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_stream_readable.js
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_stream_readable.js
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			// Copyright Joyent, Inc. and other Node contributors.
			//
			// Permission is hereby granted, free of charge, to any person obtaining a
			// copy of this software and associated documentation files (the
			// "Software"), to deal in the Software without restriction, including
			// without limitation the rights to use, copy, modify, merge, publish,
			// distribute, sublicense, and/or sell copies of the Software, and to permit
			// persons to whom the Software is furnished to do so, subject to the
			// following conditions:
			//
			// The above copyright notice and this permission notice shall be included
			// in all copies or substantial portions of the Software.
			//
			// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
			// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
			// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN
			// NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
			// DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
			// OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE
			// USE OR OTHER DEALINGS IN THE SOFTWARE.
			'use strict';

			module.exports = Readable;
			/<replacement>/

			var Duplex;
			/</replacement>/

			Readable.ReadableState = ReadableState;
			/<replacement>/

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

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

			/<replacement>/


			var Stream = require('./internal/streams/stream');
			/</replacement>/


			var Buffer = require('buffer').Buffer;

			var OurUint8Array = global.Uint8Array \|\| function () {};

			function _uint8ArrayToBuffer(chunk) {
			return Buffer.from(chunk);
			}

			function _isUint8Array(obj) {
			return Buffer.isBuffer(obj) \|\| obj instanceof OurUint8Array;
			}
			/<replacement>/


			var debugUtil = require('util');

			var debug;

			if (debugUtil && debugUtil.debuglog) {
			debug = debugUtil.debuglog('stream');
			} else {
			debug = function debug() {};
			}
			/</replacement>/


			var BufferList = require('./internal/streams/buffer_list');

			var destroyImpl = require('./internal/streams/destroy');

			var _require = require('./internal/streams/state'),
			getHighWaterMark = _require.getHighWaterMark;

			var _require$codes = require('../errors').codes,
			ERR_INVALID_ARG_TYPE = _require$codes.ERR_INVALID_ARG_TYPE,
			ERR_STREAM_PUSH_AFTER_EOF = _require$codes.ERR_STREAM_PUSH_AFTER_EOF,
			ERR_METHOD_NOT_IMPLEMENTED = _require$codes.ERR_METHOD_NOT_IMPLEMENTED,
			ERR_STREAM_UNSHIFT_AFTER_END_EVENT = _require$codes.ERR_STREAM_UNSHIFT_AFTER_END_EVENT; // Lazy loaded to improve the startup performance.


			var StringDecoder;
			var createReadableStreamAsyncIterator;
			var from;

			require('inherits')(Readable, Stream);

			var errorOrDestroy = destroyImpl.errorOrDestroy;
			var kProxyEvents = ['error', 'close', 'destroy', 'pause', 'resume'];

			function prependListener(emitter, event, fn) {
			// Sadly this is not cacheable as some libraries bundle their own
			// event emitter implementation with them.
			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
			// 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 (Array.isArray(emitter._events[event])) emitter._events[event].unshift(fn);else emitter._events[event] = [fn, emitter._events[event]];
			}

			function ReadableState(options, stream, isDuplex) {
			Duplex = Duplex \|\| require('./_stream_duplex');
			options = options \|\| {}; // Duplex streams are both readable and writable, but share
			// the same options object.
			// However, some cases require setting options to different
			// values for the readable and the writable sides of the duplex stream.
			// These options can be provided separately as readableXXX and writableXXX.

			if (typeof isDuplex !== 'boolean') isDuplex = stream instanceof Duplex; // 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 (isDuplex) 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"

			this.highWaterMark = getHighWaterMark(this, options, 'readableHighWaterMark', isDuplex); // 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 event 'readable'/'data' is emitted
			// 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 read 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;
			this.paused = true; // Should close be emitted on destroy. Defaults to true.

