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stream: optimize webstreams pipeTo further #62079

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stream: optimize webstreams pipeTo further #62079

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dd496c2
stream: optimize webstreams pipeTo
MattiasBuelens Mar 1, 2026
3479d39
fixup! do not use writer public API
MattiasBuelens Mar 1, 2026
b8f166c
fixup! optimize backpressure check
MattiasBuelens Mar 1, 2026
911f895
fixup! wait for ready only if there is backpressure
MattiasBuelens Mar 2, 2026
7b31401
fixup! disturbed is already true at start of pipeTo
MattiasBuelens Mar 2, 2026
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26 changes: 12 additions & 14 deletions lib/internal/webstreams/readablestream.js
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Original file line number Diff line number Diff line change
Expand Up @@ -1532,10 +1532,12 @@ function readableStreamPipeTo(
}

async function step() {
if (shuttingDown)
return true;
if (shuttingDown) return true;

await writer[kState].ready.promise;
if (dest[kState].backpressure) {
await writer[kState].ready.promise;
if (shuttingDown) return true;
}

const controller = source[kState].controller;

Expand All @@ -1549,7 +1551,6 @@ function readableStreamPipeTo(
while (controller[kState].queue.length > 0) {
if (shuttingDown) return true;

source[kState].disturbed = true;
const chunk = dequeueValue(controller);

if (controller[kState].closeRequested && !controller[kState].queue.length) {
Expand All @@ -1563,20 +1564,17 @@ function readableStreamPipeTo(
setPromiseHandled(state.currentWrite);

// Check backpressure after each write
if (dest[kState].state === 'writable') {
const desiredSize = writer.desiredSize;
if (desiredSize !== null && desiredSize <= 0) {
// Backpressure - stop batch and wait for ready
break;
}
if (dest[kState].backpressure) {
// Backpressure - stop batch and wait for ready
break;
} else if (dest[kState].state !== 'writable' || writableStreamCloseQueuedOrInFlight(dest)) {
// Closing or erroring - stop batch and wait for shutdown
break;
}
}

// Trigger pull if needed after batch
if (source[kState].state === 'readable' &&
!controller[kState].closeRequested) {
readableStreamDefaultControllerCallPullIfNeeded(controller);
}
readableStreamDefaultControllerCallPullIfNeeded(controller);

// Check if stream closed during batch
if (source[kState].state === 'closed') {
Expand Down