stream: keep webstream stream states in fast-mode objects#65625

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stream: keep webstream stream states in fast-mode objects #65625

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1695e7b
stream: keep webstream stream states in fast-mode objects
mcollina Aug 28, 2026
aaa47dc
stream: avoid promise allocation for parked transform writes
mcollina Aug 28, 2026
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76 changes: 76 additions & 0 deletions benchmark/webstreams/lifecycle.js
View file
Open in desktop
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,76 @@
'use strict';
const common = require('../common.js');
const assert = require('assert');
const {
ReadableStream,
WritableStream,
TransformStream,
} = require('node:stream/web');

const bench = common.createBenchmark(main, {
n: [5e4],
kind: ['readable', 'pipe-to', 'pipe-through'],
});

const chunk = Buffer.alloc(1024);

function makeSource() {
let i = 0;
return {
pull(controller) {
if (i++ < 4)
controller.enqueue(chunk);
else
controller.close();
},
};
}

async function readable(n) {
let chunks = 0;
bench.start();
for (let i = 0; i < n; i++) {
const reader = new ReadableStream(makeSource()).getReader();
while (!(await reader.read()).done) chunks++;
}
bench.end(n);
assert.strictEqual(chunks, n * 4);
}

async function pipeTo(n) {
let chunks = 0;
bench.start();
for (let i = 0; i < n; i++) {
await new ReadableStream(makeSource())
.pipeTo(new WritableStream({ write() { chunks++; } }));
}
bench.end(n);
assert.strictEqual(chunks, n * 4);
}

async function pipeThrough(n) {
let chunks = 0;
bench.start();
for (let i = 0; i < n; i++) {
const reader = new ReadableStream(makeSource())
.pipeThrough(new TransformStream())
.getReader();
while (!(await reader.read()).done) chunks++;
}
bench.end(n);
assert.strictEqual(chunks, n * 4);
}

function main({ n, kind }) {
switch (kind) {
case 'readable':
readable(n);
break;
case 'pipe-to':
pipeTo(n);
break;
case 'pipe-through':
pipeThrough(n);
break;
}
}
38 changes: 23 additions & 15 deletions lib/internal/webstreams/readablestream.js
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -1419,22 +1419,30 @@ const isReadableStreamBYOBReader =

// ---- ReadableStream Implementation

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class ReadableStreamTransferState {
writable = undefined;
port1 = undefined;
port2 = undefined;
promise = undefined;
}
ObjectSetPrototypeOf(ReadableStreamTransferState.prototype, null);

class ReadableStreamState {
closedPromise = undefined;
disturbed = false;
reader = undefined;
state = 'readable';
storedError = undefined;
controller = undefined;
transfer = new ReadableStreamTransferState();
}
ObjectSetPrototypeOf(ReadableStreamState.prototype, null);

function createReadableStreamState() {
return {
__proto__: null,
closedPromise: undefined,
disturbed: false,
reader: undefined,
state: 'readable',
storedError: undefined,
transfer: {
__proto__: null,
writable: undefined,
port1: undefined,
port2: undefined,
promise: undefined,
},
};
return new ReadableStreamState();
}

function readableStreamFromIterable(iterable) {
Expand Down
112 changes: 62 additions & 50 deletions lib/internal/webstreams/transformstream.js
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -253,21 +253,38 @@ ObjectDefineProperties(TransformStream.prototype, {
[SymbolToStringTag]: getNonWritablePropertyDescriptor(TransformStream.name),
});

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class TransformStreamState {
readable = undefined;
writable = undefined;
controller = undefined;
backpressure = undefined;
// Continuation slots replacing the spec's
// [[backpressureChangePromise]]; see transformStreamSetBackpressure.
pullPending = false;
pendingWriteParked = false;
pendingWriteChunk = undefined;
writeContinuation = undefined;
}
ObjectSetPrototypeOf(TransformStreamState.prototype, null);

class TransformStreamControllerState {
stream = undefined;
transformAlgorithm = undefined;
flushAlgorithm = undefined;
cancelAlgorithm = undefined;
performTransformRejected = undefined;
finishPromise = undefined;
}
ObjectSetPrototypeOf(TransformStreamControllerState.prototype, null);

function InternalTransferredTransformStream() {
ObjectSetPrototypeOf(this, TransformStream.prototype);
markTransferMode(this, false, true);
this[kType] = 'TransformStream';
this[kState] = {
__proto__: null,
readable: undefined,
writable: undefined,
backpressure: undefined,
pullPending: false,
pendingWrite: undefined,
pendingWriteChunk: undefined,
writeContinuation: undefined,
controller: undefined,
};
this[kState] = new TransformStreamState();
}

ObjectSetPrototypeOf(InternalTransferredTransformStream.prototype, TransformStream.prototype);
Expand DownExpand Up@@ -388,19 +405,10 @@ function initializeTransformStream(
readableSizeAlgorithm,
);

stream[kState] = {
__proto__: null,
readable,
writable,
controller: undefined,
backpressure: undefined,
// Continuation slots replacing the spec's
// [[backpressureChangePromise]]; see transformStreamSetBackpressure.
pullPending: false,
pendingWrite: undefined,
pendingWriteChunk: undefined,
writeContinuation: undefined,
};
const state = new TransformStreamState();
state.readable = readable;
state.writable = writable;
stream[kState] = state;

transformStreamSetBackpressure(stream, true);
}
Expand DownExpand Up@@ -457,7 +465,7 @@ function transformStreamSetBackpressure(stream, backpressure) {
kResolvedPromise,
state.readable[kState].controller[kState].pullFulfilled);
}
} else if (state.pendingWrite !== undefined) {
} else if (state.pendingWriteParked) {
PromisePrototypeThen(kResolvedPromise, state.writeContinuation);
}
}
Expand All@@ -470,14 +478,12 @@ function setupTransformStreamDefaultController(
cancelAlgorithm) {
assert(isTransformStream(stream));
assert(stream[kState].controller === undefined);
controller[kState] = {
__proto__: null,
stream,
transformAlgorithm,
flushAlgorithm,
cancelAlgorithm,
performTransformRejected: undefined,
};
const controllerState = new TransformStreamControllerState();
controllerState.stream = stream;
controllerState.transformAlgorithm = transformAlgorithm;
controllerState.flushAlgorithm = flushAlgorithm;
controllerState.cancelAlgorithm = cancelAlgorithm;
controller[kState] = controllerState;
stream[kState].controller = controller;
}

Expand DownExpand Up@@ -603,35 +609,41 @@ function transformStreamDefaultSinkWriteAlgorithm(stream, chunk) {
} = state;
assert(writable[kState].state === 'writable');
if (state.backpressure) {
// Park the chunk and one promise record; the backpressure -> false
// flip delivers the cached continuation (see
// transformStreamSetBackpressure) at the same microtask position as
// the old [[backpressureChangePromise]] reaction. The continuation
// resolves the sink promise with the perform-transform promise, so
// adoption reproduces the old derived-chain settle depth exactly.
// The writable dispatches a single write at a time, so one pending
// slot suffices.
assert(state.pendingWrite === undefined);
const pendingWrite = PromiseWithResolvers();
state.pendingWrite = pendingWrite;
// Park the chunk; the backpressure -> false flip delivers the cached
// continuation (see transformStreamSetBackpressure) at the same
// microtask position as the old [[backpressureChangePromise]]
// reaction. The continuation completes the parked write by wiring
// the perform-transform promise directly to the writable
// controller's write reactions (they exist: the controller creates
// them before invoking the write algorithm), replacing the promise
// record the old code allocated and resolved per parked chunk. The
// writable dispatches a single write at a time, so one pending slot
// suffices.
assert(!state.pendingWriteParked);
state.pendingWriteParked = true;
state.pendingWriteChunk = chunk;
state.writeContinuation ??= () => {
const pending = state.pendingWrite;
const pendingChunk = state.pendingWriteChunk;
state.pendingWrite = undefined;
state.pendingWriteParked = false;
state.pendingWriteChunk = undefined;
const writableState = state.writable[kState];
const writableControllerState = writableState.controller[kState];
if (writableState.state === 'erroring') {
pending.reject(writableState.storedError);
const error = writableState.storedError;
PromisePrototypeThen(
kResolvedPromise,
() => writableControllerState.writeRejected(error));
return;
}
assert(writableState.state === 'writable');
pending.resolve(
PromisePrototypeThen(
transformStreamDefaultControllerPerformTransform(
controller,
pendingChunk));
pendingChunk),
writableControllerState.writeFulfilled,
writableControllerState.writeRejected);
};
return pendingWrite.promise;
return kParkedAlgorithmResult;
}
return transformStreamDefaultControllerPerformTransform(controller, chunk);
}
Expand Down
63 changes: 35 additions & 28 deletions lib/internal/webstreams/writablestream.js
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -596,35 +596,42 @@ const isWritableStreamDefaultWriter =
const isWritableStreamDefaultController =
isBrandCheck('WritableStreamDefaultController');

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class WritableStreamTransferState {
readable = undefined;
port1 = undefined;
port2 = undefined;
promise = undefined;
}
ObjectSetPrototypeOf(WritableStreamTransferState.prototype, null);

class WritableStreamState {
closedPromise = undefined;
closeRequest = kNilRequest;
// Mirrors "closeRequest or inFlightCloseRequest is pending"; kept as a
// flag because the predicate runs several times per chunk on the write
// hot path.
closeQueuedOrInFlight = false;
inFlightWriteRequest = kNilRequest;
inFlightCloseRequest = kNilRequest;
pendingAbortRequest = kNilPendingAbortRequest;
backpressure = false;
controller = undefined;
state = 'writable';
storedError = undefined;
// Ring-buffer request queue, materialized lazily on the first pending
// write (see writableStreamAddWriteRequest) so construction allocates
// no request storage.
writeRequests = kEmptyQueue;
writer = undefined;
transfer = new WritableStreamTransferState();
}
ObjectSetPrototypeOf(WritableStreamState.prototype, null);

function createWritableStreamState() {
return {
__proto__: null,
closedPromise: undefined,
closeRequest: kNilRequest,
// Mirrors "closeRequest or inFlightCloseRequest is pending"; kept as a
// flag because the predicate runs several times per chunk on the write
// hot path.
closeQueuedOrInFlight: false,
inFlightWriteRequest: kNilRequest,
inFlightCloseRequest: kNilRequest,
pendingAbortRequest: kNilPendingAbortRequest,
backpressure: false,
controller: undefined,
state: 'writable',
storedError: undefined,
// Ring-buffer request queue, materialized lazily on the first pending
// write (see writableStreamAddWriteRequest) so construction allocates
// no request storage.
writeRequests: kEmptyQueue,
writer: undefined,
transfer: {
__proto__: null,
readable: undefined,
port1: undefined,
port2: undefined,
promise: undefined,
},
};
return new WritableStreamState();
}

function isWritableStreamLocked(stream) {
Expand Down
Loading
Loading
, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

