Make event-handlers edge-triggered and move socket-state to Dart.

runtime/bin/socket.cc

 // 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.
 
 #include "bin/io_buffer.h"
 #include "bin/isolate_data.h"
 #include "bin/socket.h"
 #include "bin/dartutils.h"
 #include "bin/thread.h"
 #include "bin/utils.h"
@@ skipping 206 matching lines @@
 void FUNCTION_NAME(Socket_WriteList)(Dart_NativeArguments args) {
   static bool short_socket_writes = Dart_IsVMFlagSet("short_socket_write");
   intptr_t socket =
       Socket::GetSocketIdNativeField(Dart_GetNativeArgument(args, 0));
   Dart_Handle buffer_obj = Dart_GetNativeArgument(args, 1);
   ASSERT(Dart_IsList(buffer_obj));
   intptr_t offset =
       DartUtils::GetIntptrValue(Dart_GetNativeArgument(args, 2));
   intptr_t length =
       DartUtils::GetIntptrValue(Dart_GetNativeArgument(args, 3));
+  bool short_write = false;
   if (short_socket_writes) {
+    if (length > 1) short_write = true;
     length = (length + 1) / 2;
   }
   Dart_TypedData_Type type;
   uint8_t* buffer = NULL;
   intptr_t len;
   Dart_Handle result = Dart_TypedDataAcquireData(
       buffer_obj, &type, reinterpret_cast<void**>(&buffer), &len);
   if (Dart_IsError(result)) Dart_PropagateError(result);
   ASSERT((offset + length) <= len);
   buffer += offset;
   intptr_t bytes_written = Socket::Write(socket, buffer, length);
   if (bytes_written >= 0) {
     Dart_TypedDataReleaseData(buffer_obj);
-    Dart_SetReturnValue(args, Dart_NewInteger(bytes_written));
+    if (short_write) {
+      // If the write was forced 'short', indicate by returning the negative
+      // number of bytes. A forced short write may not trigger a write event.
+      Dart_SetReturnValue(args, Dart_NewInteger(-bytes_written));
+    } else {
+      Dart_SetReturnValue(args, Dart_NewInteger(bytes_written));
+    }
   } else {
     // Extract OSError before we release data, as it may override the error.
     OSError os_error;
     Dart_TypedDataReleaseData(buffer_obj);
     Dart_SetReturnValue(args, DartUtils::NewDartOSError(&os_error));
   }
 }
 
 
 void FUNCTION_NAME(Socket_SendTo)(Dart_NativeArguments args) {
@@ skipping 438 matching lines @@
 intptr_t Socket::GetSocketIdNativeField(Dart_Handle socket_obj) {
   intptr_t socket = 0;
   Dart_Handle err =
       Dart_GetNativeInstanceField(socket_obj, kSocketIdNativeField, &socket);
   if (Dart_IsError(err)) Dart_PropagateError(err);
   return socket;
 }
 
 }  // namespace bin
 }  // namespace dart