1 //===- llvm/Support/PointerLikeTypeTraits.h - Pointer Traits ----*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 // This file defines the PointerLikeTypeTraits class. This allows data
11 // structures to reason about pointers and other things that are pointer sized.
13 //===----------------------------------------------------------------------===//
15 #ifndef LLVM_SUPPORT_POINTERLIKETYPETRAITS_H
16 #define LLVM_SUPPORT_POINTERLIKETYPETRAITS_H
18 #include "llvm/Support/DataTypes.h"
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
26 class PointerLikeTypeTraits {
29 // getNumLowBitsAvailable
32 // Provide PointerLikeTypeTraits for non-cvr pointers.
34 class PointerLikeTypeTraits<T*> {
36 static inline void *getAsVoidPointer(T* P) { return P; }
37 static inline T *getFromVoidPointer(void *P) {
38 return static_cast<T*>(P);
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.
45 /// All clients should use assertions to do a run-time check to ensure that
46 /// this is actually true.
47 enum { NumLowBitsAvailable = 3 };
50 // Provide PointerLikeTypeTraits for const pointers.
52 class PointerLikeTypeTraits<const T*> {
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);
58 enum { NumLowBitsAvailable = 3 };
61 // Pointers to pointers are only 4-byte aligned on 32-bit systems.
63 class PointerLikeTypeTraits<T**> {
65 static inline void *getAsVoidPointer(T** P) { return P; }
66 static inline T **getFromVoidPointer(void *P) {
67 return static_cast<T**>(P);
69 enum { NumLowBitsAvailable = 2 };
75 // Provide PointerLikeTypeTraits for uintptr_t.
77 class PointerLikeTypeTraits<uintptr_t> {
79 static inline void *getAsVoidPointer(uintptr_t P) {
80 return reinterpret_cast<void*>(P);
82 static inline uintptr_t getFromVoidPointer(void *P) {
83 return reinterpret_cast<uintptr_t>(P);
85 // No bits are available!
86 enum { NumLowBitsAvailable = 0 };
89 } // end namespace llvm