Implement async file API on top of isolates.

runtime/bin/file.dart

 // Copyright (c) 2011, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 interface File factory _File {
   /**
    * Create a File object.
    */
   File(String name);
 
@@ skipping 70 matching lines @@
   int readListSync(List<int> buffer, int offset, int bytes);
 
   /**
    * Write a single byte to the file. If the byte cannot be written
    * the [errorHandler] is called. When all pending write operations
    * have finished the [noPendingWriteHandler] is called.
    */
   void writeByte(int value);
 
   /**
-   * Synchronously write a single byte to the file. Returns true if
-   * the byte was successfully written and false otherwise.
+   * Synchronously write a single byte to the file. Returns the
+   * number of bytes successfully written.
    */
-  bool writeByteSync(int value);
+  int writeByteSync(int value);
 
   /**
    * Write a List<int> to the file. If the list cannot be written the
    * [errorHandler] is called. When all pending write operations have
    * finished the [noPendingWriteHandler] is called.
    */
   void writeList(List<int> buffer, int offset, int bytes);
 
   /**
-   * Synchronously write a List<int> to the file. Returns true if the
-   * list was successfully written and false otherwise.
+   * Synchronously write a List<int> to the file. Returns the number
+   * of bytes successfully written.
    */
-  bool writeListSync(List<int> buffer, int offset, int bytes);
+  int writeListSync(List<int> buffer, int offset, int bytes);
 
   /**
    * Write a string to the file. If the string cannot be written the
    * [errorHandler] is called. When all pending write operations have
    * finished the [noPendingWriteHandler] is called.
    */
   // TODO(ager): writeString should take an encoding.
   void writeString(String string);
 
   /**
-   * Synchronously write a single string to the file. Returns true if
-   * the string was successfully written and false otherwise.
+   * Synchronously write a single string to the file. Returns the number
+   * of characters successfully written.
    */
   // TODO(ager): writeStringSync should take an encoding.
-  bool writeStringSync(String string);
+  int writeStringSync(String string);
 
   /**
    * Get the current position of the file. When the operation
    * completes the [positionHandler] is called with the position.
    */
   void position();
 
   /**
    * Synchronously get the current position of the file.
    */
   int positionSync();
 
   /**
    * Get the length of the file. When the operation completes the
    * [lengthHandler] is called with the length.
    */
   void length();
 
   /**
    * Get the length of the file. When the operation completes the
    * [lengthHandler] is called with the length.
    */
   int lengthSync();
 
   /**
-   * Flush the contents of the file to disk. If there are no pending
-   * write operation after the flush operation completes, the
-   * [noPendingWriteHandler] is called.
+   * Flush the contents of the file to disk. The [flushHandler] is
+   * called when the flush operation completes.
    */
    void flush();
 
   /**
    * Synchronously flush the contents of the file to disk.
    */
   void flushSync();
 
   /**
    * Create a new independent input stream for the file. The file
@@ skipping 13 matching lines @@
   String get name();
 
   // Event handlers.
   void set existsHandler(void handler(bool exists));
   void set createHandler(void handler());
   void set openHandler(void handler());
   void set closeHandler(void handler());
   void set readByteHandler(void handler(int byte));
   void set readListHandler(void handler(int read));
   void set noPendingWriteHandler(void handler());
+  void set positionHandler(void handler(int position));
+  void set lengthHandler(void handler(int length));
+  void set flushHandler(void handler());
   void set errorHandler(void handler(String error));
 }
 
 
 interface FileInputStream extends InputStream {
   void close();
 }
 
 
 interface FileOutputStream extends OutputStream {
 }
 
 
 class FileIOException implements Exception {
   const FileIOException([String this.message = ""]);
   String toString() => "FileIOException: $message";
   final String message;
 }