Security-55163.44.tar.gz

[apple/security.git] / libsecurity_utilities / lib / refcount.h

diff --git a/libsecurity_utilities/lib/refcount.h b/libsecurity_utilities/lib/refcount.h
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+/*
+ * Copyright (c) 2000-2004 Apple Computer, Inc. All Rights Reserved.
+ * 
+ * @APPLE_LICENSE_HEADER_START@
+ * 
+ * This file contains Original Code and/or Modifications of Original Code
+ * as defined in and that are subject to the Apple Public Source License
+ * Version 2.0 (the 'License'). You may not use this file except in
+ * compliance with the License. Please obtain a copy of the License at
+ * http://www.opensource.apple.com/apsl/ and read it before using this
+ * file.
+ * 
+ * The Original Code and all software distributed under the License are
+ * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
+ * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
+ * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
+ * Please see the License for the specific language governing rights and
+ * limitations under the License.
+ * 
+ * @APPLE_LICENSE_HEADER_END@
+ */
+
+
+/*
+       Based on code donated by Perry Kiehtreiber
+ */
+#ifndef _SECURITY_REFCOUNT_H_
+#define _SECURITY_REFCOUNT_H_
+
+#include <security_utilities/threading.h>
+
+namespace Security {
+
+
+//
+// RefCount/RefPointer - a simple reference counting facility.
+//
+// To make an object reference-counted, inherit from RefCount. To track refcounted
+// objects, use RefPointer<TheType>, where TheType must inherit from RefCount.
+//
+// RefCount is thread safe - any number of threads can hold and manipulate references
+// in parallel. It does however NOT protect the contents of your object - just the
+// reference count itself. If you need to share your object contents, you must provide
+// appropriate locking yourself.
+//
+// There is no (thread safe) way to determine whether you are the only thread holding
+// a pointer to a particular RefCount object. Thus there is no (thread safe)
+// way to "demand copy" a RefCount subclass. Trust me; it's been tried. Don't.
+//
+
+#if !defined(DEBUG_REFCOUNTS)
+# define DEBUG_REFCOUNTS 1
+#endif
+
+#if DEBUG_REFCOUNTS
+# define RCDEBUG(_kind, _args...)      SECURITY_DEBUG_REFCOUNT_##_kind((void *)this, ##_args)
+#else
+# define RCDEBUG(kind) /* nothing */
+#endif
+
+
+//
+// Base class for reference counted objects
+//
+class RefCount {       
+public:
+       RefCount() : mRefCount(0) { RCDEBUG(CREATE); }
+
+protected:
+       template <class T> friend class RefPointer;
+
+       void ref() const                        { ++mRefCount; RCDEBUG(UP, mRefCount); }
+       unsigned int unref() const      { RCDEBUG(DOWN, mRefCount - 1); return --mRefCount; }
+       
+       // if you call this for anything but debug output, you will go to hell (free handbasket included)
+       unsigned int refCountForDebuggingOnly() const { return mRefCount; }
+
+private:
+    mutable AtomicCounter<unsigned int> mRefCount;
+};
+
+
+//
+// A pointer type supported by reference counts.
+// T must be derived from RefCount.
+//
+template <class T>
+class RefPointer {
+       template <class Sub> friend class RefPointer; // share with other instances
+public:
+       RefPointer() : ptr(0) {}                        // default to NULL pointer
+       RefPointer(const RefPointer& p) { if (p) p->ref(); ptr = p.ptr; }
+       RefPointer(T *p) { if (p) p->ref(); ptr = p; }
+       
+       template <class Sub>
+       RefPointer(const RefPointer<Sub>& p) { if (p) p->ref(); ptr = p.ptr; }
+    
+       ~RefPointer() { release(); }
+
+       RefPointer& operator = (const RefPointer& p)    { setPointer(p.ptr); return *this; }
+       RefPointer& operator = (T * p)                                  { setPointer(p); return *this; }
+
+       template <class Sub>
+       RefPointer& operator = (const RefPointer<Sub>& p) { setPointer(p.ptr); return *this; }
+
+       // dereference operations
+    T* get () const                            { _check(); return ptr; }       // mimic auto_ptr
+       operator T * () const           { _check(); return ptr; }
+       T * operator -> () const        { _check(); return ptr; }
+       T & operator * () const         { _check(); return *ptr; }
+
+protected:
+       void release()
+    {
+        if (ptr && ptr->unref() == 0)
+        {
+            delete ptr;
+            ptr = NULL;
+        }
+    }
+       
+    void setPointer(T *p) { if (p) p->ref(); release(); ptr = p; }
+       
+       void _check() const { }
+
+       T *ptr;
+};
+
+template <class T>
+bool operator <(const RefPointer<T> &r1, const RefPointer<T> &r2)
+{
+       T *p1 = r1.get(), *p2 = r2.get();
+       return p1 && p2 ? *p1 < *p2 : p1 < p2;
+}
+
+template <class T>
+bool operator ==(const RefPointer<T> &r1, const RefPointer<T> &r2)
+{
+       T *p1 = r1.get(), *p2 = r2.get();
+       return p1 && p2 ? *p1 == *p2 : p1 == p2;
+}
+
+template <class T>
+bool operator !=(const RefPointer<T> &r1, const RefPointer<T> &r2)
+{
+       T *p1 = r1.get(), *p2 = r2.get();
+       return p1 && p2 ? *p1 != *p2 : p1 != p2;
+}
+
+} // end namespace Security
+
+#endif // !_SECURITY_REFCOUNT_H_