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ContentEncoderMiddleware.js
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ContentEncoderMiddleware.js
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import { promisify } from 'node:util';
import {
// @ts-expect-error Bad types
BrotliCompress, Deflate, Gzip,
constants as ZlibContants,
brotliCompress, brotliCompressSync,
deflate, deflateSync,
gzip, gzipSync,
} from 'node:zlib';
import { parseQualityValues } from '../utils/qualityValues.js';
const { BROTLI_OPERATION_FLUSH, Z_SYNC_FLUSH } = ZlibContants;
/** @typedef {import('http').IncomingHttpHeaders} IncomingHttpHeaders */
/** @typedef {import('../lib/HttpRequest.js').default} HttpRequest */
/** @typedef {import('../lib/HttpResponse.js').default} HttpResponse */
/** @typedef {import('../types').MiddlewareFunction} MiddlewareFunction */
/** @typedef {import('../types').ResponseFinalizer} ResponseFinalizer */
/** @typedef {'br'|'gzip'|'deflate'|'identity'|'*'} COMPATIBLE_ENCODING */
const DEFAULT_MINIMUM_SIZE = 256;
const DEFAULT_ASYNC_THRESHOLD = 64 * 1024;
/**
* @typedef ContentEncoderMiddlewareOptions
* @prop {number} [chunkSize]
* @prop {boolean} [respondNotAcceptable=false]
* @prop {'br'|'gzip'|'deflate'|'identity'} [preferredEncoding='identity']
* Minimum content size before using any compression
* @prop {number} [minimumSize=DEFAULT_MINIMUM_SIZE]
* Minimum content size before using async compression
* @prop {number} [asyncThreshold=DEFAULT_ASYNC_THRESHOLD]
*/
/** @type {COMPATIBLE_ENCODING[]} */
const COMPATIBLE_ENCODINGS = ['br', 'gzip', 'deflate', 'identity', '*'];
export default class ContentEncoderMiddleware {
/** @param {ContentEncoderMiddlewareOptions} [options] */
constructor(options = {}) {
this.chunkSize = options.chunkSize;
this.respondNotAcceptable = options.respondNotAcceptable === true;
this.preferredEncoding = options.preferredEncoding ?? 'identity';
this.minimumSize = options.minimumSize ?? DEFAULT_MINIMUM_SIZE;
this.asyncThreshold = options.asyncThreshold ?? DEFAULT_ASYNC_THRESHOLD;
this.finalizeResponse = this.finalizeResponse.bind(this);
}
static BrotliCompressAsync = promisify(brotliCompress);
static GzipAsync = promisify(gzip);
static DeflateAsync = promisify(deflate);
/**
* @param {IncomingHttpHeaders} headers
* @throws {NotAcceptableException} Error with `NOT_ACCEPTIBLE` message
* @return {COMPATIBLE_ENCODING}
*/
static chooseEncoding(headers) {
/**
* A request without an Accept-Encoding header field implies that the
* user agent has no preferences regarding content-codings. Although
* this allows the server to use any content-coding in a response, it
* does not imply that the user agent will be able to correctly process
* all encodings.
*/
if ('accept-encoding' in headers === false) {
return '*';
}
const acceptString = /** @type {string} */ (headers['accept-encoding']);
const encodings = parseQualityValues(acceptString?.toLowerCase());
if (!encodings.size) {
/**
* An Accept-Encoding header field with a combined field-value that is
* empty implies that the user agent does not want any content-coding in
* response.
*/
return 'identity';
}
let encoding = COMPATIBLE_ENCODINGS[0];
const allowWildcards = (encodings.get('*')?.q !== 0);
const encodingEntries = [...encodings.entries()];
// @ts-ignore Cannot cast to COMPATIBLE_ENCODINGS
encoding = (encodingEntries.find(([value, spec]) => spec.q !== 0 && COMPATIBLE_ENCODINGS.includes(value))?.[0]);
if (allowWildcards && (encoding === '*' || !encoding)) {
// Server preference
// Get first compatible encoding not specified
encoding = COMPATIBLE_ENCODINGS.find((value) => !encodings.has(value));
}
if (allowWildcards && !encoding) {
// Get highest q'd compatible encoding not q=0 or '*'
// @ts-ignore Cannot cast to COMPATIBLE_ENCODINGS
encoding = /** @type {COMPATIBLE_ENCODINGS} */ encodingEntries
// @ts-ignore Cannot cast to COMPATIBLE_ENCODINGS
.find(([value, spec]) => spec.q !== 0 && value !== '*' && COMPATIBLE_ENCODINGS.includes(value))?.[0];
}
if (!encoding) {
throw new Error('NOT_ACCEPTABLE');
}
return encoding;
}
/**
* @param {HttpResponse} response
* @return {void}
*/
addTransformStream(response) {
/** @type {COMPATIBLE_ENCODING} */
let parsedEncoding;
if (this.respondNotAcceptable) {
// Parse now to catch the error;
try {
parsedEncoding = ContentEncoderMiddleware.chooseEncoding(response.request.headers);
} catch (error) {
if (error?.message === 'NOT_ACCEPTABLE') {
response.status = 406;
response.end();
throw new Error('NOT_ACCEPTABLE');
}
// Unknown error
throw error;
}
}
/** @return {string} */
const getContentEncoding = () => {
if (!parsedEncoding) {
try {
parsedEncoding = ContentEncoderMiddleware.chooseEncoding(response.request.headers);
} catch (error) {
if (error?.message !== 'NOT_ACCEPTABLE') {
throw error;
}
}
}
if (!parsedEncoding || parsedEncoding === '*') {
parsedEncoding = this.preferredEncoding || 'identity';
}
response.headers['content-encoding'] = parsedEncoding;
return parsedEncoding;
};
let encoding = response.request.headers['content-encoding'];
// Only continue if unset (missing header). Blank is still considered set.
