node/test/simple/test-stream2-writable.js

// Copyright Joyent, Inc. and other Node contributors.
//
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// "Software"), to deal in the Software without restriction, including
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// persons to whom the Software is furnished to do so, subject to the
// following conditions:
//
// The above copyright notice and this permission notice shall be included
// in all copies or substantial portions of the Software.
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// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
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var common = require('../common.js');
var W = require('_stream_writable');
var assert = require('assert');

var util = require('util');
util.inherits(TestWriter, W);

function TestWriter() {
  W.apply(this, arguments);
  this.buffer = [];
  this.written = 0;
}

TestWriter.prototype._write = function(chunk, cb) {
  // simulate a small unpredictable latency
  setTimeout(function() {
    this.buffer.push(chunk.toString());
    this.written += chunk.length;
    cb();
  }.bind(this), Math.floor(Math.random() * 10));
};

var chunks = new Array(50);
for (var i = 0; i < chunks.length; i++) {
  chunks[i] = new Array(i + 1).join('x');
}

// tiny node-tap lookalike.
var tests = [];
function test(name, fn) {
  tests.push([name, fn]);
}

function run() {
  var next = tests.shift();
  if (!next)
    return console.log('ok');

  var name = next[0];
  var fn = next[1];
  console.log('# %s', name);
  fn({
    same: assert.deepEqual,
    equal: assert.equal,
    end: run
  });
}

process.nextTick(run);

test('write fast', function(t) {
  var tw = new TestWriter({
    lowWaterMark: 5,
    highWaterMark: 100
  });

  tw.on('finish', function() {
    t.same(tw.buffer, chunks, 'got chunks in the right order');
    t.end();
  });

  chunks.forEach(function(chunk) {
    // screw backpressure.  Just buffer it all up.
    tw.write(chunk);
  });
  tw.end();
});

test('write slow', function(t) {
  var tw = new TestWriter({
    lowWaterMark: 5,
    highWaterMark: 100
  });

  tw.on('finish', function() {
    t.same(tw.buffer, chunks, 'got chunks in the right order');
    t.end();
  });

  var i = 0;
  (function W() {
    tw.write(chunks[i++]);
    if (i < chunks.length)
      setTimeout(W, 10);
    else
      tw.end();
  })();
});

test('write backpressure', function(t) {
  var tw = new TestWriter({
    lowWaterMark: 5,
    highWaterMark: 50
  });

  var drains = 0;

  tw.on('finish', function() {
    t.same(tw.buffer, chunks, 'got chunks in the right order');
    t.equal(drains, 17);
    t.end();
  });

  tw.on('drain', function() {
    drains++;
  });

  var i = 0;
  (function W() {
    do {
      var ret = tw.write(chunks[i++]);
    } while (ret !== false && i < chunks.length);

    if (i < chunks.length) {
      assert(tw._writableState.length >= 50);
      tw.once('drain', W);
    } else {
      tw.end();
    }
  })();
});