refcnt.hh

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/*
 * Copyright (c) 2002-2005 The Regents of The University of Michigan
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met: redistributions of source code must retain the above copyright
 * notice, this list of conditions and the following disclaimer;
 * redistributions in binary form must reproduce the above copyright
 * notice, this list of conditions and the following disclaimer in the
 * documentation and/or other materials provided with the distribution;
 * neither the name of the copyright holders nor the names of its
 * contributors may be used to endorse or promote products derived from
 * this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
 * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * Authors: Nathan Binkert
 */

#ifndef __BASE_REFCNT_HH__
#define __BASE_REFCNT_HH__

class RefCounted
{
  private:
    // The reference count is mutable because one may want to
    // reference count a const pointer.  This really is OK because
    // const is about logical constness of the object not really about
    // strictly disallowing an object to change.
    mutable int count;

  private:
    // Don't allow a default copy constructor or copy operator on
    // these objects because the default operation will copy the
    // reference count as well and we certainly don't want that.
    RefCounted(const RefCounted &);
    RefCounted &operator=(const RefCounted &);

  public:
    RefCounted() : count(0) {}

    virtual ~RefCounted() {}

    void incref() { ++count; }

    void decref() { if (--count <= 0) delete this; }
};

template <class T>
class RefCountingPtr
{
  protected:
    T *data;

    void
    copy(T *d)
    {
        data = d;
        if (data)
            data->incref();
    }

    void
    del()
    {
        if (data)
            data->decref();
    }

    void
    set(T *d)
    {
        // Need to check if we're actually changing because otherwise
        // we could delete the last reference before adding the new
        // reference.
        if (data != d) {
            del();
            copy(d);
        }
    }

  public:
    RefCountingPtr() : data(0) {}

    RefCountingPtr(T *data) { copy(data); }

    RefCountingPtr(const RefCountingPtr &r) { copy(r.data); }

    ~RefCountingPtr() { del(); }

    // The following pointer access functions are const because they
    // don't actually change the pointer, though the user could change
    // what is pointed to.  This is analagous to a "Foo * const".

    T *operator->() const { return data; }

    T &operator*() const { return *data; }

    T *get() const { return data; }

    const RefCountingPtr &operator=(T *p) { set(p); return *this; }

    const RefCountingPtr &operator=(const RefCountingPtr &r)
    { return operator=(r.data); }

    bool operator!() const { return data == 0; }

    operator bool() const { return data != 0; }
};

template<class T>
inline bool operator==(const RefCountingPtr<T> &l, const RefCountingPtr<T> &r)
{ return l.get() == r.get(); }

template<class T>
inline bool operator==(const RefCountingPtr<T> &l, const T *r)
{ return l.get() == r; }

template<class T>
inline bool operator==(const T *l, const RefCountingPtr<T> &r)
{ return l == r.get(); }

template<class T>
inline bool operator!=(const RefCountingPtr<T> &l, const RefCountingPtr<T> &r)
{ return l.get() != r.get(); }

template<class T>
inline bool operator!=(const RefCountingPtr<T> &l, const T *r)
{ return l.get() != r; }

template<class T>
inline bool operator!=(const T *l, const RefCountingPtr<T> &r)
{ return l != r.get(); }

#endif // __BASE_REFCNT_HH__