			this.emitClose = options.emitClose !== false; // Should .destroy() be called after 'end' (and potentially 'finish')

			this.autoDestroy = !!options.autoDestroy; // has it been destroyed

			this.destroyed = 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'; // 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;
			}
			}

			function Readable(options) {
			Duplex = Duplex \|\| require('./_stream_duplex');
			if (!(this instanceof Readable)) return new Readable(options); // Checking for a Stream.Duplex instance is faster here instead of inside
			// the ReadableState constructor, at least with V8 6.5

			var isDuplex = this instanceof Duplex;
			this._readableState = new ReadableState(options, this, isDuplex); // legacy

			this.readable = true;

			if (options) {
			if (typeof options.read === 'function') this._read = options.read;
			if (typeof options.destroy === 'function') this._destroy = options.destroy;
			}

			Stream.call(this);
			}

			Object.defineProperty(Readable.prototype, 'destroyed', {
			// making it explicit this property is not enumerable
			// because otherwise some prototype manipulation in
			// userland will fail
			enumerable: false,
			get: function get() {
			if (this._readableState === undefined) {
			return false;
			}

			return this._readableState.destroyed;
			},
			set: function set(value) {
			// we ignore the value if the stream
			// has not been initialized yet
			if (!this._readableState) {
			return;
			} // backward compatibility, the user is explicitly
			// managing destroyed


			this._readableState.destroyed = value;
			}
			});
			Readable.prototype.destroy = destroyImpl.destroy;
			Readable.prototype._undestroy = destroyImpl.undestroy;

			Readable.prototype._destroy = function (err, cb) {
			cb(err);
			}; // 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;
			var skipChunkCheck;

			if (!state.objectMode) {
			if (typeof chunk === 'string') {
			encoding = encoding \|\| state.defaultEncoding;

			if (encoding !== state.encoding) {
			chunk = Buffer.from(chunk, encoding);
			encoding = '';
			}

			skipChunkCheck = true;
			}
			} else {
			skipChunkCheck = true;
			}

			return readableAddChunk(this, chunk, encoding, false, skipChunkCheck);
			}; // Unshift should always be something directly out of read()


			Readable.prototype.unshift = function (chunk) {
			return readableAddChunk(this, chunk, null, true, false);
			};

			function readableAddChunk(stream, chunk, encoding, addToFront, skipChunkCheck) {
			debug('readableAddChunk', chunk);
			var state = stream._readableState;

			if (chunk === null) {
			state.reading = false;
			onEofChunk(stream, state);
			} else {
			var er;
			if (!skipChunkCheck) er = chunkInvalid(state, chunk);

			if (er) {
			errorOrDestroy(stream, er);
			} else if (state.objectMode \|\| chunk && chunk.length > 0) {
			if (typeof chunk !== 'string' && !state.objectMode && Object.getPrototypeOf(chunk) !== Buffer.prototype) {
			chunk = _uint8ArrayToBuffer(chunk);
			}

			if (addToFront) {
			if (state.endEmitted) errorOrDestroy(stream, new ERR_STREAM_UNSHIFT_AFTER_END_EVENT());else addChunk(stream, state, chunk, true);
			} else if (state.ended) {
			errorOrDestroy(stream, new ERR_STREAM_PUSH_AFTER_EOF());
			} else if (state.destroyed) {
			return false;
			} else {
			state.reading = false;

			if (state.decoder && !encoding) {
			chunk = state.decoder.write(chunk);
			if (state.objectMode \|\| chunk.length !== 0) addChunk(stream, state, chunk, false);else maybeReadMore(stream, state);
			} else {
			addChunk(stream, state, chunk, false);
			}
			}
			} else if (!addToFront) {
			state.reading = false;
			maybeReadMore(stream, state);
			}
			} // We can push more data if we are below the highWaterMark.
			// 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.