Skip to content
stream: keep webstream stream states in fast-mode objects#65625

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 Open

mcollina
wants to merge
2
commits into

base:main
Choose a base branch

from


+253

−93

 Open


stream: keep webstream stream states in fast-mode objects
#65625
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1695e7b

stream: keep webstream stream states in fast-mode objects


mcollina Aug 28, 2026
aaa47dc

stream: avoid promise allocation for parked transform writes


mcollina Aug 28, 2026

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76 changes: 76 additions & 0 deletions
benchmark/webstreams/lifecycle.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,76 @@
'use strict';
const common = require('../common.js');
const assert = require('assert');
const {
 ReadableStream,
 WritableStream,
 TransformStream,
} = require('node:stream/web');

const bench = common.createBenchmark(main, {
 n: [5e4],
 kind: ['readable', 'pipe-to', 'pipe-through'],
});

const chunk = Buffer.alloc(1024);

function makeSource() {
 let i = 0;
 return {
 pull(controller) {
 if (i++ < 4)
 controller.enqueue(chunk);
 else
 controller.close();
 },
 };
}

async function readable(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 const reader = new ReadableStream(makeSource()).getReader();
 while (!(await reader.read()).done) chunks++;
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

async function pipeTo(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 await new ReadableStream(makeSource())
 .pipeTo(new WritableStream({ write() { chunks++; } }));
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

async function pipeThrough(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 const reader = new ReadableStream(makeSource())
 .pipeThrough(new TransformStream())
 .getReader();
 while (!(await reader.read()).done) chunks++;
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

function main({ n, kind }) {
 switch (kind) {
 case 'readable':
 readable(n);
 break;
 case 'pipe-to':
 pipeTo(n);
 break;
 case 'pipe-through':
 pipeThrough(n);
 break;
 }
}

38 changes: 23 additions & 15 deletions
lib/internal/webstreams/readablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1419,22 +1419,30 @@ const isReadableStreamBYOBReader =

// ---- ReadableStream Implementation

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class ReadableStreamTransferState {
 writable = undefined;
 port1 = undefined;
 port2 = undefined;
 promise = undefined;
}
ObjectSetPrototypeOf(ReadableStreamTransferState.prototype, null);

class ReadableStreamState {
 closedPromise = undefined;
 disturbed = false;
 reader = undefined;
 state = 'readable';
 storedError = undefined;
 controller = undefined;
 transfer = new ReadableStreamTransferState();
}
ObjectSetPrototypeOf(ReadableStreamState.prototype, null);

function createReadableStreamState() {
 return {
 __proto__: null,
 closedPromise: undefined,
 disturbed: false,
 reader: undefined,
 state: 'readable',
 storedError: undefined,
 transfer: {
 __proto__: null,
 writable: undefined,
 port1: undefined,
 port2: undefined,
 promise: undefined,
 },
 };
 return new ReadableStreamState();
}

function readableStreamFromIterable(iterable) {
Expand Down

112 changes: 62 additions & 50 deletions
lib/internal/webstreams/transformstream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -253,21 +253,38 @@ ObjectDefineProperties(TransformStream.prototype, {
 [SymbolToStringTag]: getNonWritablePropertyDescriptor(TransformStream.name),
});

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class TransformStreamState {
 readable = undefined;
 writable = undefined;
 controller = undefined;
 backpressure = undefined;
 // Continuation slots replacing the spec's
 // [[backpressureChangePromise]]; see transformStreamSetBackpressure.
 pullPending = false;
 pendingWriteParked = false;
 pendingWriteChunk = undefined;
 writeContinuation = undefined;
}
ObjectSetPrototypeOf(TransformStreamState.prototype, null);

class TransformStreamControllerState {
 stream = undefined;
 transformAlgorithm = undefined;
 flushAlgorithm = undefined;
 cancelAlgorithm = undefined;
 performTransformRejected = undefined;
 finishPromise = undefined;
}
ObjectSetPrototypeOf(TransformStreamControllerState.prototype, null);

function InternalTransferredTransformStream() {
 ObjectSetPrototypeOf(this, TransformStream.prototype);
 markTransferMode(this, false, true);
 this[kType] = 'TransformStream';
 this[kState] = {
 __proto__: null,
 readable: undefined,
 writable: undefined,
 backpressure: undefined,
 pullPending: false,
 pendingWrite: undefined,
 pendingWriteChunk: undefined,
 writeContinuation: undefined,
 controller: undefined,
 };
 this[kState] = new TransformStreamState();
}

ObjectSetPrototypeOf(InternalTransferredTransformStream.prototype, TransformStream.prototype);
Expand DownExpand Up@@ -388,19 +405,10 @@ function initializeTransformStream(
 readableSizeAlgorithm,
 );

 stream[kState] = {
 __proto__: null,
 readable,
 writable,
 controller: undefined,
 backpressure: undefined,
 // Continuation slots replacing the spec's
 // [[backpressureChangePromise]]; see transformStreamSetBackpressure.
 pullPending: false,
 pendingWrite: undefined,
 pendingWriteChunk: undefined,
 writeContinuation: undefined,
 };
 const state = new TransformStreamState();
 state.readable = readable;
 state.writable = writable;
 stream[kState] = state;

 transformStreamSetBackpressure(stream, true);
}
Expand DownExpand Up@@ -457,7 +465,7 @@ function transformStreamSetBackpressure(stream, backpressure) {
 kResolvedPromise,
 state.readable[kState].controller[kState].pullFulfilled);
 }
 } else if (state.pendingWrite !== undefined) {
 } else if (state.pendingWriteParked) {
 PromisePrototypeThen(kResolvedPromise, state.writeContinuation);
 }
}
Expand All@@ -470,14 +478,12 @@ function setupTransformStreamDefaultController(
 cancelAlgorithm) {
 assert(isTransformStream(stream));
 assert(stream[kState].controller === undefined);
 controller[kState] = {
 __proto__: null,
 stream,
 transformAlgorithm,
 flushAlgorithm,
 cancelAlgorithm,
 performTransformRejected: undefined,
 };
 const controllerState = new TransformStreamControllerState();
 controllerState.stream = stream;
 controllerState.transformAlgorithm = transformAlgorithm;
 controllerState.flushAlgorithm = flushAlgorithm;
 controllerState.cancelAlgorithm = cancelAlgorithm;
 controller[kState] = controllerState;
 stream[kState].controller = controller;
}

Expand DownExpand Up@@ -603,35 +609,41 @@ function transformStreamDefaultSinkWriteAlgorithm(stream, chunk) {
 } = state;
 assert(writable[kState].state === 'writable');
 if (state.backpressure) {
 // Park the chunk and one promise record; the backpressure -> false
 // flip delivers the cached continuation (see
 // transformStreamSetBackpressure) at the same microtask position as
 // the old [[backpressureChangePromise]] reaction. The continuation
 // resolves the sink promise with the perform-transform promise, so
 // adoption reproduces the old derived-chain settle depth exactly.
 // The writable dispatches a single write at a time, so one pending
 // slot suffices.
 assert(state.pendingWrite === undefined);
 const pendingWrite = PromiseWithResolvers();
 state.pendingWrite = pendingWrite;
 // Park the chunk; the backpressure -> false flip delivers the cached
 // continuation (see transformStreamSetBackpressure) at the same
 // microtask position as the old [[backpressureChangePromise]]
 // reaction. The continuation completes the parked write by wiring
 // the perform-transform promise directly to the writable
 // controller's write reactions (they exist: the controller creates
 // them before invoking the write algorithm), replacing the promise
 // record the old code allocated and resolved per parked chunk. The
 // writable dispatches a single write at a time, so one pending slot
 // suffices.
 assert(!state.pendingWriteParked);
 state.pendingWriteParked = true;
 state.pendingWriteChunk = chunk;
 state.writeContinuation ??= () => {
 const pending = state.pendingWrite;
 const pendingChunk = state.pendingWriteChunk;
 state.pendingWrite = undefined;
 state.pendingWriteParked = false;
 state.pendingWriteChunk = undefined;
 const writableState = state.writable[kState];
 const writableControllerState = writableState.controller[kState];
 if (writableState.state === 'erroring') {
 pending.reject(writableState.storedError);
 const error = writableState.storedError;
 PromisePrototypeThen(
 kResolvedPromise,
 () => writableControllerState.writeRejected(error));
 return;
 }
 assert(writableState.state === 'writable');
pending.resolve(
PromisePrototypeThen(
 transformStreamDefaultControllerPerformTransform(
 controller,
 pendingChunk));
 pendingChunk),
 writableControllerState.writeFulfilled,
 writableControllerState.writeRejected);
 };
 return pendingWrite.promise;
 return kParkedAlgorithmResult;
 }
 return transformStreamDefaultControllerPerformTransform(controller, chunk);
}
Expand Down

63 changes: 35 additions & 28 deletions
lib/internal/webstreams/writablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -596,35 +596,42 @@ const isWritableStreamDefaultWriter =
const isWritableStreamDefaultController =
 isBrandCheck('WritableStreamDefaultController');

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class WritableStreamTransferState {
 readable = undefined;
 port1 = undefined;
 port2 = undefined;
 promise = undefined;
}
ObjectSetPrototypeOf(WritableStreamTransferState.prototype, null);

class WritableStreamState {
 closedPromise = undefined;
 closeRequest = kNilRequest;
 // Mirrors "closeRequest or inFlightCloseRequest is pending"; kept as a
 // flag because the predicate runs several times per chunk on the write
 // hot path.
 closeQueuedOrInFlight = false;
 inFlightWriteRequest = kNilRequest;
 inFlightCloseRequest = kNilRequest;
 pendingAbortRequest = kNilPendingAbortRequest;
 backpressure = false;
 controller = undefined;
 state = 'writable';
 storedError = undefined;
 // Ring-buffer request queue, materialized lazily on the first pending
 // write (see writableStreamAddWriteRequest) so construction allocates
 // no request storage.
 writeRequests = kEmptyQueue;
 writer = undefined;
 transfer = new WritableStreamTransferState();
}
ObjectSetPrototypeOf(WritableStreamState.prototype, null);

function createWritableStreamState() {
 return {
 __proto__: null,
 closedPromise: undefined,
 closeRequest: kNilRequest,
 // Mirrors "closeRequest or inFlightCloseRequest is pending"; kept as a
 // flag because the predicate runs several times per chunk on the write
 // hot path.
 closeQueuedOrInFlight: false,
 inFlightWriteRequest: kNilRequest,
 inFlightCloseRequest: kNilRequest,
 pendingAbortRequest: kNilPendingAbortRequest,
 backpressure: false,
 controller: undefined,
 state: 'writable',
 storedError: undefined,
 // Ring-buffer request queue, materialized lazily on the first pending
 // write (see writableStreamAddWriteRequest) so construction allocates
 // no request storage.
 writeRequests: kEmptyQueue,
 writer: undefined,
 transfer: {
 __proto__: null,
 readable: undefined,
 port1: undefined,
 port2: undefined,
 promise: undefined,
 },
 };
 return new WritableStreamState();
}

function isWritableStreamLocked(stream) {
Expand Down
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
stream: keep webstream stream states in fast-mode objects#65625

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stream: keep webstream stream states in fast-mode objects
#65625
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1695e7b

stream: keep webstream stream states in fast-mode objects


mcollina Aug 28, 2026
aaa47dc

stream: avoid promise allocation for parked transform writes


mcollina Aug 28, 2026

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76 changes: 76 additions & 0 deletions
benchmark/webstreams/lifecycle.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,76 @@
'use strict';
const common = require('../common.js');
const assert = require('assert');
const {
 ReadableStream,
 WritableStream,
 TransformStream,
} = require('node:stream/web');

const bench = common.createBenchmark(main, {
 n: [5e4],
 kind: ['readable', 'pipe-to', 'pipe-through'],
});

const chunk = Buffer.alloc(1024);

function makeSource() {
 let i = 0;
 return {
 pull(controller) {
 if (i++ < 4)
 controller.enqueue(chunk);
 else
 controller.close();
 },
 };
}

async function readable(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 const reader = new ReadableStream(makeSource()).getReader();
 while (!(await reader.read()).done) chunks++;
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

async function pipeTo(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 await new ReadableStream(makeSource())
 .pipeTo(new WritableStream({ write() { chunks++; } }));
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

async function pipeThrough(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 const reader = new ReadableStream(makeSource())
 .pipeThrough(new TransformStream())
 .getReader();
 while (!(await reader.read()).done) chunks++;
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

function main({ n, kind }) {
 switch (kind) {
 case 'readable':
 readable(n);
 break;
 case 'pipe-to':
 pipeTo(n);
 break;
 case 'pipe-through':
 pipeThrough(n);
 break;
 }
}

