node/test/parallel/test-stream2-push.js

'use strict';
require('../common');
let stream = require('stream');
const Readable = stream.Readable;
const Writable = stream.Writable;
const assert = require('assert');

const EE = require('events').EventEmitter;


// a mock thing a bit like the net.Socket/tcp_wrap.handle interaction

stream = new Readable({
  highWaterMark: 16,
  encoding: 'utf8'
});

const source = new EE();

stream._read = function() {
  console.error('stream._read');
  readStart();
};

let ended = false;
stream.on('end', function() {
  ended = true;
});

source.on('data', function(chunk) {
  const ret = stream.push(chunk);
  console.error('data', stream._readableState.length);
  if (!ret)
    readStop();
});

source.on('end', function() {
  stream.push(null);
});

let reading = false;

function readStart() {
  console.error('readStart');
  reading = true;
}

function readStop() {
  console.error('readStop');
  reading = false;
  process.nextTick(function() {
    const r = stream.read();
    if (r !== null)
      writer.write(r);
  });
}

let writer = new Writable({
  decodeStrings: false
});

const written = [];

const expectWritten =
  [ 'asdfgasdfgasdfgasdfg',
    'asdfgasdfgasdfgasdfg',
    'asdfgasdfgasdfgasdfg',
    'asdfgasdfgasdfgasdfg',
    'asdfgasdfgasdfgasdfg',
    'asdfgasdfgasdfgasdfg' ];

writer._write = function(chunk, encoding, cb) {
  console.error('WRITE %s', chunk);
  written.push(chunk);
  process.nextTick(cb);
};

writer.on('finish', finish);


// now emit some chunks.

const chunk = 'asdfg';

let set = 0;
readStart();
data();
function data() {
  assert(reading);
  source.emit('data', chunk);
  assert(reading);
  source.emit('data', chunk);
  assert(reading);
  source.emit('data', chunk);
  assert(reading);
  source.emit('data', chunk);
  assert(!reading);
  if (set++ < 5)
    setTimeout(data, 10);
  else
    end();
}

function finish() {
  console.error('finish');
  assert.deepStrictEqual(written, expectWritten);
  console.log('ok');
}

function end() {
  source.emit('end');
  assert(!reading);
  writer.end(stream.read());
  setImmediate(function() {
    assert(ended);
  });
}