win: Add HandleToInt() and IntToHandle()

util/win/handle.cc

+// 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 {
+
+int HandleToInt(HANDLE handle) {
+  return base::checked_cast<int>(reinterpret_cast<intptr_t>(handle));

[scottmg, 2015/11/05 18:03:18]

I would have made these uintptr_t and uint32_t. Do handles have to be be <
0x8000`0000? Otherwise it seems odd to have them go negative especially when
they're being sent as %xs.

[Mark Mentovai, 2015/11/05 18:26:14]

scottmg wrote:
INVALID_HANDLE_VALUE is -1, so we have to use ints for sign-extension to do the
right thing, otherwise in 64-bit processes, we’d convert (HANDLE)
INVALID_HANDLE_VALUE → (unsigned) 0xffffffff → (HANDLE) 0xffffffff, which isn’t
a nice clean round-trip.

I could do static_cast<unsigned
int>(base::checked_cast<int>(reinterpret_cast<intptr_t>(handle))); (or uint32_t
instead of unsigned int) if that would be better.

I could also just document why I chose int. Probably makes more sense in this
.cc than in the .h, since it’s kind of a detail.

What do you think?

[scottmg, 2015/11/05 18:40:04]

Gotcha. I think what you did seem right then. We should probably changed the
uint32_ts in the registration protocol and elsewhere to ints in that case.

+}
+
+HANDLE IntToHandle(int handle_int) {
+  return reinterpret_cast<HANDLE>(static_cast<intptr_t>(handle_int));
+}
+
+}  // namespace crashpad