# all files / lib/ _stream_writable.js

95.52% Statements 277/290
94% Branches 141/150
90.91% Functions 30/33
96.58% Lines 254/263

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     // A bit simpler than readable streams.
    // Implement an async ._write(chunk, encoding, cb), and it'll handle all
    // the drain event emission and buffering.

    'use strict';

    module.exports = Writable;

    /*<replacement>*/
    var processNextTick = require('process-nextick-args');
    /*</replacement>*/

    /*<replacement>*/
    var asyncWrite = !process.browser && ['v0.10', 'v0.9.'].indexOf(process.version.slice(0, 5)) > -1 ? setImmediate : processNextTick;
    /*</replacement>*/

    Writable.WritableState = WritableState;

    /*<replacement>*/
    var util = require('core-util-is');
    util.inherits = require('inherits');
    /*</replacement>*/

    /*<replacement>*/
    var internalUtil = {
      deprecate: require('util-deprecate')
    };
    /*</replacement>*/

    /*<replacement>*/
    var Stream;
    (function () {
      try {
        Stream = require('st' + 'ream');
      } catch (_) {} finally {
        Iif (!Stream) Stream = require('events').EventEmitter;
      }
    })();
    /*</replacement>*/

    var Buffer = require('buffer').Buffer;
    /*<replacement>*/
    var bufferShim = require('buffer-shims');
    /*</replacement>*/

    util.inherits(Writable, Stream);

    function nop() {}

    function WriteReq(chunk, encoding, cb) {
      this.chunk = chunk;
      this.encoding = encoding;
      this.callback = cb;
      this.next = null;
    }

    var Duplex;
    function WritableState(options, stream) {
      Duplex = Duplex || require('./_stream_duplex');

      options = options || {};

      // 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;

      // 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 = this.objectMode ? 16 : 16 * 1024;
      this.highWaterMark = hwm || hwm === 0 ? hwm : defaultHwm;

      // 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.bufferedRequest = null;
      this.lastBufferedRequest = null;

      // 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;

      // count buffered requests
      this.bufferedRequestCount = 0;

      // allocate the first CorkedRequest, there is always
      // one allocated and free to use, and we maintain at most two
      this.corkedRequestsFree = new CorkedRequest(this);
    }

    WritableState.prototype.getBuffer = function writableStateGetBuffer() {
      var current = this.bufferedRequest;
      var out = [];
      while (current) {
        out.push(current);
        current = current.next;
      }
      return out;
    };

    (function () {
      try {
        Object.defineProperty(WritableState.prototype, 'buffer', {
          get: internalUtil.deprecate(function () {
            return this.getBuffer();
          }, '_writableState.buffer is deprecated. Use _writableState.getBuffer ' + 'instead.')
        });
      } catch (_) {}
    })();

    var Duplex;
    function Writable(options) {
      Duplex = 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;

      if (options) {
        if (typeof options.write === 'function') this._write = options.write;

        if (typeof options.writev === 'function') this._writev = options.writev;
      }

      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, cb) {
      var er = new Error('write after end');
      // TODO: defer error events consistently everywhere, not just the cb
      stream.emit('error', er);
      processNextTick(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;
      var er = false;
      // Always throw error if a null is written
      // if we are not in object mode then throw
      // if it is not a buffer, string, or undefined.
      if (chunk === null) {
        er = new TypeError('May not write null values to stream');
      } else if (!Buffer.isBuffer(chunk) && typeof chunk !== 'string' && chunk !== undefined && !state.objectMode) {
        er = new TypeError('Invalid non-string/buffer chunk');
      }
      if (er) {
        stream.emit('error', er);
        processNextTick(cb, er);
        valid = false;
      }
      return valid;
    }

    Writable.prototype.write = function (chunk, encoding, cb) {
      var state = this._writableState;
      var ret = false;

      if (typeof encoding === 'function') {
        cb = encoding;
        encoding = null;
      }

      if (Buffer.isBuffer(chunk)) encoding = 'buffer';else if (!encoding) encoding = state.defaultEncoding;

      if (typeof cb !== 'function') cb = nop;

      if (state.ended) writeAfterEnd(this, 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;

