node/test/parallel/test-stream-readable-flow-recursion.js

// Copyright Joyent, Inc. and other Node contributors.
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'use strict';
require('../common');
const assert = require('assert');

// this test verifies that passing a huge number to read(size)
// will push up the highWaterMark, and cause the stream to read
// more data continuously, but without triggering a nextTick
// warning or RangeError.

const Readable = require('stream').Readable;

// throw an error if we trigger a nextTick warning.
process.throwDeprecation = true;

const stream = new Readable({ highWaterMark: 2 });
let reads = 0;
let total = 5000;
stream._read = function(size) {
  reads++;
  size = Math.min(size, total);
  total -= size;
  if (size === 0)
    stream.push(null);
  else
    stream.push(Buffer.allocUnsafe(size));
};

let depth = 0;

function flow(stream, size, callback) {
  depth += 1;
  const chunk = stream.read(size);

  if (!chunk)
    stream.once('readable', flow.bind(null, stream, size, callback));
  else
    callback(chunk);

  depth -= 1;
  console.log(`flow(${depth}): exit`);
}

flow(stream, 5000, function() {
  console.log(`complete (${depth})`);
});

process.on('exit', function(code) {
  assert.strictEqual(reads, 2);
  // we pushed up the high water mark
  assert.strictEqual(stream._readableState.highWaterMark, 8192);
  // length is 0 right now, because we pulled it all out.
  assert.strictEqual(stream._readableState.length, 0);
  assert(!code);
  assert.strictEqual(depth, 0);
  console.log('ok');
});