PointerLikeTypeTraits.h revision 193323 
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
20namespace 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.
25template <typename T>
26class PointerLikeTypeTraits {
27  // getAsVoidPointer
28  // getFromVoidPointer
29  // getNumLowBitsAvailable
30};
31
32// Provide PointerLikeTypeTraits for non-cvr pointers.
33template<typename T>
34class PointerLikeTypeTraits<T*> {
35public:
36  static inline void *getAsVoidPointer(T* P) { return P; }
37  static inline T *getFromVoidPointer(void *P) {
38    return static_cast<T*>(P);
39  }
40
41  /// Note, we assume here that malloc returns objects at least 8-byte aligned.
42  /// However, this may be wrong, or pointers may be from something other than
43  /// malloc.  In this case, you should specialize this template to reduce this.
44  ///
45  /// All clients should use assertions to do a run-time check to ensure that
46  /// this is actually true.
47  enum { NumLowBitsAvailable = 2 };
48};
49
50// Provide PointerLikeTypeTraits for const pointers.
51template<typename T>
52class PointerLikeTypeTraits<const T*> {
53public:
54  static inline const void *getAsVoidPointer(const T* P) { return P; }
55  static inline const T *getFromVoidPointer(const void *P) {
56    return static_cast<const T*>(P);
57  }
58  enum { NumLowBitsAvailable = 2 };
59};
60
61// Provide PointerLikeTypeTraits for uintptr_t.
62template<>
63class PointerLikeTypeTraits<uintptr_t> {
64public:
65  static inline void *getAsVoidPointer(uintptr_t P) {
66    return reinterpret_cast<void*>(P);
67  }
68  static inline uintptr_t getFromVoidPointer(void *P) {
69    return reinterpret_cast<uintptr_t>(P);
70  }
71  // No bits are available!
72  enum { NumLowBitsAvailable = 0 };
73};
74
75} // end namespace llvm
76
77#endif
78