text: '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 {
          if (!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;
  if (debugUtil && debugUtil.debuglog) {
      debug = debugUtil.debuglog('stream');
  } else {
      debug = function () {
      };
  }
  /*</replacement>*/
  
  var BufferList = require('./internal/streams/BufferList');
  var StringDecoder;
  
  util.inherits(Readable, Stream);
  
  function prependListener(emitter, event, fn) {
      if (typeof emitter.prependListener === 'function') {
          return emitter.prependListener(event, fn);
      } else {
          // This is a 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 if (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;
  
      // A linked list is used to store data chunks instead of an array because the
      // linked list can remove elements from the beginning faster than
      // array.shift()
      this.buffer = new BufferList();
      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);
      if (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) {
      if (n >= MAX_HWM) {
          n = MAX_HWM;
      } else {
          // Get the next highest power of 2 to prevent increasing hwm excessively in
          // tiny amounts
          n--;
          n |= n >>> 1;
          n |= n >>> 2;
          n |= n >>> 4;
          n |= n >>> 8;
          n |= n >>> 16;
          n++;
      }
      return n;
  }
  
  // This function is designed to be inlinable, so please take care when making
  // changes to the function body.
  function howMuchToRead(n, state) {
      if (n <= 0 || state.length === 0 && state.ended) return 0;
      if (state.objectMode) return 1;
      if (n !== n) {
          // Only flow one buffer at a time
          if (state.flowing && state.length) return state.buffer.head.data.length; else return state.length;
      }
      // If we're asking for more than the current hwm, then raise the hwm.
      if (n > state.highWaterMark) state.highWaterMark = computeNewHighWaterMark(n);
      if (n <= state.length) return n;
      // Don't have enough
      if (!state.ended) {
          state.needReadable = true;
          return 0;
      }
      return state.length;
  }
  
  // you can override either this method, or the async _read(n) below.
  Readable.prototype.read = function (n) {
      debug('read', n);
      n = parseInt(n, 10);
      var state = this._readableState;
      var nOrig = n;
  
      if (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);
      } else 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 (!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;
      } else {
          state.length -= n;
      }
  
      if (state.length === 0) {
          // If we have nothing in the buffer, then we want to know
          // as soon as we *do* get something into the buffer.
          if (!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) endReadable(this);
      }
  
      if (ret !== null) this.emit('data', ret);
  
      return ret;
  };
  
  function chunkInvalid(state, chunk) {
      var er = null;
      if (!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();
      }
  
      // If the user pushes more data while we're writing to dest then we'll end up
      // in ondata again. However, we only want to increase awaitDrain once because
      // dest will only emit one 'drain' event for the multiple writes.
      // => Introduce a guard on increasing awaitDrain.
      var increasedAwaitDrain = false;
      src.on('data', ondata);
      function ondata(chunk) {
          debug('ondata');
          increasedAwaitDrain = false;
          var ret = dest.write(chunk);
          if (false === ret && !increasedAwaitDrain) {
              // 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++;
                  increasedAwaitDrain = true;
              }
              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.
      if (state.pipesCount === 1) {
          // passed in one, but it's not the right one.
          if (dest && dest !== state.pipes) return this;
  
          if (!dest) dest = state.pipes;
  
          // got a match.
          state.pipes = null;
          state.pipesCount = 0;
          state.flowing = false;
          if (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 (ev === 'data') {
          // Start flowing on next tick if stream isn't explicitly paused
          if (this._readableState.flowing !== false) this.resume();
      } else if (ev === 'readable') {
          var state = this._readableState;
          if (!state.endEmitted && !state.readableListening) {
              state.readableListening = state.needReadable = true;
              state.emittedReadable = false;
              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;
      state.awaitDrain = 0;
      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);
      while (state.flowing && stream.read() !== null) {
      }
  }
  
  // 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');
          if (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) {
          if (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.
  // This function is designed to be inlinable, so please take care when making
  // changes to the function body.
  function fromList(n, state) {
      // nothing buffered
      if (state.length === 0) return null;
  
      var ret;
      if (state.objectMode) ret = state.buffer.shift(); else if (!n || n >= state.length) {
          // read it all, truncate the list
          if (state.decoder) ret = state.buffer.join(''); else if (state.buffer.length === 1) ret = state.buffer.head.data; else ret = state.buffer.concat(state.length);
          state.buffer.clear();
      } else {
          // read part of list
          ret = fromListPartial(n, state.buffer, state.decoder);
      }
  
      return ret;
  }
  
  // Extracts only enough buffered data to satisfy the amount requested.
  // This function is designed to be inlinable, so please take care when making
  // changes to the function body.
  function fromListPartial(n, list, hasStrings) {
      var ret;
      if (n < list.head.data.length) {
          // slice is the same for buffers and strings
          ret = list.head.data.slice(0, n);
          list.head.data = list.head.data.slice(n);
      } else if (n === list.head.data.length) {
          // first chunk is a perfect match
          ret = list.shift();
      } else {
          // result spans more than one buffer
          ret = hasStrings ? copyFromBufferString(n, list) : copyFromBuffer(n, list);
      }
      return ret;
  }
  
  // Copies a specified amount of characters from the list of buffered data
  // chunks.
  // This function is designed to be inlinable, so please take care when making
  // changes to the function body.
  function copyFromBufferString(n, list) {
      var p = list.head;
      var c = 1;
      var ret = p.data;
      n -= ret.length;
      while (p = p.next) {
          var str = p.data;
          var nb = n > str.length ? str.length : n;
          if (nb === str.length) ret += str; else ret += str.slice(0, n);
          n -= nb;
          if (n === 0) {
              if (nb === str.length) {
                  ++c;
                  if (p.next) list.head = p.next; else list.head = list.tail = null;
              } else {
                  list.head = p;
                  p.data = str.slice(nb);
              }
              break;
          }
          ++c;
      }
      list.length -= c;
      return ret;
  }
  
  // Copies a specified amount of bytes from the list of buffered data chunks.
  // This function is designed to be inlinable, so please take care when making
  // changes to the function body.
  function copyFromBuffer(n, list) {
      var ret = bufferShim.allocUnsafe(n);
      var p = list.head;
      var c = 1;
      p.data.copy(ret);
      n -= p.data.length;
      while (p = p.next) {
          var buf = p.data;
          var nb = n > buf.length ? buf.length : n;
          buf.copy(ret, ret.length - n, 0, nb);
          n -= nb;
          if (n === 0) {
              if (nb === buf.length) {
                  ++c;
                  if (p.next) list.head = p.next; else list.head = list.tail = null;
              } else {
                  list.head = p;
                  p.data = buf.slice(nb);
              }
              break;
          }
          ++c;
      }
      list.length -= c;
      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.
      if (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;
  }