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 4-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*> {
53  typedef PointerLikeTypeTraits<T*> NonConst;
54
55public:
56  static inline const void *getAsVoidPointer(const T* P) {
57    return NonConst::getAsVoidPointer(const_cast<T*>(P));
58  }
59  static inline const T *getFromVoidPointer(const void *P) {
60    return NonConst::getFromVoidPointer(const_cast<void*>(P));
61  }
62  enum { NumLowBitsAvailable = NonConst::NumLowBitsAvailable };
63};
64
65// Provide PointerLikeTypeTraits for uintptr_t.
66template<>
67class PointerLikeTypeTraits<uintptr_t> {
68public:
69  static inline void *getAsVoidPointer(uintptr_t P) {
70    return reinterpret_cast<void*>(P);
71  }
72  static inline uintptr_t getFromVoidPointer(void *P) {
73    return reinterpret_cast<uintptr_t>(P);
74  }
75  // No bits are available!
76  enum { NumLowBitsAvailable = 0 };
77};
78
79} // end namespace llvm
80
81#endif
82