libscim-dev 1.4.18-2 / usr / include / scim-1.0 / scim_pointer.h

/** @file scim_pointer.h
 * @brief Smart pointer class interface.
 * 
 * Provides a reference-counted-object aware smart pointer class.
 *
 * Most code of this file are came from Inti project.
 */

/*
 * Smart Common Input Method
 * 
 * Copyright (c) 2002-2005 James Su <suzhe@tsinghua.org.cn>
 * Copyright (c) 2002 The Inti Development Team.
 *
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this program; if not, write to the
 * Free Software Foundation, Inc., 59 Temple Place, Suite 330,
 * Boston, MA  02111-1307  USA
 *
 * $Id: scim_pointer.h,v 1.11 2005/01/10 08:30:54 suzhe Exp $
 */

#ifndef __SCIM_POINTER_H
#define __SCIM_POINTER_H

namespace scim {

/**
 * @addtogroup Accessories
 * @{
 */

/**
 * @class Pointer 
 * @brief Smart pointer template class.
 * 
 * Pointer is a standard auto_ptr-like smart pointer for managing heap 
 * allocated reference counted objects. T must be a class derived from
 * scim::ReferencedObject.
 */

template <typename T>
class Pointer
{
    T *t;

    void set(T *object)
    {
        if (object)
        {
            if (!object->is_referenced())
                object->ref();
            object->set_referenced(false);
        }
        if (t)
            t->unref();
        t = object;
    }

    template<typename T1, typename T2>
    friend bool operator == (const Pointer<T1>& t1, const Pointer<T2>& t2);

public:
//! @name Constructors
//! @{

    Pointer(T *object = 0) : t(0)
    {
        set(object);
    }
    //!< Construct a new smart pointer.
    //!< @param object - a pointer to an object allocated on the heap.
    //!<
    //!< <BR>Initialize a new Pointer with any dumb pointer.

    Pointer(const Pointer& src) : t(0)
    {
        set(src.get());
    }
    //!< Copy constructor.
    //!< @param src - a reference to a smart pointer.
    //!<
    //!< <BR>Initialize a new Pointer with any compatible Pointer.

    template <typename T1>
    Pointer(const Pointer<T1>& src)    : t(0)
    {
        set(src.get());
    }
    //!< Copy constructor.
    //!< @param src - a Pointer to type T1 where T1 is derived from T.
    //!<
    //!< <BR>Initialize a new Pointer of type T from a Pointer of type T1,
    //!< only if T1 is derived from T.

    ~Pointer()
    {
        set(0);
    }
    //!< Destructor.
    //!< Decreases the object reference count.

    Pointer& operator=(T *object)
    {
        set(object);
        return *this;
    }
    //!< Assignment operator.
    //!< @param object - a pointer to an object allocated on the heap.
    //!<
    //!< <BR>Releases the current dumb pointer, if any and assigns <EM>object</EM>
    //!< to this Pointer, incrementing its reference count.

    Pointer& operator=(const Pointer& src)
    {
        set(src.get());
        return *this;
    }
    //!< Assignment operator.
    //!< @param src - a reference to a smart pointer.
    //!<
    //!< <BR>Releases the current dumb pointer, if any and assigns the dumb pointer
    //!< managed by <EM>src</EM> to this Pointer, incrementing its reference count.

    template <typename T1>
    Pointer& operator=(const Pointer<T1>& src)
    {
        set(src.get());
        return *this;
    }
    //!< Assignment operator.
    //!< @param src - a Pointer to type T1 where T1 is derived from T.
    //!<
    //!< <BR>Releases the current dumb pointer, if any and assigns the dumb pointer 
    //!< of type T1 managed by <EM>src</EM> to this Pointer as a dumb pointer of type T,
    //!< only if T1 is derived from T. The reference count is incremented.

//! @}
//! @name Accessors
//! @{

    T& operator*() const
    {
        return *get();
    }
    //!< Dereference operator.
    //!< @return a reference to the object pointed to by the dumb pointer.

