Function WritableState

lib/internal/streams/writable.js:301–359

(options, stream, isDuplex)

});

function WritableState(options, stream, isDuplex) {
  // Bit map field to store WritableState more efficiently with 1 bit per field
  // instead of a V8 slot per field.
  this[kState] = kSync | kConstructed | kEmitClose | kAutoDestroy;

  if (options?.objectMode)
    this[kState] |= kObjectMode;

  if (isDuplex && options?.writableObjectMode)
    this[kState] |= kObjectMode;

  // 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().
  this.highWaterMark = options ?
    getHighWaterMark(this, options, 'writableHighWaterMark', isDuplex) :
    getDefaultHighWaterMark(false);

  if (!options || options.decodeStrings !== false) this[kState] |= kDecodeStrings;

  // Should close be emitted on destroy. Defaults to true.
  if (options && options.emitClose === false) this[kState] &= ~kEmitClose;

  // Should .destroy() be called after 'end' (and potentially 'finish').
  if (options && options.autoDestroy === false) this[kState] &= ~kAutoDestroy;

  // 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.
  const defaultEncoding = options ? options.defaultEncoding : null;
  if (defaultEncoding == null || defaultEncoding === 'utf8' || defaultEncoding === 'utf-8') {
    this[kState] |= kDefaultUTF8Encoding;
  } else if (Buffer.isEncoding(defaultEncoding)) {
    this[kState] &= ~kDefaultUTF8Encoding;
    this[kDefaultEncodingValue] = defaultEncoding;
  } else {
    throw new ERR_UNKNOWN_ENCODING(defaultEncoding);
  }

  // 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;

  // When true all writes will be buffered until .uncork() call.
  this.corked = 0;

  // The callback that's passed to _write(chunk, cb).
  this.onwrite = (er) => onwrite(stream, er);

  // The amount that is being written when _write is called.
  this.writelen = 0;

  resetBuffer(this);

  // Number of pending user-supplied write callbacks
  // this must be 0 before 'finish' can be emitted.
  this.pendingcb = 0;