The Tor Browser: comparison testing/xpcshell/node-http2/node_modules/http2-protocol/lib/flow.js

comparison: testing/xpcshell/node-http2/node_modules/http2-protocol/lib/flow.js

testing/xpcshell/node-http2/node_modules/http2-protocol/lib/flow.js

changeset 0: 6474c204b198

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+:9ffa7d46c511
+var assert = require('assert');
+// The Flow class
+// ==============
+// Flow is a [Duplex stream][1] subclass which implements HTTP/2 flow control. It is designed to be
+// subclassed by [Connection](connection.html) and the `upstream` component of [Stream](stream.html).
+// [1]: http://nodejs.org/api/stream.html#stream_class_stream_duplex
+var Duplex  = require('stream').Duplex;
+exports.Flow = Flow;
+// Public API
+// ----------
+// * **Event: 'error' (type)**: signals an error
+//
+// * **setInitialWindow(size)**: the initial flow control window size can be changed *any time*
+//   ([as described in the standard][1]) using this method
+//
+// [1]: http://tools.ietf.org/html/draft-ietf-httpbis-http2-10#section-6.9.2
+// API for child classes
+// ---------------------
+// * **new Flow([flowControlId])**: creating a new flow that will listen for WINDOW_UPDATES frames
+//   with the given `flowControlId` (or every update frame if not given)
+//
+// * **_send()**: called when more frames should be pushed. The child class is expected to override
+//   this (instead of the `_read` method of the Duplex class).
+//
+// * **_receive(frame, readyCallback)**: called when there's an incoming frame. The child class is
+//   expected to override this (instead of the `_write` method of the Duplex class).
+//
+// * **push(frame): bool**: schedules `frame` for sending.
+//
+//   Returns `true` if it needs more frames in the output queue, `false` if the output queue is
+//   full, and `null` if did not push the frame into the output queue (instead, it pushed it into
+//   the flow control queue).
+//
+// * **read(limit): frame**: like the regular `read`, but the 'flow control size' (0 for non-DATA
+//   frames, length of the payload for DATA frames) of the returned frame will be under `limit`.
+//   Small exception: pass -1 as `limit` if the max. flow control size is 0. `read(0)` means the
+//   same thing as [in the original API](http://nodejs.org/api/stream.html#stream_stream_read_0).
+//
+// * **getLastQueuedFrame(): frame**: returns the last frame in output buffers
+//
+// * **_log**: the Flow class uses the `_log` object of the parent
+// Constructor
+// -----------
+// When a HTTP/2.0 connection is first established, new streams are created with an initial flow
+// control window size of 65535 bytes.
+var INITIAL_WINDOW_SIZE = 65535;
+// `flowControlId` is needed if only specific WINDOW_UPDATEs should be watched.
+function Flow(flowControlId) {
+Duplex.call(this, { objectMode: true });
+this._window = this._initialWindow = INITIAL_WINDOW_SIZE;
+this._flowControlId = flowControlId;
+this._queue = [];
+this._ended = false;
+this._received = 0;
+}
+Flow.prototype = Object.create(Duplex.prototype, { constructor: { value: Flow } });
+// Incoming frames
+// ---------------
+// `_receive` is called when there's an incoming frame.
+Flow.prototype._receive = function _receive(frame, callback) {
+throw new Error('The _receive(frame, callback) method has to be overridden by the child class!');
+};
+// `_receive` is called by `_write` which in turn is [called by Duplex][1] when someone `write()`s
+// to the flow. It emits the 'receiving' event and notifies the window size tracking code if the
+// incoming frame is a WINDOW_UPDATE.
+// [1]: http://nodejs.org/api/stream.html#stream_writable_write_chunk_encoding_callback_1
+Flow.prototype._write = function _write(frame, encoding, callback) {
+if (frame.flags.END_STREAM || (frame.type === 'RST_STREAM')) {
+this._ended = true;
+}
+if ((frame.type === 'DATA') && (frame.data.length > 0)) {
+this._receive(frame, function() {
+this._received += frame.data.length;
+if (!this._restoreWindowTimer) {
+this._restoreWindowTimer = setImmediate(this._restoreWindow.bind(this));
+}
+callback();
+}.bind(this));
+}
+else {
+this._receive(frame, callback);
+}
+if ((frame.type === 'WINDOW_UPDATE') &&
+((this._flowControlId === undefined) || (frame.stream === this._flowControlId))) {
+this._updateWindow(frame);
+}
+};
+// `_restoreWindow` basically acknowledges the DATA frames received since it's last call. It sends
+// a WINDOW_UPDATE that restores the flow control window of the remote end.
