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Node.js
Why is Readable.read(size) always returning the whole readable data?
#5154
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by
crackle2k
ericmorand
asked this question in
Q&A
Replies: 1 comment 1 reply
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The simplest fix is to slice the result after reading: const partialData = (readable.read(16) ?? '').slice(0, 16);
console.log(partialData.length); // 16Or if you want a stream that genuinely yields data in controlled chunk sizes from the start, use a custom Readable that pushes in pieces: import { Readable } from "node:stream";
function chunkedReadable(str, chunkSize) {
let offset = 0;
return new Readable({
read() {
if (offset >= str.length) return this.push(null);
this.push(str.slice(offset, offset + chunkSize));
offset += chunkSize;
}
});
}
const readable = chunkedReadable('1'.repeat(1000000), 16);
const partialData = readable.read(16);
console.log(partialData.length); // 16 |
1 reply
Answer selected by
ericmorand
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Readable.from()when passed a plain string treats the whole thing as a single chunk, so by the time you call.read(16)the internal buffer already has one 1,000,000-byte chunk in it and Node returns that whole chunk rather than slicing it.The simplest fix is to slice the result after reading:
Or if you want a stream that genuinely yields data in controlled chunk sizes from the start, use a custom Readable that pushes in pieces: