1  // Copyright Joyent, Inc. and other Node contributors.
   2  //
   3  // Permission is hereby granted, free of charge, to any person obtaining a
   4  // copy of this software and associated documentation files (the
   5  // "Software"), to deal in the Software without restriction, including
   6  // without limitation the rights to use, copy, modify, merge, publish,
   7  // distribute, sublicense, and/or sell copies of the Software, and to permit
   8  // persons to whom the Software is furnished to do so, subject to the
   9  // following conditions:
  10  //
  11  // The above copyright notice and this permission notice shall be included
  12  // in all copies or substantial portions of the Software.
  13  //
  14  // THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
  15  // OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
  16  // MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
  17  // NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
  18  // DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
  19  // OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
  20  // USE OR OTHER DEALINGS IN THE SOFTWARE.
  21  'use strict';
  22  
  23  module.exports = Readable;
  24  /*<replacement>*/
  25  
  26  var Duplex;
  27  /*</replacement>*/
  28  
  29  Readable.ReadableState = ReadableState;
  30  /*<replacement>*/
  31  
  32  var EE = require('events').EventEmitter;
  33  
  34  var EElistenerCount = function EElistenerCount(emitter, type) {
  35    return emitter.listeners(type).length;
  36  };
  37  /*</replacement>*/
  38  
  39  /*<replacement>*/
  40  
  41  
  42  var Stream = require('./internal/streams/stream');
  43  /*</replacement>*/
  44  
  45  
  46  var Buffer = require('buffer').Buffer;
  47  
  48  var OurUint8Array = global.Uint8Array || function () {};
  49  
  50  function _uint8ArrayToBuffer(chunk) {
  51    return Buffer.from(chunk);
  52  }
  53  
  54  function _isUint8Array(obj) {
  55    return Buffer.isBuffer(obj) || obj instanceof OurUint8Array;
  56  }
  57  /*<replacement>*/
  58  
  59  
  60  var debugUtil = require('util');
  61  
  62  var debug;
  63  
  64  if (debugUtil && debugUtil.debuglog) {
  65    debug = debugUtil.debuglog('stream');
  66  } else {
  67    debug = function debug() {};
  68  }
  69  /*</replacement>*/
  70  
  71  
  72  var BufferList = require('./internal/streams/buffer_list');
  73  
  74  var destroyImpl = require('./internal/streams/destroy');
  75  
  76  var _require = require('./internal/streams/state'),
  77      getHighWaterMark = _require.getHighWaterMark;
  78  
  79  var _require$codes = require('../errors').codes,
  80      ERR_INVALID_ARG_TYPE = _require$codes.ERR_INVALID_ARG_TYPE,
  81      ERR_STREAM_PUSH_AFTER_EOF = _require$codes.ERR_STREAM_PUSH_AFTER_EOF,
  82      ERR_METHOD_NOT_IMPLEMENTED = _require$codes.ERR_METHOD_NOT_IMPLEMENTED,
  83      ERR_STREAM_UNSHIFT_AFTER_END_EVENT = _require$codes.ERR_STREAM_UNSHIFT_AFTER_END_EVENT; // Lazy loaded to improve the startup performance.
  84  
  85  
  86  var StringDecoder;
  87  var createReadableStreamAsyncIterator;
  88  var from;
  89  
  90  require('inherits')(Readable, Stream);
  91  
  92  var errorOrDestroy = destroyImpl.errorOrDestroy;
  93  var kProxyEvents = ['error', 'close', 'destroy', 'pause', 'resume'];
  94  
  95  function prependListener(emitter, event, fn) {
  96    // Sadly this is not cacheable as some libraries bundle their own
  97    // event emitter implementation with them.
  98    if (typeof emitter.prependListener === 'function') return emitter.prependListener(event, fn); // This is a hack to make sure that our error handler is attached before any
  99    // userland ones.  NEVER DO THIS. This is here only because this code needs
 100    // to continue to work with older versions of Node.js that do not include
 101    // the prependListener() method. The goal is to eventually remove this hack.
 102  
 103    if (!emitter._events || !emitter._events[event]) emitter.on(event, fn);else if (Array.isArray(emitter._events[event])) emitter._events[event].unshift(fn);else emitter._events[event] = [fn, emitter._events[event]];
 104  }
 105  
 106  function ReadableState(options, stream, isDuplex) {
 107    Duplex = Duplex || require('./_stream_duplex');
 108    options = options || {}; // Duplex streams are both readable and writable, but share
 109    // the same options object.
 110    // However, some cases require setting options to different
 111    // values for the readable and the writable sides of the duplex stream.
 112    // These options can be provided separately as readableXXX and writableXXX.
