0
0
mirror of https://github.com/nodejs/node.git synced 2024-11-30 15:30:56 +01:00
nodejs/lib/_stream_writable.js
isaacs 049903e333 stream: Split Writable logic into small functions
1. Get rid of unnecessary 'finishing' flag
2. Dont check both ending and ended. Extraneous.

Also: Remove extraneous 'finishing' flag, and don't check both 'ending'
and 'ended', since checking just 'ending' is sufficient.
2013-03-05 14:26:34 -08:00

354 lines
9.8 KiB
JavaScript

// 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.
// A bit simpler than readable streams.
// Implement an async ._write(chunk, cb), and it'll handle all
// the drain event emission and buffering.
module.exports = Writable;
Writable.WritableState = WritableState;
var util = require('util');
var assert = require('assert');
var Stream = require('stream');
util.inherits(Writable, Stream);
function WritableState(options, stream) {
options = options || {};
// the point at which write() starts returning false
// Note: 0 is a valid value, means that we always return false if
// the entire buffer is not flushed immediately on write()
var hwm = options.highWaterMark;
this.highWaterMark = (hwm || hwm === 0) ? hwm : 16 * 1024;
// object stream flag to indicate whether or not this stream
// contains buffers or objects.
this.objectMode = !!options.objectMode;
// cast to ints.
this.highWaterMark = ~~this.highWaterMark;
this.needDrain = false;
// at the start of calling end()
this.ending = false;
// when end() has been called, and returned
this.ended = false;
// when 'finish' is emitted
this.finished = false;
// should we decode strings into buffers before passing to _write?
// this is here so that some node-core streams can optimize string
// handling at a lower level.
var noDecode = options.decodeStrings === false;
this.decodeStrings = !noDecode;
// not an actual buffer we keep track of, but a measurement
// of how much we're waiting to get pushed to some underlying
// socket or file.
this.length = 0;
// a flag to see when we're in the middle of a write.
this.writing = 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, becuase any
// actions that shouldn't happen until "later" should generally also
// not happen before the first write call.
this.sync = true;
// a flag to know if we're processing previously buffered items, which
// may call the _write() callback in the same tick, so that we don't
// end up in an overlapped onwrite situation.
this.bufferProcessing = false;
// the callback that's passed to _write(chunk,cb)
this.onwrite = function(er) {
onwrite(stream, er);
};
// the callback that the user supplies to write(chunk,encoding,cb)
this.writecb = null;
// the amount that is being written when _write is called.
this.writelen = 0;
this.buffer = [];
}
function Writable(options) {
// Writable ctor is applied to Duplexes, though they're not
// instanceof Writable, they're instanceof Readable.
if (!(this instanceof Writable) && !(this instanceof Stream.Duplex))
return new Writable(options);
this._writableState = new WritableState(options, this);
// legacy.
this.writable = true;
Stream.call(this);
}
// Otherwise people can pipe Writable streams, which is just wrong.
Writable.prototype.pipe = function() {
this.emit('error', new Error('Cannot pipe. Not readable.'));
};
function writeAfterEnd(stream, state, cb) {
var er = new Error('write after end');
// TODO: defer error events consistently everywhere, not just the cb
stream.emit('error', er);
process.nextTick(function() {
cb(er);
});
}
// If we get something that is not a buffer, string, null, or undefined,
// and we're not in objectMode, then that's an error.
// Otherwise stream chunks are all considered to be of length=1, and the
// watermarks determine how many objects to keep in the buffer, rather than
// how many bytes or characters.
function validChunk(stream, state, chunk, cb) {
var valid = true;
if (!Buffer.isBuffer(chunk) &&
'string' !== typeof chunk &&
chunk !== null &&
chunk !== undefined &&
!state.objectMode) {
var er = new TypeError('Invalid non-string/buffer chunk');
stream.emit('error', er);
process.nextTick(function() {
cb(er);
});
valid = false;
}
return valid;
}
function decodeChunk(state, chunk, encoding) {
if (!state.objectMode &&
state.decodeStrings !== false &&
typeof chunk === 'string') {
