Only allow one async operation on RandomAccessFile at a time.

sdk/lib/io/file_impl.dart

Index: sdk/lib/io/file_impl.dart
diff --git a/sdk/lib/io/file_impl.dart b/sdk/lib/io/file_impl.dart
index 1dce796efc46c74f6049a15b331138c286971bf2..04f56c7417bb519376c4c28ef821322eee149399 100644
--- a/sdk/lib/io/file_impl.dart
+++ b/sdk/lib/io/file_impl.dart
@@ -531,17 +531,13 @@ class _File extends FileSystemEntity implements File {
 class _RandomAccessFile implements RandomAccessFile {
   final String path;
   int _id;
+  bool _asyncDispatched = false;
   SendPort _fileService;
 
   _RandomAccessFile(int this._id, String this.path);
 
   Future<RandomAccessFile> close() {
-    if (closed) return _closedException();
-    // Set the id_ to 0 (NULL) to ensure the no more async requests
-    // can be issued for this file.
-    int id = _id;
-    _id = 0;
-    return _IOService.dispatch(_FILE_CLOSE, [id]).then((result) {
+    return _dispatch(_FILE_CLOSE, [_id], markClosed: true).then((result) {
       if (result != -1) {
         _id = result;
         return this;
@@ -563,8 +559,7 @@ class _RandomAccessFile implements RandomAccessFile {
   }
 
   Future<int> readByte() {
-    if (closed) return _closedException();
-    return _IOService.dispatch(_FILE_READ_BYTE, [_id]).then((response) {
+    return _dispatch(_FILE_READ_BYTE, [_id]).then((response) {
       if (_isErrorResponse(response)) {
         throw _exceptionFromResponse(response, "readByte failed", path);
       }
@@ -587,8 +582,7 @@ class _RandomAccessFile implements RandomAccessFile {
     if (bytes is !int) {
       throw new ArgumentError(bytes);
     }
-    if (closed) return _closedException();
-    return _IOService.dispatch(_FILE_READ, [_id, bytes]).then((response) {
+    return _dispatch(_FILE_READ, [_id, bytes]).then((response) {
       if (_isErrorResponse(response)) {
         throw _exceptionFromResponse(response, "read failed", path);
       }
@@ -616,11 +610,10 @@ class _RandomAccessFile implements RandomAccessFile {
         (end != null && end is !int)) {
       throw new ArgumentError();
     }
-    if (closed) return _closedException();
     if (start == null) start = 0;
     if (end == null) end = buffer.length;
     int length = end - start;
-    return _IOService.dispatch(_FILE_READ_INTO, [_id, length]).then((response) {
+    return _dispatch(_FILE_READ_INTO, [_id, length]).then((response) {
       if (_isErrorResponse(response)) {
         throw _exceptionFromResponse(response, "readInto failed", path);
       }
@@ -663,8 +656,7 @@ class _RandomAccessFile implements RandomAccessFile {
     if (value is !int) {
       throw new ArgumentError(value);
     }
-    if (closed) return _closedException();
-    return _IOService.dispatch(_FILE_WRITE_BYTE, [_id, value]).then((response) {
+    return _dispatch(_FILE_WRITE_BYTE, [_id, value]).then((response) {
       if (_isErrorResponse(response)) {
         throw _exceptionFromResponse(response, "writeByte failed", path);
       }
@@ -693,8 +685,6 @@ class _RandomAccessFile implements RandomAccessFile {
       throw new ArgumentError("Invalid arguments to writeFrom");
     }
 