 113  
 114    if (typeof isDuplex !== 'boolean') isDuplex = stream instanceof Duplex; // object stream flag. Used to make read(n) ignore n and to
 115    // make all the buffer merging and length checks go away
 116  
 117    this.objectMode = !!options.objectMode;
 118    if (isDuplex) this.objectMode = this.objectMode || !!options.readableObjectMode; // the point at which it stops calling _read() to fill the buffer
 119    // Note: 0 is a valid value, means "don't call _read preemptively ever"
 120  
 121    this.highWaterMark = getHighWaterMark(this, options, 'readableHighWaterMark', isDuplex); // A linked list is used to store data chunks instead of an array because the
 122    // linked list can remove elements from the beginning faster than
 123    // array.shift()
 124  
 125    this.buffer = new BufferList();
 126    this.length = 0;
 127    this.pipes = null;
 128    this.pipesCount = 0;
 129    this.flowing = null;
 130    this.ended = false;
 131    this.endEmitted = false;
 132    this.reading = false; // a flag to be able to tell if the event 'readable'/'data' is emitted
 133    // immediately, or on a later tick.  We set this to true at first, because
 134    // any actions that shouldn't happen until "later" should generally also
 135    // not happen before the first read call.
 136  
 137    this.sync = true; // whenever we return null, then we set a flag to say
 138    // that we're awaiting a 'readable' event emission.
 139  
 140    this.needReadable = false;
 141    this.emittedReadable = false;
 142    this.readableListening = false;
 143    this.resumeScheduled = false;
 144    this.paused = true; // Should close be emitted on destroy. Defaults to true.
 145  
 146    this.emitClose = options.emitClose !== false; // Should .destroy() be called after 'end' (and potentially 'finish')
 147  
 148    this.autoDestroy = !!options.autoDestroy; // has it been destroyed
 149  
 150    this.destroyed = false; // Crypto is kind of old and crusty.  Historically, its default string
 151    // encoding is 'binary' so we have to make this configurable.
 152    // Everything else in the universe uses 'utf8', though.
 153  
 154    this.defaultEncoding = options.defaultEncoding || 'utf8'; // the number of writers that are awaiting a drain event in .pipe()s
 155  
 156    this.awaitDrain = 0; // if true, a maybeReadMore has been scheduled
 157  
 158    this.readingMore = false;
 159    this.decoder = null;
 160    this.encoding = null;
 161  
 162    if (options.encoding) {
 163      if (!StringDecoder) StringDecoder = require('string_decoder/').StringDecoder;
 164      this.decoder = new StringDecoder(options.encoding);
 165      this.encoding = options.encoding;
 166    }
 167  }
 168  
 169  function Readable(options) {
 170    Duplex = Duplex || require('./_stream_duplex');
 171    if (!(this instanceof Readable)) return new Readable(options); // Checking for a Stream.Duplex instance is faster here instead of inside
 172    // the ReadableState constructor, at least with V8 6.5
 173  
 174    var isDuplex = this instanceof Duplex;
 175    this._readableState = new ReadableState(options, this, isDuplex); // legacy
 176  
 177    this.readable = true;
 178  
 179    if (options) {
 180      if (typeof options.read === 'function') this._read = options.read;
 181      if (typeof options.destroy === 'function') this._destroy = options.destroy;
 182    }
 183  
 184    Stream.call(this);
 185  }
 186  
 187  Object.defineProperty(Readable.prototype, 'destroyed', {
 188    // making it explicit this property is not enumerable
 189    // because otherwise some prototype manipulation in
 190    // userland will fail
 191    enumerable: false,
 192    get: function get() {
 193      if (this._readableState === undefined) {
 194        return false;
 195      }
 196  
 197      return this._readableState.destroyed;
 198    },
 199    set: function set(value) {
 200      // we ignore the value if the stream
 201      // has not been initialized yet
 202      if (!this._readableState) {
 203        return;
 204      } // backward compatibility, the user is explicitly
 205      // managing destroyed
 206  
 207  
 208      this._readableState.destroyed = value;
 209    }
 210  });
 211  Readable.prototype.destroy = destroyImpl.destroy;
 212  Readable.prototype._undestroy = destroyImpl.undestroy;
 213  
 214  Readable.prototype._destroy = function (err, cb) {
 215    cb(err);
 216  }; // Manually shove something into the read() buffer.
 217  // This returns true if the highWaterMark has not been hit yet,
 218  // similar to how Writable.write() returns true if you should
 219  // write() some more.
 220  
 221  
 222  Readable.prototype.push = function (chunk, encoding) {
 223    var state = this._readableState;
 224    var skipChunkCheck;
 225  
 226    if (!state.objectMode) {
 227      if (typeof chunk === 'string') {
 228        encoding = encoding || state.defaultEncoding;
 229  
 230        if (encoding !== state.encoding) {
 231          chunk = Buffer.from(chunk, encoding);
 232          encoding = '';
 233        }
 234  
 235        skipChunkCheck = true;
 236      }
 237    } else {
 238      skipChunkCheck = true;
 239    }
 240  
 241    return readableAddChunk(this, chunk, encoding, false, skipChunkCheck);
 242  }; // Unshift should *always* be something directly out of read()
 243  
 244  
 245  Readable.prototype.unshift = function (chunk) {
 246    return readableAddChunk(this, chunk, null, true, false);
 247  };
 248  
 249  function readableAddChunk(stream, chunk, encoding, addToFront, skipChunkCheck) {
 250    debug('readableAddChunk', chunk);
 251    var state = stream._readableState;
 252  
 253    if (chunk === null) {
 254      state.reading = false;
 255      onEofChunk(stream, state);
 256    } else {
 257      var er;
 258      if (!skipChunkCheck) er = chunkInvalid(state, chunk);
 259  
 260      if (er) {
 261        errorOrDestroy(stream, er);
 262      } else if (state.objectMode || chunk && chunk.length > 0) {
 263        if (typeof chunk !== 'string' && !state.objectMode && Object.getPrototypeOf(chunk) !== Buffer.prototype) {
 264          chunk = _uint8ArrayToBuffer(chunk);
 265        }
 266  
 267        if (addToFront) {
 268          if (state.endEmitted) errorOrDestroy(stream, new ERR_STREAM_UNSHIFT_AFTER_END_EVENT());else addChunk(stream, state, chunk, true);
 269        } else if (state.ended) {
 270          errorOrDestroy(stream, new ERR_STREAM_PUSH_AFTER_EOF());
 271        } else if (state.destroyed) {
 272          return false;
 273        } else {
 274          state.reading = false;
 275  
 276          if (state.decoder && !encoding) {
 277            chunk = state.decoder.write(chunk);
 278            if (state.objectMode || chunk.length !== 0) addChunk(stream, state, chunk, false);else maybeReadMore(stream, state);
 279          } else {
 280            addChunk(stream, state, chunk, false);
 281          }
 282        }
 283      } else if (!addToFront) {
 284        state.reading = false;
 285        maybeReadMore(stream, state);
 286      }
 287    } // We can push more data if we are below the highWaterMark.
