text: // 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;
  
  /*<replacement>*/
  var Buffer = require('buffer').Buffer;
  /*</replacement>*/
  
  Writable.WritableState = WritableState;
  
  
  /*<replacement>*/
  var util = require('core-util-is');
  util.inherits = require('inherits');
  /*</replacement>*/
  
  var Stream = require('stream');
  
  util.inherits(Writable, Stream);
  
  function WriteReq(chunk, encoding, cb) {
    this.chunk = chunk;
    this.encoding = encoding;
    this.callback = cb;
  }
  
  function WritableState(options, stream) {
    var Duplex = require('./_stream_duplex');
  
    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;
    var defaultHwm = options.objectMode ? 16 : 16 * 1024;
    this.highWaterMark = (hwm || hwm === 0) ? hwm : defaultHwm;
  
    // object stream flag to indicate whether or not this stream
    // contains buffers or objects.
    this.objectMode = !!options.objectMode;
  
    if (stream instanceof Duplex)
      this.objectMode = this.objectMode || !!options.writableObjectMode;
  
    // 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;
  
    // 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';
  
    // 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;
  
    // when true all writes will be buffered until .uncork() call
    this.corked = 0;
  
    // 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;
  
    // 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 = [];
  
    // number of pending user-supplied write callbacks
    // this must be 0 before 'finish' can be emitted
    this.pendingcb = 0;
  
    // emit prefinish if the only thing we're waiting for is _write cbs
    // This is relevant for synchronous Transform streams
    this.prefinished = false;
  
    // True if the error was already emitted and should not be thrown again
    this.errorEmitted = false;
  }
  
  function Writable(options) {
    var Duplex = require('./_stream_duplex');
  
    // Writable ctor is applied to Duplexes, though they're not
    // instanceof Writable, they're instanceof Readable.
    if (!(this instanceof Writable) && !(this instanceof 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 (!util.isBuffer(chunk) &&
        !util.isString(chunk) &&
        !util.isNullOrUndefined(chunk) &&
        !state.objectMode) {
      var er = new TypeError('Invalid non-string/buffer chunk');
      stream.emit('error', er);
      process.nextTick(function() {
        cb(er);
      });
      valid = false;
    }
    return valid;
  }
  
  Writable.prototype.write = function(chunk, encoding, cb) {
    var state = this._writableState;
    var ret = false;
  
    if (util.isFunction(encoding)) {
      cb = encoding;
      encoding = null;
    }
  
    if (util.isBuffer(chunk))
      encoding = 'buffer';
    else if (!encoding)
      encoding = state.defaultEncoding;
  
    if (!util.isFunction(cb))
      cb = function() {};
  
    if (state.ended)
      writeAfterEnd(this, state, cb);
    else if (validChunk(this, state, chunk, cb)) {
      state.pendingcb++;
      ret = writeOrBuffer(this, state, chunk, encoding, cb);
    }
  
    return ret;
  };
  
  Writable.prototype.cork = function() {
    var state = this._writableState;
  
    state.corked++;
  };
  
  Writable.prototype.uncork = function() {
    var state = this._writableState;
  
    if (state.corked) {
      state.corked--;
  
      if (!state.writing &&
          !state.corked &&
          !state.finished &&
          !state.bufferProcessing &&
          state.buffer.length)
        clearBuffer(this, state);
    }
  };
  
  function decodeChunk(state, chunk, encoding) {
    if (!state.objectMode &&
        state.decodeStrings !== false &&
        util.isString(chunk)) {
      chunk = new Buffer(chunk, encoding);
    }
    return chunk;
  }
  
