Change async read buffer sizes on Windows

runtime/bin/eventhandler_win.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 "platform/globals.h"
 #if defined(TARGET_OS_WINDOWS)
 
 #include "bin/eventhandler.h"
 
 #include <process.h>  // NOLINT
 #include <winsock2.h>  // NOLINT
 #include <ws2tcpip.h>  // NOLINT
 #include <mswsock.h>  // NOLINT
 
 #include "bin/builtin.h"
 #include "bin/dartutils.h"
 #include "bin/log.h"
 #include "bin/socket.h"
 #include "bin/utils.h"
 #include "platform/thread.h"
 
 
 namespace dart {
 namespace bin {
 
-static const int kBufferSize = 32 * 1024;
+static const int kBufferSize = 64 * 1024;
+static const int kStdioBufferSize = 16 * 1024;
 
 static const int kInfinityTimeout = -1;
 static const int kTimeoutId = -1;
 static const int kShutdownId = -2;
 
 IOBuffer* IOBuffer::AllocateBuffer(int buffer_size, Operation operation) {
   IOBuffer* buffer = new(buffer_size) IOBuffer(buffer_size, operation);
   return buffer;
 }
 
@@ skipping 168 matching lines @@
 
 static unsigned int __stdcall ReadFileThread(void* args) {
   Handle* handle = reinterpret_cast<Handle*>(args);
   handle->ReadSyncCompleteAsync();
   return 0;
 }
 
 
 void Handle::ReadSyncCompleteAsync() {
   ASSERT(pending_read_ != NULL);
+  ASSERT(pending_read_->GetBufferSize() >= kStdioBufferSize);
+
+  DWORD buffer_size = pending_read_->GetBufferSize();
+  if (GetFileType(handle_) == FILE_TYPE_CHAR) {
+    buffer_size = kStdioBufferSize;
+  }
   DWORD bytes_read = 0;
   BOOL ok = ReadFile(handle_,
                      pending_read_->GetBufferStart(),
-                     pending_read_->GetBufferSize(),
+                     buffer_size,
                      &bytes_read,
                      NULL);
   if (!ok) {
     if (GetLastError() != ERROR_BROKEN_PIPE) {
       Log::PrintErr("ReadFile failed %d\n", GetLastError());
     }
     bytes_read = 0;
   }
   OVERLAPPED* overlapped = pending_read_->GetCleanOverlapped();
   ok = PostQueuedCompletionStatus(event_handler_->completion_port(),
@@ skipping 762 matching lines @@
 
 
 void EventHandlerImplementation::Shutdown() {
   SendData(kShutdownId, 0, 0);
 }
 
 }  // namespace bin
 }  // namespace dart
 
 #endif  // defined(TARGET_OS_WINDOWS)