 288    // Also, if we have no data yet, we can stand some more bytes.
 289    // This is to work around cases where hwm=0, such as the repl.
 290  
 291  
 292    return !state.ended && (state.length < state.highWaterMark || state.length === 0);
 293  }
 294  
 295  function addChunk(stream, state, chunk, addToFront) {
 296    if (state.flowing && state.length === 0 && !state.sync) {
 297      state.awaitDrain = 0;
 298      stream.emit('data', chunk);
 299    } else {
 300      // update the buffer info.
 301      state.length += state.objectMode ? 1 : chunk.length;
 302      if (addToFront) state.buffer.unshift(chunk);else state.buffer.push(chunk);
 303      if (state.needReadable) emitReadable(stream);
 304    }
 305  
 306    maybeReadMore(stream, state);
 307  }
 308  
 309  function chunkInvalid(state, chunk) {
 310    var er;
 311  
 312    if (!_isUint8Array(chunk) && typeof chunk !== 'string' && chunk !== undefined && !state.objectMode) {
 313      er = new ERR_INVALID_ARG_TYPE('chunk', ['string', 'Buffer', 'Uint8Array'], chunk);
 314    }
 315  
 316    return er;
 317  }
 318  
 319  Readable.prototype.isPaused = function () {
 320    return this._readableState.flowing === false;
 321  }; // backwards compatibility.
 322  
 323  
 324  Readable.prototype.setEncoding = function (enc) {
 325    if (!StringDecoder) StringDecoder = require('string_decoder/').StringDecoder;
 326    var decoder = new StringDecoder(enc);
 327    this._readableState.decoder = decoder; // If setEncoding(null), decoder.encoding equals utf8
 328  
 329    this._readableState.encoding = this._readableState.decoder.encoding; // Iterate over current buffer to convert already stored Buffers:
 330  
 331    var p = this._readableState.buffer.head;
 332    var content = '';
 333  
 334    while (p !== null) {
 335      content += decoder.write(p.data);
 336      p = p.next;
 337    }
 338  
 339    this._readableState.buffer.clear();
 340  
 341    if (content !== '') this._readableState.buffer.push(content);
 342    this._readableState.length = content.length;
 343    return this;
 344  }; // Don't raise the hwm > 1GB
 345  
 346  
 347  var MAX_HWM = 0x40000000;
 348  
 349  function computeNewHighWaterMark(n) {
 350    if (n >= MAX_HWM) {
 351      // TODO(ronag): Throw ERR_VALUE_OUT_OF_RANGE.
 352      n = MAX_HWM;
 353    } else {
 354      // Get the next highest power of 2 to prevent increasing hwm excessively in
 355      // tiny amounts
 356      n--;
 357      n |= n >>> 1;
 358      n |= n >>> 2;
 359      n |= n >>> 4;
 360      n |= n >>> 8;
 361      n |= n >>> 16;
 362      n++;
 363    }
 364  
 365    return n;
 366  } // This function is designed to be inlinable, so please take care when making
 367  // changes to the function body.
 368  
 369  
 370  function howMuchToRead(n, state) {
 371    if (n <= 0 || state.length === 0 && state.ended) return 0;
 372    if (state.objectMode) return 1;
 373  
 374    if (n !== n) {
 375      // Only flow one buffer at a time
 376      if (state.flowing && state.length) return state.buffer.head.data.length;else return state.length;
 377    } // If we're asking for more than the current hwm, then raise the hwm.
 378  
 379  
 380    if (n > state.highWaterMark) state.highWaterMark = computeNewHighWaterMark(n);
 381    if (n <= state.length) return n; // Don't have enough
 382  
 383    if (!state.ended) {
 384      state.needReadable = true;
 385      return 0;
 386    }
 387  
 388    return state.length;
 389  } // you can override either this method, or the async _read(n) below.
