Error reporting on File in dart:io

runtime/bin/utils_win.cc

Index: runtime/bin/utils_win.cc
diff --git a/runtime/bin/utils_win.cc b/runtime/bin/utils_win.cc
new file mode 100644
index 0000000000000000000000000000000000000000..29491cba5b4f33b42c8330f36a9d814f9578eb0e
--- /dev/null
+++ b/runtime/bin/utils_win.cc
@@ -0,0 +1,31 @@
+// 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 <errno.h>
+
+#include "bin/utils.h"
+
+OSError::OSError() : code_(0), message_(NULL) {
+  set_code(GetLastError());
+
+  static const int kMaxMessageLength = 256;
+  char message[kMaxMessageLength];
+  DWORD message_size =
+      FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
+                    NULL,
+                    code_,
+                    MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
+                    message,
+                    kMaxMessageLength,
+                    NULL);
+  if (message_size == 0) {
+    if (GetLastError() != ERROR_INSUFFICIENT_BUFFER) {
+      fprintf(stderr, "FormatMessage failed %d\n", GetLastError());
+    }
+    snprintf(message, kMaxMessageLength, "OS Error %d", code_);
+  }
+  message[kMaxMessageLength - 1] = '\0';
+
+  SetMessage(message);
+}