intrusive_ptr.h

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#ifndef XAPIAN_INCLUDED_INTRUSIVE_PTR_H
#define XAPIAN_INCLUDED_INTRUSIVE_PTR_H
 
//
//  Based on Boost's intrusive_ptr.hpp
//
//  Copyright (c) 2001, 2002 Peter Dimov
//  Copyright (c) 2011,2013,2014,2015,2017,2022 Olly Betts
//
// Distributed under the Boost Software License, Version 1.0.
//
// Boost Software License - Version 1.0 - August 17th, 2003
//
// Permission is hereby granted, free of charge, to any person or organization
// obtaining a copy of the software and accompanying documentation covered by
// this license (the "Software") to use, reproduce, display, distribute,
// execute, and transmit the Software, and to prepare derivative works of the
// Software, and to permit third-parties to whom the Software is furnished to
// do so, all subject to the following:
//
// The copyright notices in the Software and this entire statement, including
// the above license grant, this restriction and the following disclaimer,
// must be included in all copies of the Software, in whole or in part, and
// all derivative works of the Software, unless such copies or derivative
// works are solely in the form of machine-executable object code generated by
// a source language processor.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE, TITLE AND NON-INFRINGEMENT. IN NO EVENT
// SHALL THE COPYRIGHT HOLDERS OR ANYONE DISTRIBUTING THE SOFTWARE BE LIABLE
// FOR ANY DAMAGES OR OTHER LIABILITY, WHETHER IN CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//
//  See http://www.boost.org/libs/smart_ptr/intrusive_ptr.html for documentation.
//
 
#if !defined XAPIAN_IN_XAPIAN_H && !defined XAPIAN_LIB_BUILD
# error Never use <xapian/intrusive_ptr.h> directly; include <xapian.h> instead.
#endif
 
#include <xapian/attributes.h>
#include <xapian/visibility.h>
 
namespace Xapian {
namespace Internal {
 
class intrusive_base {
    intrusive_base(const intrusive_base&);
 
    void operator=(const intrusive_base&);
 
  public:
    intrusive_base() : _refs(0) { }
 
    /* There's no need for a virtual destructor here as we never delete a
     * subclass of intrusive_base by calling delete on intrusive_base*.
     */
 
    mutable unsigned _refs;
};
 
//
//  intrusive_ptr
//
 
template<class T> class intrusive_ptr
{
private:
 
    typedef intrusive_ptr this_type;
 
public:
 
    intrusive_ptr(): px( 0 )
    {
    }
 
    intrusive_ptr( T * p): px( p )
    {
        if( px != 0 ) ++px->_refs;
    }
 
    template<class U>
    intrusive_ptr( intrusive_ptr<U> const & rhs )
    : px( rhs.get() )
    {
        if( px != 0 ) ++px->_refs;
    }
 
    intrusive_ptr(intrusive_ptr const & rhs): px( rhs.px )
    {
        if( px != 0 ) ++px->_refs;
    }
 
    ~intrusive_ptr()
    {
        if( px != 0 && --px->_refs == 0 ) delete px;
    }
 
    intrusive_ptr(intrusive_ptr && rhs) : px( rhs.px )
    {
        rhs.px = 0;
    }
 
    intrusive_ptr & operator=(intrusive_ptr && rhs)
    {
        this_type( static_cast< intrusive_ptr && >( rhs ) ).swap(*this);
        return *this;
    }
 
    template<class U> friend class intrusive_ptr;
 
    template<class U>
    intrusive_ptr(intrusive_ptr<U> && rhs) : px( rhs.px )
    {
        rhs.px = 0;
    }
 
    template<class U>
    intrusive_ptr & operator=(intrusive_ptr<U> && rhs)
    {
        this_type( static_cast< intrusive_ptr<U> && >( rhs ) ).swap(*this);
        return *this;
    }
 
    intrusive_ptr & operator=(intrusive_ptr const & rhs)
    {
        this_type(rhs).swap(*this);
        return *this;
    }
 
    intrusive_ptr & operator=(T * rhs)
    {
        this_type(rhs).swap(*this);
        return *this;
    }
 
    T * get() const
    {
        return px;
    }
 
    T & operator*() const
    {
        return *px;
    }
 
    T * operator->() const
    {
        return px;
    }
 
    void swap(intrusive_ptr & rhs)
    {
        T * tmp = px;
        px = rhs.px;
        rhs.px = tmp;
    }
 
    explicit operator bool() const
    {
        return px != nullptr;
    }
 
private:
 
