Adding library level docs for async, io, convert and fixing a bug in dart:core

sdk/lib/io/io.dart

Index: sdk/lib/io/io.dart
diff --git a/sdk/lib/io/io.dart b/sdk/lib/io/io.dart
index 1cf9c4d3999a2d01fc97c60475e1f8e651d756e9..d0c1f58e11d560ba5a4a7ada503303b549891b58 100644
--- a/sdk/lib/io/io.dart
+++ b/sdk/lib/io/io.dart
@@ -5,12 +5,193 @@
 /**
  * File, socket, HTTP, and other I/O support for server applications.
  *
- * The IO library is used for Dart server applications,
+ * The I/O library is used for Dart server applications,
  * which run on a stand-alone Dart VM from the command line.
- * *This library does not work in browser based applications.*
+ * *This library does not work in browser-based applications.*
  *
  * This library allows you to work with files, directories,
  * sockets, processes, HTTP servers and clients, and more.
+ *
+ * To use this library in your code:
+ *
+ *     import 'dart:io';
+ *
+ * *Note:* Many operations related to input and output are asynchronous
+ * and are handled using [Future]s or [Stream]s, both of which
+ * are defined in the `dart:async` library.
+ *
+ * ## File, Directory, and Link
+ *
+ * An instance of [File], [Directory], or [Link] represents a file,
+ * directory, or link, respectively, in the native file system.
+ *
+ * You can manipulate the file system through objects of these types.
+ * For example, you can rename a file or directory:
+ *
+ *     File myFile = new File('myFile.txt');
+ *     myFile.rename('yourFile.txt').then((_) => print('file renamed'));
+ *
+ * Many methods provided by the File, Directory, and Link classes
+ * run asynchronously and return a Future.
+ *
+ * ## FileSystemEntity
+ *
+ * File, Directory, and Link all extend [FileSystemEntity].
+ * In addition to being the superclass for these classes,
+ * FileSystemEntity has a number of static methods for working with paths.
+ *
+ * To get information about a path,
+ * you can use the FileSystemEntity static methods
+ * such as 'isDirectory', 'isFile', and 'exists'.
+ * Because file system access involves I/O, these methods
+ * are asynchronous and return a Future.
+ *
+ *     FileSystemEntity.isDirectory(myPath).then((isDir) {
+ *       if (isDir) {
+ *         print('$myPath is a directory');
+ *       } else {
+ *         print('$myPath is not a directory');
+ *       }
+ *     });
+ *
+ * ## HttpServer and HttpClient
+ *
+ * The classes [HttpServer] and [HttpClient]
+ * provide HTTP server and HTTP client functionality.
+ *
+ * The [HttpServer] class provides the basic functionality for
+ * implementing an HTTP server.
+ * For some higher-level building-blocks, we recommend that you try
+ * the [http_server](https://pub.dartlang.org/packages/http_server)
+ * pub package, which contains
+ * a set of high-level classes that, together with the [HttpServer] class
+ * in this library, make it easier to implement HTTP servers.
+ *
+ * ## Process
+ *
+ * The [Process] class provides a way to run a process on
+ * the native machine.
+ * For example, the following code spawns a process that recursively lists
+ * the files under `web`.
+ *
+ *     Process.start('ls', ['-R', 'web']).then((process) {
+ *       stdout.addStream(process.stdout);
+ *       stderr.addStream(process.stderr);
+ *       process.exitCode.then(print);
+ *     });
+ *
+ * Using `start()` returns a Future, which completes with a [Process] object when
+ * the process has started. This [Process] object allows you to interact with the
+ * process while it is running. Using `run()` returns a Future, which completes with
+ * a [ProcessResult] object when the spawned process has terminated. This
+ * [ProcessResult] object collects the output and exit code from the process. 
+ *
+ * When using `start()`,
+ * you need to read all data coming on the stdout and stderr streams otherwise
+ * the system resources will not be freed.
+ *
+ * ## WebSocket
+ *
+ * The [WebSocket] class provides support for the web socket protocol. This allows
+ * full-duplex communications between client and server applications.
