src/lib/util/ref/ref.h

//
// ref.h --- definitions of the reference counting classes
//
// Copyright (C) 1996 Limit Point Systems, Inc.
//
// Author: Curtis Janssen <cljanss@limitpt.com>
// Maintainer: LPS
//
// This file is part of the SC Toolkit.
//
// The SC Toolkit is free software; you can redistribute it and/or modify
// it under the terms of the GNU Library General Public License as published by
// the Free Software Foundation; either version 2, or (at your option)
// any later version.
//
// The SC Toolkit 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 Library General Public License for more details.
//
// You should have received a copy of the GNU Library General Public License
// along with the SC Toolkit; see the file COPYING.LIB.  If not, write to
// the Free Software Foundation, 675 Mass Ave, Cambridge, MA 02139, USA.
//
// The U.S. Government is granted a limited license as per AL 91-7.
//

//   This is the main include file for the reference counting classes.
// This includes two other files: reftmpl.h and refmacr.h.  The
// former is a template declaration for the reference counted classes
// and the latter is generated from the former by a perl script and
// provides CPP macros that declare reference counting classes.
//
//   The behaviour of the package can be modified with the following five
// macros, each of which should be undefined, 0, or 1:
//
// REF_CHECK_STACK:  If this is 1 referenced objects are checked to see if they
// reside on the stack, in which case storage for the object is not managed,
// if management is enabled.  This feature can be confused by multiple threads
// and memory checking libraries.
//
// REF_MANAGE:  If this is 1 the manage and unmanage members are enabled.
//
// REF_CHECK_MAX_NREF:  If this is 1 the reference count is checked before
// it is incremented to make sure it isn't too big.
//
// REF_CHECK_MIN_NREF:  If this is 1 the reference count is checked before
// it is decremented to make sure it isn't already zero.
//
// REF_USE_LOCKS:  If this is 1 then critical regions are locked before they
// are entered.  This prevents erroneous behavior when multiple threads
// share reference counted objects.  This will slow down certain operations,
// so it should be set to 0 if your application does not need to be thread
// safe.
//
// If a macro is undefined, then the behaviour is architecture
// dependent--usually, the macro will be set to 1 in this case.
// For maximum efficiency and for normal operation after the program is
// debugged, compile with all of the above macros defined to zero.
// This can also be done with -DREF_OPTIMIZE.
//
//   An include file can be used to set these options as well.  This has
// the advantage that dependency checking will force an automatic
// recompile of all affected files if the options change.  The file
// <scconfig.h> will be include if -DHAVE_CONFIG_H is specified.
//
//   Note that all source code that uses references must be compiled with
// the same value REF_MANAGE.  Changing this can change the storage layout
// and the interpretation of the reference count data.


#ifdef __GNUC__
#pragma interface
#endif

#ifndef _util_ref_ref_h
#define _util_ref_ref_h

#include <iostream>
#include <stdlib.h>
#include <limits.h>

#include <util/ref/identity.h>

#ifdef HAVE_CONFIG_H
#include <scconfig.h>
#endif

#ifdef REF_OPTIMIZE
#ifndef REF_CHECK_STACK
# define REF_CHECK_STACK   0
#endif
#ifndef REF_MANAGE
# define REF_MANAGE        0
#endif
#ifndef REF_CHECK_MAX_NREF
# define REF_CHECK_MAX_NREF 0
#endif
#ifndef REF_CHECK_MIN_NREF
# define REF_CHECK_MIN_NREF 0
#endif
#endif

#ifdef SUNMOS
#ifndef REF_CHECK_STACK
#define REF_CHECK_STACK 0
#endif
#else
#ifndef REF_CHECK_STACK
#define REF_CHECK_STACK 0
#endif
#endif

#ifndef REF_MANAGE
#define REF_MANAGE 1
#endif

#ifndef REF_CHECK_MAX_NREF
#define REF_CHECK_MAX_NREF 1
#endif

#ifndef REF_CHECK_MIN_NREF
#define REF_CHECK_MIN_NREF 1
#endif

#ifndef REF_USE_LOCKS
#  if HAVE_STHREAD || HAVE_CREATETHREAD || HAVE_PTHREAD
#    define REF_USE_LOCKS 1
#  endif
#endif

