streams2: The new stream base classes

lib/_stream_duplex.js

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+// 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 duplex stream is just a stream that is both readable and writable.
+// Since JS doesn't have multiple prototypal inheritance, this class
+// prototypally inherits from Readable, and then parasitically from
+// Writable.
+
+module.exports = Duplex;
+var util = require('util');
+var Readable = require('_stream_readable');
+var Writable = require('_stream_writable');
+
+util.inherits(Duplex, Readable);
+
+Object.keys(Writable.prototype).forEach(function(method) {
+  if (!Duplex.prototype[method])
+    Duplex.prototype[method] = Writable.prototype[method];
+});
+
+function Duplex(options) {
+  Readable.call(this, options);
+  Writable.call(this, options);
+
+  this.allowHalfOpen = true;
+  if (options && options.allowHalfOpen === false)
+    this.allowHalfOpen = false;
+
+  this.once('finish', onfinish);
+  this.once('end', onend);
+}
+
+// the no-half-open enforcers.
+function onfinish() {
+  // if we allow half-open state, or if the readable side ended,
+  // then we're ok.
+  if (this.allowHalfOpen || this._readableState.ended)
+    return;
+
+  // mark that we're done.
+  this._readableState.ended = true;
+
+  // tell the user
+  if (this._readableState.length === 0)
+    this.emit('end');
+  else
+    this.emit('readable');
+}
+
+function onend() {
+  // if we allow half-open state, or if the writable side ended,
+  // then we're ok.
+  if (this.allowHalfOpen || this._writableState.ended)
+    return;
+
+  // just in case the user is about to call write() again.
+  this.write = function() {
+    return false;
+  };
+
+  // no more data can be written.
+  this.end();
+}

lib/_stream_passthrough.js

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+// 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 passthrough stream.
+// basically just the most minimal sort of Transform stream.
+// Every written chunk gets output as-is.
+
+module.exports = PassThrough;
+
+var Transform = require('_stream_transform');
+var util = require('util');
+util.inherits(PassThrough, Transform);
+
+function PassThrough(options) {
+  Transform.call(this, options);
+}
+
+PassThrough.prototype._transform = function(chunk, output, cb) {
+  output(chunk);
+  cb();
+};