			return !state.ended && (state.length < state.highWaterMark \|\| state.length === 0);
			}

			function addChunk(stream, state, chunk, addToFront) {
			if (state.flowing && state.length === 0 && !state.sync) {
			state.awaitDrain = 0;
			stream.emit('data', chunk);
			} 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);
			}

			function chunkInvalid(state, chunk) {
			var er;

			if (!_isUint8Array(chunk) && typeof chunk !== 'string' && chunk !== undefined && !state.objectMode) {
			er = new ERR_INVALID_ARG_TYPE('chunk', ['string', 'Buffer', 'Uint8Array'], chunk);
			}

			return er;
			}

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


			Readable.prototype.setEncoding = function (enc) {
			if (!StringDecoder) StringDecoder = require('string_decoder/').StringDecoder;
			var decoder = new StringDecoder(enc);
			this._readableState.decoder = decoder; // If setEncoding(null), decoder.encoding equals utf8

			this._readableState.encoding = this._readableState.decoder.encoding; // Iterate over current buffer to convert already stored Buffers:

			var p = this._readableState.buffer.head;
			var content = '';

			while (p !== null) {
			content += decoder.write(p.data);
			p = p.next;
			}

			this._readableState.buffer.clear();

			if (content !== '') this._readableState.buffer.push(content);
			this._readableState.length = content.length;
			return this;
			}; // Don't raise the hwm > 1GB


			var MAX_HWM = 0x40000000;

			function computeNewHighWaterMark(n) {
			if (n >= MAX_HWM) {
			// TODO(ronag): Throw ERR_VALUE_OUT_OF_RANGE.
			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.highWaterMark !== 0 ? state.length >= state.highWaterMark : state.length > 0) \|\| 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 = state.length <= state.highWaterMark;
			n = 0;
			} else {
			state.length -= n;
			state.awaitDrain = 0;
			}

			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 onEofChunk(stream, state) {
			debug('onEofChunk');
			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;

			if (state.sync) {
			// if we are sync, wait until next tick to emit the data.
			// Otherwise we risk emitting data in the flow()
			// the readable code triggers during a read() call
			emitReadable(stream);
			} else {
			// emit 'readable' now to make sure it gets picked up.
			state.needReadable = false;

			if (!state.emittedReadable) {
			state.emittedReadable = true;
			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;
			debug('emitReadable', state.needReadable, state.emittedReadable);
			state.needReadable = false;

			if (!state.emittedReadable) {
			debug('emitReadable', state.flowing);
			state.emittedReadable = true;
			process.nextTick(emitReadable_, stream);
			}
			}

			function emitReadable_(stream) {
			var state = stream._readableState;
			debug('emitReadable_', state.destroyed, state.length, state.ended);

			if (!state.destroyed && (state.length \|\| state.ended)) {
			stream.emit('readable');
			state.emittedReadable = false;
			} // The stream needs another readable event if
			// 1. It is not flowing, as the flow mechanism will take
			// care of it.
			// 2. It is not ended.
			// 3. It is below the highWaterMark, so we can schedule
			// another readable later.


			state.needReadable = !state.flowing && !state.ended && state.length <= state.highWaterMark;
			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;
			process.nextTick(maybeReadMore_, stream, state);
			}
			}

			function maybeReadMore_(stream, state) {
			// Attempt to read more data if we should.
			//
			// The conditions for reading more data are (one of):
			// - Not enough data buffered (state.length < state.highWaterMark). The loop
			// is responsible for filling the buffer with enough data if such data
			// is available. If highWaterMark is 0 and we are not in the flowing mode
			// we should _not_ attempt to buffer any extra data. We'll get more data
			// when the stream consumer calls read() instead.
			// - No data in the buffer, and the stream is in flowing mode. In this mode
			// the loop below is responsible for ensuring read() is called. Failing to
			// call read here would abort the flow and there's no other mechanism for
			// continuing the flow if the stream consumer has just subscribed to the
			// 'data' event.
			//
			// In addition to the above conditions to keep reading data, the following
			// conditions prevent the data from being read:
			// - The stream has ended (state.ended).
			// - There is already a pending 'read' operation (state.reading). This is a
			// case where the the stream has called the implementation defined _read()
			// method, but they are processing the call asynchronously and have _not_
			// called push() with new data. In this case we skip performing more
			// read()s. The execution ends in this method again after the _read() ends
			// up calling push() with more data.
			while (!state.reading && !state.ended && (state.length < state.highWaterMark \|\| state.flowing && state.length === 0)) {
			var len = state.length;
			debug('maybeReadMore read 0');
			stream.read(0);
			if (len === state.length) // didn't get any data, stop spinning.
			break;
			}