chunk = new Buffer(chunk, encoding);
}
return chunk;
}
Writable.prototype.write = function(chunk, encoding, cb) {
var state = this._writableState;
var ret = false;
if (typeof encoding === 'function') {
cb = encoding;
encoding = null;
}
if (!encoding)
encoding = 'utf8';
if (typeof cb !== 'function')
cb = function() {};
if (state.ended)
writeAfterEnd(this, state, cb);
else if (validChunk(this, state, chunk, cb))
ret = writeOrBuffer(this, state, chunk, encoding, cb);
return ret;
};
// if we're already writing something, then just put this
// in the queue, and wait our turn. Otherwise, call _write
// If we return false, then we need a drain event, so set that flag.
function writeOrBuffer(stream, state, chunk, encoding, cb) {
chunk = decodeChunk(state, chunk, encoding);
var len = state.objectMode ? 1 : chunk.length;
// XXX Remove. _write() should take an encoding.
if (state.decodeStrings === false)
chunk = [chunk, encoding];
state.length += len;
var ret = state.length < state.highWaterMark;
state.needDrain = !ret;
if (state.writing)
state.buffer.push([chunk, cb]); // XXX [chunk,encoding,cb]
else
doWrite(stream, state, len, chunk, encoding, cb);
return ret;
}
function doWrite(stream, state, len, chunk, encoding, cb) {
state.writelen = len;
state.writecb = cb;
state.writing = true;
state.sync = true;
// XXX stream._write(chunk, encoding, state.onwrite)
stream._write(chunk, state.onwrite);
state.sync = false;
}
function onwriteError(stream, state, sync, er, cb) {
if (sync)
process.nextTick(function() {
cb(er);
});
else
cb(er);
stream.emit('error', er);
}
function onwriteStateUpdate(state) {
state.writing = false;
state.writecb = null;
state.length -= state.writelen;
state.writelen = 0;
}
function onwrite(stream, er) {
var state = stream._writableState;
var sync = state.sync;
var cb = state.writecb;
onwriteStateUpdate(state);
if (er)
onwriteError(stream, state, sync, er, cb);
else {
if (!finishMaybe(stream, state)) {
if (state.length === 0 && state.needDrain)
onwriteDrain(stream, state);
if (!state.bufferProcessing && state.buffer.length)
clearBuffer(stream, state);
}
if (sync)
process.nextTick(cb);
else
cb();
}
}
// Must force callback to be called on nextTick, so that we don't
// emit 'drain' before the write() consumer gets the 'false' return
// value, and has a chance to attach a 'drain' listener.
function onwriteDrain(stream, state) {
process.nextTick(function() {
if (state.needDrain) {
state.needDrain = false;
stream.emit('drain');
}
});
}
// if there's something in the buffer waiting, then process it
function clearBuffer(stream, state) {
state.bufferProcessing = true;
// XXX buffer entry should be [chunk, encoding, cb]
for (var c = 0; c < state.buffer.length; c++) {
var chunkCb = state.buffer[c];
var chunk = chunkCb[0];
var cb = chunkCb[1];
var encoding = '';
var len;
if (state.objectMode)
len = 1;
else if (false === state.decodeStrings) {
len = chunk[0].length;
encoding = chunk[1];
} else
len = chunk.length;
doWrite(stream, state, len, chunk, encoding, cb);
// if we didn't call the onwrite immediately, then
// it means that we need to wait until it does.
// also, that means that the chunk and cb are currently
// being processed, so move the buffer counter past them.
if (state.writing) {
c++;
break;
}
}
state.bufferProcessing = false;
if (c < state.buffer.length)
state.buffer = state.buffer.slice(c);
else
state.buffer.length = 0;
}
Writable.prototype._write = function(chunk, cb) {
process.nextTick(function() {
cb(new Error('not implemented'));
});
};
Writable.prototype.end = function(chunk, encoding, cb) {
var state = this._writableState;
if (typeof chunk === 'function') {
cb = chunk;
chunk = null;
encoding = null;
} else if (typeof encoding === 'function') {
cb = encoding;
encoding = null;
}
if (typeof chunk !== 'undefined' && chunk !== null)
this.write(chunk, encoding);
// ignore unnecessary end() calls.
if (!state.ending && !state.finished)
endWritable(this, state, cb);
};
function finishMaybe(stream, state) {
if (state.ending && state.length === 0 && !state.finished) {
state.finished = true;
stream.emit('finish');
}
return state.finished;
}
function endWritable(stream, state, cb) {
state.ending = true;
finishMaybe(stream, state);
if (cb) {
if (state.finished)
process.nextTick(cb);
else
stream.once('finish', cb);
}
state.ended = true;
}