'use strict';

const common = require('../common.js');

const { ReadableStream } = require('node:stream/web');

// Benchmark for reading from a pre-buffered ReadableStream.

// This measures the fast path optimization where data is already

// queued in the controller, avoiding DefaultReadRequest allocation.

const bench = common.createBenchmark(main, {

n: [1e5],

bufferSize: [1, 10, 100, 1000],

});

async function main({ n, bufferSize }) {

let enqueued = 0;

const rs = new ReadableStream({

start(controller) {

// Pre-fill the buffer

for (let i = 0; i < bufferSize; i++) {

controller.enqueue('a');

enqueued++;

}

},

pull(controller) {

// Refill buffer when pulled

const toEnqueue = Math.min(bufferSize, n - enqueued);

for (let i = 0; i < toEnqueue; i++) {

controller.enqueue('a');

enqueued++;

}

if (enqueued >= n) {

controller.close();

}

},

}, {

// Use buffer size as high water mark to allow pre-buffering

highWaterMark: bufferSize,

});

const reader = rs.getReader();

let x = null;

let reads = 0;

bench.start();

while (reads < n) {

const { value, done } = await reader.read();

if (done) break;

x = value;

reads++;

}

bench.end(reads);

console.assert(x);

}