38 changes: 23 additions & 15 deletions
lib/internal/webstreams/readablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1419,22 +1419,30 @@ const isReadableStreamBYOBReader =

// ---- ReadableStream Implementation

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class ReadableStreamTransferState {
 writable = undefined;
 port1 = undefined;
 port2 = undefined;
 promise = undefined;
}
ObjectSetPrototypeOf(ReadableStreamTransferState.prototype, null);

class ReadableStreamState {
 closedPromise = undefined;
 disturbed = false;
 reader = undefined;
 state = 'readable';
 storedError = undefined;
 controller = undefined;
 transfer = new ReadableStreamTransferState();
}
ObjectSetPrototypeOf(ReadableStreamState.prototype, null);

function createReadableStreamState() {
 return {
 __proto__: null,
 closedPromise: undefined,
 disturbed: false,
 reader: undefined,
 state: 'readable',
 storedError: undefined,
 transfer: {
 __proto__: null,
 writable: undefined,
 port1: undefined,
 port2: undefined,
 promise: undefined,
 },
 };
 return new ReadableStreamState();
}

function readableStreamFromIterable(iterable) {
Expand Down

112 changes: 62 additions & 50 deletions
lib/internal/webstreams/transformstream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -253,21 +253,38 @@ ObjectDefineProperties(TransformStream.prototype, {
 [SymbolToStringTag]: getNonWritablePropertyDescriptor(TransformStream.name),
});

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class TransformStreamState {
 readable = undefined;
 writable = undefined;
 controller = undefined;
 backpressure = undefined;
 // Continuation slots replacing the spec's
 // [[backpressureChangePromise]]; see transformStreamSetBackpressure.
 pullPending = false;
 pendingWriteParked = false;
 pendingWriteChunk = undefined;
 writeContinuation = undefined;
}
ObjectSetPrototypeOf(TransformStreamState.prototype, null);

class TransformStreamControllerState {
 stream = undefined;
 transformAlgorithm = undefined;
 flushAlgorithm = undefined;
 cancelAlgorithm = undefined;
 performTransformRejected = undefined;
 finishPromise = undefined;
}
ObjectSetPrototypeOf(TransformStreamControllerState.prototype, null);

function InternalTransferredTransformStream() {
 ObjectSetPrototypeOf(this, TransformStream.prototype);
 markTransferMode(this, false, true);
 this[kType] = 'TransformStream';
 this[kState] = {
 __proto__: null,
 readable: undefined,
 writable: undefined,
 backpressure: undefined,
 pullPending: false,
 pendingWrite: undefined,
 pendingWriteChunk: undefined,
 writeContinuation: undefined,
 controller: undefined,
 };
 this[kState] = new TransformStreamState();
}

ObjectSetPrototypeOf(InternalTransferredTransformStream.prototype, TransformStream.prototype);
Expand DownExpand Up@@ -388,19 +405,10 @@ function initializeTransformStream(
 readableSizeAlgorithm,
 );

 stream[kState] = {
 __proto__: null,
 readable,
 writable,
 controller: undefined,
 backpressure: undefined,
 // Continuation slots replacing the spec's
 // [[backpressureChangePromise]]; see transformStreamSetBackpressure.
 pullPending: false,
 pendingWrite: undefined,
 pendingWriteChunk: undefined,
 writeContinuation: undefined,
 };
 const state = new TransformStreamState();
 state.readable = readable;
 state.writable = writable;
 stream[kState] = state;

 transformStreamSetBackpressure(stream, true);
}
Expand DownExpand Up@@ -457,7 +465,7 @@ function transformStreamSetBackpressure(stream, backpressure) {
 kResolvedPromise,
 state.readable[kState].controller[kState].pullFulfilled);
 }
 } else if (state.pendingWrite !== undefined) {
 } else if (state.pendingWriteParked) {
 PromisePrototypeThen(kResolvedPromise, state.writeContinuation);
 }
}
Expand All@@ -470,14 +478,12 @@ function setupTransformStreamDefaultController(
 cancelAlgorithm) {
 assert(isTransformStream(stream));
 assert(stream[kState].controller === undefined);
 controller[kState] = {
 __proto__: null,
 stream,
 transformAlgorithm,
 flushAlgorithm,
 cancelAlgorithm,
 performTransformRejected: undefined,
 };
 const controllerState = new TransformStreamControllerState();
 controllerState.stream = stream;
 controllerState.transformAlgorithm = transformAlgorithm;
 controllerState.flushAlgorithm = flushAlgorithm;
 controllerState.cancelAlgorithm = cancelAlgorithm;
 controller[kState] = controllerState;
 stream[kState].controller = controller;
}

Expand DownExpand Up@@ -603,35 +609,41 @@ function transformStreamDefaultSinkWriteAlgorithm(stream, chunk) {
 } = state;
 assert(writable[kState].state === 'writable');
 if (state.backpressure) {
 // Park the chunk and one promise record; the backpressure -> false
 // flip delivers the cached continuation (see
 // transformStreamSetBackpressure) at the same microtask position as
 // the old [[backpressureChangePromise]] reaction. The continuation
 // resolves the sink promise with the perform-transform promise, so
 // adoption reproduces the old derived-chain settle depth exactly.
 // The writable dispatches a single write at a time, so one pending
 // slot suffices.
 assert(state.pendingWrite === undefined);
 const pendingWrite = PromiseWithResolvers();
 state.pendingWrite = pendingWrite;
 // Park the chunk; the backpressure -> false flip delivers the cached
 // continuation (see transformStreamSetBackpressure) at the same
 // microtask position as the old [[backpressureChangePromise]]
 // reaction. The continuation completes the parked write by wiring
 // the perform-transform promise directly to the writable
 // controller's write reactions (they exist: the controller creates
 // them before invoking the write algorithm), replacing the promise
 // record the old code allocated and resolved per parked chunk. The
 // writable dispatches a single write at a time, so one pending slot
 // suffices.
 assert(!state.pendingWriteParked);
 state.pendingWriteParked = true;
 state.pendingWriteChunk = chunk;
 state.writeContinuation ??= () => {
 const pending = state.pendingWrite;
 const pendingChunk = state.pendingWriteChunk;
 state.pendingWrite = undefined;
 state.pendingWriteParked = false;
 state.pendingWriteChunk = undefined;
 const writableState = state.writable[kState];
 const writableControllerState = writableState.controller[kState];
 if (writableState.state === 'erroring') {
 pending.reject(writableState.storedError);
 const error = writableState.storedError;
 PromisePrototypeThen(
 kResolvedPromise,
 () => writableControllerState.writeRejected(error));
 return;
 }
 assert(writableState.state === 'writable');
pending.resolve(
PromisePrototypeThen(
 transformStreamDefaultControllerPerformTransform(
 controller,
 pendingChunk));
 pendingChunk),
 writableControllerState.writeFulfilled,
 writableControllerState.writeRejected);
 };
 return pendingWrite.promise;
 return kParkedAlgorithmResult;
 }
 return transformStreamDefaultControllerPerformTransform(controller, chunk);
}
Expand Down

63 changes: 35 additions & 28 deletions
lib/internal/webstreams/writablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -596,35 +596,42 @@ const isWritableStreamDefaultWriter =
const isWritableStreamDefaultController =
 isBrandCheck('WritableStreamDefaultController');

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class WritableStreamTransferState {
 readable = undefined;
 port1 = undefined;
 port2 = undefined;
 promise = undefined;
}
ObjectSetPrototypeOf(WritableStreamTransferState.prototype, null);

class WritableStreamState {
 closedPromise = undefined;
 closeRequest = kNilRequest;
 // Mirrors "closeRequest or inFlightCloseRequest is pending"; kept as a
 // flag because the predicate runs several times per chunk on the write
 // hot path.
 closeQueuedOrInFlight = false;
 inFlightWriteRequest = kNilRequest;
 inFlightCloseRequest = kNilRequest;
 pendingAbortRequest = kNilPendingAbortRequest;
 backpressure = false;
 controller = undefined;
 state = 'writable';
 storedError = undefined;
 // Ring-buffer request queue, materialized lazily on the first pending
 // write (see writableStreamAddWriteRequest) so construction allocates
 // no request storage.
 writeRequests = kEmptyQueue;
 writer = undefined;
 transfer = new WritableStreamTransferState();
}
ObjectSetPrototypeOf(WritableStreamState.prototype, null);

function createWritableStreamState() {
 return {
 __proto__: null,
 closedPromise: undefined,
 closeRequest: kNilRequest,
 // Mirrors "closeRequest or inFlightCloseRequest is pending"; kept as a
 // flag because the predicate runs several times per chunk on the write
 // hot path.
 closeQueuedOrInFlight: false,
 inFlightWriteRequest: kNilRequest,
 inFlightCloseRequest: kNilRequest,
 pendingAbortRequest: kNilPendingAbortRequest,
 backpressure: false,
 controller: undefined,
 state: 'writable',
 storedError: undefined,
 // Ring-buffer request queue, materialized lazily on the first pending
 // write (see writableStreamAddWriteRequest) so construction allocates
 // no request storage.
 writeRequests: kEmptyQueue,
 writer: undefined,
 transfer: {
 __proto__: null,
 readable: undefined,
 port1: undefined,
 port2: undefined,
 promise: undefined,
 },
 };
 return new WritableStreamState();
}

function isWritableStreamLocked(stream) {
Expand Down
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Highlight search terms from Google/DuckDuckGo/Bing referrer\n(function() {\n var ref = document.referrer;\n var terms = [];\n \n if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {\n var url = new URL(ref);\n var q = url.searchParams.get('q') || url.searchParams.get('p');\n if (q) {\n terms = q.split(/\\s+/).filter(function(t) { return t.length > 2; });\n }\n }\n \n if (terms.length === 0) return;\n \n var style = document.createElement('style');\n style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';\n document.head.appendChild(style);\n \n function highlight(node) {\n if (node.nodeType === 3) { // text node\n var text = node.textContent;\n var found = false;\n terms.forEach(function(term) {\n var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\\]\\\\]/g, '\\\\') + ')', 'gi');\n if (regex.test(text)) {\n found = true;\n var frag = document.createDocumentFragment();\n var parts = text.split(regex);\n parts.forEach(function(part, i) {\n if (i % 2 === 0) {\n frag.appendChild(document.createTextNode(part));\n } else {\n var span = document.createElement('span');\n span.className = 'userscript-highlight';\n span.textContent = part;\n frag.appendChild(span);\n }\n });\n node.parentNode.replaceChild(frag, node);\n }\n });\n } else if (node.nodeType === 1 && node.childNodes) { // element\n var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];\n if (!skipTags.includes(node.tagName)) {\n Array.from(node.childNodes).forEach(highlight);\n }\n }\n }\n \n highlight(document.body);\n \n // Re-highlight on dynamic content\n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1 || node.nodeType === 3) highlight(node);\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Highlight Search Terms");
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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mcollina
wants to merge
2
commits into

