Chunk Extensions

For a message encoded by Transfer-Encoding: chunked, each data chunk is allowed to contain zero or more chunk-extensions. These extensions immediately follow the chunk-size, for the sake of supplying per-chunk metadata (such as a signature or hash), mid-message control information, or randomization of message body size.

Each extension is a name-value pair with = as a separator, such as language = en; multiple extensions are combined with ; as a separator, such as language=en; city=London.

An example of carring chunk extensions:

HTTP/1.1 200 OK
Transfer-Encoding: chunked

9; language=en; city=London\r\n
Developer\r\n
0\r\n
\r\n

Trailers

Messages encoded with Transfer-Encoding: chunked are allowed to carry trailers at the end. Trailer is actually one or more HTTP response header fields, allowing the sender to add additional meta-information at the end of a message. These meta-information may be dynamically generated with the sending of the message body, such as message integrity check, message Digital signature, or the final state of the message after processing, etc.

Note: Only when the client sets trailers in the request header TE (TE: trailers), the server can carry Trailer in the response.

An example of carring trailers:

HTTP/1.1 200 OK
Transfer-Encoding: chunked
Trailer: Expires

9\r\n
Developer\r\n
0\r\n
Expires: Wed, 21 Oct 2015 07:28:00 GMT\r\n
\r\n

Chunk Extensions

To extract chunk extensions:

import netkit/http/metadata
import netkit/http/chunk

let metadata = HttpMetadata(
  kind: HttpMetadataKind.ChunkExtensions,
  extensions: "; a1=v1; a2=v2"
)
let extensions = parseChunkExtensions(metadata.extensions)
assert extensions[0].name = "a1"
assert extensions[0].value = "v1"
assert extensions[1].name = "a2"
assert extensions[1].value = "v2"

Trailers

To extract trailers:

import netkit/http/metadata
import netkit/http/chunk

let metadata = HttpMetadata(
  kind: HttpMetadataKind.ChunkTrailers,
  trailers: @["Expires: Wed, 21 Oct 2015 07:28:00 GMT"]
)
let tailers = parseChunkTrailers(metadata.trailers)
assert tailers["Expires"][0] == "Wed, 21 Oct 2015 07:28:00 GMT"