+Flow.prototype._restoreWindow = function _restoreWindow() {
+delete this._restoreWindowTimer;
+if (!this._ended && (this._received > 0)) {
+this.push({
+type: 'WINDOW_UPDATE',
+flags: {},
+stream: this._flowControlId,
+window_size: this._received
+});
+this._received = 0;
+}
+};
+// Outgoing frames - sending procedure
+// -----------------------------------
+//                                         flow
+//                +-------------------------------------------------+
+//                |                                                 |
+//                +--------+           +---------+                  |
+//        read()  | output |  _read()  | flow    |  _send()         |
+//     <----------|        |<----------| control |<-------------    |
+//                | buffer |           | buffer  |                  |
+//                +--------+           +---------+                  |
+//                | input  |                                        |
+//     ---------->|        |----------------------------------->    |
+//       write()  | buffer |  _write()              _receive()      |
+//                +--------+                                        |
+//                |                                                 |
+//                +-------------------------------------------------+
+// `_send` is called when more frames should be pushed to the output buffer.
+Flow.prototype._send = function _send() {
+throw new Error('The _send() method has to be overridden by the child class!');
+};
+// `_send` is called by `_read` which is in turn [called by Duplex][1] when it wants to have more
+// items in the output queue.
+// [1]: http://nodejs.org/api/stream.html#stream_writable_write_chunk_encoding_callback_1
+Flow.prototype._read = function _read() {
+// * if the flow control queue is empty, then let the user push more frames
+if (this._queue.length === 0) {
+this._send();
+}
+// * if there are items in the flow control queue, then let's put them into the output queue (to
+//   the extent it is possible with respect to the window size and output queue feedback)
+else if (this._window > 0) {
+this._readableState.sync = true; // to avoid reentrant calls
+do {
+var moreNeeded = this._push(this._queue[0]);
+if (moreNeeded !== null) {
+this._queue.shift();
+}
+} while (moreNeeded && (this._queue.length > 0));
+this._readableState.sync = false;
+assert((moreNeeded == false) ||                              // * output queue is full
+(this._queue.length === 0) ||                         // * flow control queue is empty
+(!this._window && (this._queue[0].type === 'DATA'))); // * waiting for window update
+}
+// * otherwise, come back when the flow control window is positive
+else {
+this.once('window_update', this._read);
+}
+};
+var MAX_PAYLOAD_SIZE = 4096; // Must not be greater than MAX_HTTP_PAYLOAD_SIZE which is 16383
+// `read(limit)` is like the `read` of the Readable class, but it guarantess that the 'flow control
+// size' (0 for non-DATA frames, length of the payload for DATA frames) of the returned frame will
+// be under `limit`.
+Flow.prototype.read = function read(limit) {
+if (limit === 0) {
+return Duplex.prototype.read.call(this, 0);
+} else if (limit === -1) {
+limit = 0;
+} else if ((limit === undefined) || (limit > MAX_PAYLOAD_SIZE)) {
+limit = MAX_PAYLOAD_SIZE;
+}
+// * Looking at the first frame in the queue without pulling it out if possible. This will save
+//   a costly unshift if the frame proves to be too large to return.
+var firstInQueue = this._readableState.buffer[0];
+var frame = firstInQueue || Duplex.prototype.read.call(this);
+if ((frame === null) || (frame.type !== 'DATA') || (frame.data.length <= limit)) {
+if (firstInQueue) {
+Duplex.prototype.read.call(this);
+}
+return frame;
+}
+else if (limit <= 0) {
+if (!firstInQueue) {
+this.unshift(frame);
+}
+return null;
+}
+else {
+this._log.trace({ frame: frame, size: frame.data.length, forwardable: limit },
+'Splitting out forwardable part of a DATA frame.');
+var forwardable = {
+type: 'DATA',
+flags: {},
+stream: frame.stream,
+data: frame.data.slice(0, limit)
+};
+frame.data = frame.data.slice(limit);
+if (!firstInQueue) {
+this.unshift(frame);
+}
+return forwardable;
+}
+};
+// `_parentPush` pushes the given `frame` into the output queue
+Flow.prototype._parentPush = function _parentPush(frame) {
+this._log.trace({ frame: frame }, 'Pushing frame into the output queue');
+if (frame && (frame.type === 'DATA') && (this._window !== Infinity)) {
+this._log.trace({ window: this._window, by: frame.data.length },
+'Decreasing flow control window size.');
+this._window -= frame.data.length;
+assert(this._window >= 0);
+}
+return Duplex.prototype.push.call(this, frame);
+};
+// `_push(frame)` pushes `frame` into the output queue and decreases the flow control window size.
