("accept-ranges"), "bytes");
assertEquals(await response.text(), "fghij");

yield:

HTTP/<VERSION> 206
Content-Range: bytes 5-9/26
Accept-Ranges: bytes

fghij

Multi-range request

For multi-range request, response body will convert to a multipart content.

It compliant with RFC 9110, 14.6. Media Type multipart/byteranges.

import { rangeRequest } from "https://deno.land/x/range_request_middleware@$VERSION/mod.ts";
import {
  assert,
  assertEquals,
  assertThrows,
} from "https://deno.land/std/testing/asserts.ts";

const middleware = rangeRequest();
const request = new Request("test:", {
  headers: { range: "bytes=5-9, 20-, -5" },
});
const response = await middleware(
  request,
  () => new Response("abcdefghijklmnopqrstuvwxyz"),
);

assertEquals(response.status, 206);
assertEquals(
  response.headers.get(
    "content-type",
  ),
  "multipart/byteranges; boundary=<boundary-delimiter>",
);
assertEquals(
  await response.text(),
  `--<boundary-delimiter>
Content-Type: text/plain;charset=UTF-8
Content-Range: 5-9/26

fghij
--<boundary-delimiter>
Content-Type: text/plain;charset=UTF-8
Content-Range: 20-25/26

uvwxyz
--<boundary-delimiter>
Content-Type: text/plain;charset=UTF-8
Content-Range: 21-25/26

vwxyz
--<boundary-delimiter>--`,
);

yield:

HTTP/<VERSION> 206
Content-Type: multipart/byteranges; boundary=<BOUNDARY-DELIMITER>
Accept-Ranges: bytes

--<BOUNDARY-DELIMITER>
Content-Type: text/plain;charset=UTF-8
Content-Range: 5-9/26

fghij
--<BOUNDARY-DELIMITER>
Content-Type: text/plain;charset=UTF-8
Content-Range: 20-25/26

uvwxyz
--<BOUNDARY-DELIMITER>
Content-Type: text/plain;charset=UTF-8
Content-Range: 21-25/26

vwxyz
--<BOUNDARY-DELIMITER>--

Conditions

There are several conditions that must be met in order for middleware to execute.

If the following conditions are not met, invalid and the response will not modify.

• Request method is GET.
• Request has Range header
• Request does not include If-Range header
• Request Range header is valid syntax
• Request Range header is valid semantics
• Response status code is 200
• Response does not include Content-Range header
• Response does not include Accept-Ranges header or its value is not none
• Response includes Content-Type header
• Response body is readable

Note that if there is an If-Range header, do nothing.

Unsatisfiable

If conditions is met and the following conditions are not met ,unsatisfiable, and it is not possible to meet partial response.

• If a valid ranges-specifier contains at least one satisfactory range-spec, as defined in the indicated range-unit

In this case, the handler response will merge to 416(Range Not Satisfiable) response.

A example of how unsatisfiable can happen:

If receive un unknown range unit.

import {
  type Handler,
  rangeRequest,
} from "https://deno.land/x/range_request_middleware@$VERSION/mod.ts";
import { assert, assertEquals } from "https://deno.land/std/testing/asserts.ts";

declare const handler: Handler;
const middleware = rangeRequest();
const response = await middleware(
  new Request("test:", { headers: { range: "<unknown-unit>=<other-range>" } }),
  handler,
);

assertEquals(response.status, 416);
assert(response.headers.has("content-range"));

Satisfiable

If the conditions and unsatisfiable are met, satisfiable, and partial response will return.

The handler response will merge to 206(Partial Content) response.

Merging

The response of the handler and the response of Range.respond will merge .

The following elements are merged shallowly, giving priority to the Response of Range.respond.

• HTTP Status code
• HTTP Content
• HTTP Headers

Range

Range abstracts partial response.

Middleware factories can accept Range objects and implement own range request protocols.

Range is the following structure:

The middleware supports the following range request protocols by default:

• bytes(ByteRange)

ByteRange

bytes range unit is used to express subranges of a representation data’s octet sequence.

ByteRange supports single and multiple range requests.

Compliant with RFC 9110, 14.1.2. Byte Ranges.

Effects

Middleware may make changes to the following HTTP messages:

• HTTP Content
• HTTP Headers
  • Accept-Ranges
  • Content-Range
  • Content-Type
• HTTP Status code
  • 206(Partial Content)
  • 416(Range Not Satisfiable)

License

Copyright © 2023-present httpland.

Released under the MIT license