Prepare wpiutil for merge into allwpilib.

wpiutil/src/main/native/include/llvm/IntrusiveRefCntPtr.h

@@ -0,0 +1,288 @@
+//== llvm/ADT/IntrusiveRefCntPtr.h - Smart Refcounting Pointer ---*- C++ -*-==//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines IntrusiveRefCntPtr, a template class that
+// implements a "smart" pointer for objects that maintain their own
+// internal reference count, and RefCountedBase/RefCountedBaseVPTR, two
+// generic base classes for objects that wish to have their lifetimes
+// managed using reference counting.
+//
+// IntrusiveRefCntPtr is similar to Boost's intrusive_ptr with added
+// LLVM-style casting.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_INTRUSIVEREFCNTPTR_H
+#define LLVM_ADT_INTRUSIVEREFCNTPTR_H
+
+#include <atomic>
+#include <cassert>
+#include <cstddef>
+
+namespace llvm {
+
+  template <class T>
+  class IntrusiveRefCntPtr;
+
+//===----------------------------------------------------------------------===//
+/// RefCountedBase - A generic base class for objects that wish to
+///  have their lifetimes managed using reference counts. Classes
+///  subclass RefCountedBase to obtain such functionality, and are
+///  typically handled with IntrusiveRefCntPtr "smart pointers" (see below)
+///  which automatically handle the management of reference counts.
+///  Objects that subclass RefCountedBase should not be allocated on
+///  the stack, as invoking "delete" (which is called when the
+///  reference count hits 0) on such objects is an error.
+//===----------------------------------------------------------------------===//
+  template <class Derived>
+  class RefCountedBase {
+    mutable unsigned ref_cnt;
+
+  public:
+    RefCountedBase() : ref_cnt(0) {}
+    RefCountedBase(const RefCountedBase &) : ref_cnt(0) {}
+
+    void Retain() const { ++ref_cnt; }
+    void Release() const {
+      assert (ref_cnt > 0 && "Reference count is already zero.");
+      if (--ref_cnt == 0) delete static_cast<const Derived*>(this);
+    }
+  };
+
+//===----------------------------------------------------------------------===//
+/// RefCountedBaseVPTR - A class that has the same function as
+///  RefCountedBase, but with a virtual destructor. Should be used
+///  instead of RefCountedBase for classes that already have virtual
+///  methods to enforce dynamic allocation via 'new'. Classes that
+///  inherit from RefCountedBaseVPTR can't be allocated on stack -
+///  attempting to do this will produce a compile error.
+//===----------------------------------------------------------------------===//
+  class RefCountedBaseVPTR {
+    mutable unsigned ref_cnt;
+    virtual void anchor();
+
+  protected:
+    RefCountedBaseVPTR() : ref_cnt(0) {}
+    RefCountedBaseVPTR(const RefCountedBaseVPTR &) : ref_cnt(0) {}
+
+    virtual ~RefCountedBaseVPTR() {}
+
+    void Retain() const { ++ref_cnt; }
+    void Release() const {
+      assert (ref_cnt > 0 && "Reference count is already zero.");
+      if (--ref_cnt == 0) delete this;
+    }
+
+    template <typename T>
+    friend struct IntrusiveRefCntPtrInfo;
+  };
+
+
+  template <typename T> struct IntrusiveRefCntPtrInfo {
+    static void retain(T *obj) { obj->Retain(); }
+    static void release(T *obj) { obj->Release(); }
+  };
+
+/// \brief A thread-safe version of \c llvm::RefCountedBase.
+///
+/// A generic base class for objects that wish to have their lifetimes managed
+/// using reference counts. Classes subclass \c ThreadSafeRefCountedBase to
+/// obtain such functionality, and are typically handled with
+/// \c IntrusiveRefCntPtr "smart pointers" which automatically handle the
+/// management of reference counts.
+template <class Derived>
+class ThreadSafeRefCountedBase {
+  mutable std::atomic<int> RefCount;
+
+protected:
+  ThreadSafeRefCountedBase() : RefCount(0) {}
+
+public:
+  void Retain() const { ++RefCount; }
+
+  void Release() const {
+    int NewRefCount = --RefCount;
+    assert(NewRefCount >= 0 && "Reference count was already zero.");
+    if (NewRefCount == 0)
+      delete static_cast<const Derived*>(this);
+  }
+};
+
+//===----------------------------------------------------------------------===//
+/// IntrusiveRefCntPtr - A template class that implements a "smart pointer"
+///  that assumes the wrapped object has a reference count associated
+///  with it that can be managed via calls to
+///  IntrusivePtrAddRef/IntrusivePtrRelease.  The smart pointers
+///  manage reference counts via the RAII idiom: upon creation of
+///  smart pointer the reference count of the wrapped object is
+///  incremented and upon destruction of the smart pointer the
+///  reference count is decremented.  This class also safely handles
+///  wrapping NULL pointers.
