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permessage-deflate.js
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Tue, Feb 4, 11:59

permessage-deflate.js
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'use strict';
const zlib = require('zlib');
const bufferUtil = require('./buffer-util');
const Limiter = require('./limiter');
const { kStatusCode } = require('./constants');
const FastBuffer = Buffer[Symbol.species];
const TRAILER = Buffer.from([0x00, 0x00, 0xff, 0xff]);
const kPerMessageDeflate = Symbol('permessage-deflate');
const kTotalLength = Symbol('total-length');
const kCallback = Symbol('callback');
const kBuffers = Symbol('buffers');
const kError = Symbol('error');
//
// We limit zlib concurrency, which prevents severe memory fragmentation
// as documented in https://github.com/nodejs/node/issues/8871#issuecomment-250915913
// and https://github.com/websockets/ws/issues/1202
//
// Intentionally global; it's the global thread pool that's an issue.
//
let zlibLimiter;
/**
* permessage-deflate implementation.
*/
class PerMessageDeflate {
/**
* Creates a PerMessageDeflate instance.
*
* @param {Object} [options] Configuration options
* @param {(Boolean|Number)} [options.clientMaxWindowBits] Advertise support
* for, or request, a custom client window size
* @param {Boolean} [options.clientNoContextTakeover=false] Advertise/
* acknowledge disabling of client context takeover
* @param {Number} [options.concurrencyLimit=10] The number of concurrent
* calls to zlib
* @param {(Boolean|Number)} [options.serverMaxWindowBits] Request/confirm the
* use of a custom server window size
* @param {Boolean} [options.serverNoContextTakeover=false] Request/accept
* disabling of server context takeover
* @param {Number} [options.threshold=1024] Size (in bytes) below which
* messages should not be compressed if context takeover is disabled
* @param {Object} [options.zlibDeflateOptions] Options to pass to zlib on
* deflate
* @param {Object} [options.zlibInflateOptions] Options to pass to zlib on
* inflate
* @param {Boolean} [isServer=false] Create the instance in either server or
* client mode
* @param {Number} [maxPayload=0] The maximum allowed message length
*/
constructor(options, isServer, maxPayload) {
this._maxPayload = maxPayload | 0;
this._options = options || {};
this._threshold =
this._options.threshold !== undefined ? this._options.threshold : 1024;
this._isServer = !!isServer;
this._deflate = null;
this._inflate = null;
this.params = null;
if (!zlibLimiter) {
const concurrency =
this._options.concurrencyLimit !== undefined
? this._options.concurrencyLimit
: 10;
zlibLimiter = new Limiter(concurrency);
}
}
/**
* @type {String}
*/
static get extensionName() {
return 'permessage-deflate';
}
/**
* Create an extension negotiation offer.
*
* @return {Object} Extension parameters
* @public
*/
offer() {
const params = {};
if (this._options.serverNoContextTakeover) {
params.server_no_context_takeover = true;
}
if (this._options.clientNoContextTakeover) {
params.client_no_context_takeover = true;
}
if (this._options.serverMaxWindowBits) {
params.server_max_window_bits = this._options.serverMaxWindowBits;
}
if (this._options.clientMaxWindowBits) {
params.client_max_window_bits = this._options.clientMaxWindowBits;
} else if (this._options.clientMaxWindowBits == null) {
params.client_max_window_bits = true;
}
return params;
}
/**
* Accept an extension negotiation offer/response.
*
* @param {Array} configurations The extension negotiation offers/reponse
* @return {Object} Accepted configuration
* @public
*/
accept(configurations) {
configurations = this.normalizeParams(configurations);
this.params = this._isServer
? this.acceptAsServer(configurations)
: this.acceptAsClient(configurations);
return this.params;
}
/**
* Releases all resources used by the extension.
*
* @public
*/
cleanup() {
if (this._inflate) {
this._inflate.close();
this._inflate = null;
}
if (this._deflate) {
const callback = this._deflate[kCallback];
this._deflate.close();
this._deflate = null;
if (callback) {
callback(
new Error(
'The deflate stream was closed while data was being processed'
)
);
}
}
}
/**
* Accept an extension negotiation offer.