-    if (closed) return _closedException();
-
     _BufferAndStart result;
     try {
       result = _ensureFastAndSerializableByteData(buffer, start, end);
@@ -707,7 +697,7 @@ class _RandomAccessFile implements RandomAccessFile {
     request[1] = result.buffer;
     request[2] = result.start;
     request[3] = end - (start - result.start);
-    return _IOService.dispatch(_FILE_WRITE_FROM, request).then((response) {
+    return _dispatch(_FILE_WRITE_FROM, request).then((response) {
       if (_isErrorResponse(response)) {
         throw _exceptionFromResponse(response, "writeFrom failed", path);
       }
@@ -757,8 +747,7 @@ class _RandomAccessFile implements RandomAccessFile {
   }
 
   Future<int> position() {
-    if (closed) return _closedException();
-    return _IOService.dispatch(_FILE_POSITION, [_id]).then((response) {
+    return _dispatch(_FILE_POSITION, [_id]).then((response) {
       if (_isErrorResponse(response)) {
         throw _exceptionFromResponse(response, "position failed", path);
       }
@@ -778,8 +767,7 @@ class _RandomAccessFile implements RandomAccessFile {
   }
 
   Future<RandomAccessFile> setPosition(int position) {
-    if (closed) return _closedException();
-    return _IOService.dispatch(_FILE_SET_POSITION, [_id, position])
+    return _dispatch(_FILE_SET_POSITION, [_id, position])
         .then((response) {
           if (_isErrorResponse(response)) {
             throw _exceptionFromResponse(response, "setPosition failed", path);
@@ -799,8 +787,7 @@ class _RandomAccessFile implements RandomAccessFile {
   }
 
   Future<RandomAccessFile> truncate(int length) {
-    if (closed) return _closedException();
-    return _IOService.dispatch(_FILE_TRUNCATE, [_id, length]).then((response) {
+    return _dispatch(_FILE_TRUNCATE, [_id, length]).then((response) {
       if (_isErrorResponse(response)) {
         throw _exceptionFromResponse(response, "truncate failed", path);
       }
@@ -819,8 +806,7 @@ class _RandomAccessFile implements RandomAccessFile {
   }
 
   Future<int> length() {
-    if (closed) return _closedException();
-    return _IOService.dispatch(_FILE_LENGTH, [_id]).then((response) {
+    return _dispatch(_FILE_LENGTH, [_id]).then((response) {
       if (_isErrorResponse(response)) {
         throw _exceptionFromResponse(response, "length failed", path);
       }
@@ -840,8 +826,7 @@ class _RandomAccessFile implements RandomAccessFile {
   }
 
   Future<RandomAccessFile> flush() {
-    if (closed) return _closedException();
-    return _IOService.dispatch(_FILE_FLUSH, [_id]).then((response) {
+    return _dispatch(_FILE_FLUSH, [_id]).then((response) {
       if (_isErrorResponse(response)) {
         throw _exceptionFromResponse(response,
                                      "flush failed",
@@ -863,13 +848,29 @@ class _RandomAccessFile implements RandomAccessFile {
 
   bool get closed => _id == 0;
 
-  void _checkNotClosed() {
+  Future _dispatch(int request, List data, { bool markClosed: false }) {
     if (closed) {
-      throw new FileException("File closed", path);
+      return new Future.error(new FileException("File closed", path));
+    }
+    if (_asyncDispatched) {
+      var msg = "A file operation is already issued for this RandomAccessFile";

[Søren Gjesse, 2013/09/26 18:31:19]

How about a message something like this: "An async operation is currently
pending"?

[Anders Johnsen, 2013/10/01 10:50:40]

Done.

+      return new Future.error(new FileException(msg, path));
+    }
+    if (markClosed) {
+      // Set the id_ to 0 (NULL) to ensure the no more async requests
+      // can be issued for this file.
+      _id = 0;
     }
+    _asyncDispatched = true;
+    return _IOService.dispatch(request, data)
+        .whenComplete(() {
+          _asyncDispatched = false;
+        });
   }
 
-  Future _closedException() {
-    return new Future.error(new FileException("File closed", path));
+  void _checkNotClosed() {
+    if (closed) {
+      throw new FileException("File closed", path);
+    }
   }
 }