			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) {
			errorOrDestroy(this, new ERR_METHOD_NOT_IMPLEMENTED('_read()'));
			};

			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 : unpipe;
			if (state.endEmitted) process.nextTick(endFn);else src.once('end', endFn);
			dest.on('unpipe', onunpipe);

			function onunpipe(readable, unpipeInfo) {
			debug('onunpipe');

			if (readable === src) {
			if (unpipeInfo && unpipeInfo.hasUnpiped === false) {
			unpipeInfo.hasUnpiped = true;
			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', unpipe);
			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);
			debug('dest.write', ret);

			if (ret === false) {
			// 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', state.awaitDrain);
			state.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) errorOrDestroy(dest, 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 pipeOnDrainFunctionResult() {
			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;
			var unpipeInfo = {
			hasUnpiped: false
			}; // 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, unpipeInfo);
			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, {
			hasUnpiped: false
			});
			}

			return this;
			} // try to find the right one.


			var index = indexOf(state.pipes, dest);
			if (index === -1) return this;
			state.pipes.splice(index, 1);
			state.pipesCount -= 1;
			if (state.pipesCount === 1) state.pipes = state.pipes[0];
			dest.emit('unpipe', this, unpipeInfo);
			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);
			var state = this._readableState;

			if (ev === 'data') {
			// update readableListening so that resume() may be a no-op
			// a few lines down. This is needed to support once('readable').
			state.readableListening = this.listenerCount('readable') > 0; // Try start flowing on next tick if stream isn't explicitly paused

			if (state.flowing !== false) this.resume();
			} else if (ev === 'readable') {
			if (!state.endEmitted && !state.readableListening) {
			state.readableListening = state.needReadable = true;
			state.flowing = false;
			state.emittedReadable = false;
			debug('on readable', state.length, state.reading);

			if (state.length) {
			emitReadable(this);
			} else if (!state.reading) {
			process.nextTick(nReadingNextTick, this);
			}
			}
			}

			return res;
			};

			Readable.prototype.addListener = Readable.prototype.on;

			Readable.prototype.removeListener = function (ev, fn) {
			var res = Stream.prototype.removeListener.call(this, ev, fn);

			if (ev === 'readable') {
			// We need to check if there is someone still listening to
			// readable and reset the state. However this needs to happen
			// after readable has been emitted but before I/O (nextTick) to
			// support once('readable', fn) cycles. This means that calling
			// resume within the same tick will have no
			// effect.
			process.nextTick(updateReadableListening, this);
			}

			return res;
			};

			Readable.prototype.removeAllListeners = function (ev) {
			var res = Stream.prototype.removeAllListeners.apply(this, arguments);

			if (ev === 'readable' \|\| ev === undefined) {
			// We need to check if there is someone still listening to
			// readable and reset the state. However this needs to happen
			// after readable has been emitted but before I/O (nextTick) to
			// support once('readable', fn) cycles. This means that calling
			// resume within the same tick will have no
			// effect.
			process.nextTick(updateReadableListening, this);
			}

			return res;
			};

			function updateReadableListening(self) {
			var state = self._readableState;
			state.readableListening = self.listenerCount('readable') > 0;

			if (state.resumeScheduled && !state.paused) {
			// flowing needs to be set to true now, otherwise
			// the upcoming resume will not flow.
			state.flowing = true; // crude way to check if we should resume
			} else if (self.listenerCount('data') > 0) {
			self.resume();
			}
			}

			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'); // we flow only if there is no one listening
			// for readable, but we still have to call
			// resume()

			state.flowing = !state.readableListening;
			resume(this, state);
			}

			state.paused = false;
			return this;
			};