*
* @param {Array} offers The extension negotiation offers
* @return {Object} Accepted configuration
* @private
*/
acceptAsServer(offers) {
const opts = this._options;
const accepted = offers.find((params) => {
if (
(opts.serverNoContextTakeover === false &&
params.server_no_context_takeover) ||
(params.server_max_window_bits &&
(opts.serverMaxWindowBits === false ||
(typeof opts.serverMaxWindowBits === 'number' &&
opts.serverMaxWindowBits > params.server_max_window_bits))) ||
(typeof opts.clientMaxWindowBits === 'number' &&
!params.client_max_window_bits)
) {
return false;
}
return true;
});
if (!accepted) {
throw new Error('None of the extension offers can be accepted');
}
if (opts.serverNoContextTakeover) {
accepted.server_no_context_takeover = true;
}
if (opts.clientNoContextTakeover) {
accepted.client_no_context_takeover = true;
}
if (typeof opts.serverMaxWindowBits === 'number') {
accepted.server_max_window_bits = opts.serverMaxWindowBits;
}
if (typeof opts.clientMaxWindowBits === 'number') {
accepted.client_max_window_bits = opts.clientMaxWindowBits;
} else if (
accepted.client_max_window_bits === true ||
opts.clientMaxWindowBits === false
) {
delete accepted.client_max_window_bits;
}
return accepted;
}
/**
* Accept the extension negotiation response.
*
* @param {Array} response The extension negotiation response
* @return {Object} Accepted configuration
* @private
*/
acceptAsClient(response) {
const params = response[0];
if (
this._options.clientNoContextTakeover === false &&
params.client_no_context_takeover
) {
throw new Error('Unexpected parameter "client_no_context_takeover"');
}
if (!params.client_max_window_bits) {
if (typeof this._options.clientMaxWindowBits === 'number') {
params.client_max_window_bits = this._options.clientMaxWindowBits;
}
} else if (
this._options.clientMaxWindowBits === false ||
(typeof this._options.clientMaxWindowBits === 'number' &&
params.client_max_window_bits > this._options.clientMaxWindowBits)
) {
throw new Error(
'Unexpected or invalid parameter "client_max_window_bits"'
);
}
return params;
}
/**
* Normalize parameters.
*
* @param {Array} configurations The extension negotiation offers/reponse
* @return {Array} The offers/response with normalized parameters
* @private
*/
normalizeParams(configurations) {
configurations.forEach((params) => {
Object.keys(params).forEach((key) => {
let value = params[key];
if (value.length > 1) {
throw new Error(`Parameter "${key}" must have only a single value`);
}
value = value[0];
if (key === 'client_max_window_bits') {
if (value !== true) {
const num = +value;
if (!Number.isInteger(num) || num < 8 || num > 15) {
throw new TypeError(
`Invalid value for parameter "${key}": ${value}`
);
}
value = num;
} else if (!this._isServer) {
throw new TypeError(
`Invalid value for parameter "${key}": ${value}`
);
}
} else if (key === 'server_max_window_bits') {
const num = +value;
if (!Number.isInteger(num) || num < 8 || num > 15) {
throw new TypeError(
`Invalid value for parameter "${key}": ${value}`
);
}
value = num;
} else if (
key === 'client_no_context_takeover' ||
key === 'server_no_context_takeover'
) {
if (value !== true) {
throw new TypeError(
`Invalid value for parameter "${key}": ${value}`
);
}
} else {
throw new Error(`Unknown parameter "${key}"`);
}
params[key] = value;
});
});
return configurations;
}
/**
* Decompress data. Concurrency limited.
*
* @param {Buffer} data Compressed data
* @param {Boolean} fin Specifies whether or not this is the last fragment
* @param {Function} callback Callback
* @public
*/
decompress(data, fin, callback) {
zlibLimiter.add((done) => {
this._decompress(data, fin, (err, result) => {
done();
callback(err, result);
});
});
}
/**
* Compress data. Concurrency limited.
*
* @param {(Buffer|String)} data Data to compress
* @param {Boolean} fin Specifies whether or not this is the last fragment
* @param {Function} callback Callback
* @public
*/
compress(data, fin, callback) {
zlibLimiter.add((done) => {
this._compress(data, fin, (err, result) => {
done();
callback(err, result);
});
});
}
/**
* Decompress data.
