# all files / lib/ _stream_readable.js

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87.22% Branches 307/352
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     'use strict';

    module.exports = Readable;

    /*<replacement>*/
    var processNextTick = require('process-nextick-args');
    /*</replacement>*/

    /*<replacement>*/
    var isArray = require('isarray');
    /*</replacement>*/

    Readable.ReadableState = ReadableState;

    /*<replacement>*/
    var EE = require('events').EventEmitter;

    var EElistenerCount = function (emitter, type) {
      return emitter.listeners(type).length;
    };
    /*</replacement>*/

    /*<replacement>*/
    var Stream;
    (function () {
      try {
        Stream = require('st' + 'ream');
      } catch (_) {} finally {
        Iif (!Stream) Stream = require('events').EventEmitter;
      }
    })();
    /*</replacement>*/

    var Buffer = require('buffer').Buffer;
    /*<replacement>*/
    var bufferShim = require('buffer-shims');
    /*</replacement>*/

    /*<replacement>*/
    var util = require('core-util-is');
    util.inherits = require('inherits');
    /*</replacement>*/

    /*<replacement>*/
    var debugUtil = require('util');
    var debug = void 0;
    Eif (debugUtil && debugUtil.debuglog) {
      debug = debugUtil.debuglog('stream');
    } else {
      debug = function () {};
    }
    /*</replacement>*/

    var StringDecoder;

    util.inherits(Readable, Stream);

    var hasPrependListener = typeof EE.prototype.prependListener === 'function';

    function prependListener(emitter, event, fn) {
      Iif (hasPrependListener) return emitter.prependListener(event, fn);

      // This is a brutally ugly hack to make sure that our error handler
      // is attached before any userland ones.  NEVER DO THIS. This is here
      // only because this code needs to continue to work with older versions
      // of Node.js that do not include the prependListener() method. The goal
      // is to eventually remove this hack.
      if (!emitter._events || !emitter._events[event]) emitter.on(event, fn);else Iif (isArray(emitter._events[event])) emitter._events[event].unshift(fn);else emitter._events[event] = [fn, emitter._events[event]];
    }

    var Duplex;
    function ReadableState(options, stream) {
      Duplex = Duplex || require('./_stream_duplex');

      options = options || {};

      // object stream flag. Used to make read(n) ignore n and to
      // make all the buffer merging and length checks go away
      this.objectMode = !!options.objectMode;

      if (stream instanceof Duplex) this.objectMode = this.objectMode || !!options.readableObjectMode;

      // the point at which it stops calling _read() to fill the buffer
      // Note: 0 is a valid value, means "don't call _read preemptively ever"
      var hwm = options.highWaterMark;
      var defaultHwm = this.objectMode ? 16 : 16 * 1024;
      this.highWaterMark = hwm || hwm === 0 ? hwm : defaultHwm;

      // cast to ints.
      this.highWaterMark = ~ ~this.highWaterMark;

      this.buffer = [];
      this.length = 0;
      this.pipes = null;
      this.pipesCount = 0;
      this.flowing = null;
      this.ended = false;
      this.endEmitted = false;
      this.reading = false;

      // a flag to be able to tell if the onwrite cb is called immediately,
      // or on a later tick.  We set this to true at first, because any
      // actions that shouldn't happen until "later" should generally also
      // not happen before the first write call.
      this.sync = true;

      // whenever we return null, then we set a flag to say
      // that we're awaiting a 'readable' event emission.
      this.needReadable = false;
      this.emittedReadable = false;
      this.readableListening = false;
      this.resumeScheduled = false;

      // Crypto is kind of old and crusty.  Historically, its default string
      // encoding is 'binary' so we have to make this configurable.
      // Everything else in the universe uses 'utf8', though.
      this.defaultEncoding = options.defaultEncoding || 'utf8';

      // when piping, we only care about 'readable' events that happen
      // after read()ing all the bytes and not getting any pushback.
      this.ranOut = false;

      // the number of writers that are awaiting a drain event in .pipe()s
      this.awaitDrain = 0;

      // if true, a maybeReadMore has been scheduled
      this.readingMore = false;

      this.decoder = null;
      this.encoding = null;
      if (options.encoding) {
        if (!StringDecoder) StringDecoder = require('string_decoder/').StringDecoder;
        this.decoder = new StringDecoder(options.encoding);
        this.encoding = options.encoding;
      }
    }

    var Duplex;
    function Readable(options) {
      Duplex = Duplex || require('./_stream_duplex');

      if (!(this instanceof Readable)) return new Readable(options);

      this._readableState = new ReadableState(options, this);