#ifndef REF_ALWAYS_USE_LOCKS
#  define REF_ALWAYS_USE_LOCKS 1
#endif

#if REF_CHECK_STACK
#include <unistd.h>
#ifndef HAVE_SBRK_DEC
extern "C" void * sbrk(ssize_t);
#endif
#define DO_REF_CHECK_STACK(p) (((void*) (p) > sbrk(0)) && (p)->managed())
#else // REF_CHECK_STACK
#define DO_REF_CHECK_STACK(p) (0)
#endif // REF_CHECK_STACK

#if REF_MANAGE
#define DO_REF_UNMANAGE(p) ((p)->unmanage())
#else // REF_MANAGE
#define DO_REF_UNMANAGE(p)
#endif // REF_MANAGE

#if REF_USE_LOCKS
#define __REF_LOCK__(p) p->lock_ptr()
#define __REF_UNLOCK__(p) p->unlock_ptr()
#if REF_ALWAYS_USE_LOCKS
#define __REF_INITLOCK__() use_locks(true)
#else
#define __REF_INITLOCK__() ref_lock_ = 0xff
#endif
#else
#define __REF_LOCK__(p)
#define __REF_UNLOCK__(p)
#define __REF_INITLOCK__()
#endif

namespace sc {

typedef unsigned long refcount_t;

class RefCount: public Identity {
  private:
#if REF_MANAGE
#  define REF_MAX_NREF (UINT_MAX - 1)
#  define REF_MANAGED_CODE UINT_MAX
#else
#  define REF_MAX_NREF UINT_MAX
#endif
    unsigned int _reference_count_;
#if REF_USE_LOCKS
    unsigned char ref_lock_;
#endif

    void error(const char*) const;
    void too_many_refs() const;
    void not_enough_refs() const;
  protected:
    RefCount(): _reference_count_(0) {
        __REF_INITLOCK__();
        //std::cout << "ref_lock_ = " << (int) ref_lock_ << std::endl;
      }
    RefCount(const RefCount&): _reference_count_(0) {
        __REF_INITLOCK__();
        //std::cout << "ref_lock_ = " << (int) ref_lock_ << std::endl;
      }

    // Assigment should not overwrite the reference count.
    RefCount& operator=(const RefCount&) { return *this; }
  public:
    virtual ~RefCount();

    int lock_ptr() const;
    int unlock_ptr() const;

    void use_locks(bool inVal);

    refcount_t nreference() const {
#       if REF_MANAGE
        if (!managed()) return 1;
#       endif
        return _reference_count_;
      }

    refcount_t reference() {
#       if REF_MANAGE
        if (!managed()) return 1;
#       endif
        __REF_LOCK__(this);
#       if REF_CHECK_MAX_NREF
        if (_reference_count_ >= REF_MAX_NREF) too_many_refs();
#       endif
        _reference_count_++;
        refcount_t r = _reference_count_;
        __REF_UNLOCK__(this);
        return r;
      }

    refcount_t dereference() {
#       if REF_MANAGE
        if (!managed()) return 1;
#       endif
        __REF_LOCK__(this);
#       if REF_CHECK_MIN_NREF
        if (_reference_count_ == 0) not_enough_refs();
#       endif
        _reference_count_--;
        refcount_t r = _reference_count_;
        __REF_UNLOCK__(this);
        return r;
      }

#if REF_MANAGE
    int managed() const {
        return _reference_count_ != REF_MANAGED_CODE;
      }
    void unmanage() {
        _reference_count_ = REF_MANAGED_CODE;
      }
#else // REF_MANAGE
    int managed() const { return 1; }
#endif // REF_MANAGE
};

class RefBase {
  protected:
    void warn ( const char * msg) const;
    void warn_ref_to_stack() const;
    void warn_skip_stack_delete() const;
    void warn_bad_ref_count() const;
    void ref_info(RefCount*p,std::ostream& os) const;
    void ref_info(std::ostream& os) const;
    void check_pointer() const;
    void reference(RefCount *);
    int dereference(RefCount *);
  public:
    RefBase() {};
    virtual ~RefBase();
    virtual RefCount* parentpointer() const = 0;
    void require_nonnull() const;
};