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

			function resume_(stream, state) {
			debug('resume', state.reading);

			if (!state.reading) {
			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 (this._readableState.flowing !== false) {
			debug('pause');
			this._readableState.flowing = false;
			this.emit('pause');
			}

			this._readableState.paused = true;
			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 _this = this;

			var state = this._readableState;
			var paused = false;
			stream.on('end', function () {
			debug('wrapped end');

			if (state.decoder && !state.ended) {
			var chunk = state.decoder.end();
			if (chunk && chunk.length) _this.push(chunk);
			}

			_this.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 = _this.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 methodWrap(method) {
			return function methodWrapReturnFunction() {
			return stream[method].apply(stream, arguments);
			};
			}(i);
			}
			} // proxy certain important events.


			for (var n = 0; n < kProxyEvents.length; n++) {
			stream.on(kProxyEvents[n], this.emit.bind(this, kProxyEvents[n]));
			} // when we try to consume some more bytes, simply unpause the
			// underlying stream.


			this._read = function (n) {
			debug('wrapped _read', n);

			if (paused) {
			paused = false;
			stream.resume();
			}
			};

			return this;
			};

			if (typeof Symbol === 'function') {
			Readable.prototype[Symbol.asyncIterator] = function () {
			if (createReadableStreamAsyncIterator === undefined) {
			createReadableStreamAsyncIterator = require('./internal/streams/async_iterator');
			}

			return createReadableStreamAsyncIterator(this);
			};
			}

			Object.defineProperty(Readable.prototype, 'readableHighWaterMark', {
			// making it explicit this property is not enumerable
			// because otherwise some prototype manipulation in
			// userland will fail
			enumerable: false,
			get: function get() {
			return this._readableState.highWaterMark;
			}
			});
			Object.defineProperty(Readable.prototype, 'readableBuffer', {
			// making it explicit this property is not enumerable
			// because otherwise some prototype manipulation in
			// userland will fail
			enumerable: false,
			get: function get() {
			return this._readableState && this._readableState.buffer;
			}
			});
			Object.defineProperty(Readable.prototype, 'readableFlowing', {
			// making it explicit this property is not enumerable
			// because otherwise some prototype manipulation in
			// userland will fail
			enumerable: false,
			get: function get() {
			return this._readableState.flowing;
			},
			set: function set(state) {
			if (this._readableState) {
			this._readableState.flowing = state;
			}
			}
			}); // exposed for testing purposes only.

			Readable._fromList = fromList;
			Object.defineProperty(Readable.prototype, 'readableLength', {
			// making it explicit this property is not enumerable
			// because otherwise some prototype manipulation in
			// userland will fail
			enumerable: false,
			get: function get() {
			return this._readableState.length;
			}
			}); // 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.first();else ret = state.buffer.concat(state.length);
			state.buffer.clear();
			} else {
			// read part of list
			ret = state.buffer.consume(n, state.decoder);
			}
			return ret;
			}

			function endReadable(stream) {
			var state = stream._readableState;
			debug('endReadable', state.endEmitted);

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

			function endReadableNT(state, stream) {
			debug('endReadableNT', state.endEmitted, state.length); // Check that we didn't get one last unshift.

			if (!state.endEmitted && state.length === 0) {
			state.endEmitted = true;
			stream.readable = false;
			stream.emit('end');

			if (state.autoDestroy) {
			// In case of duplex streams we need a way to detect
			// if the writable side is ready for autoDestroy as well
			var wState = stream._writableState;

			if (!wState \|\| wState.autoDestroy && wState.finished) {
			stream.destroy();
			}
			}
			}
			}

			if (typeof Symbol === 'function') {
			Readable.from = function (iterable, opts) {
			if (from === undefined) {
			from = require('./internal/streams/from');
			}

			return from(Readable, iterable, opts);
			};
			}

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

			return -1;
			}

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rOACCT/node_modules/readable-stream/lib/_stream_readable.js
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