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buffer: improve blob read performance #42117

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Merged
merged 1 commit into from
Feb 27, 2022
Merged

buffer: improve blob read performance #42117

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11 changes: 6 additions & 5 deletions lib/internal/blob.js
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Original file line number Diff line number Diff line change
Expand Up @@ -64,6 +64,7 @@ const {

const kHandle = Symbol('kHandle');
const kState = Symbol('kState');
const kIndex = Symbol('kIndex');
const kType = Symbol('kType');
const kLength = Symbol('kLength');
const kArrayBufferPromise = Symbol('kArrayBufferPromise');
Expand Down Expand Up @@ -323,17 +324,17 @@ class Blob {
return new lazyReadableStream({
async start() {
this[kState] = await self.arrayBuffer();
this[kIndex] = 0;
},

pull(controller) {
if (this[kState].byteLength <= kMaxChunkSize) {
controller.enqueue(new Uint8Array(this[kState]));
if (this[kState].byteLength - this[kIndex] <= kMaxChunkSize) {
controller.enqueue(new Uint8Array(this[kState], this[kIndex]));
controller.close();
this[kState] = undefined;
} else {
const slice = this[kState].slice(0, kMaxChunkSize);
this[kState] = this[kState].slice(kMaxChunkSize);
controller.enqueue(new Uint8Array(slice));
controller.enqueue(new Uint8Array(this[kState], this[kIndex], kMaxChunkSize));
this[kIndex] += kMaxChunkSize;
}
}
});
Expand Down