    T * px;
};
 
template<class T, class U> inline bool operator==(intrusive_ptr<T> const & a, intrusive_ptr<U> const & b)
{
    return a.get() == b.get();
}
 
template<class T, class U> inline bool operator!=(intrusive_ptr<T> const & a, intrusive_ptr<U> const & b)
{
    return a.get() != b.get();
}
 
template<class T, class U> inline bool operator==(intrusive_ptr<T> const & a, U * b)
{
    return a.get() == b;
}
 
template<class T, class U> inline bool operator!=(intrusive_ptr<T> const & a, U * b)
{
    return a.get() != b;
}
 
template<class T, class U> inline bool operator==(T * a, intrusive_ptr<U> const & b)
{
    return a == b.get();
}
 
template<class T, class U> inline bool operator!=(T * a, intrusive_ptr<U> const & b)
{
    return a != b.get();
}
 
template<class T> class intrusive_ptr_nonnull
{
private:
 
    typedef intrusive_ptr_nonnull this_type;
 
public:
 
    intrusive_ptr_nonnull( T * p) XAPIAN_NONNULL() : px( p )
    {
        ++px->_refs;
    }
 
    template<class U>
    intrusive_ptr_nonnull( intrusive_ptr_nonnull<U> const & rhs )
    : px( rhs.get() )
    {
        ++px->_refs;
    }
 
    intrusive_ptr_nonnull(intrusive_ptr_nonnull const & rhs): px( rhs.px )
    {
        ++px->_refs;
    }
 
    ~intrusive_ptr_nonnull()
    {
        if( px && --px->_refs == 0 ) delete px;
    }
 
    intrusive_ptr_nonnull(intrusive_ptr_nonnull && rhs) : px( rhs.px )
    {
        rhs.px = 0;
    }
 
    intrusive_ptr_nonnull & operator=(intrusive_ptr_nonnull && rhs)
    {
        this_type( static_cast< intrusive_ptr_nonnull && >( rhs ) ).swap(*this);
        return *this;
    }
 
    template<class U> friend class intrusive_ptr_nonnull;
 
    template<class U>
    intrusive_ptr_nonnull(intrusive_ptr_nonnull<U> && rhs) : px( rhs.px )
    {
        rhs.px = 0;
    }
 
    template<class U>
    intrusive_ptr_nonnull & operator=(intrusive_ptr_nonnull<U> && rhs)
    {
        this_type( static_cast< intrusive_ptr_nonnull<U> && >( rhs ) ).swap(*this);
        return *this;
    }
 
    intrusive_ptr_nonnull & operator=(intrusive_ptr_nonnull const & rhs)
    {
        this_type(rhs).swap(*this);
        return *this;
    }
 
    intrusive_ptr_nonnull & operator=(T * rhs) XAPIAN_NONNULL()
    {
        this_type(rhs).swap(*this);
        return *this;
    }
 
    T * get() const
    {
        return px;
    }
 
    T & operator*() const
    {
        return *px;
    }
 
    T * operator->() const
    {
        return px;
    }
 
    void swap(intrusive_ptr_nonnull & rhs)
    {
        T * tmp = px;
        px = rhs.px;
        rhs.px = tmp;
    }
 
    // No operator bool() here - the held pointer should only be NULL if this
    // pointer has been moved from, and in that case it's not valid to use its
    // value so it seems more helpful to error on attempts to check if the
    // pointer is NULL.
 
private:
 
    T * px;
};
 
template<class T, class U> inline bool operator==(intrusive_ptr_nonnull<T> const & a, intrusive_ptr_nonnull<U> const & b)
{
    return a.get() == b.get();
}
 
template<class T, class U> inline bool operator!=(intrusive_ptr_nonnull<T> const & a, intrusive_ptr_nonnull<U> const & b)
{
    return a.get() != b.get();
}
 
template<class T, class U> inline bool operator==(intrusive_ptr_nonnull<T> const & a, U * b)
{
    return a.get() == b;
}
 
template<class T, class U> inline bool operator!=(intrusive_ptr_nonnull<T> const & a, U * b)
{
    return a.get() != b;
}
 
template<class T, class U> inline bool operator==(T * a, intrusive_ptr_nonnull<U> const & b)
{
    return a == b.get();
}
 
template<class T, class U> inline bool operator!=(T * a, intrusive_ptr_nonnull<U> const & b)
{
    return a != b.get();
}
 
class XAPIAN_VISIBILITY_DEFAULT opt_intrusive_base {
  public:
    opt_intrusive_base(const opt_intrusive_base&) : _refs(0) { }
 