      // legacy
      this.readable = true;

      if (options && typeof options.read === 'function') this._read = options.read;

      Stream.call(this);
    }

    // Manually shove something into the read() buffer.
    // This returns true if the highWaterMark has not been hit yet,
    // similar to how Writable.write() returns true if you should
    // write() some more.
    Readable.prototype.push = function (chunk, encoding) {
      var state = this._readableState;

      if (!state.objectMode && typeof chunk === 'string') {
        encoding = encoding || state.defaultEncoding;
        if (encoding !== state.encoding) {
          chunk = bufferShim.from(chunk, encoding);
          encoding = '';
        }
      }

      return readableAddChunk(this, state, chunk, encoding, false);
    };

    // Unshift should *always* be something directly out of read()
    Readable.prototype.unshift = function (chunk) {
      var state = this._readableState;
      return readableAddChunk(this, state, chunk, '', true);
    };

    Readable.prototype.isPaused = function () {
      return this._readableState.flowing === false;
    };

    function readableAddChunk(stream, state, chunk, encoding, addToFront) {
      var er = chunkInvalid(state, chunk);
      Iif (er) {
        stream.emit('error', er);
      } else if (chunk === null) {
        state.reading = false;
        onEofChunk(stream, state);
      } else if (state.objectMode || chunk && chunk.length > 0) {
        if (state.ended && !addToFront) {
          var e = new Error('stream.push() after EOF');
          stream.emit('error', e);
        } else if (state.endEmitted && addToFront) {
          var _e = new Error('stream.unshift() after end event');
          stream.emit('error', _e);
        } else {
          var skipAdd;
          if (state.decoder && !addToFront && !encoding) {
            chunk = state.decoder.write(chunk);
            skipAdd = !state.objectMode && chunk.length === 0;
          }

          if (!addToFront) state.reading = false;

          // Don't add to the buffer if we've decoded to an empty string chunk and
          // we're not in object mode
          if (!skipAdd) {
            // if we want the data now, just emit it.
            if (state.flowing && state.length === 0 && !state.sync) {
              stream.emit('data', chunk);
              stream.read(0);
            } else {
              // update the buffer info.
              state.length += state.objectMode ? 1 : chunk.length;
              if (addToFront) state.buffer.unshift(chunk);else state.buffer.push(chunk);

              if (state.needReadable) emitReadable(stream);
            }
          }

          maybeReadMore(stream, state);
        }
      } else if (!addToFront) {
        state.reading = false;
      }

      return needMoreData(state);
    }

    // if it's past the high water mark, we can push in some more.
    // Also, if we have no data yet, we can stand some
    // more bytes.  This is to work around cases where hwm=0,
    // such as the repl.  Also, if the push() triggered a
    // readable event, and the user called read(largeNumber) such that
    // needReadable was set, then we ought to push more, so that another
    // 'readable' event will be triggered.
    function needMoreData(state) {
      return !state.ended && (state.needReadable || state.length < state.highWaterMark || state.length === 0);
    }

    // backwards compatibility.
    Readable.prototype.setEncoding = function (enc) {
      if (!StringDecoder) StringDecoder = require('string_decoder/').StringDecoder;
      this._readableState.decoder = new StringDecoder(enc);
      this._readableState.encoding = enc;
      return this;
    };

    // Don't raise the hwm > 8MB
    var MAX_HWM = 0x800000;
    function computeNewHighWaterMark(n) {
      Iif (n >= MAX_HWM) {
        n = MAX_HWM;
      } else {
        // Get the next highest power of 2
        n--;
        n |= n >>> 1;
        n |= n >>> 2;
        n |= n >>> 4;
        n |= n >>> 8;
        n |= n >>> 16;
        n++;
      }
      return n;
    }

    function howMuchToRead(n, state) {
      if (state.length === 0 && state.ended) return 0;

      if (state.objectMode) return n === 0 ? 0 : 1;

      if (n === null || isNaN(n)) {
        // only flow one buffer at a time
        if (state.flowing && state.buffer.length) return state.buffer[0].length;else return state.length;
      }

      if (n <= 0) return 0;

      // If we're asking for more than the target buffer level,
      // then raise the water mark.  Bump up to the next highest
      // power of 2, to prevent increasing it excessively in tiny
      // amounts.
      if (n > state.highWaterMark) state.highWaterMark = computeNewHighWaterMark(n);

