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node_modules/lazystream/lib/lazystream.js

@@ -0,0 +1,54 @@
+var util = require('util');
+var PassThrough = require('readable-stream/passthrough');
+
+module.exports = {
+  Readable: Readable,
+  Writable: Writable
+};
+
+util.inherits(Readable, PassThrough);
+util.inherits(Writable, PassThrough);
+
+// Patch the given method of instance so that the callback
+// is executed once, before the actual method is called the
+// first time.
+function beforeFirstCall(instance, method, callback) {
+  instance[method] = function() {
+    delete instance[method];
+    callback.apply(this, arguments);
+    return this[method].apply(this, arguments);
+  };
+}
+
+function Readable(fn, options) {
+  if (!(this instanceof Readable))
+    return new Readable(fn, options);
+
+  PassThrough.call(this, options);
+
+  beforeFirstCall(this, '_read', function() {
+    var source = fn.call(this, options);
+    var emit = this.emit.bind(this, 'error');
+    source.on('error', emit);
+    source.pipe(this);
+  });
+
+  this.emit('readable');
+}
+
+function Writable(fn, options) {
+  if (!(this instanceof Writable))
+    return new Writable(fn, options);
+
+  PassThrough.call(this, options);
+
+  beforeFirstCall(this, '_write', function() {
+    var destination = fn.call(this, options);
+    var emit = this.emit.bind(this, 'error');
+    destination.on('error', emit);
+    this.pipe(destination);
+  });
+
+  this.emit('writable');
+}
+