1 //===- llvm/Support/PointerLikeTypeTraits.h - Pointer Traits ----*- 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 // This file defines the PointerLikeTypeTraits class.  This allows data
11 // structures to reason about pointers and other things that are pointer sized.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #ifndef LLVM_SUPPORT_POINTERLIKETYPETRAITS_H
16 #define LLVM_SUPPORT_POINTERLIKETYPETRAITS_H
17 
18 #include "llvm/Support/DataTypes.h"
19 
20 namespace llvm {
21 
22 /// PointerLikeTypeTraits - This is a traits object that is used to handle
23 /// pointer types and things that are just wrappers for pointers as a uniform
24 /// entity.
25 template <typename T>
26 class PointerLikeTypeTraits {
27   // getAsVoidPointer
28   // getFromVoidPointer
29   // getNumLowBitsAvailable
30 };
31 
32 // Provide PointerLikeTypeTraits for non-cvr pointers.
33 template<typename T>
34 class PointerLikeTypeTraits<T*> {
35 public:
getAsVoidPointer(T * P)36   static inline void *getAsVoidPointer(T *P) { return P; }
getFromVoidPointer(void * P)37   static inline T *getFromVoidPointer(void *P) { return static_cast<T *>(P); }
38 
39   /// Note, we assume here that malloc returns objects at least 4-byte aligned.
40   /// However, this may be wrong, or pointers may be from something other than
41   /// malloc.  In this case, you should specialize this template to reduce this.
42   ///
43   /// All clients should use assertions to do a run-time check to ensure that
44   /// this is actually true.
45   enum { NumLowBitsAvailable = 2 };
46 };
47 
48 // Provide PointerLikeTypeTraits for const pointers.
49 template<typename T>
50 class PointerLikeTypeTraits<const T*> {
51   typedef PointerLikeTypeTraits<T*> NonConst;
52 
53 public:
getAsVoidPointer(const T * P)54   static inline const void *getAsVoidPointer(const T* P) {
55     return NonConst::getAsVoidPointer(const_cast<T*>(P));
56   }
getFromVoidPointer(const void * P)57   static inline const T *getFromVoidPointer(const void *P) {
58     return NonConst::getFromVoidPointer(const_cast<void*>(P));
59   }
60   enum { NumLowBitsAvailable = NonConst::NumLowBitsAvailable };
61 };
62 
63 // Provide PointerLikeTypeTraits for uintptr_t.
64 template<>
65 class PointerLikeTypeTraits<uintptr_t> {
66 public:
getAsVoidPointer(uintptr_t P)67   static inline void *getAsVoidPointer(uintptr_t P) {
68     return reinterpret_cast<void*>(P);
69   }
getFromVoidPointer(void * P)70   static inline uintptr_t getFromVoidPointer(void *P) {
71     return reinterpret_cast<uintptr_t>(P);
72   }
73   // No bits are available!
74   enum { NumLowBitsAvailable = 0 };
75 };
76 
77 } // end namespace llvm
78 
79 #endif
80