      // don't have that much.  return null, unless we've ended.
      if (n > state.length) {
        if (!state.ended) {
          state.needReadable = true;
          return 0;
        } else {
          return state.length;
        }
      }

      return n;
    }

    // you can override either this method, or the async _read(n) below.
    Readable.prototype.read = function (n) {
      debug('read', n);
      var state = this._readableState;
      var nOrig = n;

      if (typeof n !== 'number' || n > 0) state.emittedReadable = false;

      // if we're doing read(0) to trigger a readable event, but we
      // already have a bunch of data in the buffer, then just trigger
      // the 'readable' event and move on.
      if (n === 0 && state.needReadable && (state.length >= state.highWaterMark || state.ended)) {
        debug('read: emitReadable', state.length, state.ended);
        if (state.length === 0 && state.ended) endReadable(this);else emitReadable(this);
        return null;
      }

      n = howMuchToRead(n, state);

      // if we've ended, and we're now clear, then finish it up.
      if (n === 0 && state.ended) {
        if (state.length === 0) endReadable(this);
        return null;
      }

      // All the actual chunk generation logic needs to be
      // *below* the call to _read.  The reason is that in certain
      // synthetic stream cases, such as passthrough streams, _read
      // may be a completely synchronous operation which may change
      // the state of the read buffer, providing enough data when
      // before there was *not* enough.
      //
      // So, the steps are:
      // 1. Figure out what the state of things will be after we do
      // a read from the buffer.
      //
      // 2. If that resulting state will trigger a _read, then call _read.
      // Note that this may be asynchronous, or synchronous.  Yes, it is
      // deeply ugly to write APIs this way, but that still doesn't mean
      // that the Readable class should behave improperly, as streams are
      // designed to be sync/async agnostic.
      // Take note if the _read call is sync or async (ie, if the read call
      // has returned yet), so that we know whether or not it's safe to emit
      // 'readable' etc.
      //
      // 3. Actually pull the requested chunks out of the buffer and return.

      // if we need a readable event, then we need to do some reading.
      var doRead = state.needReadable;
      debug('need readable', doRead);

      // if we currently have less than the highWaterMark, then also read some
      if (state.length === 0 || state.length - n < state.highWaterMark) {
        doRead = true;
        debug('length less than watermark', doRead);
      }

      // however, if we've ended, then there's no point, and if we're already
      // reading, then it's unnecessary.
      if (state.ended || state.reading) {
        doRead = false;
        debug('reading or ended', doRead);
      }

      if (doRead) {
        debug('do read');
        state.reading = true;
        state.sync = true;
        // if the length is currently zero, then we *need* a readable event.
        if (state.length === 0) state.needReadable = true;
        // call internal read method
        this._read(state.highWaterMark);
        state.sync = false;
      }

      // If _read pushed data synchronously, then `reading` will be false,
      // and we need to re-evaluate how much data we can return to the user.
      if (doRead && !state.reading) n = howMuchToRead(nOrig, state);

      var ret;
      if (n > 0) ret = fromList(n, state);else ret = null;

      if (ret === null) {
        state.needReadable = true;
        n = 0;
      }

      state.length -= n;

      // If we have nothing in the buffer, then we want to know
      // as soon as we *do* get something into the buffer.
      if (state.length === 0 && !state.ended) state.needReadable = true;

      // If we tried to read() past the EOF, then emit end on the next tick.
      if (nOrig !== n && state.ended && state.length === 0) endReadable(this);

      if (ret !== null) this.emit('data', ret);

      return ret;
    };

    function chunkInvalid(state, chunk) {
      var er = null;
      Iif (!Buffer.isBuffer(chunk) && typeof chunk !== 'string' && chunk !== null && chunk !== undefined && !state.objectMode) {
        er = new TypeError('Invalid non-string/buffer chunk');
      }
      return er;
    }

    function onEofChunk(stream, state) {
      if (state.ended) return;
      if (state.decoder) {
        var chunk = state.decoder.end();
        if (chunk && chunk.length) {
          state.buffer.push(chunk);
          state.length += state.objectMode ? 1 : chunk.length;
        }
      }
      state.ended = true;

      // emit 'readable' now to make sure it gets picked up.
      emitReadable(stream);
    }

