mirror of
https://github.com/vercel-labs/scriptc.git
synced 2026-11-01 07:33:12 +08:00
Chris Tate
9632906b4d
Taking the head entry of a Readable's buffer moved every remaining entry down one slot, so draining a queue of n buffered chunks cost O(n²). The buffer now keeps the index of its first entry: a take advances it, a push at the tail moves the entries down only when at least half the slots are free at the front (and grows otherwise), and unshift takes a freed front slot when there is one. The drop, trace and boxing loops walk the entries from that index. The stream-buffered-drain runtime workload buffers 200,000 objects and 100,000 Buffers before draining them; corpus 8533 covers reads across entries, unshift into a freed slot and onto a part-read head, setEncoding after takes, and object-mode takes, unshifts and pushes.
37 lines
1.2 KiB
TypeScript
37 lines
1.2 KiB
TypeScript
// Readable streams that buffer many chunks before anyone reads them, then
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// drain: 200,000 objects pushed into an object-mode Readable and taken
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// with read() in a 'readable' handler, and 100,000 small Buffers pushed
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// into a byte-mode Readable and piped into a Writable.
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import { Readable, Writable } from "node:stream";
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const objects = new Readable({ objectMode: true, highWaterMark: 16, read() {} });
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for (let i = 0; i < 200000; i++) objects.push({ id: i, qty: i % 9 });
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objects.push(null);
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let taken = 0;
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let qty = 0;
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objects.on("readable", () => {
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let row: { id: number; qty: number } | null;
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while ((row = objects.read() as { id: number; qty: number } | null) !== null) {
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taken++;
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qty += row.qty;
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}
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});
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objects.on("end", () => {
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console.log(`objects taken=${taken} qty=${qty}`);
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const bytes = new Readable({ read() {} });
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for (let i = 0; i < 100000; i++) bytes.push(Buffer.from([i & 0xff, (i >> 8) & 0xff, 7]));
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bytes.push(null);
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let length = 0;
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let sum = 0;
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const sink = new Writable({
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write(chunk: Buffer, _enc, cb) {
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length += chunk.length;
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for (const b of chunk) sum = (sum + b) % 65521;
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cb();
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},
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});
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sink.on("finish", () => console.log(`bytes length=${length} sum=${sum}`));
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bytes.pipe(sink);
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});
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