Rewrite IOSink documentation, plus some clean-up.

sdk/lib/io/io_sink.dart

Index: sdk/lib/io/io_sink.dart
diff --git a/sdk/lib/io/io_sink.dart b/sdk/lib/io/io_sink.dart
index 2d6719d6a8f43140ee3e916fd1b5c583ea9874be..b1c05a02542b9a412e1440f49c83df226210fe42 100644
--- a/sdk/lib/io/io_sink.dart
+++ b/sdk/lib/io/io_sink.dart
@@ -5,20 +5,27 @@
 part of dart.io;
 
 /**
- * Helper class to wrap a [StreamConsumer<List<int>>] and provide
- * utility functions for writing to the StreamConsumer directly. The
- * [IOSink] buffers the input given by all [StringSink] methods and will delay
- * an [addStream] until the buffer is flushed.
+ * A combined byte and text output.
  *
- * When the [IOSink] is bound to a stream (through [addStream]) any call
- * to the [IOSink] will throw a [StateError]. When the [addStream] completes,
- * the [IOSink] will again be open for all calls.
+ * An [IOSink] combines a [StreamSink] of bytes with a [StringSink],
+ * and allows easy output of both bytes and text.
+ *
+ * Writing text ([write]) and adding bytes ([add]) may be interleaved freely.
+ *
+ * While a stream is being added using [addStream], any further attempts
+ * to add or write to the [IOSink] will fail until the [addStream] completes.
  *
  * If data is added to the [IOSink] after the sink is closed, the data will be
  * ignored. Use the [done] future to be notified when the [IOSink] is closed.
  */
 abstract class IOSink implements StreamSink<List<int>>, StringSink {
-  // TODO(ajohnsen): Make _encodingMutable an argument.
+
+  /**
+   * Create an [IOSink] that outputs to a [target] [StreamConsumer] of bytes.
+   *
+   * Text written to [StreamSink] methods is encoded to bytes using [encoding]
+   * before being output on [target].
+   */
   factory IOSink(StreamConsumer<List<int>> target,
                  {Encoding encoding: UTF8})
       => new _IOSinkImpl(target, encoding);
@@ -30,7 +37,7 @@ abstract class IOSink implements StreamSink<List<int>>, StringSink {
   Encoding encoding;
 
   /**
-   * Adds [data] to the target consumer, ignoring [encoding].
+   * Adds byte [data] to the target consumer, ignoring [encoding].
    *
    * The [encoding] does not apply to this method, and the `data` list is passed
    * directly to the target consumer as a stream event.
@@ -58,7 +65,7 @@ abstract class IOSink implements StreamSink<List<int>>, StringSink {
    * Iterates over the given [objects] and [write]s them in sequence.
    *
    * If [separator] is provided, a `write` with the `separator` is performed
-   * between any two elements of `objects`.
+   * between any two elements of objects`.
    *
    * This operation is non-blocking. See [flush] or [done] for how to get any
    * errors generated by this call.
@@ -75,7 +82,7 @@ abstract class IOSink implements StreamSink<List<int>>, StringSink {
   void writeln([Object obj = ""]);
 
   /**
-   * Writes the [charCode] to `this`.
+   * Writes the character of [charCode].
    *
    * This method is equivalent to `write(new String.fromCharCode(charCode))`.
    *
@@ -107,7 +114,7 @@ abstract class IOSink implements StreamSink<List<int>>, StringSink {
    * Returns a [Future] that completes once all buffered data is accepted by the
    * to underlying [StreamConsumer].
    *
-   * It's an error to call this method, while an [addStream] is incomplete.
+   * This method must not be called while an [addStream] is incomplete.
    *
    * NOTE: This is not necessarily the same as the data being flushed by the
    * operating system.
@@ -129,17 +136,14 @@ abstract class IOSink implements StreamSink<List<int>>, StringSink {
 
 class _StreamSinkImpl<T> implements StreamSink<T> {
   final StreamConsumer<T> _target;
-  Completer _doneCompleter = new Completer();
-  Future _doneFuture;
+  final Completer _doneCompleter = new Completer();
   StreamController<T> _controllerInstance;
   Completer _controllerCompleter;
   bool _isClosed = false;
   bool _isBound = false;
   bool _hasError = false;
 