// This allows forced encoding (eg: use gzip regardless of size; always identity)
// Unset means server preference
if (encoding == null) {
encoding = getContentEncoding().toLowerCase?.();
}
const isEventStream = response.headers['content-type']?.includes('text/event-stream');
let newStream;
switch (encoding) {
case 'br':
// @ts-expect-error Bad types
newStream = new BrotliCompress({
chunkSize: this.chunkSize,
flush: isEventStream ? BROTLI_OPERATION_FLUSH : undefined,
});
break;
case 'gzip':
// @ts-expect-error Bad types
newStream = new Gzip({
chunkSize: this.chunkSize,
flush: isEventStream ? Z_SYNC_FLUSH : undefined,
});
break;
case 'deflate':
// @ts-expect-error Bad types
newStream = new Deflate({
chunkSize: this.chunkSize,
flush: isEventStream ? Z_SYNC_FLUSH : undefined,
});
break;
default:
return;
}
response.pipes.push(newStream);
}
/** @type {ResponseFinalizer} */
finalizeResponse(response) {
if (response.isStreaming) {
this.addTransformStream(response);
return true;
}
if (response.body == null) return true;
/** @type {COMPATIBLE_ENCODING} */
let parsedEncoding;
if (this.respondNotAcceptable) {
// Parse now to catch the error;
try {
parsedEncoding = ContentEncoderMiddleware.chooseEncoding(response.request.headers);
} catch (error) {
if (error?.message === 'NOT_ACCEPTABLE') {
// Strip content
response.body = null;
response.status = 206;
return false;
}
// Unknown error
throw error;
}
}
if (!Buffer.isBuffer(response.body)) return true;
/** @return {string} */
const getContentEncoding = () => {
if (!parsedEncoding) {
try {
parsedEncoding = ContentEncoderMiddleware.chooseEncoding(response.request.headers);
} catch (error) {
if (error?.message !== 'NOT_ACCEPTABLE') {
throw error;
}
}
}
if (!parsedEncoding || parsedEncoding === '*') {
parsedEncoding = this.preferredEncoding || 'identity';
}
response.headers['content-encoding'] = parsedEncoding;
return parsedEncoding;
};
let encoding = /** @type {string} */ (response.headers['content-encoding']);
// Only continue if unset (missing header). Blank is still considered set.
// This allows forced encoding (eg: use gzip regardless of size; always identity)
// Unset means server preference
if (encoding == null) {
encoding = (response.body.length < this.minimumSize) ? 'identity' : getContentEncoding().toLowerCase?.();
}
const options = { chunkSize: this.chunkSize };
if (response.body.length < this.asyncThreshold) {
switch (encoding) {
case 'br':
response.body = brotliCompressSync(response.body, options);
break;
case 'gzip':
response.body = gzipSync(response.body, options);
break;
case 'deflate':
response.body = deflateSync(response.body, options);
break;
default:
}
return true;
}
let promise;
switch (encoding) {
case 'br':
promise = ContentEncoderMiddleware.BrotliCompressAsync(response.body, options);
break;
case 'gzip':
promise = ContentEncoderMiddleware.GzipAsync(response.body, options);
break;
case 'deflate':
promise = ContentEncoderMiddleware.DeflateAsync(response.body, options);
break;
default:
return true;
}
return promise.then((result) => {
response.body = result;
return true;
});
}
/**
* Implements `Accept-Encoding`
* https://tools.ietf.org/html/rfc7231#section-5.3.4
* @type {MiddlewareFunction}
*/
execute({ response }) {
response.finalizers.push(this.finalizeResponse);
}
}