    T* operator->() const
    {
        return get();
    }
    //!< Member selection operator.
    //!< @return the dumb pointer.

    operator T*() const
    {
        return get();
    }
    //!< Conversion operator.
    //!< Converts a Pointer into its dumb pointer: the C pointer it manages.
    //!< Normally it is considered pretty evil to mix smart and regular pointers.
    //!< In scim you can safely if you just follow the reference counting rules
    //!< for each of them. You can never call delete on Pointer either because
    //!< you don't call delete on scim objects; you call unref().

    T* get() const
    {
        return t;
    }
    //!< Returns the dumb pointer; the regular C pointer managed by the Pointer.
    //!< @return the dumb pointer.

    bool null() const
    {
        return t == 0;
    }
    //!< Returns true if the Pointer has no dumb pointer.

//! @}
//! @name Methods
//! @{

    T* release()
    {
        T *tmp = t;
        if (tmp)
            tmp->ref();
        set(0);
        return tmp;
    }
    //!< Releases the dumb pointer.
    //!< @return the regular C pointer previously managed by the Pointer.
    //!<
    //!< <BR>Before releasing the dumb pointer its reference count is incremented
    //!< to prevent it being destroyed. You must call unref() on the pointer to
    //!< prevent a memory leak.

    void reset(T *object = 0)
    {
        set(object);
    }
    //!< Sets a new dumb pointer for the Pointer to manage.
    //!< @param object - the new dumb pointer.
    //!<
    //!< <BR>Releases the current dumb pointer, if any, and assigns <EM>object</EM>
    //!< to the Pointer, incrementing its reference count.
    
//! @}
};

//! @name Equality operators
//! @{

template<typename T1, typename T2>
inline bool operator == (const Pointer<T1>& t1, const Pointer<T2>& t2)
{
    return t1.t == t2.t;
}
//!< Compares two Pointers.
//!< @return <EM>true</EM> if both Pointers manage to same dumb pointer.

template<typename T1, typename T2>
inline bool operator != (const Pointer<T1>& t1, const Pointer<T2>& t2)
{
    return !(t1 == t2);
}
//!< Compares two Pointers.
//!< @return <EM>true</EM> if both Pointers manage a different dumb pointer.

//! @}
//! @name C++-style casting functions
//! @{

template <typename To, typename From>
inline Pointer<To>
cast_const(const Pointer<From>& from)
{
    return Pointer<To>(from ? const_cast<To*>(from.get()) : 0);
}
//!< Removes the <EM>const</EM> qualifier from a managed const dumb pointer.
//!< @param from - a Pointer that manages a const dumb pointer.
//!< @return a new Pointer that manages the non-const dumb pointer.
//!<
//!< <BR>Calls <EM>const_cast</EM> on the dumb pointer and returns the non-const
//!< pointer as a new Pointer.

template <typename To, typename From>
inline Pointer<To>
cast_dynamic(const Pointer<From>& from)
{
    return Pointer<To>(dynamic_cast<To*>(from.get()));
}
//!< Casts a managed polymophic dumb pointer down or across its inheritance heirarchy.
//!< @param from - a Pointer managing a polymophic dumb pointer of type From.
//!< @return a new Pointer managing the dumb pointer as a base or sibling pointer of type <EM>To</EM>.
//!<
//!< <BR>Calls <EM>dynmaic_cast</EM> to safely cast a managed polymophic dumb pointer
//!< of type <EM>From</EM> to a base, derived or sibling class pointer of type <EM>To</EM>.

template <typename To, typename From>
inline Pointer<To>
cast_static(const Pointer<From>& from)
{
    return Pointer<To>(from ? static_cast<To*>(from.get()) : 0);
}
//!< Casts a managed dumb pointer to a pointer to a related type.
//!< @param from - a Pointer managing a dumb pointer of type From.
//!< @return a new Pointer managing the dumb pointer as a pointer of type <EM>To</EM>.
//!<
//!< <BR>Calls <EM>static_cast</EM> to cast a dumb pointer of type <EM>From</EM> to a 
//!< pointer of type <EM>To</EM>.

//! @}

/** @} */

} // namespace scim

#endif //__SCIM_POINTER_H

/*
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*/