Make SharedMemoryHandle a class on Mac.

base/memory/shared_memory_handle.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef BASE_MEMORY_SHARED_MEMORY_HANDLE_H_
+#define BASE_MEMORY_SHARED_MEMORY_HANDLE_H_
+
+#include "build/build_config.h"
+
+#if defined(OS_WIN)
+#include <windows.h>
+#elif defined(OS_MACOSX) && !defined(OS_IOS)
+#include <sys/types.h>
+#include "base/base_export.h"
+#include "base/file_descriptor_posix.h"
+#include "base/macros.h"
+#elif defined(OS_POSIX)
+#include <sys/types.h>
+#include "base/file_descriptor_posix.h"
+#endif
+
+namespace base {
+
+class Pickle;
+
+// SharedMemoryHandle is a platform specific type which represents
+// the underlying OS handle to a shared memory segment.
+#if defined(OS_WIN)
+typedef HANDLE SharedMemoryHandle;
+#elif defined(OS_MACOSX) && !defined(OS_IOS)
+
+class BASE_EXPORT SharedMemoryHandle {
+ public:
+  enum Mechanism {

[Robert Sesek, 2015/06/15 21:34:33]

"Mechanism" seems very verbose to me. Does "Type" sound OK to you?

[erikchen, 2015/06/16 00:59:27]

I think "Type" is a poor choice for a type, since the word "type" is already
heavily overloaded. That being said, I think debating this point costs more than
the additional round-trip review latency, so I've changed the enum to be Type.

[Robert Sesek, 2015/06/16 22:53:05]

If it were just "Type" I'd agree, but since the fully qualified name is
SharedMemoryHandle::Type, I think that's fairly descriptive.

+    // Indicates that the SharedMemoryHandle is backed by a POSIX fd.
+    POSIX,
+    // Indicates that the SharedMemoryHandle is backed by the Mach primitive
+    // "memory object".
+    MACH,
+  };
+
+  // The default constructor returns an invalid SharedMemoryHandle.
+  SharedMemoryHandle();
+
+  // Constructs a SharedMemoryHandle backed by |file_descriptor|.
+  explicit SharedMemoryHandle(const FileDescriptor& file_descriptor);
+
+  // Constructs a SharedMemoryHandle backed by the components of a
+  // FileDescriptor.
+  SharedMemoryHandle(int fd, bool auto_close);
+
+  // Standard copy constructor. The new instance shares the underlying OS
+  // primitives.
+  SharedMemoryHandle(const SharedMemoryHandle& handle);
+
+  // Standard assignment operator. The updated instance shares the underlying
+  // OS primitives.
+  SharedMemoryHandle& operator=(const SharedMemoryHandle& handle);
+
+  // Comparison operators.
+  bool operator==(const SharedMemoryHandle& handle) const;
+  bool operator!=(const SharedMemoryHandle& handle) const;
+
+  // Serializes the mechanism.
+  void WriteMechanismToPickle(Pickle* pickle) const;
+
+  // Deserializes the mechanism from the pickle iterator.
+  bool ReadMechanismFromPickle(PickleIterator* iterator);
+
+  // Whether the instance is backed by a POSIX fd.
+  bool IsBackedByPOSIXFd() const;
+
+  // Returns the POSIX fd backing the SharedMemoryHandle. Requires that the

[Robert Sesek, 2015/06/15 21:34:32]

Is this necessary if there's also GetFileDescriptor()->fd ?

[erikchen, 2015/06/16 00:59:27]

Nope. I've removed this method. I prefer to keep the setter. (Theoretically, we
could use the non-const GetFileDescriptor(), but I would like to use that method
as little as possible, since exposing instance-internal pointers is not a good
interface.)

+  // SharedMemoryHandle be backed by a POSIX fd.
+  int GetFileHandle() const;
+
+  // Sets the POSIX fd backing the SharedMemoryHandle. Requires that the
+  // SharedMemoryHandle be backed by a POSIX fd.
+  void SetFileHandle(int fd, bool auto_close);
+
+  // Returns the address of the POSIX FileDescriptor backing the
+  // SharedMemoryHandle.
+  FileDescriptor* GetFileDescriptor();
+  const FileDescriptor* GetFileDescriptor() const;
+
+  // Duplicates the underlying OS resources.

[Robert Sesek, 2015/06/15 21:34:33]

Move this up to be after or before teh assignment operator?

[erikchen, 2015/06/16 00:59:27]

Sure, done

+  SharedMemoryHandle Duplicate() const;
+
+ private:
+  Mechanism mechanism_;
+  FileDescriptor file_descriptor_;
+};
+#elif defined(OS_POSIX)
+typedef FileDescriptor SharedMemoryHandle;
+#endif
+
+}  // namespace base
+
+#endif  // BASE_MEMORY_SHARED_MEMORY_HANDLE_H_