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 {
+
+// 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 {
+    // Indicates that the SharedMemoryHandle is backed by a POSIX fd.
+    POSIX_FD = 0,

[Robert Sesek, 2015/06/05 19:27:14]

I think just POSIX and MACH are better names.

[erikchen, 2015/06/06 01:47:00]

Done.

+    // Indicates that the SharedMemoryHandle is backed by the Mach primitive
+    // "memory object".
+    MACH_PRIMITIVE = 1,
+  };
+
+  // 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;
+
+  // Returns the mechanism that backs the SharedMemoryHandle for wire transfer.
+  uint32_t GetMechanismForWire() const;

[Robert Sesek, 2015/06/05 19:27:14]

These names are kind of awkward. Why not just have SharedMemoryHandle pickle and
depickle itself? Add WriteToPickle(Pickle*) and ReadFromPickle(PickleIterator*),
and then none of the implementation details need to leak.

[erikchen, 2015/06/06 01:47:00]

I moved the mechanism logic into this class, but the FD logic needs to be
exposed since reading/writing attachments is a Chrome IPC addition onto
base::Pickle.

+
+  // Sets the mechanism used to back the SharedMemoryHandle.
+  // Returns whether |mechanism| was a valid input.
+  bool SetMechanismFromWire(uint32_t mechanism);
+
+  // Whether the instance is backed by a POSIX fd.
+  bool IsBackedByPOSIXFd() const;
+
+  // Returns the POSIX fd backing the SharedMemoryHandle. Requires that the
+  // 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.
+  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_