1 //===-- MIUtilSingletonBase.h -----------------------------------*- C++ -*-===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 
10 #pragma once
11 
12 namespace MI {
13 
14 //   MI::ISingleton base class usage:
15 //
16 //   class CMIDerivedClass
17 //       : public MI::ISingleton< CMIDerivedClass >
18 //   {
19 //       friend MI::ISingleton< CMIDerivedClass >;
20 //
21 //   // Overridden:
22 //   public:
23 //       // From MI::ISingleton
24 //       bool Initialize() override;
25 //       bool Shutdown() override;
26 //   };
27 
28 //++
29 //============================================================================
30 // Details: Base class for the singleton pattern.
31 // Gotchas: Derived class must specify MI::ISingleton<> as a friend class.
32 //--
33 template <typename T> class ISingleton {
34   // Statics:
35 public:
36   // Return an instance of the derived class
Instance()37   static T &Instance() {
38     // This will fail if the derived class has not
39     // declared itself to be a friend of MI::ISingleton
40     static T instance;
41 
42     return instance;
43   }
44 
45   // Overrideable:
46 public:
47   virtual bool Initialize() = 0;
48   virtual bool Shutdown() = 0;
49   //
~ISingleton()50   /* dtor */ virtual ~ISingleton() {}
51 };
52 
53 } // namespace MI
54