Change file opening operation to set position at the end of the file when FileMode.APPEND is used.

runtime/bin/file_impl.dart

 // Copyright (c) 2012, 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.
 
 class _FileInputStream extends _BaseDataInputStream implements InputStream {
   _FileInputStream(File file) {
     _file = file.openSync();
     _length = _file.lengthSync();
     _streamMarkedClosed = true;
     _checkScheduleCallbacks();
@@ skipping 31 matching lines @@
     _closed = true;
   }
 
   RandomAccessFile _file;
   int _length;
   bool _closed = false;
 }
 
 
 class _FileOutputStream implements OutputStream {
-  _FileOutputStream(File file) {
-    _file = file.openSync(FileMode.WRITE);
+  _FileOutputStream(File file, FileMode mode) {
+    _file = file.openSync(mode);
   }
 
   bool write(List<int> buffer, [bool copyBuffer = false]) {
     return _write(buffer, 0, buffer.length);
   }
 
   bool writeFrom(List<int> buffer, [int offset = 0, int len]) {
     return _write(
         buffer, offset, (len == null) ? buffer.length - offset : len);
   }
@@ skipping 520 matching lines @@
     }
     var handleOpenResult = (id, ignored) {
       // If no open handler is present, close the file immediately to
       // avoid leaking an open file descriptor.
       var handler = _openHandler;
       if (handler === null) {
         handler = (file) => file.close();
       }
       if (id != 0) {
         var randomAccessFile = new _RandomAccessFile(id, _name);
+        if (mode == FileMode.APPEND) {
+          _FileUtils.setPosition(id, _FileUtils.length(id));

[Mads Ager (google), 2012/02/07 08:37:31]

Please do this in the C++ code instead. Here you are turning what should be an
async operation into a sync operation for the setting of the position. The C++
code knows about the mode as well and can set the position as part of the open
call. That will happen on a separate thread and will not block the main dart
thread.

[ricow1, 2012/02/07 09:16:22]

Done, I placed these in the platform specific files, let me know if you wan't me
to do something like:
if (file != NULL && mode == kAppend) {
  file->SetPosition(file->Length());
}
in File_Open in file.cc instead (it seems that we normally only do one platform
specific call per file.cc native method so I did the same)  

+        }
         handler(randomAccessFile);
       } else if (_errorHandler != null) {
         _errorHandler("Cannot open file: $_name");
       }
     };
     var operation = new _OpenOperation(_name, mode._mode);
     _scheduler.enqueue(operation, handleOpenResult);
   }
 
   RandomAccessFile openSync([FileMode mode = FileMode.READ]) {
     if (_asyncUsed) {
       throw new FileIOException(
           "Mixed use of synchronous and asynchronous API");
     }
     if (mode != FileMode.READ &&
         mode != FileMode.WRITE &&
         mode != FileMode.APPEND) {
       throw new FileIOException("Unknown file mode. Use FileMode.READ, " +
                                 "FileMode.WRITE or FileMode.APPEND.");
     }
     var id = _FileUtils.checkedOpen(_name, mode._mode);
     if (id == 0) {
       throw new FileIOException("Cannot open file: $_name");
     }
+    if (mode == FileMode.APPEND) {
+      _FileUtils.setPosition(id, _FileUtils.length(id));

[Mads Ager (google), 2012/02/07 08:37:31]

Ditto. This is actually fine because this is the sync version, but if open in
the C++ code takes care of it you don't need this.

[ricow1, 2012/02/07 09:16:22]

Done.

+    }
     return new _RandomAccessFile(id, _name);
   }
 
   void fullPath() {
     _asyncUsed = true;
     var handleFullPathResult = (result, ignored) {
       var handler = _fullPathHandler;
       if (handler == null) handler = (path) => null;
       if (result != null) {
         handler(result);
@@ skipping 12 matching lines @@
     }
     String result = _FileUtils.checkedFullPath(_name);
     if (result == null) {
       throw new FileIOException("fullPath failed");
     }
     return result;
   }
 
   InputStream openInputStream() => new _FileInputStream(this);
 
-  OutputStream openOutputStream() => new _FileOutputStream(this);
+  OutputStream openOutputStream([FileMode mode = FileMode.WRITE]) {
+    if (mode != FileMode.WRITE &&
+        mode != FileMode.APPEND) {
+      throw new FileIOException(
+          "Wrong FileMode. Use FileMode.WRITE or FileMode.APPEND");
+    }
+    return new _FileOutputStream(this, mode);
+  }
 
   String get name() => _name;
 
   void set existsHandler(void handler(bool exists)) {
     _existsHandler = handler;
   }
 
   void set createHandler(void handler()) {
     _createHandler = handler;
   }
@@ skipping 429 matching lines @@
   var _readByteHandler;
   var _readListHandler;
   var _noPendingWriteHandler;
   var _positionHandler;
   var _setPositionHandler;
   var _truncateHandler;
   var _lengthHandler;
   var _flushHandler;
   var _errorHandler;
 }