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 #include <type_traits> 20 21 namespace llvm { 22 23 /// A traits type that is used to handle pointer types and things that are just 24 /// wrappers for pointers as a uniform entity. 25 template <typename T> struct PointerLikeTypeTraits; 26 27 namespace detail { 28 /// A tiny meta function to compute the log2 of a compile time constant. 29 template <size_t N> 30 struct ConstantLog2 31 : std::integral_constant<size_t, ConstantLog2<N / 2>::value + 1> {}; 32 template <> struct ConstantLog2<1> : std::integral_constant<size_t, 0> {}; 33 34 // Provide a trait to check if T is pointer-like. 35 template <typename T, typename U = void> struct HasPointerLikeTypeTraits { 36 static const bool value = false; 37 }; 38 39 // sizeof(T) is valid only for a complete T. 40 template <typename T> struct HasPointerLikeTypeTraits< 41 T, decltype((sizeof(PointerLikeTypeTraits<T>) + sizeof(T)), void())> { 42 static const bool value = true; 43 }; 44 45 template <typename T> struct IsPointerLike { 46 static const bool value = HasPointerLikeTypeTraits<T>::value; 47 }; 48 49 template <typename T> struct IsPointerLike<T *> { 50 static const bool value = true; 51 }; 52 } // namespace detail 53 54 // Provide PointerLikeTypeTraits for non-cvr pointers. 55 template <typename T> struct PointerLikeTypeTraits<T *> { 56 static inline void *getAsVoidPointer(T *P) { return P; } 57 static inline T *getFromVoidPointer(void *P) { return static_cast<T *>(P); } 58 59 enum { NumLowBitsAvailable = detail::ConstantLog2<alignof(T)>::value }; 60 }; 61 62 template <> struct PointerLikeTypeTraits<void *> { 63 static inline void *getAsVoidPointer(void *P) { return P; } 64 static inline void *getFromVoidPointer(void *P) { return P; } 65 66 /// Note, we assume here that void* is related to raw malloc'ed memory and 67 /// that malloc returns objects at least 4-byte aligned. However, this may be 68 /// wrong, or pointers may be from something other than malloc. In this case, 69 /// you should specify a real typed pointer or avoid this template. 70 /// 71 /// All clients should use assertions to do a run-time check to ensure that 72 /// this is actually true. 73 enum { NumLowBitsAvailable = 2 }; 74 }; 75 76 // Provide PointerLikeTypeTraits for const things. 77 template <typename T> struct PointerLikeTypeTraits<const T> { 78 typedef PointerLikeTypeTraits<T> NonConst; 79 80 static inline const void *getAsVoidPointer(const T P) { 81 return NonConst::getAsVoidPointer(P); 82 } 83 static inline const T getFromVoidPointer(const void *P) { 84 return NonConst::getFromVoidPointer(const_cast<void *>(P)); 85 } 86 enum { NumLowBitsAvailable = NonConst::NumLowBitsAvailable }; 87 }; 88 89 // Provide PointerLikeTypeTraits for const pointers. 90 template <typename T> struct PointerLikeTypeTraits<const T *> { 91 typedef PointerLikeTypeTraits<T *> NonConst; 92 93 static inline const void *getAsVoidPointer(const T *P) { 94 return NonConst::getAsVoidPointer(const_cast<T *>(P)); 95 } 96 static inline const T *getFromVoidPointer(const void *P) { 97 return NonConst::getFromVoidPointer(const_cast<void *>(P)); 98 } 99 enum { NumLowBitsAvailable = NonConst::NumLowBitsAvailable }; 100 }; 101 102 // Provide PointerLikeTypeTraits for uintptr_t. 103 template <> struct PointerLikeTypeTraits<uintptr_t> { 104 static inline void *getAsVoidPointer(uintptr_t P) { 105 return reinterpret_cast<void *>(P); 106 } 107 static inline uintptr_t getFromVoidPointer(void *P) { 108 return reinterpret_cast<uintptr_t>(P); 109 } 110 // No bits are available! 111 enum { NumLowBitsAvailable = 0 }; 112 }; 113 114 } // end namespace llvm 115 116 #endif 117