  // 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);
    if (util.isBuffer(chunk))
      encoding = 'buffer';
    var len = state.objectMode ? 1 : chunk.length;
  
    state.length += len;
  
    var ret = state.length < state.highWaterMark;
    // we must ensure that previous needDrain will not be reset to false.
    if (!ret)
      state.needDrain = true;
  
    if (state.writing || state.corked)
      state.buffer.push(new WriteReq(chunk, encoding, cb));
    else
      doWrite(stream, state, false, len, chunk, encoding, cb);
  
    return ret;
  }
  
  function doWrite(stream, state, writev, len, chunk, encoding, cb) {
    state.writelen = len;
    state.writecb = cb;
    state.writing = true;
    state.sync = true;
    if (writev)
      stream._writev(chunk, state.onwrite);
    else
      stream._write(chunk, encoding, state.onwrite);
    state.sync = false;
  }
  
  function onwriteError(stream, state, sync, er, cb) {
    if (sync)
      process.nextTick(function() {
        state.pendingcb--;
        cb(er);
      });
    else {
      state.pendingcb--;
      cb(er);
    }
  
    stream._writableState.errorEmitted = true;
    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 {
      // Check if we're actually ready to finish, but don't emit yet
      var finished = needFinish(stream, state);
  
      if (!finished &&
          !state.corked &&
          !state.bufferProcessing &&
          state.buffer.length) {
        clearBuffer(stream, state);
      }
  
      if (sync) {
        process.nextTick(function() {
          afterWrite(stream, state, finished, cb);
        });
      } else {
        afterWrite(stream, state, finished, cb);
      }
    }
  }
  
  function afterWrite(stream, state, finished, cb) {
    if (!finished)
      onwriteDrain(stream, state);
    state.pendingcb--;
    cb();
    finishMaybe(stream, state);
  }
  
  // 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) {
    if (state.length === 0 && 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;
  
    if (stream._writev && state.buffer.length > 1) {
      // Fast case, write everything using _writev()
      var cbs = [];
      for (var c = 0; c < state.buffer.length; c++)
        cbs.push(state.buffer[c].callback);
  
      // count the one we are adding, as well.
      // TODO(isaacs) clean this up
      state.pendingcb++;
      doWrite(stream, state, true, state.length, state.buffer, '', function(err) {
        for (var i = 0; i < cbs.length; i++) {
          state.pendingcb--;
          cbs[i](err);
        }
      });
  
      // Clear buffer
      state.buffer = [];
    } else {
      // Slow case, write chunks one-by-one
      for (var c = 0; c < state.buffer.length; c++) {
        var entry = state.buffer[c];
        var chunk = entry.chunk;
        var encoding = entry.encoding;
        var cb = entry.callback;
        var len = state.objectMode ? 1 : chunk.length;
  
        doWrite(stream, state, false, 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;
        }
      }
  
      if (c < state.buffer.length)
        state.buffer = state.buffer.slice(c);
      else
        state.buffer.length = 0;
    }
  
    state.bufferProcessing = false;
  }
  
  Writable.prototype._write = function(chunk, encoding, cb) {
    cb(new Error('not implemented'));
  
  };
  
  Writable.prototype._writev = null;
  
  Writable.prototype.end = function(chunk, encoding, cb) {
    var state = this._writableState;
  
    if (util.isFunction(chunk)) {
      cb = chunk;
      chunk = null;
      encoding = null;
    } else if (util.isFunction(encoding)) {
      cb = encoding;
      encoding = null;
    }
  
    if (!util.isNullOrUndefined(chunk))
      this.write(chunk, encoding);
  
    // .end() fully uncorks
    if (state.corked) {
      state.corked = 1;
      this.uncork();
    }
  
    // ignore unnecessary end() calls.
    if (!state.ending && !state.finished)
      endWritable(this, state, cb);
  };
  
  
  function needFinish(stream, state) {
    return (state.ending &&
            state.length === 0 &&
            !state.finished &&
            !state.writing);
  }
  
  function prefinish(stream, state) {
    if (!state.prefinished) {
      state.prefinished = true;
      stream.emit('prefinish');
    }
  }
  
  function finishMaybe(stream, state) {
    var need = needFinish(stream, state);
    if (need) {
      if (state.pendingcb === 0) {
        prefinish(stream, state);
        state.finished = true;
        stream.emit('finish');
      } else
        prefinish(stream, state);
    }
    return need;
  }
  
  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;
  }
  