*
* @param {Buffer} data Compressed data
* @param {Boolean} fin Specifies whether or not this is the last fragment
* @param {Function} callback Callback
* @private
*/
_decompress(data, fin, callback) {
const endpoint = this._isServer ? 'client' : 'server';
if (!this._inflate) {
const key = `${endpoint}_max_window_bits`;
const windowBits =
typeof this.params[key] !== 'number'
? zlib.Z_DEFAULT_WINDOWBITS
: this.params[key];
this._inflate = zlib.createInflateRaw({
...this._options.zlibInflateOptions,
windowBits
});
this._inflate[kPerMessageDeflate] = this;
this._inflate[kTotalLength] = 0;
this._inflate[kBuffers] = [];
this._inflate.on('error', inflateOnError);
this._inflate.on('data', inflateOnData);
}
this._inflate[kCallback] = callback;
this._inflate.write(data);
if (fin) this._inflate.write(TRAILER);
this._inflate.flush(() => {
const err = this._inflate[kError];
if (err) {
this._inflate.close();
this._inflate = null;
callback(err);
return;
}
const data = bufferUtil.concat(
this._inflate[kBuffers],
this._inflate[kTotalLength]
);
if (this._inflate._readableState.endEmitted) {
this._inflate.close();
this._inflate = null;
} else {
this._inflate[kTotalLength] = 0;
this._inflate[kBuffers] = [];
if (fin && this.params[`${endpoint}_no_context_takeover`]) {
this._inflate.reset();
}
}
callback(null, data);
});
}
/**
* Compress data.
*
* @param {(Buffer|String)} data Data to compress
* @param {Boolean} fin Specifies whether or not this is the last fragment
* @param {Function} callback Callback
* @private
*/
_compress(data, fin, callback) {
const endpoint = this._isServer ? 'server' : 'client';
if (!this._deflate) {
const key = `${endpoint}_max_window_bits`;
const windowBits =
typeof this.params[key] !== 'number'
? zlib.Z_DEFAULT_WINDOWBITS
: this.params[key];
this._deflate = zlib.createDeflateRaw({
...this._options.zlibDeflateOptions,
windowBits
});
this._deflate[kTotalLength] = 0;
this._deflate[kBuffers] = [];
this._deflate.on('data', deflateOnData);
}
this._deflate[kCallback] = callback;
this._deflate.write(data);
this._deflate.flush(zlib.Z_SYNC_FLUSH, () => {
if (!this._deflate) {
//
// The deflate stream was closed while data was being processed.
//
return;
}
let data = bufferUtil.concat(
this._deflate[kBuffers],
this._deflate[kTotalLength]
);
if (fin) {
data = new FastBuffer(data.buffer, data.byteOffset, data.length - 4);
}
//
// Ensure that the callback will not be called again in
// `PerMessageDeflate#cleanup()`.
//
this._deflate[kCallback] = null;
this._deflate[kTotalLength] = 0;
this._deflate[kBuffers] = [];
if (fin && this.params[`${endpoint}_no_context_takeover`]) {
this._deflate.reset();
}
callback(null, data);
});
}
}
module.exports = PerMessageDeflate;
/**
* The listener of the `zlib.DeflateRaw` stream `'data'` event.
*
* @param {Buffer} chunk A chunk of data
* @private
*/
function deflateOnData(chunk) {
this[kBuffers].push(chunk);
this[kTotalLength] += chunk.length;
}
/**
* The listener of the `zlib.InflateRaw` stream `'data'` event.
*
* @param {Buffer} chunk A chunk of data
* @private
*/
function inflateOnData(chunk) {
this[kTotalLength] += chunk.length;
if (
this[kPerMessageDeflate]._maxPayload < 1 ||
this[kTotalLength] <= this[kPerMessageDeflate]._maxPayload
) {
this[kBuffers].push(chunk);
return;
}
this[kError] = new RangeError('Max payload size exceeded');
this[kError].code = 'WS_ERR_UNSUPPORTED_MESSAGE_LENGTH';
this[kError][kStatusCode] = 1009;
this.removeListener('data', inflateOnData);
this.reset();
}
/**
* The listener of the `zlib.InflateRaw` stream `'error'` event.
*
* @param {Error} err The emitted error
* @private
*/
function inflateOnError(err) {
//
// There is no need to call `Zlib#close()` as the handle is automatically
// closed when an error is emitted.
//
this[kPerMessageDeflate]._inflate = null;
err[kStatusCode] = 1007;
this[kCallback](err);
}

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