src/llvm/include/llvm/ADT/IntrusiveRefCntPtr.h

   1 //== llvm/ADT/IntrusiveRefCntPtr.h - Smart Refcounting Pointer ---*- 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 IntrusiveRefCntPtr, a template class that
  11 // implements a "smart" pointer for objects that maintain their own
  12 // internal reference count, and RefCountedBase/RefCountedBaseVPTR, two
  13 // generic base classes for objects that wish to have their lifetimes
  14 // managed using reference counting.
  15 //
  16 // IntrusiveRefCntPtr is similar to Boost's intrusive_ptr with added
  17 // LLVM-style casting.
  18 //
  19 //===----------------------------------------------------------------------===//
  20
  21 #ifndef LLVM_ADT_INTRUSIVE_REF_CNT_PTR
  22 #define LLVM_ADT_INTRUSIVE_REF_CNT_PTR
  23
  24 #include "llvm/Support/Casting.h"
  25 #include "llvm/Support/Compiler.h"
  26 #include <memory>
  27
  28 namespace llvm {
  29
  30   template <class T>
  31   class IntrusiveRefCntPtr;
  32
  33 //===----------------------------------------------------------------------===//
  34 /// RefCountedBase - A generic base class for objects that wish to
  35 ///  have their lifetimes managed using reference counts. Classes
  36 ///  subclass RefCountedBase to obtain such functionality, and are
  37 ///  typically handled with IntrusiveRefCntPtr "smart pointers" (see below)
  38 ///  which automatically handle the management of reference counts.
  39 ///  Objects that subclass RefCountedBase should not be allocated on
  40 ///  the stack, as invoking "delete" (which is called when the
  41 ///  reference count hits 0) on such objects is an error.
  42 //===----------------------------------------------------------------------===//
  43   template <class Derived>
  44   class RefCountedBase {
  45     mutable unsigned ref_cnt;
  46
  47   public:
  48     RefCountedBase() : ref_cnt(0) {}
  49     RefCountedBase(const RefCountedBase &) : ref_cnt(0) {}
  50
  51     void Retain() const { ++ref_cnt; }
  52     void Release() const {
  53       assert (ref_cnt > 0 && "Reference count is already zero.");
  54       if (--ref_cnt == 0) delete static_cast<const Derived*>(this);
  55     }
  56   };
  57
  58 //===----------------------------------------------------------------------===//
  59 /// RefCountedBaseVPTR - A class that has the same function as
  60 ///  RefCountedBase, but with a virtual destructor. Should be used
  61 ///  instead of RefCountedBase for classes that already have virtual
  62 ///  methods to enforce dynamic allocation via 'new'. Classes that
  63 ///  inherit from RefCountedBaseVPTR can't be allocated on stack -
  64 ///  attempting to do this will produce a compile error.
  65 //===----------------------------------------------------------------------===//
  66   class RefCountedBaseVPTR {
  67     mutable unsigned ref_cnt;
  68     virtual void anchor();
  69
  70   protected:
  71     RefCountedBaseVPTR() : ref_cnt(0) {}
  72     RefCountedBaseVPTR(const RefCountedBaseVPTR &) : ref_cnt(0) {}
  73
  74     virtual ~RefCountedBaseVPTR() {}
  75
  76     void Retain() const { ++ref_cnt; }
  77     void Release() const {
  78       assert (ref_cnt > 0 && "Reference count is already zero.");
  79       if (--ref_cnt == 0) delete this;
  80     }
  81
  82     template <typename T>
  83     friend struct IntrusiveRefCntPtrInfo;
  84   };
  85
  86
  87   template <typename T> struct IntrusiveRefCntPtrInfo {
  88     static void retain(T *obj) { obj->Retain(); }
  89     static void release(T *obj) { obj->Release(); }
  90   };
  91
  92 //===----------------------------------------------------------------------===//
  93 /// IntrusiveRefCntPtr - A template class that implements a "smart pointer"
  94 ///  that assumes the wrapped object has a reference count associated
  95 ///  with it that can be managed via calls to
  96 ///  IntrusivePtrAddRef/IntrusivePtrRelease.  The smart pointers
  97 ///  manage reference counts via the RAII idiom: upon creation of
  98 ///  smart pointer the reference count of the wrapped object is
  99 ///  incremented and upon destruction of the smart pointer the
 100 ///  reference count is decremented.  This class also safely handles
 101 ///  wrapping NULL pointers.
 102 ///
 103 /// Reference counting is implemented via calls to
 104 ///  Obj->Retain()/Obj->Release(). Release() is required to destroy
 105 ///  the object when the reference count reaches zero. Inheriting from
 106 ///  RefCountedBase/RefCountedBaseVPTR takes care of this
 107 ///  automatically.