    // Don't emit readable right away in sync mode, because this can trigger
    // another read() call => stack overflow.  This way, it might trigger
    // a nextTick recursion warning, but that's not so bad.
    function emitReadable(stream) {
      var state = stream._readableState;
      state.needReadable = false;
      if (!state.emittedReadable) {
        debug('emitReadable', state.flowing);
        state.emittedReadable = true;
        if (state.sync) processNextTick(emitReadable_, stream);else emitReadable_(stream);
      }
    }

    function emitReadable_(stream) {
      debug('emit readable');
      stream.emit('readable');
      flow(stream);
    }

    // at this point, the user has presumably seen the 'readable' event,
    // and called read() to consume some data.  that may have triggered
    // in turn another _read(n) call, in which case reading = true if
    // it's in progress.
    // However, if we're not ended, or reading, and the length < hwm,
    // then go ahead and try to read some more preemptively.
    function maybeReadMore(stream, state) {
      if (!state.readingMore) {
        state.readingMore = true;
        processNextTick(maybeReadMore_, stream, state);
      }
    }

    function maybeReadMore_(stream, state) {
      var len = state.length;
      while (!state.reading && !state.flowing && !state.ended && state.length < state.highWaterMark) {
        debug('maybeReadMore read 0');
        stream.read(0);
        if (len === state.length)
          // didn't get any data, stop spinning.
          break;else len = state.length;
      }
      state.readingMore = false;
    }

    // abstract method.  to be overridden in specific implementation classes.
    // call cb(er, data) where data is <= n in length.
    // for virtual (non-string, non-buffer) streams, "length" is somewhat
    // arbitrary, and perhaps not very meaningful.
    Readable.prototype._read = function (n) {
      this.emit('error', new Error('not implemented'));
    };

    Readable.prototype.pipe = function (dest, pipeOpts) {
      var src = this;
      var state = this._readableState;

      switch (state.pipesCount) {
        case 0:
          state.pipes = dest;
          break;
        case 1:
          state.pipes = [state.pipes, dest];
          break;
        default:
          state.pipes.push(dest);
          break;
      }
      state.pipesCount += 1;
      debug('pipe count=%d opts=%j', state.pipesCount, pipeOpts);

      var doEnd = (!pipeOpts || pipeOpts.end !== false) && dest !== process.stdout && dest !== process.stderr;

      var endFn = doEnd ? onend : cleanup;
      if (state.endEmitted) processNextTick(endFn);else src.once('end', endFn);

      dest.on('unpipe', onunpipe);
      function onunpipe(readable) {
        debug('onunpipe');
        if (readable === src) {
          cleanup();
        }
      }

      function onend() {
        debug('onend');
        dest.end();
      }

      // when the dest drains, it reduces the awaitDrain counter
      // on the source.  This would be more elegant with a .once()
      // handler in flow(), but adding and removing repeatedly is
      // too slow.
      var ondrain = pipeOnDrain(src);
      dest.on('drain', ondrain);

      var cleanedUp = false;
      function cleanup() {
        debug('cleanup');
        // cleanup event handlers once the pipe is broken
        dest.removeListener('close', onclose);
        dest.removeListener('finish', onfinish);
        dest.removeListener('drain', ondrain);
        dest.removeListener('error', onerror);
        dest.removeListener('unpipe', onunpipe);
        src.removeListener('end', onend);
        src.removeListener('end', cleanup);
        src.removeListener('data', ondata);

        cleanedUp = true;

        // if the reader is waiting for a drain event from this
        // specific writer, then it would cause it to never start
        // flowing again.
        // So, if this is awaiting a drain, then we just call it now.
        // If we don't know, then assume that we are waiting for one.
        if (state.awaitDrain && (!dest._writableState || dest._writableState.needDrain)) ondrain();
      }

      src.on('data', ondata);
      function ondata(chunk) {
        debug('ondata');
        var ret = dest.write(chunk);
        if (false === ret) {
          // If the user unpiped during `dest.write()`, it is possible
          // to get stuck in a permanently paused state if that write
          // also returned false.
          // => Check whether `dest` is still a piping destination.
          if ((state.pipesCount === 1 && state.pipes === dest || state.pipesCount > 1 && indexOf(state.pipes, dest) !== -1) && !cleanedUp) {
            debug('false write response, pause', src._readableState.awaitDrain);
            src._readableState.awaitDrain++;
          }
          src.pause();
        }
      }