-  _StreamSinkImpl(this._target) {
-    _doneFuture = _doneCompleter.future;
-  }
+  _StreamSinkImpl(this._target);
 
   void add(T data) {
     if (_isClosed) return;
@@ -180,8 +184,8 @@ class _StreamSinkImpl<T> implements StreamSink<T> {
     var future = _controllerCompleter.future;
     _controllerInstance.close();
     return future.whenComplete(() {
-          _isBound = false;
-        });
+      _isBound = false;
+    });
   }
 
   Future close() {
@@ -203,19 +207,19 @@ class _StreamSinkImpl<T> implements StreamSink<T> {
     _target.close().then(_completeDoneValue, onError: _completeDoneError);
   }
 
-  Future get done => _doneFuture;
+  Future get done => _doneCompleter.future;
 
   void _completeDoneValue(value) {
-    if (_doneCompleter == null) return;
-    _doneCompleter.complete(value);
-    _doneCompleter = null;
+    if (!_doneCompleter.isCompleted) {
+      _doneCompleter.complete(value);
+    }
   }
 
   void _completeDoneError(error, StackTrace stackTrace) {
-    if (_doneCompleter == null) return;
-    _hasError = true;
-    _doneCompleter.completeError(error, stackTrace);
-    _doneCompleter = null;
+    if (!_doneCompleter.isCompleted) {
+      _hasError = true;
+      _doneCompleter.completeError(error, stackTrace);
+    }
   }
 
   StreamController<T> get _controller {
@@ -228,32 +232,29 @@ class _StreamSinkImpl<T> implements StreamSink<T> {
     if (_controllerInstance == null) {
       _controllerInstance = new StreamController<T>(sync: true);
       _controllerCompleter = new Completer();
-      _target.addStream(_controller.stream)
-          .then(
-              (_) {
-                if (_isBound) {
-                  // A new stream takes over - forward values to that stream.
-                  _controllerCompleter.complete(this);
-                  _controllerCompleter = null;
-                  _controllerInstance = null;
-                } else {
-                  // No new stream, .close was called. Close _target.
-                  _closeTarget();
-                }
-              },
-              onError: (error, stackTrace) {
-                if (_isBound) {
-                  // A new stream takes over - forward errors to that stream.
-                  _controllerCompleter.completeError(error, stackTrace);
-                  _controllerCompleter = null;
-                  _controllerInstance = null;
-                } else {
-                  // No new stream. No need to close target, as it have already
-                  // failed.
-                  _completeDoneError(error, stackTrace);
-                }
-              });
-    }
+      _target.addStream(_controller.stream).then((_) {
+        if (_isBound) {
+          // A new stream takes over - forward values to that stream.
+          _controllerCompleter.complete(this);
+          _controllerCompleter = null;
+          _controllerInstance = null;
+        } else {
+          // No new stream, .close was called. Close _target.
+          _closeTarget();
+        }
+      }, onError: (error, stackTrace) {
+        if (_isBound) {
+          // A new stream takes over - forward errors to that stream.
+          _controllerCompleter.completeError(error, stackTrace);
+          _controllerCompleter = null;
+          _controllerInstance = null;
+        } else {
+          // No new stream. No need to close target, as it has already
+          // failed.
+          _completeDoneError(error, stackTrace);
+        }
+      });
+   }
     return _controllerInstance;
   }
 }
@@ -297,8 +298,8 @@ class _IOSinkImpl extends _StreamSinkImpl<List<int>> implements IOSink {
     }
   }
 
-  void writeln([Object obj = ""]) {
-    write(obj);
+  void writeln([Object object = ""]) {
+    write(object);
     write("\n");
   }