 390  
 391  
 392  Readable.prototype.read = function (n) {
 393    debug('read', n);
 394    n = parseInt(n, 10);
 395    var state = this._readableState;
 396    var nOrig = n;
 397    if (n !== 0) state.emittedReadable = false; // if we're doing read(0) to trigger a readable event, but we
 398    // already have a bunch of data in the buffer, then just trigger
 399    // the 'readable' event and move on.
 400  
 401    if (n === 0 && state.needReadable && ((state.highWaterMark !== 0 ? state.length >= state.highWaterMark : state.length > 0) || state.ended)) {
 402      debug('read: emitReadable', state.length, state.ended);
 403      if (state.length === 0 && state.ended) endReadable(this);else emitReadable(this);
 404      return null;
 405    }
 406  
 407    n = howMuchToRead(n, state); // if we've ended, and we're now clear, then finish it up.
 408  
 409    if (n === 0 && state.ended) {
 410      if (state.length === 0) endReadable(this);
 411      return null;
 412    } // All the actual chunk generation logic needs to be
 413    // *below* the call to _read.  The reason is that in certain
 414    // synthetic stream cases, such as passthrough streams, _read
 415    // may be a completely synchronous operation which may change
 416    // the state of the read buffer, providing enough data when
 417    // before there was *not* enough.
 418    //
 419    // So, the steps are:
 420    // 1. Figure out what the state of things will be after we do
 421    // a read from the buffer.
 422    //
 423    // 2. If that resulting state will trigger a _read, then call _read.
 424    // Note that this may be asynchronous, or synchronous.  Yes, it is
 425    // deeply ugly to write APIs this way, but that still doesn't mean
 426    // that the Readable class should behave improperly, as streams are
 427    // designed to be sync/async agnostic.
 428    // Take note if the _read call is sync or async (ie, if the read call
 429    // has returned yet), so that we know whether or not it's safe to emit
 430    // 'readable' etc.
 431    //
 432    // 3. Actually pull the requested chunks out of the buffer and return.
 433    // if we need a readable event, then we need to do some reading.
 434  
 435  
 436    var doRead = state.needReadable;
 437    debug('need readable', doRead); // if we currently have less than the highWaterMark, then also read some
 438  
 439    if (state.length === 0 || state.length - n < state.highWaterMark) {
 440      doRead = true;
 441      debug('length less than watermark', doRead);
 442    } // however, if we've ended, then there's no point, and if we're already
 443    // reading, then it's unnecessary.
 444  
 445  
 446    if (state.ended || state.reading) {
 447      doRead = false;
 448      debug('reading or ended', doRead);
 449    } else if (doRead) {
 450      debug('do read');
 451      state.reading = true;
 452      state.sync = true; // if the length is currently zero, then we *need* a readable event.
 453  
 454      if (state.length === 0) state.needReadable = true; // call internal read method
 455  
 456      this._read(state.highWaterMark);
 457  
 458      state.sync = false; // If _read pushed data synchronously, then `reading` will be false,
 459      // and we need to re-evaluate how much data we can return to the user.
 460  
 461      if (!state.reading) n = howMuchToRead(nOrig, state);
 462    }
 463  
 464    var ret;
 465    if (n > 0) ret = fromList(n, state);else ret = null;
 466  
 467    if (ret === null) {
 468      state.needReadable = state.length <= state.highWaterMark;
 469      n = 0;
 470    } else {
 471      state.length -= n;
 472      state.awaitDrain = 0;
 473    }
 474  
 475    if (state.length === 0) {
 476      // If we have nothing in the buffer, then we want to know
 477      // as soon as we *do* get something into the buffer.
 478      if (!state.ended) state.needReadable = true; // If we tried to read() past the EOF, then emit end on the next tick.
 479  
 480      if (nOrig !== n && state.ended) endReadable(this);
 481    }
 482  
 483    if (ret !== null) this.emit('data', ret);
 484    return ret;
 485  };
 486  
 487  function onEofChunk(stream, state) {
 488    debug('onEofChunk');
 489    if (state.ended) return;
 490  
 491    if (state.decoder) {
 492      var chunk = state.decoder.end();
 493  
 494      if (chunk && chunk.length) {
 495        state.buffer.push(chunk);
 496        state.length += state.objectMode ? 1 : chunk.length;
 497      }
 498    }
 499  
 500    state.ended = true;
 501  
 502    if (state.sync) {
 503      // if we are sync, wait until next tick to emit the data.
 504      // Otherwise we risk emitting data in the flow()
 505      // the readable code triggers during a read() call
 506      emitReadable(stream);
 507    } else {
 508      // emit 'readable' now to make sure it gets picked up.
 509      state.needReadable = false;
 510  
 511      if (!state.emittedReadable) {
 512        state.emittedReadable = true;
 513        emitReadable_(stream);
 514      }
 515    }
 516  } // Don't emit readable right away in sync mode, because this can trigger
 517  // another read() call => stack overflow.  This way, it might trigger
 518  // a nextTick recursion warning, but that's not so bad.