template <class T>
class  Ref  : public RefBase {
  public:
    typedef T element_type;
  private:
    T* p;
  public:
    Ref(): p(0) {}
    Ref(T*a) : p(0)
    {
      if (a) {
          p = a;
          reference(p);
        }
    }
    Ref(const Ref<T> &a) : p(0)
    {
      if (a.pointer()) {
          p = a.pointer();
          reference(p);
        }
    }
    template <class A> Ref(const Ref<A> &a): p(0)
    {
      if (a.pointer()) {
          p = a.pointer();
          reference(p);
        }
    }
//      /** Create a reference to the object a.  Do a
//          dynamic_cast to convert a to the appropiate type. */
//      Ref(const RefBase&a) {
//          p = dynamic_cast<T*>(a.parentpointer());
//          reference(p);
//        }
//      /** Create a reference to the object a.  Do a
//          dynamic_cast to convert a to the appropiate type. */
//      Ref(RefCount*a): p(0) {
//        operator<<(a);
//        }
    ~Ref()
    {
      clear();
    }
    T* operator->() const { return p; }
    T* pointer() const { return p; }
    RefCount *parentpointer() const { return p; }

    operator T*() const { return p; }
    T& operator *() const { return *p; };
    int null() const { return p == 0; }
    int nonnull() const { return p != 0; }
    template <class A> int operator==(const Ref<A>&a) const
        { return eq(p,a.pointer()); }
    template <class A> int operator>=(const Ref<A>&a) const
        { return ge(p,a.pointer()); }
    template <class A> int operator<=(const Ref<A>&a) const
        { return le(p,a.pointer()); }
    template <class A> int operator>(const Ref<A>&a) const
        { return gt(p,a.pointer()); }
    template <class A> int operator<(const Ref<A>&a) const
        { return lt(p,a.pointer()); }
    template <class A> int operator!=(const Ref<A>&a) const
        { return ne(p,a.pointer()); }
    int compare(const Ref<T> &a) const {
      return eq(p,a.p)?0:((lt(p,a.p)?-1:1));
    }
    void clear()
    {
      if (p) {
          int ref = dereference(p);
          if (ref == 0)
              delete p;
          p = 0;
        }
    }
    Ref<T>& operator=(const Ref<T> & c)
    {
      T *cp = c.pointer();
      if (cp) {
          cp->reference();
          clear();
          p=cp;
        }
      else {
          clear();
        }
      return *this;
    }
    template <class A> Ref<T>& operator=(const Ref<A> & c)
    {
      A *cp = c.pointer();
      if (cp) {
          cp->reference();
          clear();
          p=cp;
        }
      else {
          clear();
        }
      return *this;
    }
    Ref<T>& operator<<(const RefBase&a) {
        T* cr = dynamic_cast<T*>(a.parentpointer());
        if (cr) {
            reference(cr);
            clear();
          }
        p = cr;
        return *this;
      }
    Ref<T>& operator<<(RefCount *a) {
        T* cr = dynamic_cast<T*>(a);
        if (cr) assign_pointer(cr);
        else if (a && a->nreference() <= 0) delete a;
        return *this;
      }
    Ref<T>& operator=(T* cr)
    {
      assign_pointer(cr);
      return *this;
    }
    void assign_pointer(T* cr)
    {
      if (cr) {
          if (DO_REF_CHECK_STACK(cr)) {
              DO_REF_UNMANAGE(cr);
              warn_ref_to_stack();
            }
          cr->reference();
        }
      clear();
      p = cr;
    }
    void check_pointer() const
    {
      if (p && p->nreference() <= 0) {
          warn_bad_ref_count();
        }
    }
    void ref_info(std::ostream& os) const
    {
      RefBase::ref_info(p,os);
    }
    void warn(const char*s) const { RefBase::warn(s); }
};

template <typename T, typename EqualTo = std::equal_to<T> >
struct RefObjectEqual {
  bool operator()(const Ref<T>& obj1, const Ref<T>& obj2) {
    EqualTo equal_functor;
    return equal_functor(*obj1,*obj2);
  }
};

}

#endif

// ///////////////////////////////////////////////////////////////////////////

// Local Variables:
// mode: c++
// c-file-style: "CLJ"
// End:

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