Socket.available should never return a negative value.

runtime/bin/socket.cc

 // 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.
 
 #include "bin/socket.h"
 #include "bin/dartutils.h"
 #include "bin/thread.h"
 #include "bin/utils.h"
 
 #include "platform/globals.h"
@@ skipping 21 matching lines @@
   }
   Dart_ExitScope();
 }
 
 
 void FUNCTION_NAME(Socket_Available)(Dart_NativeArguments args) {
   Dart_EnterScope();
   int64_t socket = DartUtils::GetIntegerField(Dart_GetNativeArgument(args, 0),
                                               DartUtils::kIdFieldName);
   intptr_t available = Socket::Available(socket);
-  Dart_SetReturnValue(args, Dart_NewInteger(available));
+  if (available >= 0) {
+    Dart_SetReturnValue(args, Dart_NewInteger(available));
+  } else {
+    Dart_SetReturnValue(args, DartUtils::NewDartOSError());
+  }
   Dart_ExitScope();
 }
 
 
 void FUNCTION_NAME(Socket_ReadList)(Dart_NativeArguments args) {
   Dart_EnterScope();
   intptr_t socket =
       DartUtils::GetIntegerField(Dart_GetNativeArgument(args, 0),
                                  DartUtils::kIdFieldName);
   Dart_Handle buffer_obj = Dart_GetNativeArgument(args, 1);
@@ skipping 260 matching lines @@
   Dart_EnterScope();
   Dart_SetReturnValue(args, Dart_Null());
   Dart_Port service_port = Socket::GetServicePort();
   if (service_port != kIllegalPort) {
     // Return a send port for the service port.
     Dart_Handle send_port = Dart_NewSendPort(service_port);
     Dart_SetReturnValue(args, send_port);
   }
   Dart_ExitScope();
 }