 519  
 520  
 521  function emitReadable(stream) {
 522    var state = stream._readableState;
 523    debug('emitReadable', state.needReadable, state.emittedReadable);
 524    state.needReadable = false;
 525  
 526    if (!state.emittedReadable) {
 527      debug('emitReadable', state.flowing);
 528      state.emittedReadable = true;
 529      process.nextTick(emitReadable_, stream);
 530    }
 531  }
 532  
 533  function emitReadable_(stream) {
 534    var state = stream._readableState;
 535    debug('emitReadable_', state.destroyed, state.length, state.ended);
 536  
 537    if (!state.destroyed && (state.length || state.ended)) {
 538      stream.emit('readable');
 539      state.emittedReadable = false;
 540    } // The stream needs another readable event if
 541    // 1. It is not flowing, as the flow mechanism will take
 542    //    care of it.
 543    // 2. It is not ended.
 544    // 3. It is below the highWaterMark, so we can schedule
 545    //    another readable later.
 546  
 547  
 548    state.needReadable = !state.flowing && !state.ended && state.length <= state.highWaterMark;
 549    flow(stream);
 550  } // at this point, the user has presumably seen the 'readable' event,
 551  // and called read() to consume some data.  that may have triggered
 552  // in turn another _read(n) call, in which case reading = true if
 553  // it's in progress.
 554  // However, if we're not ended, or reading, and the length < hwm,
 555  // then go ahead and try to read some more preemptively.
 556  
 557  
 558  function maybeReadMore(stream, state) {
 559    if (!state.readingMore) {
 560      state.readingMore = true;
 561      process.nextTick(maybeReadMore_, stream, state);
 562    }
 563  }
 564  
 565  function maybeReadMore_(stream, state) {
 566    // Attempt to read more data if we should.
 567    //
 568    // The conditions for reading more data are (one of):
 569    // - Not enough data buffered (state.length < state.highWaterMark). The loop
 570    //   is responsible for filling the buffer with enough data if such data
 571    //   is available. If highWaterMark is 0 and we are not in the flowing mode
 572    //   we should _not_ attempt to buffer any extra data. We'll get more data
 573    //   when the stream consumer calls read() instead.
 574    // - No data in the buffer, and the stream is in flowing mode. In this mode
 575    //   the loop below is responsible for ensuring read() is called. Failing to
 576    //   call read here would abort the flow and there's no other mechanism for
 577    //   continuing the flow if the stream consumer has just subscribed to the
 578    //   'data' event.
 579    //
 580    // In addition to the above conditions to keep reading data, the following
 581    // conditions prevent the data from being read:
 582    // - The stream has ended (state.ended).
 583    // - There is already a pending 'read' operation (state.reading). This is a
 584    //   case where the the stream has called the implementation defined _read()
 585    //   method, but they are processing the call asynchronously and have _not_
 586    //   called push() with new data. In this case we skip performing more
 587    //   read()s. The execution ends in this method again after the _read() ends
 588    //   up calling push() with more data.
 589    while (!state.reading && !state.ended && (state.length < state.highWaterMark || state.flowing && state.length === 0)) {
 590      var len = state.length;
 591      debug('maybeReadMore read 0');
 592      stream.read(0);
 593      if (len === state.length) // didn't get any data, stop spinning.
 594        break;
 595    }
 596  
 597    state.readingMore = false;
 598  } // abstract method.  to be overridden in specific implementation classes.
 599  // call cb(er, data) where data is <= n in length.
 600  // for virtual (non-string, non-buffer) streams, "length" is somewhat
 601  // arbitrary, and perhaps not very meaningful.
 602  
 603  
 604  Readable.prototype._read = function (n) {
 605    errorOrDestroy(this, new ERR_METHOD_NOT_IMPLEMENTED('_read()'));
 606  };
 607  
 608  Readable.prototype.pipe = function (dest, pipeOpts) {
 609    var src = this;
 610    var state = this._readableState;
 611  
 612    switch (state.pipesCount) {
 613      case 0:
 614        state.pipes = dest;
 615        break;
 616  
 617      case 1:
 618        state.pipes = [state.pipes, dest];
 619        break;
 620  
 621      default:
 622        state.pipes.push(dest);
 623        break;
 624    }
 625  
 626    state.pipesCount += 1;
 627    debug('pipe count=%d opts=%j', state.pipesCount, pipeOpts);
 628    var doEnd = (!pipeOpts || pipeOpts.end !== false) && dest !== process.stdout && dest !== process.stderr;
 629    var endFn = doEnd ? onend : unpipe;
 630    if (state.endEmitted) process.nextTick(endFn);else src.once('end', endFn);
 631    dest.on('unpipe', onunpipe);
 632  
 633    function onunpipe(readable, unpipeInfo) {
 634      debug('onunpipe');
 635  
 636      if (readable === src) {
 637        if (unpipeInfo && unpipeInfo.hasUnpiped === false) {
 638          unpipeInfo.hasUnpiped = true;
 639          cleanup();
 640        }
 641      }
 642    }
 643  
 644    function onend() {
 645      debug('onend');
 646      dest.end();
 647    } // when the dest drains, it reduces the awaitDrain counter
 648    // on the source.  This would be more elegant with a .once()
 649    // handler in flow(), but adding and removing repeatedly is
 650    // too slow.
