Enforce handle ownership in base::Process

base/process/process.h

 // Copyright (c) 2011 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_PROCESS_PROCESS_PROCESS_H_
 #define BASE_PROCESS_PROCESS_PROCESS_H_
 
 #include "base/base_export.h"
 #include "base/basictypes.h"
+#include "base/move.h"
 #include "base/process/process_handle.h"
 #include "build/build_config.h"
 
+#if defined(OS_WIN)
+#include "base/win/scoped_handle.h"
+#endif
+
 namespace base {
 
+// Provides a move-only encapsulation of a process.
+//
+// This object is not tied to the lifetime of the underlying process: the
+// process may be killed and this object may still around, and it will still
+// claim to be valid. The actual behavior in that case is OS dependent like so:
+//
+// Windows: The underlying ProcessHandle will be valid after the process dies
+// and can be used to gather some information about that process, but most
+// methods will obviously fail.
+//
+// POSIX: The underlying PorcessHandle is not guaranteed to remain valid after
+// the process dies, and it may be reused by the system, which means that it may
+// end up pointing to the wrong process.
 class BASE_EXPORT Process {
+  MOVE_ONLY_TYPE_FOR_CPP_03(Process, RValue)
+
  public:
-  Process() : process_(kNullProcessHandle) {
-  }
+  explicit Process(ProcessHandle handle = kNullProcessHandle);
 
-  explicit Process(ProcessHandle handle) : process_(handle) {
-  }
+  // Move constructor for C++03 move emulation of this type.
+  Process(RValue other);
 
-  // A handle to the current process.
+  // The destructor does not terminate the process.
+  ~Process() {}
+
+  // Move operator= for C++03 move emulation of this type.
+  Process& operator=(RValue other);
+
+  // Returns an object for the current process.
   static Process Current();
 
+  // Returns true if processes can be backgrounded.
   static bool CanBackgroundProcesses();
 
-  // Get/Set the handle for this process. The handle will be 0 if the process
-  // is no longer running.
-  ProcessHandle handle() const { return process_; }
-  void set_handle(ProcessHandle handle) {
-    process_ = handle;
-  }
+  // Returns true if this objects represents a valid process.
+  bool IsValid() const;
+
+  // Returns a handle for this process. There is no guarantee about when that
+  // handle becomes invalid because this object retains ownership.
+  ProcessHandle Handle() const;
+
+  // Returns a second object that represents this process.
+  Process Duplicate() const;
 
   // Get the PID for this process.
   ProcessId pid() const;
 
-  // Is the this process the current process.
+  // Returns true if this process is the current process.
   bool is_current() const;
 
   // Close the process handle. This will not terminate the process.
   void Close();
 
-  // Terminates the process with extreme prejudice. The given result code will
-  // be the exit code of the process. If the process has already exited, this
-  // will do nothing.
+  // Terminates the process with extreme prejudice. The given |result_code| will
+  // be the exit code of the process.
+  // NOTE: On POSIX |result_code| is ignored.
   void Terminate(int result_code);
 
   // A process is backgrounded when it's priority is lower than normal.
   // Return true if this process is backgrounded, false otherwise.
   bool IsProcessBackgrounded() const;
 
-  // Set a process as backgrounded. If value is true, the priority
-  // of the process will be lowered. If value is false, the priority
-  // of the process will be made "normal" - equivalent to default
-  // process priority.
+  // Set a process as backgrounded. If value is true, the priority of the
+  // process will be lowered. If value is false, the priority of the process
+  // will be made "normal" - equivalent to default process priority.
   // Returns true if the priority was changed, false otherwise.
   bool SetProcessBackgrounded(bool value);
 
   // Returns an integer representing the priority of a process. The meaning
   // of this value is OS dependent.
   int GetPriority() const;
 
  private:
+#if defined(OS_WIN)
+  bool is_current_process_;
+  win::ScopedHandle process_;
+#else
   ProcessHandle process_;
+#endif
 };
 
 }  // namespace base
 
 #endif  // BASE_PROCESS_PROCESS_PROCESS_H_