lib/_stream_readable.js
// 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;
Readable.ReadableState = ReadableState;
var EE = require('events').EventEmitter;
var Stream = require('stream');
var Buffer = require('buffer').Buffer;
var util = require('util');
var StringDecoder;
var debug = util.debuglog('stream');
util.inherits(Readable, Stream);
function ReadableState(options, stream) {
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 Stream.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;
// 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;
}
}
function Readable(options) {
if (!(this instanceof Readable))
return new Readable(options);
this._readableState = new ReadableState(options, this);
// legacy
this.readable = true;
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 (util.isString(chunk) && !state.objectMode) {
encoding = encoding || state.defaultEncoding;
if (encoding !== state.encoding) {
chunk = new Buffer(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 {
if (state.decoder && !addToFront && !encoding)
chunk = state.decoder.write(chunk);
if (!addToFront)
state.reading = false;
// 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 > 128MB
var MAX_HWM = 0x800000;
function roundUpToNextPowerOf2(n) {
if (n >= MAX_HWM) {
n = MAX_HWM;
} else {
// Get the next highest power of 2
n--;
for (var p = 1; p < 32; p <<= 1) n |= n >> p;
n++;
}
return n;
}
function howMuchToRead(n, state) {
if (state.length === 0 && state.ended)
return 0;
if (state.objectMode)
return n === 0 ? 0 : 1;
if (util.isNull(n) || 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 = roundUpToNextPowerOf2(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 (!util.isNumber(n) || 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 (util.isNull(ret)) {
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 (!util.isNull(ret))
this.emit('data', ret);
return ret;
};
function chunkInvalid(state, chunk) {
var er = null;
if (!util.isBuffer(chunk) &&
!util.isString(chunk) &&
!util.isNullOrUndefined(chunk) &&
!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)
process.nextTick(function() {
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;
process.nextTick(function() {
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)
process.nextTick(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);
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);
// 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) {
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 (EE.listenerCount(dest, 'error') === 0)
dest.emit('error', er);
}
// This is a brutally ugly hack to make sure that our error handler
// is attached before any userland ones. NEVER DO THIS.
if (!dest._events || !dest._events.error)
dest.on('error', onerror);
else if (Array.isArray(dest._events.error))
dest._events.error.unshift(onerror);
else
dest._events.error = [onerror, dest._events.error];
// 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 && EE.listenerCount(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 = state.pipes.indexOf(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.readable) {
var state = this._readableState;
if (!state.readableListening) {
state.readableListening = true;
state.emittedReadable = false;
state.needReadable = true;
if (!state.reading) {
var self = this;
process.nextTick(function() {
debug('readable nexttick read 0');
self.read(0);
});
} else if (state.length) {
emitReadable(this, state);
}
}
}
return res;
};
Readable.prototype.addListener = Readable.prototype.on;
// 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;
process.nextTick(function() {
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');
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 && util.isNullOrUndefined(chunk))
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 (util.isFunction(stream[i]) && util.isUndefined(this[i])) {
this[i] = function(method) { return function() {
return stream[method].apply(stream, arguments);
}}(i);
}
}
// proxy certain important events.
var events = ['error', 'close', 'destroy', 'pause', 'resume'];
events.forEach(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;
if (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
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 = new Buffer(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.
if (state.length > 0)
throw new Error('endReadable called on non-empty stream');
if (!state.endEmitted) {
state.ended = true;
process.nextTick(function() {
// Check that we didn't get one last unshift.
if (!state.endEmitted && state.length === 0) {
state.endEmitted = true;
stream.readable = false;
stream.emit('end');
}
});
}
}