base:main
Choose a base branch

from


+253

−93

 Open


stream: keep webstream stream states in fast-mode objects
#65625
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Hold shift + click to select a range
1695e7b

stream: keep webstream stream states in fast-mode objects


mcollina Aug 28, 2026
aaa47dc

stream: avoid promise allocation for parked transform writes


mcollina Aug 28, 2026

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Filter by extension
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76 changes: 76 additions & 0 deletions
benchmark/webstreams/lifecycle.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,76 @@
'use strict';
const common = require('../common.js');
const assert = require('assert');
const {
 ReadableStream,
 WritableStream,
 TransformStream,
} = require('node:stream/web');

const bench = common.createBenchmark(main, {
 n: [5e4],
 kind: ['readable', 'pipe-to', 'pipe-through'],
});

const chunk = Buffer.alloc(1024);

function makeSource() {
 let i = 0;
 return {
 pull(controller) {
 if (i++ < 4)
 controller.enqueue(chunk);
 else
 controller.close();
 },
 };
}

async function readable(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 const reader = new ReadableStream(makeSource()).getReader();
 while (!(await reader.read()).done) chunks++;
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

async function pipeTo(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 await new ReadableStream(makeSource())
 .pipeTo(new WritableStream({ write() { chunks++; } }));
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

async function pipeThrough(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 const reader = new ReadableStream(makeSource())
 .pipeThrough(new TransformStream())
 .getReader();
 while (!(await reader.read()).done) chunks++;
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

function main({ n, kind }) {
 switch (kind) {
 case 'readable':
 readable(n);
 break;
 case 'pipe-to':
 pipeTo(n);
 break;
 case 'pipe-through':
 pipeThrough(n);
 break;
 }
}

38 changes: 23 additions & 15 deletions
lib/internal/webstreams/readablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1419,22 +1419,30 @@ const isReadableStreamBYOBReader =

// ---- ReadableStream Implementation

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class ReadableStreamTransferState {
 writable = undefined;
 port1 = undefined;
 port2 = undefined;
 promise = undefined;
}
ObjectSetPrototypeOf(ReadableStreamTransferState.prototype, null);

class ReadableStreamState {
 closedPromise = undefined;
 disturbed = false;
 reader = undefined;
 state = 'readable';
 storedError = undefined;
 controller = undefined;
 transfer = new ReadableStreamTransferState();
}
ObjectSetPrototypeOf(ReadableStreamState.prototype, null);

function createReadableStreamState() {
 return {
 __proto__: null,
 closedPromise: undefined,
 disturbed: false,
 reader: undefined,
 state: 'readable',
 storedError: undefined,
 transfer: {
 __proto__: null,
 writable: undefined,
 port1: undefined,
 port2: undefined,
 promise: undefined,
 },
 };
 return new ReadableStreamState();
}

function readableStreamFromIterable(iterable) {
Expand Down

112 changes: 62 additions & 50 deletions
lib/internal/webstreams/transformstream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -253,21 +253,38 @@ ObjectDefineProperties(TransformStream.prototype, {
 [SymbolToStringTag]: getNonWritablePropertyDescriptor(TransformStream.name),
});

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class TransformStreamState {
 readable = undefined;
 writable = undefined;
 controller = undefined;
 backpressure = undefined;
 // Continuation slots replacing the spec's
 // [[backpressureChangePromise]]; see transformStreamSetBackpressure.
 pullPending = false;
 pendingWriteParked = false;
 pendingWriteChunk = undefined;
 writeContinuation = undefined;
}
ObjectSetPrototypeOf(TransformStreamState.prototype, null);

class TransformStreamControllerState {
 stream = undefined;
 transformAlgorithm = undefined;
 flushAlgorithm = undefined;
 cancelAlgorithm = undefined;
 performTransformRejected = undefined;
 finishPromise = undefined;
}
ObjectSetPrototypeOf(TransformStreamControllerState.prototype, null);

function InternalTransferredTransformStream() {
 ObjectSetPrototypeOf(this, TransformStream.prototype);
 markTransferMode(this, false, true);
 this[kType] = 'TransformStream';
 this[kState] = {
 __proto__: null,
 readable: undefined,
 writable: undefined,
 backpressure: undefined,
 pullPending: false,
 pendingWrite: undefined,
 pendingWriteChunk: undefined,
 writeContinuation: undefined,
 controller: undefined,
 };
 this[kState] = new TransformStreamState();
}

ObjectSetPrototypeOf(InternalTransferredTransformStream.prototype, TransformStream.prototype);
Expand DownExpand Up@@ -388,19 +405,10 @@ function initializeTransformStream(
 readableSizeAlgorithm,
 );

 stream[kState] = {
 __proto__: null,
 readable,
 writable,
 controller: undefined,
 backpressure: undefined,
 // Continuation slots replacing the spec's
 // [[backpressureChangePromise]]; see transformStreamSetBackpressure.
 pullPending: false,
 pendingWrite: undefined,
 pendingWriteChunk: undefined,
 writeContinuation: undefined,
 };
 const state = new TransformStreamState();
 state.readable = readable;
 state.writable = writable;
 stream[kState] = state;

 transformStreamSetBackpressure(stream, true);
}
Expand DownExpand Up@@ -457,7 +465,7 @@ function transformStreamSetBackpressure(stream, backpressure) {
 kResolvedPromise,
 state.readable[kState].controller[kState].pullFulfilled);
 }
 } else if (state.pendingWrite !== undefined) {
 } else if (state.pendingWriteParked) {
 PromisePrototypeThen(kResolvedPromise, state.writeContinuation);
 }
}
Expand All@@ -470,14 +478,12 @@ function setupTransformStreamDefaultController(
 cancelAlgorithm) {
 assert(isTransformStream(stream));
 assert(stream[kState].controller === undefined);
 controller[kState] = {
 __proto__: null,
 stream,
 transformAlgorithm,
 flushAlgorithm,
 cancelAlgorithm,
 performTransformRejected: undefined,
 };
 const controllerState = new TransformStreamControllerState();
 controllerState.stream = stream;
 controllerState.transformAlgorithm = transformAlgorithm;
 controllerState.flushAlgorithm = flushAlgorithm;
 controllerState.cancelAlgorithm = cancelAlgorithm;
 controller[kState] = controllerState;
 stream[kState].controller = controller;
}

Expand DownExpand Up@@ -603,35 +609,41 @@ function transformStreamDefaultSinkWriteAlgorithm(stream, chunk) {
 } = state;
 assert(writable[kState].state === 'writable');
 if (state.backpressure) {
 // Park the chunk and one promise record; the backpressure -> false
 // flip delivers the cached continuation (see
 // transformStreamSetBackpressure) at the same microtask position as
 // the old [[backpressureChangePromise]] reaction. The continuation
 // resolves the sink promise with the perform-transform promise, so
 // adoption reproduces the old derived-chain settle depth exactly.
 // The writable dispatches a single write at a time, so one pending
 // slot suffices.
 assert(state.pendingWrite === undefined);
 const pendingWrite = PromiseWithResolvers();
 state.pendingWrite = pendingWrite;
 // Park the chunk; the backpressure -> false flip delivers the cached
 // continuation (see transformStreamSetBackpressure) at the same
 // microtask position as the old [[backpressureChangePromise]]
 // reaction. The continuation completes the parked write by wiring
 // the perform-transform promise directly to the writable
 // controller's write reactions (they exist: the controller creates
 // them before invoking the write algorithm), replacing the promise
 // record the old code allocated and resolved per parked chunk. The
 // writable dispatches a single write at a time, so one pending slot
 // suffices.
 assert(!state.pendingWriteParked);
 state.pendingWriteParked = true;
 state.pendingWriteChunk = chunk;
 state.writeContinuation ??= () => {
 const pending = state.pendingWrite;
 const pendingChunk = state.pendingWriteChunk;
 state.pendingWrite = undefined;
 state.pendingWriteParked = false;
 state.pendingWriteChunk = undefined;
 const writableState = state.writable[kState];
 const writableControllerState = writableState.controller[kState];
 if (writableState.state === 'erroring') {
 pending.reject(writableState.storedError);
 const error = writableState.storedError;
 PromisePrototypeThen(
 kResolvedPromise,
 () => writableControllerState.writeRejected(error));
 return;
 }
 assert(writableState.state === 'writable');
pending.resolve(
PromisePrototypeThen(
 transformStreamDefaultControllerPerformTransform(
 controller,
 pendingChunk));
 pendingChunk),
 writableControllerState.writeFulfilled,
 writableControllerState.writeRejected);
 };
 return pendingWrite.promise;
 return kParkedAlgorithmResult;
 }
 return transformStreamDefaultControllerPerformTransform(controller, chunk);
}
Expand Down

63 changes: 35 additions & 28 deletions
lib/internal/webstreams/writablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -596,35 +596,42 @@ const isWritableStreamDefaultWriter =
const isWritableStreamDefaultController =
 isBrandCheck('WritableStreamDefaultController');

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class WritableStreamTransferState {
 readable = undefined;
 port1 = undefined;
 port2 = undefined;
 promise = undefined;
}
ObjectSetPrototypeOf(WritableStreamTransferState.prototype, null);

class WritableStreamState {
 closedPromise = undefined;
 closeRequest = kNilRequest;
 // Mirrors "closeRequest or inFlightCloseRequest is pending"; kept as a
 // flag because the predicate runs several times per chunk on the write
 // hot path.
 closeQueuedOrInFlight = false;
 inFlightWriteRequest = kNilRequest;
 inFlightCloseRequest = kNilRequest;
 pendingAbortRequest = kNilPendingAbortRequest;
 backpressure = false;
 controller = undefined;
 state = 'writable';
 storedError = undefined;
 // Ring-buffer request queue, materialized lazily on the first pending
 // write (see writableStreamAddWriteRequest) so construction allocates
 // no request storage.
 writeRequests = kEmptyQueue;
 writer = undefined;
 transfer = new WritableStreamTransferState();
}
ObjectSetPrototypeOf(WritableStreamState.prototype, null);

function createWritableStreamState() {
 return {
 __proto__: null,
 closedPromise: undefined,
 closeRequest: kNilRequest,
 // Mirrors "closeRequest or inFlightCloseRequest is pending"; kept as a
 // flag because the predicate runs several times per chunk on the write
 // hot path.
 closeQueuedOrInFlight: false,
 inFlightWriteRequest: kNilRequest,
 inFlightCloseRequest: kNilRequest,
 pendingAbortRequest: kNilPendingAbortRequest,
 backpressure: false,
 controller: undefined,
 state: 'writable',
 storedError: undefined,
 // Ring-buffer request queue, materialized lazily on the first pending
 // write (see writableStreamAddWriteRequest) so construction allocates
 // no request storage.
 writeRequests: kEmptyQueue,
 writer: undefined,
 transfer: {
 __proto__: null,
 readable: undefined,
 port1: undefined,
 port2: undefined,
 promise: undefined,
 },
 };
 return new WritableStreamState();
}

function isWritableStreamLocked(stream) {
Expand Down
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Strip utm_, fbclid, gclid, etc. from all links on page\n(function() {\n var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',\n 'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',\n 'ref', 'ref_src', 'source', 'medium', 'campaign'];\n \n function cleanUrl(url) {\n try {\n var u = new URL(url, window.location.origin);\n var changed = false;\n trackingParams.forEach(function(p) {\n if (u.searchParams.has(p)) {\n u.searchParams.delete(p);\n changed = true;\n }\n });\n return changed ? u.toString() : url;\n } catch (e) {\n return url;\n }\n }\n \n function cleanLinks() {\n document.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n \n cleanLinks();\n \n var observer = new MutationObserver(function(mutations) {\n mutations.forEach(function(m) {\n m.addedNodes.forEach(function(node) {\n if (node.nodeType === 1) {\n if (node.tagName === 'A') cleanLinks();\n node.querySelectorAll('a[href]').forEach(function(a) {\n var clean = cleanUrl(a.href);\n if (clean !== a.href) a.href = clean;\n });\n }\n });\n });\n });\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Remove Tracking Parameters from Links");
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '

