win: Add HandleToInt() and IntToHandle()

util/win/handle.cc

Index: util/win/handle.cc
diff --git a/util/win/handle.cc b/util/win/handle.cc
new file mode 100644
index 0000000000000000000000000000000000000000..c53f54388ed56a285754fc343cd970a3072090f3
--- /dev/null
+++ b/util/win/handle.cc
@@ -0,0 +1,36 @@
+// Copyright 2015 The Crashpad Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "util/win/handle.h"
+
+#include <stdint.h>
+
+#include "base/numerics/safe_conversions.h"
+
+namespace crashpad {
+
+// These functions use “int” for the 32-bit integer handle type because
+// sign-extension needs to work correctly. INVALID_HANDLE_VALUE is defined as
+// ((HANDLE)(LONG_PTR)-1), and this needs to round-trip through an integer and
+// back to the same HANDLE value.
+
+int HandleToInt(HANDLE handle) {
+  return base::checked_cast<int>(reinterpret_cast<intptr_t>(handle));
+}
+
+HANDLE IntToHandle(int handle_int) {
+  return reinterpret_cast<HANDLE>(static_cast<intptr_t>(handle_int));
+}
+
+}  // namespace crashpad