Make non-copying version of BytesBuidler and make file-reads faster.

sdk/lib/io/file_impl.dart

 // Copyright (c) 2013, 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.
 
 part of dart.io;
 
 // Read the file in blocks of size 64k.
 const int _BLOCK_SIZE = 64 * 1024;
 
 
@@ skipping 418 matching lines @@
     if (mode != FileMode.WRITE &&
         mode != FileMode.APPEND) {
       throw new ArgumentError(
           "Wrong FileMode. Use FileMode.WRITE or FileMode.APPEND");
     }
     var consumer = new _FileStreamConsumer(this, mode);
     return new IOSink(consumer, encoding: encoding);
   }
 
   Future<List<int>> readAsBytes() {
-    Completer<List<int>> completer = new Completer<List<int>>();
-    var builder = new BytesBuilder();
-    openRead().listen(
-      (d) => builder.add(d),
-      onDone: () {
-        completer.complete(builder.takeBytes());
-      },
-      onError: (e, StackTrace stackTrace) {
-        completer.completeError(e, stackTrace);
-      },
-      cancelOnError: true);
-    return completer.future;
+    Future<List<int>> readDataChunked(file) {
+      var builder = new BytesBuilder(copy: false);
+      var completer = new Completer();
+      void read() {
+        file.read(_BLOCK_SIZE).then((data) {
+          if (data.length > 0) builder.add(data);
+          if (data.length == _BLOCK_SIZE) {
+            read();
+          } else {
+            completer.complete(builder.takeBytes());
+          }
+        }, onError: completer.completeError);
+      }
+      read();
+      return completer.future;
+    }
+
+    return open().then((file) {
+      return file.length().then((length) {
+        if (length == 0) {
+          // May be character device, try to read it in chunks.
+          return readDataChunked(file);
+        }
+        return file.read(length);
+      }).whenComplete(file.close);
+    });
   }
 
   List<int> readAsBytesSync() {
     var opened = openSync();
-    var builder = new BytesBuilder();
     var data;
-    while ((data = opened.readSync(_BLOCK_SIZE)).length > 0) {
-      builder.add(data);
+    var length = opened.lengthSync();
+    if (length == 0) {
+      // May be character device, try to read it in chunks.
+      var builder = new BytesBuilder(copy: false);
+      do {
+        data = opened.readSync(_BLOCK_SIZE);
+        if (data.length > 0) builder.add(data);
+      } while (data.length == _BLOCK_SIZE);
+      data = builder.takeBytes();
+    } else {
+      data = opened.readSync(length);
     }
     opened.closeSync();
-    return builder.takeBytes();
+    return data;
   }
 
   String _tryDecode(List<int> bytes, Encoding encoding) {
     try {
       return encoding.decode(bytes);
     } catch (_) {
       throw new FileSystemException(
           "Failed to decode data using encoding '${encoding.name}'", path);
     }
   }
@@ skipping 429 matching lines @@
 
   void _checkAvailable() {
     if (_asyncDispatched) {
       throw new FileSystemException("An async operation is currently pending", path);
     }
     if (closed) {
       throw new FileSystemException("File closed", path);
     }
   }
 }