 651  
 652  
 653    var ondrain = pipeOnDrain(src);
 654    dest.on('drain', ondrain);
 655    var cleanedUp = false;
 656  
 657    function cleanup() {
 658      debug('cleanup'); // cleanup event handlers once the pipe is broken
 659  
 660      dest.removeListener('close', onclose);
 661      dest.removeListener('finish', onfinish);
 662      dest.removeListener('drain', ondrain);
 663      dest.removeListener('error', onerror);
 664      dest.removeListener('unpipe', onunpipe);
 665      src.removeListener('end', onend);
 666      src.removeListener('end', unpipe);
 667      src.removeListener('data', ondata);
 668      cleanedUp = true; // if the reader is waiting for a drain event from this
 669      // specific writer, then it would cause it to never start
 670      // flowing again.
 671      // So, if this is awaiting a drain, then we just call it now.
 672      // If we don't know, then assume that we are waiting for one.
 673  
 674      if (state.awaitDrain && (!dest._writableState || dest._writableState.needDrain)) ondrain();
 675    }
 676  
 677    src.on('data', ondata);
 678  
 679    function ondata(chunk) {
 680      debug('ondata');
 681      var ret = dest.write(chunk);
 682      debug('dest.write', ret);
 683  
 684      if (ret === false) {
 685        // If the user unpiped during `dest.write()`, it is possible
 686        // to get stuck in a permanently paused state if that write
 687        // also returned false.
 688        // => Check whether `dest` is still a piping destination.
 689        if ((state.pipesCount === 1 && state.pipes === dest || state.pipesCount > 1 && indexOf(state.pipes, dest) !== -1) && !cleanedUp) {
 690          debug('false write response, pause', state.awaitDrain);
 691          state.awaitDrain++;
 692        }
 693  
 694        src.pause();
 695      }
 696    } // if the dest has an error, then stop piping into it.
 697    // however, don't suppress the throwing behavior for this.
 698  
 699  
 700    function onerror(er) {
 701      debug('onerror', er);
 702      unpipe();
 703      dest.removeListener('error', onerror);
 704      if (EElistenerCount(dest, 'error') === 0) errorOrDestroy(dest, er);
 705    } // Make sure our error handler is attached before userland ones.
 706  
 707  
 708    prependListener(dest, 'error', onerror); // Both close and finish should trigger unpipe, but only once.
 709  
 710    function onclose() {
 711      dest.removeListener('finish', onfinish);
 712      unpipe();
 713    }
 714  
 715    dest.once('close', onclose);
 716  
 717    function onfinish() {
 718      debug('onfinish');
 719      dest.removeListener('close', onclose);
 720      unpipe();
 721    }
 722  
 723    dest.once('finish', onfinish);
 724  
 725    function unpipe() {
 726      debug('unpipe');
 727      src.unpipe(dest);
 728    } // tell the dest that it's being piped to
 729  
 730  
 731    dest.emit('pipe', src); // start the flow if it hasn't been started already.
 732  
 733    if (!state.flowing) {
 734      debug('pipe resume');
 735      src.resume();
 736    }
 737  
 738    return dest;
 739  };
 740  
 741  function pipeOnDrain(src) {
 742    return function pipeOnDrainFunctionResult() {
 743      var state = src._readableState;
 744      debug('pipeOnDrain', state.awaitDrain);
 745      if (state.awaitDrain) state.awaitDrain--;
 746  
 747      if (state.awaitDrain === 0 && EElistenerCount(src, 'data')) {
 748        state.flowing = true;
 749        flow(src);
 750      }
 751    };
 752  }
 753  
 754  Readable.prototype.unpipe = function (dest) {
 755    var state = this._readableState;
 756    var unpipeInfo = {
 757      hasUnpiped: false
 758    }; // if we're not piping anywhere, then do nothing.
 759  
 760    if (state.pipesCount === 0) return this; // just one destination.  most common case.
 761  
 762    if (state.pipesCount === 1) {
 763      // passed in one, but it's not the right one.
 764      if (dest && dest !== state.pipes) return this;
 765      if (!dest) dest = state.pipes; // got a match.
 766  
 767      state.pipes = null;
 768      state.pipesCount = 0;
 769      state.flowing = false;
 770      if (dest) dest.emit('unpipe', this, unpipeInfo);
 771      return this;
 772    } // slow case. multiple pipe destinations.
 773  
 774  
 775    if (!dest) {
 776      // remove all.
 777      var dests = state.pipes;
 778      var len = state.pipesCount;
 779      state.pipes = null;
 780      state.pipesCount = 0;
 781      state.flowing = false;
 782  
 783      for (var i = 0; i < len; i++) {
 784        dests[i].emit('unpipe', this, {
 785          hasUnpiped: false
 786        });
 787      }
 788  
 789      return this;
 790    } // try to find the right one.
 791  
 792  
 793    var index = indexOf(state.pipes, dest);
 794    if (index === -1) return this;
 795    state.pipes.splice(index, 1);
 796    state.pipesCount -= 1;
 797    if (state.pipesCount === 1) state.pipes = state.pipes[0];
 798    dest.emit('unpipe', this, unpipeInfo);
 799    return this;
 800  }; // set up data events if they are asked for
 801  // Ensure readable listeners eventually get something
 802  
 803  
 804  Readable.prototype.on = function (ev, fn) {
 805    var res = Stream.prototype.on.call(this, ev, fn);
 806    var state = this._readableState;
 807  
 808    if (ev === 'data') {
 809      // update readableListening so that resume() may be a no-op
 810      // a few lines down. This is needed to support once('readable').
