first commit

build/node_modules/vinyl-fs/lib/sink.js

@@ -0,0 +1,53 @@
+'use strict';
+
+var Writable = require('readable-stream/writable');
+
+function listenerCount(stream, evt) {
+  return stream.listeners(evt).length;
+}
+
+function hasListeners(stream) {
+  return !!(listenerCount(stream, 'readable') || listenerCount(stream, 'data'));
+}
+
+function sink(stream) {
+  var sinkAdded = false;
+  var sinkStream = new Writable({
+    objectMode: true,
+    write: function(file, enc, cb) {
+      cb();
+    },
+  });
+
+  function addSink() {
+    if (sinkAdded) {
+      return;
+    }
+
+    if (hasListeners(stream)) {
+      return;
+    }
+
+    sinkAdded = true;
+    stream.pipe(sinkStream);
+  }
+
+  function removeSink(evt) {
+    if (evt !== 'readable' && evt !== 'data') {
+      return;
+    }
+
+    if (hasListeners(stream)) {
+      sinkAdded = false;
+      stream.unpipe(sinkStream);
+    }
+  }
+
+  stream.on('newListener', removeSink);
+  stream.on('removeListener', removeSink);
+  stream.on('removeListener', addSink);
+
+  return addSink;
+}
+
+module.exports = sink;