      // if the dest has an error, then stop piping into it.
      // however, don't suppress the throwing behavior for this.
      function onerror(er) {
        debug('onerror', er);
        unpipe();
        dest.removeListener('error', onerror);
        if (EElistenerCount(dest, 'error') === 0) dest.emit('error', er);
      }

      // Make sure our error handler is attached before userland ones.
      prependListener(dest, 'error', onerror);

      // Both close and finish should trigger unpipe, but only once.
      function onclose() {
        dest.removeListener('finish', onfinish);
        unpipe();
      }
      dest.once('close', onclose);
      function onfinish() {
        debug('onfinish');
        dest.removeListener('close', onclose);
        unpipe();
      }
      dest.once('finish', onfinish);

      function unpipe() {
        debug('unpipe');
        src.unpipe(dest);
      }

      // tell the dest that it's being piped to
      dest.emit('pipe', src);

      // start the flow if it hasn't been started already.
      if (!state.flowing) {
        debug('pipe resume');
        src.resume();
      }

      return dest;
    };

    function pipeOnDrain(src) {
      return function () {
        var state = src._readableState;
        debug('pipeOnDrain', state.awaitDrain);
        if (state.awaitDrain) state.awaitDrain--;
        if (state.awaitDrain === 0 && EElistenerCount(src, 'data')) {
          state.flowing = true;
          flow(src);
        }
      };
    }

    Readable.prototype.unpipe = function (dest) {
      var state = this._readableState;

      // if we're not piping anywhere, then do nothing.
      if (state.pipesCount === 0) return this;

      // just one destination.  most common case.
      Eif (state.pipesCount === 1) {
        // passed in one, but it's not the right one.
        Iif (dest && dest !== state.pipes) return this;

        Iif (!dest) dest = state.pipes;

        // got a match.
        state.pipes = null;
        state.pipesCount = 0;
        state.flowing = false;
        Eif (dest) dest.emit('unpipe', this);
        return this;
      }

      // slow case. multiple pipe destinations.

      if (!dest) {
        // remove all.
        var dests = state.pipes;
        var len = state.pipesCount;
        state.pipes = null;
        state.pipesCount = 0;
        state.flowing = false;

        for (var _i = 0; _i < len; _i++) {
          dests[_i].emit('unpipe', this);
        }return this;
      }

      // try to find the right one.
      var i = indexOf(state.pipes, dest);
      if (i === -1) return this;

      state.pipes.splice(i, 1);
      state.pipesCount -= 1;
      if (state.pipesCount === 1) state.pipes = state.pipes[0];

      dest.emit('unpipe', this);

      return this;
    };

    // set up data events if they are asked for
    // Ensure readable listeners eventually get something
    Readable.prototype.on = function (ev, fn) {
      var res = Stream.prototype.on.call(this, ev, fn);

      // If listening to data, and it has not explicitly been paused,
      // then call resume to start the flow of data on the next tick.
      if (ev === 'data' && false !== this._readableState.flowing) {
        this.resume();
      }

      if (ev === 'readable' && !this._readableState.endEmitted) {
        var state = this._readableState;
        if (!state.readableListening) {
          state.readableListening = true;
          state.emittedReadable = false;
          state.needReadable = true;
          if (!state.reading) {
            processNextTick(nReadingNextTick, this);
          } else if (state.length) {
            emitReadable(this, state);
          }
        }
      }

      return res;
    };
    Readable.prototype.addListener = Readable.prototype.on;

    function nReadingNextTick(self) {
      debug('readable nexttick read 0');
      self.read(0);
    }

    // pause() and resume() are remnants of the legacy readable stream API
    // If the user uses them, then switch into old mode.
    Readable.prototype.resume = function () {
      var state = this._readableState;
      if (!state.flowing) {
        debug('resume');
        state.flowing = true;
        resume(this, state);
      }
      return this;
    };

    function resume(stream, state) {
      if (!state.resumeScheduled) {
        state.resumeScheduled = true;
        processNextTick(resume_, stream, state);
      }
    }

    function resume_(stream, state) {
      if (!state.reading) {
        debug('resume read 0');
        stream.read(0);
      }

      state.resumeScheduled = false;
      stream.emit('resume');
      flow(stream);
      if (state.flowing && !state.reading) stream.read(0);
    }

    Readable.prototype.pause = function () {
      debug('call pause flowing=%j', this._readableState.flowing);
      if (false !== this._readableState.flowing) {
        debug('pause');
        this._readableState.flowing = false;
        this.emit('pause');
      }
      return this;
    };

    function flow(stream) {
      var state = stream._readableState;
      debug('flow', state.flowing);
      if (state.flowing) {
        do {
          var chunk = stream.read();
        } while (null !== chunk && state.flowing);
      }
    }