 811      state.readableListening = this.listenerCount('readable') > 0; // Try start flowing on next tick if stream isn't explicitly paused
 812  
 813      if (state.flowing !== false) this.resume();
 814    } else if (ev === 'readable') {
 815      if (!state.endEmitted && !state.readableListening) {
 816        state.readableListening = state.needReadable = true;
 817        state.flowing = false;
 818        state.emittedReadable = false;
 819        debug('on readable', state.length, state.reading);
 820  
 821        if (state.length) {
 822          emitReadable(this);
 823        } else if (!state.reading) {
 824          process.nextTick(nReadingNextTick, this);
 825        }
 826      }
 827    }
 828  
 829    return res;
 830  };
 831  
 832  Readable.prototype.addListener = Readable.prototype.on;
 833  
 834  Readable.prototype.removeListener = function (ev, fn) {
 835    var res = Stream.prototype.removeListener.call(this, ev, fn);
 836  
 837    if (ev === 'readable') {
 838      // We need to check if there is someone still listening to
 839      // readable and reset the state. However this needs to happen
 840      // after readable has been emitted but before I/O (nextTick) to
 841      // support once('readable', fn) cycles. This means that calling
 842      // resume within the same tick will have no
 843      // effect.
 844      process.nextTick(updateReadableListening, this);
 845    }
 846  
 847    return res;
 848  };
 849  
 850  Readable.prototype.removeAllListeners = function (ev) {
 851    var res = Stream.prototype.removeAllListeners.apply(this, arguments);
 852  
 853    if (ev === 'readable' || ev === undefined) {
 854      // We need to check if there is someone still listening to
 855      // readable and reset the state. However this needs to happen
 856      // after readable has been emitted but before I/O (nextTick) to
 857      // support once('readable', fn) cycles. This means that calling
 858      // resume within the same tick will have no
 859      // effect.
 860      process.nextTick(updateReadableListening, this);
 861    }
 862  
 863    return res;
 864  };
 865  
 866  function updateReadableListening(self) {
 867    var state = self._readableState;
 868    state.readableListening = self.listenerCount('readable') > 0;
 869  
 870    if (state.resumeScheduled && !state.paused) {
 871      // flowing needs to be set to true now, otherwise
 872      // the upcoming resume will not flow.
 873      state.flowing = true; // crude way to check if we should resume
 874    } else if (self.listenerCount('data') > 0) {
 875      self.resume();
 876    }
 877  }
 878  
 879  function nReadingNextTick(self) {
 880    debug('readable nexttick read 0');
 881    self.read(0);
 882  } // pause() and resume() are remnants of the legacy readable stream API
 883  // If the user uses them, then switch into old mode.
 884  
 885  
 886  Readable.prototype.resume = function () {
 887    var state = this._readableState;
 888  
 889    if (!state.flowing) {
 890      debug('resume'); // we flow only if there is no one listening
 891      // for readable, but we still have to call
 892      // resume()
 893  
 894      state.flowing = !state.readableListening;
 895      resume(this, state);
 896    }
 897  
 898    state.paused = false;
 899    return this;
 900  };
 901  
 902  function resume(stream, state) {
 903    if (!state.resumeScheduled) {
 904      state.resumeScheduled = true;
 905      process.nextTick(resume_, stream, state);
 906    }
 907  }
 908  
 909  function resume_(stream, state) {
 910    debug('resume', state.reading);
 911  
 912    if (!state.reading) {
 913      stream.read(0);
 914    }
 915  
 916    state.resumeScheduled = false;
 917    stream.emit('resume');
 918    flow(stream);
 919    if (state.flowing && !state.reading) stream.read(0);
 920  }
 921  
 922  Readable.prototype.pause = function () {
 923    debug('call pause flowing=%j', this._readableState.flowing);
 924  
 925    if (this._readableState.flowing !== false) {
 926      debug('pause');
 927      this._readableState.flowing = false;
 928      this.emit('pause');
 929    }
 930  
 931    this._readableState.paused = true;
 932    return this;
 933  };
 934  
 935  function flow(stream) {
 936    var state = stream._readableState;
 937    debug('flow', state.flowing);
 938  
 939    while (state.flowing && stream.read() !== null) {
 940      ;
 941    }
 942  } // wrap an old-style stream as the async data source.
 943  // This is *not* part of the readable stream interface.
 944  // It is an ugly unfortunate mess of history.
 945  
 946  
 947  Readable.prototype.wrap = function (stream) {
 948    var _this = this;
 949  
 950    var state = this._readableState;
 951    var paused = false;
 952    stream.on('end', function () {
 953      debug('wrapped end');
 954  
 955      if (state.decoder && !state.ended) {
 956        var chunk = state.decoder.end();
 957        if (chunk && chunk.length) _this.push(chunk);
 958      }
 959  
 960      _this.push(null);
 961    });
 962    stream.on('data', function (chunk) {
 963      debug('wrapped data');
 964      if (state.decoder) chunk = state.decoder.write(chunk); // don't skip over falsy values in objectMode
 965  
 966      if (state.objectMode && (chunk === null || chunk === undefined)) return;else if (!state.objectMode && (!chunk || !chunk.length)) return;
 967  
 968      var ret = _this.push(chunk);
 969  
 970      if (!ret) {
 971        paused = true;
 972        stream.pause();
 973      }
 974    }); // proxy all the other methods.