+///
+/// Reference counting is implemented via calls to
+///  Obj->Retain()/Obj->Release(). Release() is required to destroy
+///  the object when the reference count reaches zero. Inheriting from
+///  RefCountedBase/RefCountedBaseVPTR takes care of this
+///  automatically.
+//===----------------------------------------------------------------------===//
+  template <typename T>
+  class IntrusiveRefCntPtr {
+    T* Obj;
+
+  public:
+    typedef T element_type;
+
+    explicit IntrusiveRefCntPtr() : Obj(nullptr) {}
+
+    IntrusiveRefCntPtr(T* obj) : Obj(obj) {
+      retain();
+    }
+
+    IntrusiveRefCntPtr(const IntrusiveRefCntPtr& S) : Obj(S.Obj) {
+      retain();
+    }
+
+    IntrusiveRefCntPtr(IntrusiveRefCntPtr&& S) : Obj(S.Obj) {
+      S.Obj = nullptr;
+    }
+
+    template <class X>
+    IntrusiveRefCntPtr(IntrusiveRefCntPtr<X>&& S) : Obj(S.get()) {
+      S.Obj = nullptr;
+    }
+
+    template <class X>
+    IntrusiveRefCntPtr(const IntrusiveRefCntPtr<X>& S)
+      : Obj(S.get()) {
+      retain();
+    }
+
+    IntrusiveRefCntPtr& operator=(IntrusiveRefCntPtr S) {
+      swap(S);
+      return *this;
+    }
+
+    ~IntrusiveRefCntPtr() { release(); }
+
+    T& operator*() const { return *Obj; }
+
+    T* operator->() const { return Obj; }
+
+    T* get() const { return Obj; }
+
+    explicit operator bool() const { return Obj; }
+
+    void swap(IntrusiveRefCntPtr& other) {
+      T* tmp = other.Obj;
+      other.Obj = Obj;
+      Obj = tmp;
+    }
+
+    void reset() {
+      release();
+      Obj = nullptr;
+    }
+
+    void resetWithoutRelease() {
+      Obj = nullptr;
+    }
+
+  private:
+    void retain() { if (Obj) IntrusiveRefCntPtrInfo<T>::retain(Obj); }
+    void release() { if (Obj) IntrusiveRefCntPtrInfo<T>::release(Obj); }
+
+    template <typename X>
+    friend class IntrusiveRefCntPtr;
+  };
+
+  template<class T, class U>
+  inline bool operator==(const IntrusiveRefCntPtr<T>& A,
+                         const IntrusiveRefCntPtr<U>& B)
+  {
+    return A.get() == B.get();
+  }
+
+  template<class T, class U>
+  inline bool operator!=(const IntrusiveRefCntPtr<T>& A,
+                         const IntrusiveRefCntPtr<U>& B)
+  {
+    return A.get() != B.get();
+  }
+
+  template<class T, class U>
+  inline bool operator==(const IntrusiveRefCntPtr<T>& A,
+                         U* B)
+  {
+    return A.get() == B;
+  }
+
+  template<class T, class U>
+  inline bool operator!=(const IntrusiveRefCntPtr<T>& A,
+                         U* B)
+  {
+    return A.get() != B;
+  }
+
+  template<class T, class U>
+  inline bool operator==(T* A,
+                         const IntrusiveRefCntPtr<U>& B)
+  {
+    return A == B.get();
+  }
+
+  template<class T, class U>
+  inline bool operator!=(T* A,
+                         const IntrusiveRefCntPtr<U>& B)
+  {
+    return A != B.get();
+  }
+
+  template <class T>
+  bool operator==(std::nullptr_t A, const IntrusiveRefCntPtr<T> &B) {
+    return !B;
+  }
+
+  template <class T>
+  bool operator==(const IntrusiveRefCntPtr<T> &A, std::nullptr_t B) {
+    return B == A;
+  }
+
+  template <class T>
+  bool operator!=(std::nullptr_t A, const IntrusiveRefCntPtr<T> &B) {
+    return !(A == B);
+  }
+
+  template <class T>
+  bool operator!=(const IntrusiveRefCntPtr<T> &A, std::nullptr_t B) {
+    return !(A == B);
+  }
+
+//===----------------------------------------------------------------------===//
+// LLVM-style downcasting support for IntrusiveRefCntPtr objects
+//===----------------------------------------------------------------------===//
+
+  template <typename From> struct simplify_type;
+
+  template<class T> struct simplify_type<IntrusiveRefCntPtr<T> > {
+    typedef T* SimpleType;
+    static SimpleType getSimplifiedValue(IntrusiveRefCntPtr<T>& Val) {
+      return Val.get();
+    }
+  };
+
+  template<class T> struct simplify_type<const IntrusiveRefCntPtr<T> > {
+    typedef /*const*/ T* SimpleType;
+    static SimpleType getSimplifiedValue(const IntrusiveRefCntPtr<T>& Val) {
+      return Val.get();
+    }
+  };
+
+} // end namespace llvm
+
+#endif // LLVM_ADT_INTRUSIVEREFCNTPTR_H