+ * Use the WebSocket class in the `dart:html` library for web clients.
+ *
+ * A web socket server uses a normal HTTP server for accepting web socket
+ * connections. The initial handshake is a HTTP request which is then upgraded to a
+ * web socket connection.
+ * The server upgrades the request using [WebSocketTransformer]
+ * and listens for the data on the returned web socket.
+ * For example, here's a mini server that listens for 'ws' data
+ * on a WebSocket:
+ *
+ *     runZoned(() {
+ *       HttpServer.bind('127.0.0.1', 4040).then((server) {
+ *         server.listen((HttpRequest req) {
+ *           if (req.uri.path == '/ws') {
+ *             WebSocketTransformer.upgrade(req).then((socket) {
+ *               socket.listen(handleMsg);
+ *             });
+ *           }
+ *         });
+ *       });
+ *     },
+ *     onError: (e) => print("An error occurred."));
+ *
+ * The client connects to the WebSocket using the `connect()` method
+ * and a URI that uses the Web Socket protocol.
+ * The the client can write to the WebSocket with the `add()` method.
+ * For example,
+ *
+ *     WebSocket.connect('ws://127.0.0.1:4040/ws').then((socket) {
+ *       socket.add('Hello, World!');
+ *     });
+ *
+ * Check out the
+ * [dartiverse_search](https://code.google.com/p/dart/source/browse/branches/bleeding_edge/dart/samples/dartiverse_search)
+ * sample for a client/server pair that uses
+ * WebSockets to communicate.
+ *
+ * ## Socket and ServerSocket
+ *
+ * Clients and servers use [Socket]s to communicate using the TCP protocol.
+ * Use [ServerSocket] on the server side and [Socket] on the client.
+ * The server creates a listening socket using the `bind()` method and
+ * then listens for incoming connections on the socket. For example:
+ *
+ *     ServerSocket.bind('127.0.0.1', 4041)
+ *       .then((serverSocket) {
+ *         serverSocket.listen((socket) {
+ *           socket.transform(UTF8.decoder).listen(print);
+ *         });
+ *       });
+ *
+ * A client connects a Socket using the `connect()` method,
+ * which returns a Future.
+ * Using `write()`, `writeln()`, or `writeAll()` are the easiest ways to 
+ * send data over the socket.
+ * For example:
+ *
+ *     Socket.connect('127.0.0.1', 4041).then((socket) {
+ *       socket.write('Hello, World!');
+ *     });
+ *
+ * Besides [Socket] and [ServerSocket], the [RawSocket] and
+ * [RawServerSocket] classes are available for lower-level access
+ * to async socket IO.
+ *
+ * ## Standard output, error, and input streams
+ *
+ * This library provides the standard output, error, and input
+ * streams, named 'stdout', 'stderr', and 'stdin', respectively.
+ *
+ * The stdout and stderr streams are both [IOSink]s and have the same set
+ * of methods and properties.
+ *
+ * To write a string to 'stdout':
+ *
+ *     stdout.writeln('Hello, World!');
+ *
+ * To write a list of objects to 'stderr':
+ *
+ *     stderr.writeAll([ 'That ', 'is ', 'an ', 'error.', '\n']);
+ *
+ * The standard input stream is a true [Stream], so it inherits
+ * properties and methods from the Stream class.
+ *
+ * To read text synchronously from the command line
+ * (the program blocks waiting for user to type information):
+ *
+ *      String inputText = stdin.readLineSync();
+ *
+ * ## Other resources
+ *
+ * For an introduction to I/O in Dart, see the
+ * [dart:io section of the library tour]
+ * (https://www.dartlang.org/docs/dart-up-and-running/contents/ch03.html#ch03-dartio---file-and-socket-io-for-command-line-apps).
+ *
+ * To learn more about I/O in Dart, refer to the
+ * [tutorial about writing command-line apps]
+ * (https://www.dartlang.org/docs/tutorials/io/).
  */
 library dart.io;