 975    // important when wrapping filters and duplexes.
 976  
 977    for (var i in stream) {
 978      if (this[i] === undefined && typeof stream[i] === 'function') {
 979        this[i] = function methodWrap(method) {
 980          return function methodWrapReturnFunction() {
 981            return stream[method].apply(stream, arguments);
 982          };
 983        }(i);
 984      }
 985    } // proxy certain important events.
 986  
 987  
 988    for (var n = 0; n < kProxyEvents.length; n++) {
 989      stream.on(kProxyEvents[n], this.emit.bind(this, kProxyEvents[n]));
 990    } // when we try to consume some more bytes, simply unpause the
 991    // underlying stream.
 992  
 993  
 994    this._read = function (n) {
 995      debug('wrapped _read', n);
 996  
 997      if (paused) {
 998        paused = false;
 999        stream.resume();
1000      }
1001    };
1002  
1003    return this;
1004  };
1005  
1006  if (typeof Symbol === 'function') {
1007    Readable.prototype[Symbol.asyncIterator] = function () {
1008      if (createReadableStreamAsyncIterator === undefined) {
1009        createReadableStreamAsyncIterator = require('./internal/streams/async_iterator');
1010      }
1011  
1012      return createReadableStreamAsyncIterator(this);
1013    };
1014  }
1015  
1016  Object.defineProperty(Readable.prototype, 'readableHighWaterMark', {
1017    // making it explicit this property is not enumerable
1018    // because otherwise some prototype manipulation in
1019    // userland will fail
1020    enumerable: false,
1021    get: function get() {
1022      return this._readableState.highWaterMark;
1023    }
1024  });
1025  Object.defineProperty(Readable.prototype, 'readableBuffer', {
1026    // making it explicit this property is not enumerable
1027    // because otherwise some prototype manipulation in
1028    // userland will fail
1029    enumerable: false,
1030    get: function get() {
1031      return this._readableState && this._readableState.buffer;
1032    }
1033  });
1034  Object.defineProperty(Readable.prototype, 'readableFlowing', {
1035    // making it explicit this property is not enumerable
1036    // because otherwise some prototype manipulation in
1037    // userland will fail
1038    enumerable: false,
1039    get: function get() {
1040      return this._readableState.flowing;
1041    },
1042    set: function set(state) {
1043      if (this._readableState) {
1044        this._readableState.flowing = state;
1045      }
1046    }
1047  }); // exposed for testing purposes only.
1048  
1049  Readable._fromList = fromList;
1050  Object.defineProperty(Readable.prototype, 'readableLength', {
1051    // making it explicit this property is not enumerable
1052    // because otherwise some prototype manipulation in
1053    // userland will fail
1054    enumerable: false,
1055    get: function get() {
1056      return this._readableState.length;
1057    }
1058  }); // Pluck off n bytes from an array of buffers.
1059  // Length is the combined lengths of all the buffers in the list.
1060  // This function is designed to be inlinable, so please take care when making
1061  // changes to the function body.
1062  
1063  function fromList(n, state) {
1064    // nothing buffered
1065    if (state.length === 0) return null;
1066    var ret;
1067    if (state.objectMode) ret = state.buffer.shift();else if (!n || n >= state.length) {
1068      // read it all, truncate the list
1069      if (state.decoder) ret = state.buffer.join('');else if (state.buffer.length === 1) ret = state.buffer.first();else ret = state.buffer.concat(state.length);
1070      state.buffer.clear();
1071    } else {
1072      // read part of list
1073      ret = state.buffer.consume(n, state.decoder);
1074    }
1075    return ret;
1076  }
1077  
1078  function endReadable(stream) {
1079    var state = stream._readableState;
1080    debug('endReadable', state.endEmitted);
1081  
1082    if (!state.endEmitted) {
1083      state.ended = true;
1084      process.nextTick(endReadableNT, state, stream);
1085    }
1086  }
1087  
1088  function endReadableNT(state, stream) {
1089    debug('endReadableNT', state.endEmitted, state.length); // Check that we didn't get one last unshift.
1090  
1091    if (!state.endEmitted && state.length === 0) {
1092      state.endEmitted = true;
1093      stream.readable = false;
1094      stream.emit('end');
1095  
1096      if (state.autoDestroy) {
1097        // In case of duplex streams we need a way to detect
1098        // if the writable side is ready for autoDestroy as well
1099        var wState = stream._writableState;
1100  
1101        if (!wState || wState.autoDestroy && wState.finished) {
1102          stream.destroy();
1103        }
1104      }
1105    }
1106  }
1107  
1108  if (typeof Symbol === 'function') {
1109    Readable.from = function (iterable, opts) {
1110      if (from === undefined) {
1111        from = require('./internal/streams/from');
1112      }
1113  
1114      return from(Readable, iterable, opts);
1115    };
1116  }
1117  
1118  function indexOf(xs, x) {
1119    for (var i = 0, l = xs.length; i < l; i++) {
1120      if (xs[i] === x) return i;
1121    }
1122  
1123    return -1;
1124  }