    opt_intrusive_base& operator=(const opt_intrusive_base&) {
        // Don't touch _refs.
        return *this;
    }
 
    opt_intrusive_base() : _refs(0) { }
 
    /* Subclasses of opt_intrusive_base may be deleted by calling delete on a
     * pointer to opt_intrusive_base.
     */
    virtual ~opt_intrusive_base() { }
 
    void ref() const {
        if (_refs == 0)
            _refs = 2;
        else
            ++_refs;
    }
 
    void unref() const {
        if (--_refs == 1)
            delete this;
    }
 
    mutable unsigned _refs;
 
  protected:
    void release() const {
        if (_refs == 0)
            _refs = 1;
    }
};
 
//
//  opt_intrusive_ptr
//
 
template<class T> class opt_intrusive_ptr
{
private:
 
    typedef opt_intrusive_ptr this_type;
 
public:
 
    opt_intrusive_ptr(): px( 0 ), counting( false )
    {
    }
 
    opt_intrusive_ptr( T * p): px( p ), counting( px != 0 && px->_refs )
    {
        if( counting ) ++px->_refs;
    }
 
    template<class U>
    opt_intrusive_ptr( opt_intrusive_ptr<U> const & rhs )
    : px( rhs.get() ), counting( rhs.counting )
    {
        if( counting ) ++px->_refs;
    }
 
    opt_intrusive_ptr(opt_intrusive_ptr const & rhs)
    : px( rhs.px ), counting( rhs.counting )
    {
        if( counting ) ++px->_refs;
    }
 
    ~opt_intrusive_ptr()
    {
        if( counting && --px->_refs == 1 ) delete px;
    }
 
    opt_intrusive_ptr(opt_intrusive_ptr && rhs)
    : px( rhs.px ), counting( rhs.counting )
    {
        rhs.px = 0;
        rhs.counting = 0;
    }
 
    opt_intrusive_ptr & operator=(opt_intrusive_ptr && rhs)
    {
        this_type( static_cast< opt_intrusive_ptr && >( rhs ) ).swap(*this);
        return *this;
    }
 
    template<class U> friend class opt_intrusive_ptr;
 
    template<class U>
    opt_intrusive_ptr(opt_intrusive_ptr<U> && rhs)
    : px( rhs.px ), counting( rhs.counting )
    {
        rhs.px = 0;
        rhs.counting = 0;
    }
 
    template<class U>
    opt_intrusive_ptr & operator=(opt_intrusive_ptr<U> && rhs)
    {
        this_type( static_cast< opt_intrusive_ptr<U> && >( rhs ) ).swap(*this);
        return *this;
    }
 
    opt_intrusive_ptr & operator=(opt_intrusive_ptr const & rhs)
    {
        this_type(rhs).swap(*this);
        return *this;
    }
 
    opt_intrusive_ptr & operator=(T * rhs)
    {
        this_type(rhs).swap(*this);
        return *this;
    }
 
    T * get() const
    {
        return px;
    }
 
    T & operator*() const
    {
        return *px;
    }
 
    T * operator->() const
    {
        return px;
    }
 
    void swap(opt_intrusive_ptr & rhs)
    {
        T * tmp = px;
        px = rhs.px;
        rhs.px = tmp;
        bool tmp2 = counting;
        counting = rhs.counting;
        rhs.counting = tmp2;
    }
 
    explicit operator bool() const
    {
        return px != nullptr;
    }
 
private:
 
    T * px;
 
    bool counting;
};
 
template<class T, class U> inline bool operator==(opt_intrusive_ptr<T> const & a, opt_intrusive_ptr<U> const & b)
{
    return a.get() == b.get();
}
 
template<class T, class U> inline bool operator!=(opt_intrusive_ptr<T> const & a, opt_intrusive_ptr<U> const & b)
{
    return a.get() != b.get();
}
 
template<class T, class U> inline bool operator==(opt_intrusive_ptr<T> const & a, U * b)
{
    return a.get() == b;
}
 
template<class T, class U> inline bool operator!=(opt_intrusive_ptr<T> const & a, U * b)
{
    return a.get() != b;
}
 
template<class T, class U> inline bool operator==(T * a, opt_intrusive_ptr<U> const & b)
{
    return a == b.get();
}
 
template<class T, class U> inline bool operator!=(T * a, opt_intrusive_ptr<U> const & b)
{
    return a != b.get();
}
 
}
}
 
#endif // XAPIAN_INCLUDED_INTRUSIVE_PTR_H