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stream: keep webstream stream states in fast-mode objects#65625

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#65625
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1695e7b

stream: keep webstream stream states in fast-mode objects


mcollina Aug 28, 2026
aaa47dc

stream: avoid promise allocation for parked transform writes


mcollina Aug 28, 2026

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76 changes: 76 additions & 0 deletions
benchmark/webstreams/lifecycle.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,76 @@
'use strict';
const common = require('../common.js');
const assert = require('assert');
const {
 ReadableStream,
 WritableStream,
 TransformStream,
} = require('node:stream/web');

const bench = common.createBenchmark(main, {
 n: [5e4],
 kind: ['readable', 'pipe-to', 'pipe-through'],
});

const chunk = Buffer.alloc(1024);

function makeSource() {
 let i = 0;
 return {
 pull(controller) {
 if (i++ < 4)
 controller.enqueue(chunk);
 else
 controller.close();
 },
 };
}

async function readable(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 const reader = new ReadableStream(makeSource()).getReader();
 while (!(await reader.read()).done) chunks++;
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

async function pipeTo(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 await new ReadableStream(makeSource())
 .pipeTo(new WritableStream({ write() { chunks++; } }));
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

async function pipeThrough(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 const reader = new ReadableStream(makeSource())
 .pipeThrough(new TransformStream())
 .getReader();
 while (!(await reader.read()).done) chunks++;
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

function main({ n, kind }) {
 switch (kind) {
 case 'readable':
 readable(n);
 break;
 case 'pipe-to':
 pipeTo(n);
 break;
 case 'pipe-through':
 pipeThrough(n);
 break;
 }
}

38 changes: 23 additions & 15 deletions
lib/internal/webstreams/readablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1419,22 +1419,30 @@ const isReadableStreamBYOBReader =

// ---- ReadableStream Implementation

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class ReadableStreamTransferState {
 writable = undefined;
 port1 = undefined;
 port2 = undefined;
 promise = undefined;
}
ObjectSetPrototypeOf(ReadableStreamTransferState.prototype, null);

class ReadableStreamState {
 closedPromise = undefined;
 disturbed = false;
 reader = undefined;
 state = 'readable';
 storedError = undefined;
 controller = undefined;
 transfer = new ReadableStreamTransferState();
}
ObjectSetPrototypeOf(ReadableStreamState.prototype, null);

function createReadableStreamState() {
 return {
 __proto__: null,
 closedPromise: undefined,
 disturbed: false,
 reader: undefined,
 state: 'readable',
 storedError: undefined,
 transfer: {
 __proto__: null,
 writable: undefined,
 port1: undefined,
 port2: undefined,
 promise: undefined,
 },
 };
 return new ReadableStreamState();
}

function readableStreamFromIterable(iterable) {
Expand Down

112 changes: 62 additions & 50 deletions
lib/internal/webstreams/transformstream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -253,21 +253,38 @@ ObjectDefineProperties(TransformStream.prototype, {
 [SymbolToStringTag]: getNonWritablePropertyDescriptor(TransformStream.name),
});

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class TransformStreamState {
 readable = undefined;
 writable = undefined;
 controller = undefined;
 backpressure = undefined;
 // Continuation slots replacing the spec's
 // [[backpressureChangePromise]]; see transformStreamSetBackpressure.
 pullPending = false;
 pendingWriteParked = false;
 pendingWriteChunk = undefined;
 writeContinuation = undefined;
}
ObjectSetPrototypeOf(TransformStreamState.prototype, null);

class TransformStreamControllerState {
 stream = undefined;
 transformAlgorithm = undefined;
 flushAlgorithm = undefined;
 cancelAlgorithm = undefined;
 performTransformRejected = undefined;
 finishPromise = undefined;
}
ObjectSetPrototypeOf(TransformStreamControllerState.prototype, null);

function InternalTransferredTransformStream() {
 ObjectSetPrototypeOf(this, TransformStream.prototype);
 markTransferMode(this, false, true);
 this[kType] = 'TransformStream';
 this[kState] = {
 __proto__: null,
 readable: undefined,
 writable: undefined,
 backpressure: undefined,
 pullPending: false,
 pendingWrite: undefined,
 pendingWriteChunk: undefined,
 writeContinuation: undefined,
 controller: undefined,
 };
 this[kState] = new TransformStreamState();
}

ObjectSetPrototypeOf(InternalTransferredTransformStream.prototype, TransformStream.prototype);
Expand DownExpand Up@@ -388,19 +405,10 @@ function initializeTransformStream(
 readableSizeAlgorithm,
 );

 stream[kState] = {
 __proto__: null,
 readable,
 writable,
 controller: undefined,
 backpressure: undefined,
 // Continuation slots replacing the spec's
 // [[backpressureChangePromise]]; see transformStreamSetBackpressure.
 pullPending: false,
 pendingWrite: undefined,
 pendingWriteChunk: undefined,
 writeContinuation: undefined,
 };
 const state = new TransformStreamState();
 state.readable = readable;
 state.writable = writable;
 stream[kState] = state;

 transformStreamSetBackpressure(stream, true);
}
Expand DownExpand Up@@ -457,7 +465,7 @@ function transformStreamSetBackpressure(stream, backpressure) {
 kResolvedPromise,
 state.readable[kState].controller[kState].pullFulfilled);
 }
 } else if (state.pendingWrite !== undefined) {
 } else if (state.pendingWriteParked) {
 PromisePrototypeThen(kResolvedPromise, state.writeContinuation);
 }
}
Expand All@@ -470,14 +478,12 @@ function setupTransformStreamDefaultController(
 cancelAlgorithm) {
 assert(isTransformStream(stream));
 assert(stream[kState].controller === undefined);
 controller[kState] = {
 __proto__: null,
 stream,
 transformAlgorithm,
 flushAlgorithm,
 cancelAlgorithm,
 performTransformRejected: undefined,
 };
 const controllerState = new TransformStreamControllerState();
 controllerState.stream = stream;
 controllerState.transformAlgorithm = transformAlgorithm;
 controllerState.flushAlgorithm = flushAlgorithm;
 controllerState.cancelAlgorithm = cancelAlgorithm;
 controller[kState] = controllerState;
 stream[kState].controller = controller;
}

Expand DownExpand Up@@ -603,35 +609,41 @@ function transformStreamDefaultSinkWriteAlgorithm(stream, chunk) {
 } = state;
 assert(writable[kState].state === 'writable');
 if (state.backpressure) {
 // Park the chunk and one promise record; the backpressure -> false
 // flip delivers the cached continuation (see
 // transformStreamSetBackpressure) at the same microtask position as
 // the old [[backpressureChangePromise]] reaction. The continuation
 // resolves the sink promise with the perform-transform promise, so
 // adoption reproduces the old derived-chain settle depth exactly.
 // The writable dispatches a single write at a time, so one pending
 // slot suffices.
 assert(state.pendingWrite === undefined);
 const pendingWrite = PromiseWithResolvers();
 state.pendingWrite = pendingWrite;
 // Park the chunk; the backpressure -> false flip delivers the cached
 // continuation (see transformStreamSetBackpressure) at the same
 // microtask position as the old [[backpressureChangePromise]]
 // reaction. The continuation completes the parked write by wiring
 // the perform-transform promise directly to the writable
 // controller's write reactions (they exist: the controller creates
 // them before invoking the write algorithm), replacing the promise
 // record the old code allocated and resolved per parked chunk. The
 // writable dispatches a single write at a time, so one pending slot
 // suffices.
 assert(!state.pendingWriteParked);
 state.pendingWriteParked = true;
 state.pendingWriteChunk = chunk;
 state.writeContinuation ??= () => {
 const pending = state.pendingWrite;
 const pendingChunk = state.pendingWriteChunk;
 state.pendingWrite = undefined;
 state.pendingWriteParked = false;
 state.pendingWriteChunk = undefined;
 const writableState = state.writable[kState];
 const writableControllerState = writableState.controller[kState];
 if (writableState.state === 'erroring') {
 pending.reject(writableState.storedError);
 const error = writableState.storedError;
 PromisePrototypeThen(
 kResolvedPromise,
 () => writableControllerState.writeRejected(error));
 return;
 }
 assert(writableState.state === 'writable');
pending.resolve(
PromisePrototypeThen(
 transformStreamDefaultControllerPerformTransform(
 controller,
 pendingChunk));
 pendingChunk),
 writableControllerState.writeFulfilled,
 writableControllerState.writeRejected);
 };
 return pendingWrite.promise;
 return kParkedAlgorithmResult;
 }
 return transformStreamDefaultControllerPerformTransform(controller, chunk);
}
Expand Down

63 changes: 35 additions & 28 deletions
lib/internal/webstreams/writablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -596,35 +596,42 @@ const isWritableStreamDefaultWriter =
const isWritableStreamDefaultController =
 isBrandCheck('WritableStreamDefaultController');

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class WritableStreamTransferState {
 readable = undefined;
 port1 = undefined;
 port2 = undefined;
 promise = undefined;
}
ObjectSetPrototypeOf(WritableStreamTransferState.prototype, null);

class WritableStreamState {
 closedPromise = undefined;
 closeRequest = kNilRequest;
 // Mirrors "closeRequest or inFlightCloseRequest is pending"; kept as a
 // flag because the predicate runs several times per chunk on the write
 // hot path.
 closeQueuedOrInFlight = false;
 inFlightWriteRequest = kNilRequest;
 inFlightCloseRequest = kNilRequest;
 pendingAbortRequest = kNilPendingAbortRequest;
 backpressure = false;
 controller = undefined;
 state = 'writable';
 storedError = undefined;
 // Ring-buffer request queue, materialized lazily on the first pending
 // write (see writableStreamAddWriteRequest) so construction allocates
 // no request storage.
 writeRequests = kEmptyQueue;
 writer = undefined;
 transfer = new WritableStreamTransferState();
}
ObjectSetPrototypeOf(WritableStreamState.prototype, null);

function createWritableStreamState() {
 return {
 __proto__: null,
 closedPromise: undefined,
 closeRequest: kNilRequest,
 // Mirrors "closeRequest or inFlightCloseRequest is pending"; kept as a
 // flag because the predicate runs several times per chunk on the write
 // hot path.
 closeQueuedOrInFlight: false,
 inFlightWriteRequest: kNilRequest,
 inFlightCloseRequest: kNilRequest,
 pendingAbortRequest: kNilPendingAbortRequest,
 backpressure: false,
 controller: undefined,
 state: 'writable',
 storedError: undefined,
 // Ring-buffer request queue, materialized lazily on the first pending
 // write (see writableStreamAddWriteRequest) so construction allocates
 // no request storage.
 writeRequests: kEmptyQueue,
 writer: undefined,
 transfer: {
 __proto__: null,
 readable: undefined,
 port1: undefined,
 port2: undefined,
 promise: undefined,
 },
 };
 return new WritableStreamState();
}

function isWritableStreamLocked(stream) {
Expand Down
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Auto-enable theater mode on YouTube\n(function() {\n function tryTheater() {\n var btn = document.querySelector('button[aria-label=\"Theater mode\"], ytd-player #player button[title=\"Theater mode\"]');\n if (btn && !btn.classList.contains('activated')) {\n btn.click();\n }\n }\n \n // Try immediately\n tryTheater();\n \n // Try after navigation (SPA)\n var lastUrl = location.href;\n setInterval(function() {\n if (location.href !== lastUrl) {\n lastUrl = location.href;\n setTimeout(tryTheater, 500);\n }\n }, 1000);\n \n // Also try on player load\n var observer = new MutationObserver(tryTheater);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "YouTube Theater Mode Default");
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
stream: keep webstream stream states in fast-mode objects#65625

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Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

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privacy statement. We’ll occasionally send you account related emails.

