HTTP compression middleware.
Compresses HTTP Content(body).
Compliant with RFC 9110, 8.4. Content-Encoding and RFC 9110, 12.5.3. Accept-Encoding .
For a definition of Universal HTTP middleware, see the http-middleware project.
Middleware convert message body and adds the Content-Encoding header to the
response.
Also, safely add Accept-Encoding to the Vary header in response.
import{compression}from"https://deno.land/x/compression_middleware@$VERSION/mod.ts";import{assertEquals}from"https://deno.land/std/testing/asserts.ts";constmiddleware=compression();constrequest=newRequest("test:",{headers: {"accept-encoding": "deflate;q=0.5, gzip;q=1.0",},});constresponse=awaitmiddleware(request,()=>newResponse("<body>"),);assertEquals(awaitresponse.text(),"<gzip:body>");assertEquals(response.headers.get("content-encoding"),"gzip");yield:
Content-Encoding: <encoding>Vary: accept-encodingMiddleware supports the following encodings by default:
- gzip
- deflate
You can add supported encoding.
There are two ways to add encodings:
- Encoding map
- Encoder list
In either style, the result is the same.
When encoding is added, a shallow merge is performed in favor of user-defined.
Encoding map defines a map of encoding formats and encode functions .
Example of adding brotli encoding:
import{compression,typeEncode,typeEncodingMap,}from"https://deno.land/x/compression_middleware@$VERSION/mod.ts";declareconstencodeBr: Encode;constencodingMap: EncodingMap={br: encodeBr};constmiddleware=compression(encodingMap);Encoder list defines a list of Encoder.
Encoder is a following structured object:
| Name | Type | Description |
|---|---|---|
| encoding | string | Encoding format. |
| encode | Encode | Encode stream. |
Example of adding brotli encoding:
import{compression,typeEncode,typeEncoder,}from"https://deno.land/x/compression_middleware@$VERSION/mod.ts";declareconstencodeBr: Encode;constBr: Encoder={encoding: "br",encode: encodeBr};constmiddleware=compression([Br]);Encode is an API for converting content.
interfaceEncode{(stream: ReadableStream<Uint8Array>): BodyInit|Promise<BodyInit>;}Filter media types to be compressed according to the following specifications:
If the media type includes an inherent encoding, such as a data format that is always compressed, then that encoding would not be restated in Content-Encoding even if it happens to be the same algorithm as one of the content codings.
Determine from the Content-Type response header whether the representation is
compressible.
For example, image media such as image/jpag is not compressible because it is
already compressed.
If the Response has a Content-Length header, compression may cause the actual
content length to deviate.
In that case, the Content-Length is recalculated.
import{compression}from"https://deno.land/x/compression_middleware@$VERSION/mod.ts";import{assertEquals}from"https://deno.land/std/testing/asserts.ts";declareconstrequest: Request;constmiddleware=compression();constresponse=awaitmiddleware(request,()=>newResponse("<body>",{headers: {"content-length": "<body:length>"}}),);assertEquals(awaitresponse.text(),"<gzip:body>");assertEquals(response.headers.get("content-length"),"<gzip:body:length>");Middleware may make changes to the following elements of the HTTP message.
- HTTP Content
- HTTP Headers
- Content-Encoding
- Vary
- Content-Length
Middleware is executed if all of the following conditions are met:
- Encoding matches
Accept-Encodingheader in request Content-Typeheader exists in responseContent-Encodingheader does not exists in responseCache-Controlheader does not haveno-transformdirective in response- Response body exists
- Response body is readable
- Response body is compressible
All APIs can be found in the deno doc.
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