 108 //===----------------------------------------------------------------------===//
 109   template <typename T>
 110   class IntrusiveRefCntPtr {
 111     T* Obj;
 112     typedef IntrusiveRefCntPtr this_type;
 113   public:
 114     typedef T element_type;
 115
 116     explicit IntrusiveRefCntPtr() : Obj(0) {}
 117
 118     IntrusiveRefCntPtr(T* obj) : Obj(obj) {
 119       retain();
 120     }
 121
 122     IntrusiveRefCntPtr(const IntrusiveRefCntPtr& S) : Obj(S.Obj) {
 123       retain();
 124     }
 125
 126 #if LLVM_USE_RVALUE_REFERENCES
 127     IntrusiveRefCntPtr(IntrusiveRefCntPtr&& S) : Obj(S.Obj) {
 128       S.Obj = 0;
 129     }
 130
 131     template <class X>
 132     IntrusiveRefCntPtr(IntrusiveRefCntPtr<X>&& S) : Obj(S.getPtr()) {
 133       S.Obj = 0;
 134     }
 135 #endif
 136
 137     template <class X>
 138     IntrusiveRefCntPtr(const IntrusiveRefCntPtr<X>& S)
 139       : Obj(S.getPtr()) {
 140       retain();
 141     }
 142
 143     IntrusiveRefCntPtr& operator=(IntrusiveRefCntPtr S) {
 144       swap(S);
 145       return *this;
 146     }
 147
 148     ~IntrusiveRefCntPtr() { release(); }
 149
 150     T& operator*() const { return *Obj; }
 151
 152     T* operator->() const { return Obj; }
 153
 154     T* getPtr() const { return Obj; }
 155
 156     typedef T* (IntrusiveRefCntPtr::*unspecified_bool_type) () const;
 157     operator unspecified_bool_type() const {
 158       return Obj == 0 ? 0 : &IntrusiveRefCntPtr::getPtr;
 159     }
 160
 161     void swap(IntrusiveRefCntPtr& other) {
 162       T* tmp = other.Obj;
 163       other.Obj = Obj;
 164       Obj = tmp;
 165     }
 166
 167     void reset() {
 168       release();
 169       Obj = 0;
 170     }
 171
 172     void resetWithoutRelease() {
 173       Obj = 0;
 174     }
 175
 176   private:
 177     void retain() { if (Obj) IntrusiveRefCntPtrInfo<T>::retain(Obj); }
 178     void release() { if (Obj) IntrusiveRefCntPtrInfo<T>::release(Obj); }
 179   };
 180
 181   template<class T, class U>
 182   inline bool operator==(const IntrusiveRefCntPtr<T>& A,
 183                          const IntrusiveRefCntPtr<U>& B)
 184   {
 185     return A.getPtr() == B.getPtr();
 186   }
 187
 188   template<class T, class U>
 189   inline bool operator!=(const IntrusiveRefCntPtr<T>& A,
 190                          const IntrusiveRefCntPtr<U>& B)
 191   {
 192     return A.getPtr() != B.getPtr();
 193   }
 194
 195   template<class T, class U>
 196   inline bool operator==(const IntrusiveRefCntPtr<T>& A,
 197                          U* B)
 198   {
 199     return A.getPtr() == B;
 200   }
 201
 202   template<class T, class U>
 203   inline bool operator!=(const IntrusiveRefCntPtr<T>& A,
 204                          U* B)
 205   {
 206     return A.getPtr() != B;
 207   }
 208
 209   template<class T, class U>
 210   inline bool operator==(T* A,
 211                          const IntrusiveRefCntPtr<U>& B)
 212   {
 213     return A == B.getPtr();
 214   }
 215
 216   template<class T, class U>
 217   inline bool operator!=(T* A,
 218                          const IntrusiveRefCntPtr<U>& B)
 219   {
 220     return A != B.getPtr();
 221   }
 222
 223 //===----------------------------------------------------------------------===//
 224 // LLVM-style downcasting support for IntrusiveRefCntPtr objects
 225 //===----------------------------------------------------------------------===//
 226
 227   template<class T> struct simplify_type<IntrusiveRefCntPtr<T> > {
 228     typedef T* SimpleType;
 229     static SimpleType getSimplifiedValue(const IntrusiveRefCntPtr<T>& Val) {
 230       return Val.getPtr();
 231     }
 232   };
 233
 234   template<class T> struct simplify_type<const IntrusiveRefCntPtr<T> > {
 235     typedef T* SimpleType;
 236     static SimpleType getSimplifiedValue(const IntrusiveRefCntPtr<T>& Val) {
 237       return Val.getPtr();
 238     }
 239   };
 240
 241 } // end namespace llvm
 242
 243 #endif // LLVM_ADT_INTRUSIVE_REF_CNT_PTR