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to your account

 Open

mcollina
wants to merge
2
commits into

base:main
Choose a base branch

from


+253

−93

 Open


stream: keep webstream stream states in fast-mode objects
#65625
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1695e7b

stream: keep webstream stream states in fast-mode objects


mcollina Aug 28, 2026
aaa47dc

stream: avoid promise allocation for parked transform writes


mcollina Aug 28, 2026

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76 changes: 76 additions & 0 deletions
benchmark/webstreams/lifecycle.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,76 @@
'use strict';
const common = require('../common.js');
const assert = require('assert');
const {
 ReadableStream,
 WritableStream,
 TransformStream,
} = require('node:stream/web');

const bench = common.createBenchmark(main, {
 n: [5e4],
 kind: ['readable', 'pipe-to', 'pipe-through'],
});

const chunk = Buffer.alloc(1024);

function makeSource() {
 let i = 0;
 return {
 pull(controller) {
 if (i++ < 4)
 controller.enqueue(chunk);
 else
 controller.close();
 },
 };
}

async function readable(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 const reader = new ReadableStream(makeSource()).getReader();
 while (!(await reader.read()).done) chunks++;
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

async function pipeTo(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 await new ReadableStream(makeSource())
 .pipeTo(new WritableStream({ write() { chunks++; } }));
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

async function pipeThrough(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 const reader = new ReadableStream(makeSource())
 .pipeThrough(new TransformStream())
 .getReader();
 while (!(await reader.read()).done) chunks++;
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

function main({ n, kind }) {
 switch (kind) {
 case 'readable':
 readable(n);
 break;
 case 'pipe-to':
 pipeTo(n);
 break;
 case 'pipe-through':
 pipeThrough(n);
 break;
 }
}

38 changes: 23 additions & 15 deletions
lib/internal/webstreams/readablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1419,22 +1419,30 @@ const isReadableStreamBYOBReader =

// ---- ReadableStream Implementation

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class ReadableStreamTransferState {
 writable = undefined;
 port1 = undefined;
 port2 = undefined;
 promise = undefined;
}
ObjectSetPrototypeOf(ReadableStreamTransferState.prototype, null);

class ReadableStreamState {
 closedPromise = undefined;
 disturbed = false;
 reader = undefined;
 state = 'readable';
 storedError = undefined;
 controller = undefined;
 transfer = new ReadableStreamTransferState();
}
ObjectSetPrototypeOf(ReadableStreamState.prototype, null);

function createReadableStreamState() {
 return {
 __proto__: null,
 closedPromise: undefined,
 disturbed: false,
 reader: undefined,
 state: 'readable',
 storedError: undefined,
 transfer: {
 __proto__: null,
 writable: undefined,
 port1: undefined,
 port2: undefined,
 promise: undefined,
 },
 };
 return new ReadableStreamState();
}

function readableStreamFromIterable(iterable) {
Expand Down

112 changes: 62 additions & 50 deletions
lib/internal/webstreams/transformstream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -253,21 +253,38 @@ ObjectDefineProperties(TransformStream.prototype, {
 [SymbolToStringTag]: getNonWritablePropertyDescriptor(TransformStream.name),
});

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class TransformStreamState {
 readable = undefined;
 writable = undefined;
 controller = undefined;
 backpressure = undefined;
 // Continuation slots replacing the spec's
 // [[backpressureChangePromise]]; see transformStreamSetBackpressure.
 pullPending = false;
 pendingWriteParked = false;
 pendingWriteChunk = undefined;
 writeContinuation = undefined;
}
ObjectSetPrototypeOf(TransformStreamState.prototype, null);

class TransformStreamControllerState {
 stream = undefined;
 transformAlgorithm = undefined;
 flushAlgorithm = undefined;
 cancelAlgorithm = undefined;
 performTransformRejected = undefined;
 finishPromise = undefined;
}
ObjectSetPrototypeOf(TransformStreamControllerState.prototype, null);

function InternalTransferredTransformStream() {
 ObjectSetPrototypeOf(this, TransformStream.prototype);
 markTransferMode(this, false, true);
 this[kType] = 'TransformStream';
 this[kState] = {
 __proto__: null,
 readable: undefined,
 writable: undefined,
 backpressure: undefined,
 pullPending: false,
 pendingWrite: undefined,
 pendingWriteChunk: undefined,
 writeContinuation: undefined,
 controller: undefined,
 };
 this[kState] = new TransformStreamState();
}

ObjectSetPrototypeOf(InternalTransferredTransformStream.prototype, TransformStream.prototype);
Expand DownExpand Up@@ -388,19 +405,10 @@ function initializeTransformStream(
 readableSizeAlgorithm,
 );

 stream[kState] = {
 __proto__: null,
 readable,
 writable,
 controller: undefined,
 backpressure: undefined,
 // Continuation slots replacing the spec's
 // [[backpressureChangePromise]]; see transformStreamSetBackpressure.
 pullPending: false,
 pendingWrite: undefined,
 pendingWriteChunk: undefined,
 writeContinuation: undefined,
 };
 const state = new TransformStreamState();
 state.readable = readable;
 state.writable = writable;
 stream[kState] = state;

 transformStreamSetBackpressure(stream, true);
}
Expand DownExpand Up@@ -457,7 +465,7 @@ function transformStreamSetBackpressure(stream, backpressure) {
 kResolvedPromise,
 state.readable[kState].controller[kState].pullFulfilled);
 }
 } else if (state.pendingWrite !== undefined) {
 } else if (state.pendingWriteParked) {
 PromisePrototypeThen(kResolvedPromise, state.writeContinuation);
 }
}
Expand All@@ -470,14 +478,12 @@ function setupTransformStreamDefaultController(
 cancelAlgorithm) {
 assert(isTransformStream(stream));
 assert(stream[kState].controller === undefined);
 controller[kState] = {
 __proto__: null,
 stream,
 transformAlgorithm,
 flushAlgorithm,
 cancelAlgorithm,
 performTransformRejected: undefined,
 };
 const controllerState = new TransformStreamControllerState();
 controllerState.stream = stream;
 controllerState.transformAlgorithm = transformAlgorithm;
 controllerState.flushAlgorithm = flushAlgorithm;
 controllerState.cancelAlgorithm = cancelAlgorithm;
 controller[kState] = controllerState;
 stream[kState].controller = controller;
}

Expand DownExpand Up@@ -603,35 +609,41 @@ function transformStreamDefaultSinkWriteAlgorithm(stream, chunk) {
 } = state;
 assert(writable[kState].state === 'writable');
 if (state.backpressure) {
 // Park the chunk and one promise record; the backpressure -> false
 // flip delivers the cached continuation (see
 // transformStreamSetBackpressure) at the same microtask position as
 // the old [[backpressureChangePromise]] reaction. The continuation
 // resolves the sink promise with the perform-transform promise, so
 // adoption reproduces the old derived-chain settle depth exactly.
 // The writable dispatches a single write at a time, so one pending
 // slot suffices.
 assert(state.pendingWrite === undefined);
 const pendingWrite = PromiseWithResolvers();
 state.pendingWrite = pendingWrite;
 // Park the chunk; the backpressure -> false flip delivers the cached
 // continuation (see transformStreamSetBackpressure) at the same
 // microtask position as the old [[backpressureChangePromise]]
 // reaction. The continuation completes the parked write by wiring
 // the perform-transform promise directly to the writable
 // controller's write reactions (they exist: the controller creates
 // them before invoking the write algorithm), replacing the promise
 // record the old code allocated and resolved per parked chunk. The
 // writable dispatches a single write at a time, so one pending slot
 // suffices.
 assert(!state.pendingWriteParked);
 state.pendingWriteParked = true;
 state.pendingWriteChunk = chunk;
 state.writeContinuation ??= () => {
 const pending = state.pendingWrite;
 const pendingChunk = state.pendingWriteChunk;
 state.pendingWrite = undefined;
 state.pendingWriteParked = false;
 state.pendingWriteChunk = undefined;
 const writableState = state.writable[kState];
 const writableControllerState = writableState.controller[kState];
 if (writableState.state === 'erroring') {
 pending.reject(writableState.storedError);
 const error = writableState.storedError;
 PromisePrototypeThen(
 kResolvedPromise,
 () => writableControllerState.writeRejected(error));
 return;
 }
 assert(writableState.state === 'writable');
pending.resolve(
PromisePrototypeThen(
 transformStreamDefaultControllerPerformTransform(
 controller,
 pendingChunk));
 pendingChunk),
 writableControllerState.writeFulfilled,
 writableControllerState.writeRejected);
 };
 return pendingWrite.promise;
 return kParkedAlgorithmResult;
 }
 return transformStreamDefaultControllerPerformTransform(controller, chunk);
}
Expand Down

63 changes: 35 additions & 28 deletions
lib/internal/webstreams/writablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -596,35 +596,42 @@ const isWritableStreamDefaultWriter =
const isWritableStreamDefaultController =
 isBrandCheck('WritableStreamDefaultController');

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class WritableStreamTransferState {
 readable = undefined;
 port1 = undefined;
 port2 = undefined;
 promise = undefined;
}
ObjectSetPrototypeOf(WritableStreamTransferState.prototype, null);

class WritableStreamState {
 closedPromise = undefined;
 closeRequest = kNilRequest;
 // Mirrors "closeRequest or inFlightCloseRequest is pending"; kept as a
 // flag because the predicate runs several times per chunk on the write
 // hot path.
 closeQueuedOrInFlight = false;
 inFlightWriteRequest = kNilRequest;
 inFlightCloseRequest = kNilRequest;
 pendingAbortRequest = kNilPendingAbortRequest;
 backpressure = false;
 controller = undefined;
 state = 'writable';
 storedError = undefined;
 // Ring-buffer request queue, materialized lazily on the first pending
 // write (see writableStreamAddWriteRequest) so construction allocates
 // no request storage.
 writeRequests = kEmptyQueue;
 writer = undefined;
 transfer = new WritableStreamTransferState();
}
ObjectSetPrototypeOf(WritableStreamState.prototype, null);

function createWritableStreamState() {
 return {
 __proto__: null,
 closedPromise: undefined,
 closeRequest: kNilRequest,
 // Mirrors "closeRequest or inFlightCloseRequest is pending"; kept as a
 // flag because the predicate runs several times per chunk on the write
 // hot path.
 closeQueuedOrInFlight: false,
 inFlightWriteRequest: kNilRequest,
 inFlightCloseRequest: kNilRequest,
 pendingAbortRequest: kNilPendingAbortRequest,
 backpressure: false,
 controller: undefined,
 state: 'writable',
 storedError: undefined,
 // Ring-buffer request queue, materialized lazily on the first pending
 // write (see writableStreamAddWriteRequest) so construction allocates
 // no request storage.
 writeRequests: kEmptyQueue,
 writer: undefined,
 transfer: {
 __proto__: null,
 readable: undefined,
 port1: undefined,
 port2: undefined,
 promise: undefined,
 },
 };
 return new WritableStreamState();
}

function isWritableStreamLocked(stream) {
Expand Down
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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stream: keep webstream stream states in fast-mode objects#65625