      Eif (state.corked) {
        state.corked--;

        if (!state.writing && !state.corked && !state.finished && !state.bufferProcessing && state.bufferedRequest) clearBuffer(this, state);
      }
    };

    Writable.prototype.setDefaultEncoding = function setDefaultEncoding(encoding) {
      // node::ParseEncoding() requires lower case.
      if (typeof encoding === 'string') encoding = encoding.toLowerCase();
      if (!(['hex', 'utf8', 'utf-8', 'ascii', 'binary', 'base64', 'ucs2', 'ucs-2', 'utf16le', 'utf-16le', 'raw'].indexOf((encoding + '').toLowerCase()) > -1)) throw new TypeError('Unknown encoding: ' + encoding);
      this._writableState.defaultEncoding = encoding;
      return this;
    };

    function decodeChunk(state, chunk, encoding) {
      if (!state.objectMode && state.decodeStrings !== false && typeof chunk === 'string') {
        chunk = bufferShim.from(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 (Buffer.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) {
        var last = state.lastBufferedRequest;
        state.lastBufferedRequest = new WriteReq(chunk, encoding, cb);
        if (last) {
          last.next = state.lastBufferedRequest;
        } else {
          state.bufferedRequest = state.lastBufferedRequest;
        }
        state.bufferedRequestCount += 1;
      } 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) {
      --state.pendingcb;
      if (sync) processNextTick(cb, er);else 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);

      Iif (er) onwriteError(stream, state, sync, er, cb);else {
        // Check if we're actually ready to finish, but don't emit yet
        var finished = needFinish(state);

        if (!finished && !state.corked && !state.bufferProcessing && state.bufferedRequest) {
          clearBuffer(stream, state);
        }

        if (sync) {
          /*<replacement>*/
          asyncWrite(afterWrite, stream, state, finished, cb);
          /*</replacement>*/
        } 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;
      var entry = state.bufferedRequest;

      if (stream._writev && entry && entry.next) {
        // Fast case, write everything using _writev()
        var l = state.bufferedRequestCount;
        var buffer = new Array(l);
        var holder = state.corkedRequestsFree;
        holder.entry = entry;

        var count = 0;
        while (entry) {
          buffer[count] = entry;
          entry = entry.next;
          count += 1;
        }

        doWrite(stream, state, true, state.length, buffer, '', holder.finish);

        // doWrite is almost always async, defer these to save a bit of time
        // as the hot path ends with doWrite
        state.pendingcb++;
        state.lastBufferedRequest = null;
        Iif (holder.next) {
          state.corkedRequestsFree = holder.next;
          holder.next = null;
        } else {
          state.corkedRequestsFree = new CorkedRequest(state);
        }
      } else {
        // Slow case, write chunks one-by-one
        while (entry) {
          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);
          entry = entry.next;
          // 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) {
            break;
          }
        }

        if (entry === null) state.lastBufferedRequest = null;
      }

      state.bufferedRequestCount = 0;
      state.bufferedRequest = entry;
      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 (typeof chunk === 'function') {
        cb = chunk;
        chunk = null;
        encoding = null;
      } else if (typeof encoding === 'function') {
        cb = encoding;
        encoding = null;
      }

      if (chunk !== null && chunk !== undefined) 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(state) {
      return state.ending && state.length === 0 && state.bufferedRequest === null && !state.finished && !state.writing;
    }

    function prefinish(stream, state) {
      if (!state.prefinished) {
        state.prefinished = true;
        stream.emit('prefinish');
      }
    }

    function finishMaybe(stream, state) {
      var need = needFinish(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) processNextTick(cb);else stream.once('finish', cb);
      }
      state.ended = true;
      stream.writable = false;
    }

    // It seems a linked list but it is not
    // there will be only 2 of these for each stream
    function CorkedRequest(state) {
      var _this = this;

      this.next = null;
      this.entry = null;

      this.finish = function (err) {
        var entry = _this.entry;
        _this.entry = null;
        while (entry) {
          var cb = entry.callback;
          state.pendingcb--;
          cb(err);
          entry = entry.next;
        }
        Eif (state.corkedRequestsFree) {
          state.corkedRequestsFree.next = _this;
        } else {
          state.corkedRequestsFree = _this;
        }
      };
    }