+// It is capable of splitting DATA frames into smaller parts, if the window size is not enough to
+// push the whole frame. The return value is similar to `push` except that it returns `null` if it
+// did not push the whole frame to the output queue (but maybe it did push part of the frame).
+Flow.prototype._push = function _push(frame) {
+var data = frame && (frame.type === 'DATA') && frame.data;
+if (!data || (data.length <= this._window)) {
+return this._parentPush(frame);
+}
+else if (this._window <= 0) {
+return null;
+}
+else {
+this._log.trace({ frame: frame, size: frame.data.length, forwardable: this._window },
+'Splitting out forwardable part of a DATA frame.');
+frame.data = data.slice(this._window);
+this._parentPush({
+type: 'DATA',
+flags: {},
+stream: frame.stream,
+data: data.slice(0, this._window)
+});
+return null;
+}
+};
+// Push `frame` into the flow control queue, or if it's empty, then directly into the output queue
+Flow.prototype.push = function push(frame) {
+if (frame === null) {
+this._log.debug('Enqueueing outgoing End Of Stream');
+} else {
+this._log.debug({ frame: frame }, 'Enqueueing outgoing frame');
+}
+var moreNeeded = null;
+if (this._queue.length === 0) {
+moreNeeded = this._push(frame);
+}
+if (moreNeeded === null) {
+this._queue.push(frame);
+}
+return moreNeeded;
+};
+// `getLastQueuedFrame` returns the last frame in output buffers. This is primarily used by the
+// [Stream](stream.html) class to mark the last frame with END_STREAM flag.
+Flow.prototype.getLastQueuedFrame = function getLastQueuedFrame() {
+var readableQueue = this._readableState.buffer;
+return this._queue[this._queue.length - 1] || readableQueue[readableQueue.length - 1];
+};
+// Outgoing frames - managing the window size
+// ------------------------------------------
+// Flow control window size is manipulated using the `_increaseWindow` method.
+//
+// * Invoking it with `Infinite` means turning off flow control. Flow control cannot be enabled
+//   again once disabled. Any attempt to re-enable flow control MUST be rejected with a
+//   FLOW_CONTROL_ERROR error code.
+// * A sender MUST NOT allow a flow control window to exceed 2^31 - 1 bytes. The action taken
+//   depends on it being a stream or the connection itself.
+var WINDOW_SIZE_LIMIT = Math.pow(2, 31) - 1;
+Flow.prototype._increaseWindow = function _increaseWindow(size) {
+if ((this._window === Infinity) && (size !== Infinity)) {
+this._log.error('Trying to increase flow control window after flow control was turned off.');
+this.emit('error', 'FLOW_CONTROL_ERROR');
+} else {
+this._log.trace({ window: this._window, by: size }, 'Increasing flow control window size.');
+this._window += size;
+if ((this._window !== Infinity) && (this._window > WINDOW_SIZE_LIMIT)) {
+this._log.error('Flow control window grew too large.');
+this.emit('error', 'FLOW_CONTROL_ERROR');
+} else {
+this.emit('window_update');
+}
+}
+};
+// The `_updateWindow` method gets called every time there's an incoming WINDOW_UPDATE frame. It
+// modifies the flow control window:
+//
+// * Flow control can be disabled for an individual stream by sending a WINDOW_UPDATE with the
+//   END_FLOW_CONTROL flag set. The payload of a WINDOW_UPDATE frame that has the END_FLOW_CONTROL
+//   flag set is ignored.
+// * A sender that receives a WINDOW_UPDATE frame updates the corresponding window by the amount
+//   specified in the frame.
+Flow.prototype._updateWindow = function _updateWindow(frame) {
+this._increaseWindow(frame.flags.END_FLOW_CONTROL ? Infinity : frame.window_size);
+};
+// A SETTINGS frame can alter the initial flow control window size for all current streams. When the
+// value of SETTINGS_INITIAL_WINDOW_SIZE changes, a receiver MUST adjust the size of all stream by
+// calling the `setInitialWindow` method. The window size has to be modified by the difference
+// between the new value and the old value.
+Flow.prototype.setInitialWindow = function setInitialWindow(initialWindow) {
+this._increaseWindow(initialWindow - this._initialWindow);
+this._initialWindow = initialWindow;
+};