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stream: keep webstream stream states in fast-mode objects
#65625
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1695e7b

stream: keep webstream stream states in fast-mode objects


mcollina Aug 28, 2026
aaa47dc

stream: avoid promise allocation for parked transform writes


mcollina Aug 28, 2026

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76 changes: 76 additions & 0 deletions
benchmark/webstreams/lifecycle.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,76 @@
'use strict';
const common = require('../common.js');
const assert = require('assert');
const {
 ReadableStream,
 WritableStream,
 TransformStream,
} = require('node:stream/web');

const bench = common.createBenchmark(main, {
 n: [5e4],
 kind: ['readable', 'pipe-to', 'pipe-through'],
});

const chunk = Buffer.alloc(1024);

function makeSource() {
 let i = 0;
 return {
 pull(controller) {
 if (i++ < 4)
 controller.enqueue(chunk);
 else
 controller.close();
 },
 };
}

async function readable(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 const reader = new ReadableStream(makeSource()).getReader();
 while (!(await reader.read()).done) chunks++;
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

async function pipeTo(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 await new ReadableStream(makeSource())
 .pipeTo(new WritableStream({ write() { chunks++; } }));
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

async function pipeThrough(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 const reader = new ReadableStream(makeSource())
 .pipeThrough(new TransformStream())
 .getReader();
 while (!(await reader.read()).done) chunks++;
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

function main({ n, kind }) {
 switch (kind) {
 case 'readable':
 readable(n);
 break;
 case 'pipe-to':
 pipeTo(n);
 break;
 case 'pipe-through':
 pipeThrough(n);
 break;
 }
}

38 changes: 23 additions & 15 deletions
lib/internal/webstreams/readablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1419,22 +1419,30 @@ const isReadableStreamBYOBReader =

// ---- ReadableStream Implementation

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class ReadableStreamTransferState {
 writable = undefined;
 port1 = undefined;
 port2 = undefined;
 promise = undefined;
}
ObjectSetPrototypeOf(ReadableStreamTransferState.prototype, null);

class ReadableStreamState {
 closedPromise = undefined;
 disturbed = false;
 reader = undefined;
 state = 'readable';
 storedError = undefined;
 controller = undefined;
 transfer = new ReadableStreamTransferState();
}
ObjectSetPrototypeOf(ReadableStreamState.prototype, null);

function createReadableStreamState() {
 return {
 __proto__: null,
 closedPromise: undefined,
 disturbed: false,
 reader: undefined,
 state: 'readable',
 storedError: undefined,
 transfer: {
 __proto__: null,
 writable: undefined,
 port1: undefined,
 port2: undefined,
 promise: undefined,
 },
 };
 return new ReadableStreamState();
}

function readableStreamFromIterable(iterable) {
Expand Down

112 changes: 62 additions & 50 deletions
lib/internal/webstreams/transformstream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -253,21 +253,38 @@ ObjectDefineProperties(TransformStream.prototype, {
 [SymbolToStringTag]: getNonWritablePropertyDescriptor(TransformStream.name),
});

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class TransformStreamState {
 readable = undefined;
 writable = undefined;
 controller = undefined;
 backpressure = undefined;
 // Continuation slots replacing the spec's
 // [[backpressureChangePromise]]; see transformStreamSetBackpressure.
 pullPending = false;
 pendingWriteParked = false;
 pendingWriteChunk = undefined;
 writeContinuation = undefined;
}
ObjectSetPrototypeOf(TransformStreamState.prototype, null);

class TransformStreamControllerState {
 stream = undefined;
 transformAlgorithm = undefined;
 flushAlgorithm = undefined;
 cancelAlgorithm = undefined;
 performTransformRejected = undefined;
 finishPromise = undefined;
}
ObjectSetPrototypeOf(TransformStreamControllerState.prototype, null);

function InternalTransferredTransformStream() {
 ObjectSetPrototypeOf(this, TransformStream.prototype);
 markTransferMode(this, false, true);
 this[kType] = 'TransformStream';
 this[kState] = {
 __proto__: null,
 readable: undefined,
 writable: undefined,
 backpressure: undefined,
 pullPending: false,
 pendingWrite: undefined,
 pendingWriteChunk: undefined,
 writeContinuation: undefined,
 controller: undefined,
 };
 this[kState] = new TransformStreamState();
}

ObjectSetPrototypeOf(InternalTransferredTransformStream.prototype, TransformStream.prototype);
Expand DownExpand Up@@ -388,19 +405,10 @@ function initializeTransformStream(
 readableSizeAlgorithm,
 );

 stream[kState] = {
 __proto__: null,
 readable,
 writable,
 controller: undefined,
 backpressure: undefined,
 // Continuation slots replacing the spec's
 // [[backpressureChangePromise]]; see transformStreamSetBackpressure.
 pullPending: false,
 pendingWrite: undefined,
 pendingWriteChunk: undefined,
 writeContinuation: undefined,
 };
 const state = new TransformStreamState();
 state.readable = readable;
 state.writable = writable;
 stream[kState] = state;

 transformStreamSetBackpressure(stream, true);
}
Expand DownExpand Up@@ -457,7 +465,7 @@ function transformStreamSetBackpressure(stream, backpressure) {
 kResolvedPromise,
 state.readable[kState].controller[kState].pullFulfilled);
 }
 } else if (state.pendingWrite !== undefined) {
 } else if (state.pendingWriteParked) {
 PromisePrototypeThen(kResolvedPromise, state.writeContinuation);
 }
}
Expand All@@ -470,14 +478,12 @@ function setupTransformStreamDefaultController(
 cancelAlgorithm) {
 assert(isTransformStream(stream));
 assert(stream[kState].controller === undefined);
 controller[kState] = {
 __proto__: null,
 stream,
 transformAlgorithm,
 flushAlgorithm,
 cancelAlgorithm,
 performTransformRejected: undefined,
 };
 const controllerState = new TransformStreamControllerState();
 controllerState.stream = stream;
 controllerState.transformAlgorithm = transformAlgorithm;
 controllerState.flushAlgorithm = flushAlgorithm;
 controllerState.cancelAlgorithm = cancelAlgorithm;
 controller[kState] = controllerState;
 stream[kState].controller = controller;
}

Expand DownExpand Up@@ -603,35 +609,41 @@ function transformStreamDefaultSinkWriteAlgorithm(stream, chunk) {
 } = state;
 assert(writable[kState].state === 'writable');
 if (state.backpressure) {
 // Park the chunk and one promise record; the backpressure -> false
 // flip delivers the cached continuation (see
 // transformStreamSetBackpressure) at the same microtask position as
 // the old [[backpressureChangePromise]] reaction. The continuation
 // resolves the sink promise with the perform-transform promise, so
 // adoption reproduces the old derived-chain settle depth exactly.
 // The writable dispatches a single write at a time, so one pending
 // slot suffices.
 assert(state.pendingWrite === undefined);
 const pendingWrite = PromiseWithResolvers();
 state.pendingWrite = pendingWrite;
 // Park the chunk; the backpressure -> false flip delivers the cached
 // continuation (see transformStreamSetBackpressure) at the same
 // microtask position as the old [[backpressureChangePromise]]
 // reaction. The continuation completes the parked write by wiring
 // the perform-transform promise directly to the writable
 // controller's write reactions (they exist: the controller creates
 // them before invoking the write algorithm), replacing the promise
 // record the old code allocated and resolved per parked chunk. The
 // writable dispatches a single write at a time, so one pending slot
 // suffices.
 assert(!state.pendingWriteParked);
 state.pendingWriteParked = true;
 state.pendingWriteChunk = chunk;
 state.writeContinuation ??= () => {
 const pending = state.pendingWrite;
 const pendingChunk = state.pendingWriteChunk;
 state.pendingWrite = undefined;
 state.pendingWriteParked = false;
 state.pendingWriteChunk = undefined;
 const writableState = state.writable[kState];
 const writableControllerState = writableState.controller[kState];
 if (writableState.state === 'erroring') {
 pending.reject(writableState.storedError);
 const error = writableState.storedError;
 PromisePrototypeThen(
 kResolvedPromise,
 () => writableControllerState.writeRejected(error));
 return;
 }
 assert(writableState.state === 'writable');
pending.resolve(
PromisePrototypeThen(
 transformStreamDefaultControllerPerformTransform(
 controller,
 pendingChunk));
 pendingChunk),
 writableControllerState.writeFulfilled,
 writableControllerState.writeRejected);
 };
 return pendingWrite.promise;
 return kParkedAlgorithmResult;
 }
 return transformStreamDefaultControllerPerformTransform(controller, chunk);
}
Expand Down

63 changes: 35 additions & 28 deletions
lib/internal/webstreams/writablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -596,35 +596,42 @@ const isWritableStreamDefaultWriter =
const isWritableStreamDefaultController =
 isBrandCheck('WritableStreamDefaultController');

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class WritableStreamTransferState {
 readable = undefined;
 port1 = undefined;
 port2 = undefined;
 promise = undefined;
}
ObjectSetPrototypeOf(WritableStreamTransferState.prototype, null);

class WritableStreamState {
 closedPromise = undefined;
 closeRequest = kNilRequest;
 // Mirrors "closeRequest or inFlightCloseRequest is pending"; kept as a
 // flag because the predicate runs several times per chunk on the write
 // hot path.
 closeQueuedOrInFlight = false;
 inFlightWriteRequest = kNilRequest;
 inFlightCloseRequest = kNilRequest;
 pendingAbortRequest = kNilPendingAbortRequest;
 backpressure = false;
 controller = undefined;
 state = 'writable';
 storedError = undefined;
 // Ring-buffer request queue, materialized lazily on the first pending
 // write (see writableStreamAddWriteRequest) so construction allocates
 // no request storage.
 writeRequests = kEmptyQueue;
 writer = undefined;
 transfer = new WritableStreamTransferState();
}
ObjectSetPrototypeOf(WritableStreamState.prototype, null);

function createWritableStreamState() {
 return {
 __proto__: null,
 closedPromise: undefined,
 closeRequest: kNilRequest,
 // Mirrors "closeRequest or inFlightCloseRequest is pending"; kept as a
 // flag because the predicate runs several times per chunk on the write
 // hot path.
 closeQueuedOrInFlight: false,
 inFlightWriteRequest: kNilRequest,
 inFlightCloseRequest: kNilRequest,
 pendingAbortRequest: kNilPendingAbortRequest,
 backpressure: false,
 controller: undefined,
 state: 'writable',
 storedError: undefined,
 // Ring-buffer request queue, materialized lazily on the first pending
 // write (see writableStreamAddWriteRequest) so construction allocates
 // no request storage.
 writeRequests: kEmptyQueue,
 writer: undefined,
 transfer: {
 __proto__: null,
 readable: undefined,
 port1: undefined,
 port2: undefined,
 promise: undefined,
 },
 };
 return new WritableStreamState();
}

function isWritableStreamLocked(stream) {
Expand Down
Loading
Loading

, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

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stream: keep webstream stream states in fast-mode objects#65625