    // wrap an old-style stream as the async data source.
    // This is *not* part of the readable stream interface.
    // It is an ugly unfortunate mess of history.
    Readable.prototype.wrap = function (stream) {
      var state = this._readableState;
      var paused = false;

      var self = this;
      stream.on('end', function () {
        debug('wrapped end');
        Iif (state.decoder && !state.ended) {
          var chunk = state.decoder.end();
          if (chunk && chunk.length) self.push(chunk);
        }

        self.push(null);
      });

      stream.on('data', function (chunk) {
        debug('wrapped data');
        if (state.decoder) chunk = state.decoder.write(chunk);

        // don't skip over falsy values in objectMode
        if (state.objectMode && (chunk === null || chunk === undefined)) return;else if (!state.objectMode && (!chunk || !chunk.length)) return;

        var ret = self.push(chunk);
        if (!ret) {
          paused = true;
          stream.pause();
        }
      });

      // proxy all the other methods.
      // important when wrapping filters and duplexes.
      for (var i in stream) {
        Iif (this[i] === undefined && typeof stream[i] === 'function') {
          this[i] = function (method) {
            return function () {
              return stream[method].apply(stream, arguments);
            };
          }(i);
        }
      }

      // proxy certain important events.
      var events = ['error', 'close', 'destroy', 'pause', 'resume'];
      forEach(events, function (ev) {
        stream.on(ev, self.emit.bind(self, ev));
      });

      // when we try to consume some more bytes, simply unpause the
      // underlying stream.
      self._read = function (n) {
        debug('wrapped _read', n);
        if (paused) {
          paused = false;
          stream.resume();
        }
      };

      return self;
    };

    // exposed for testing purposes only.
    Readable._fromList = fromList;

    // Pluck off n bytes from an array of buffers.
    // Length is the combined lengths of all the buffers in the list.
    function fromList(n, state) {
      var list = state.buffer;
      var length = state.length;
      var stringMode = !!state.decoder;
      var objectMode = !!state.objectMode;
      var ret;

      // nothing in the list, definitely empty.
      if (list.length === 0) return null;

      Iif (length === 0) ret = null;else if (objectMode) ret = list.shift();else if (!n || n >= length) {
        // read it all, truncate the array.
        if (stringMode) ret = list.join('');else if (list.length === 1) ret = list[0];else ret = Buffer.concat(list, length);
        list.length = 0;
      } else {
        // read just some of it.
        if (n < list[0].length) {
          // just take a part of the first list item.
          // slice is the same for buffers and strings.
          var buf = list[0];
          ret = buf.slice(0, n);
          list[0] = buf.slice(n);
        } else if (n === list[0].length) {
          // first list is a perfect match
          ret = list.shift();
        } else {
          // complex case.
          // we have enough to cover it, but it spans past the first buffer.
          if (stringMode) ret = '';else ret = bufferShim.allocUnsafe(n);

          var c = 0;
          for (var i = 0, l = list.length; i < l && c < n; i++) {
            var _buf = list[0];
            var cpy = Math.min(n - c, _buf.length);

            if (stringMode) ret += _buf.slice(0, cpy);else _buf.copy(ret, c, 0, cpy);

            if (cpy < _buf.length) list[0] = _buf.slice(cpy);else list.shift();

            c += cpy;
          }
        }
      }

      return ret;
    }

    function endReadable(stream) {
      var state = stream._readableState;

      // If we get here before consuming all the bytes, then that is a
      // bug in node.  Should never happen.
      Iif (state.length > 0) throw new Error('"endReadable()" called on non-empty stream');

      if (!state.endEmitted) {
        state.ended = true;
        processNextTick(endReadableNT, state, stream);
      }
    }

    function endReadableNT(state, stream) {
      // Check that we didn't get one last unshift.
      if (!state.endEmitted && state.length === 0) {
        state.endEmitted = true;
        stream.readable = false;
        stream.emit('end');
      }
    }

    function forEach(xs, f) {
      for (var i = 0, l = xs.length; i < l; i++) {
        f(xs[i], i);
      }
    }

    function indexOf(xs, x) {
      for (var i = 0, l = xs.length; i < l; i++) {
        if (xs[i] === x) return i;
      }
      return -1;
    }