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mcollina
wants to merge
2
commits into

base:main
Choose a base branch

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+253

−93

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stream: keep webstream stream states in fast-mode objects
#65625
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1695e7b

stream: keep webstream stream states in fast-mode objects


mcollina Aug 28, 2026
aaa47dc

stream: avoid promise allocation for parked transform writes


mcollina Aug 28, 2026

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76 changes: 76 additions & 0 deletions
benchmark/webstreams/lifecycle.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,76 @@
'use strict';
const common = require('../common.js');
const assert = require('assert');
const {
 ReadableStream,
 WritableStream,
 TransformStream,
} = require('node:stream/web');

const bench = common.createBenchmark(main, {
 n: [5e4],
 kind: ['readable', 'pipe-to', 'pipe-through'],
});

const chunk = Buffer.alloc(1024);

function makeSource() {
 let i = 0;
 return {
 pull(controller) {
 if (i++ < 4)
 controller.enqueue(chunk);
 else
 controller.close();
 },
 };
}

async function readable(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 const reader = new ReadableStream(makeSource()).getReader();
 while (!(await reader.read()).done) chunks++;
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

async function pipeTo(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 await new ReadableStream(makeSource())
 .pipeTo(new WritableStream({ write() { chunks++; } }));
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

async function pipeThrough(n) {
 let chunks = 0;
 bench.start();
 for (let i = 0; i < n; i++) {
 const reader = new ReadableStream(makeSource())
 .pipeThrough(new TransformStream())
 .getReader();
 while (!(await reader.read()).done) chunks++;
 }
 bench.end(n);
 assert.strictEqual(chunks, n * 4);
}

function main({ n, kind }) {
 switch (kind) {
 case 'readable':
 readable(n);
 break;
 case 'pipe-to':
 pipeTo(n);
 break;
 case 'pipe-through':
 pipeThrough(n);
 break;
 }
}

38 changes: 23 additions & 15 deletions
lib/internal/webstreams/readablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1419,22 +1419,30 @@ const isReadableStreamBYOBReader =

// ---- ReadableStream Implementation

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class ReadableStreamTransferState {
 writable = undefined;
 port1 = undefined;
 port2 = undefined;
 promise = undefined;
}
ObjectSetPrototypeOf(ReadableStreamTransferState.prototype, null);

class ReadableStreamState {
 closedPromise = undefined;
 disturbed = false;
 reader = undefined;
 state = 'readable';
 storedError = undefined;
 controller = undefined;
 transfer = new ReadableStreamTransferState();
}
ObjectSetPrototypeOf(ReadableStreamState.prototype, null);

function createReadableStreamState() {
 return {
 __proto__: null,
 closedPromise: undefined,
 disturbed: false,
 reader: undefined,
 state: 'readable',
 storedError: undefined,
 transfer: {
 __proto__: null,
 writable: undefined,
 port1: undefined,
 port2: undefined,
 promise: undefined,
 },
 };
 return new ReadableStreamState();
}

function readableStreamFromIterable(iterable) {
Expand Down

112 changes: 62 additions & 50 deletions
lib/internal/webstreams/transformstream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -253,21 +253,38 @@ ObjectDefineProperties(TransformStream.prototype, {
 [SymbolToStringTag]: getNonWritablePropertyDescriptor(TransformStream.name),
});

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class TransformStreamState {
 readable = undefined;
 writable = undefined;
 controller = undefined;
 backpressure = undefined;
 // Continuation slots replacing the spec's
 // [[backpressureChangePromise]]; see transformStreamSetBackpressure.
 pullPending = false;
 pendingWriteParked = false;
 pendingWriteChunk = undefined;
 writeContinuation = undefined;
}
ObjectSetPrototypeOf(TransformStreamState.prototype, null);

class TransformStreamControllerState {
 stream = undefined;
 transformAlgorithm = undefined;
 flushAlgorithm = undefined;
 cancelAlgorithm = undefined;
 performTransformRejected = undefined;
 finishPromise = undefined;
}
ObjectSetPrototypeOf(TransformStreamControllerState.prototype, null);

function InternalTransferredTransformStream() {
 ObjectSetPrototypeOf(this, TransformStream.prototype);
 markTransferMode(this, false, true);
 this[kType] = 'TransformStream';
 this[kState] = {
 __proto__: null,
 readable: undefined,
 writable: undefined,
 backpressure: undefined,
 pullPending: false,
 pendingWrite: undefined,
 pendingWriteChunk: undefined,
 writeContinuation: undefined,
 controller: undefined,
 };
 this[kState] = new TransformStreamState();
}

ObjectSetPrototypeOf(InternalTransferredTransformStream.prototype, TransformStream.prototype);
Expand DownExpand Up@@ -388,19 +405,10 @@ function initializeTransformStream(
 readableSizeAlgorithm,
 );

 stream[kState] = {
 __proto__: null,
 readable,
 writable,
 controller: undefined,
 backpressure: undefined,
 // Continuation slots replacing the spec's
 // [[backpressureChangePromise]]; see transformStreamSetBackpressure.
 pullPending: false,
 pendingWrite: undefined,
 pendingWriteChunk: undefined,
 writeContinuation: undefined,
 };
 const state = new TransformStreamState();
 state.readable = readable;
 state.writable = writable;
 stream[kState] = state;

 transformStreamSetBackpressure(stream, true);
}
Expand DownExpand Up@@ -457,7 +465,7 @@ function transformStreamSetBackpressure(stream, backpressure) {
 kResolvedPromise,
 state.readable[kState].controller[kState].pullFulfilled);
 }
 } else if (state.pendingWrite !== undefined) {
 } else if (state.pendingWriteParked) {
 PromisePrototypeThen(kResolvedPromise, state.writeContinuation);
 }
}
Expand All@@ -470,14 +478,12 @@ function setupTransformStreamDefaultController(
 cancelAlgorithm) {
 assert(isTransformStream(stream));
 assert(stream[kState].controller === undefined);
 controller[kState] = {
 __proto__: null,
 stream,
 transformAlgorithm,
 flushAlgorithm,
 cancelAlgorithm,
 performTransformRejected: undefined,
 };
 const controllerState = new TransformStreamControllerState();
 controllerState.stream = stream;
 controllerState.transformAlgorithm = transformAlgorithm;
 controllerState.flushAlgorithm = flushAlgorithm;
 controllerState.cancelAlgorithm = cancelAlgorithm;
 controller[kState] = controllerState;
 stream[kState].controller = controller;
}

Expand DownExpand Up@@ -603,35 +609,41 @@ function transformStreamDefaultSinkWriteAlgorithm(stream, chunk) {
 } = state;
 assert(writable[kState].state === 'writable');
 if (state.backpressure) {
 // Park the chunk and one promise record; the backpressure -> false
 // flip delivers the cached continuation (see
 // transformStreamSetBackpressure) at the same microtask position as
 // the old [[backpressureChangePromise]] reaction. The continuation
 // resolves the sink promise with the perform-transform promise, so
 // adoption reproduces the old derived-chain settle depth exactly.
 // The writable dispatches a single write at a time, so one pending
 // slot suffices.
 assert(state.pendingWrite === undefined);
 const pendingWrite = PromiseWithResolvers();
 state.pendingWrite = pendingWrite;
 // Park the chunk; the backpressure -> false flip delivers the cached
 // continuation (see transformStreamSetBackpressure) at the same
 // microtask position as the old [[backpressureChangePromise]]
 // reaction. The continuation completes the parked write by wiring
 // the perform-transform promise directly to the writable
 // controller's write reactions (they exist: the controller creates
 // them before invoking the write algorithm), replacing the promise
 // record the old code allocated and resolved per parked chunk. The
 // writable dispatches a single write at a time, so one pending slot
 // suffices.
 assert(!state.pendingWriteParked);
 state.pendingWriteParked = true;
 state.pendingWriteChunk = chunk;
 state.writeContinuation ??= () => {
 const pending = state.pendingWrite;
 const pendingChunk = state.pendingWriteChunk;
 state.pendingWrite = undefined;
 state.pendingWriteParked = false;
 state.pendingWriteChunk = undefined;
 const writableState = state.writable[kState];
 const writableControllerState = writableState.controller[kState];
 if (writableState.state === 'erroring') {
 pending.reject(writableState.storedError);
 const error = writableState.storedError;
 PromisePrototypeThen(
 kResolvedPromise,
 () => writableControllerState.writeRejected(error));
 return;
 }
 assert(writableState.state === 'writable');
pending.resolve(
PromisePrototypeThen(
 transformStreamDefaultControllerPerformTransform(
 controller,
 pendingChunk));
 pendingChunk),
 writableControllerState.writeFulfilled,
 writableControllerState.writeRejected);
 };
 return pendingWrite.promise;
 return kParkedAlgorithmResult;
 }
 return transformStreamDefaultControllerPerformTransform(controller, chunk);
}
Expand Down

63 changes: 35 additions & 28 deletions
lib/internal/webstreams/writablestream.js

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -596,35 +596,42 @@ const isWritableStreamDefaultWriter =
const isWritableStreamDefaultController =
 isBrandCheck('WritableStreamDefaultController');

// The state record classes null out their prototype chain to keep
// Object.prototype out of property lookups; every field ever assigned
// is declared so the shape never transitions.
class WritableStreamTransferState {
 readable = undefined;
 port1 = undefined;
 port2 = undefined;
 promise = undefined;
}
ObjectSetPrototypeOf(WritableStreamTransferState.prototype, null);

class WritableStreamState {
 closedPromise = undefined;
 closeRequest = kNilRequest;
 // Mirrors "closeRequest or inFlightCloseRequest is pending"; kept as a
 // flag because the predicate runs several times per chunk on the write
 // hot path.
 closeQueuedOrInFlight = false;
 inFlightWriteRequest = kNilRequest;
 inFlightCloseRequest = kNilRequest;
 pendingAbortRequest = kNilPendingAbortRequest;
 backpressure = false;
 controller = undefined;
 state = 'writable';
 storedError = undefined;
 // Ring-buffer request queue, materialized lazily on the first pending
 // write (see writableStreamAddWriteRequest) so construction allocates
 // no request storage.
 writeRequests = kEmptyQueue;
 writer = undefined;
 transfer = new WritableStreamTransferState();
}
ObjectSetPrototypeOf(WritableStreamState.prototype, null);

function createWritableStreamState() {
 return {
 __proto__: null,
 closedPromise: undefined,
 closeRequest: kNilRequest,
 // Mirrors "closeRequest or inFlightCloseRequest is pending"; kept as a
 // flag because the predicate runs several times per chunk on the write
 // hot path.
 closeQueuedOrInFlight: false,
 inFlightWriteRequest: kNilRequest,
 inFlightCloseRequest: kNilRequest,
 pendingAbortRequest: kNilPendingAbortRequest,
 backpressure: false,
 controller: undefined,
 state: 'writable',
 storedError: undefined,
 // Ring-buffer request queue, materialized lazily on the first pending
 // write (see writableStreamAddWriteRequest) so construction allocates
 // no request storage.
 writeRequests: kEmptyQueue,
 writer: undefined,
 transfer: {
 __proto__: null,
 readable: undefined,
 port1: undefined,
 port2: undefined,
 promise: undefined,
 },
 };
 return new WritableStreamState();
}

function isWritableStreamLocked(stream) {
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