114 lines
3.7 KiB
C
114 lines
3.7 KiB
C
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// Copyright (c) 1997-2000 Max-Planck-Institute Saarbruecken (Germany).
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// All rights reserved.
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//
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// This file is part of CGAL (www.cgal.org).
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//
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// $URL: https://github.com/CGAL/cgal/blob/v5.1/Nef_2/include/CGAL/Nef_2/geninfo.h $
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// $Id: geninfo.h 0779373 2020-03-26T13:31:46+01:00 Sébastien Loriot
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// SPDX-License-Identifier: GPL-3.0-or-later OR LicenseRef-Commercial
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//
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//
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// Author(s) : Michael Seel <seel@mpi-sb.mpg.de>
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#ifndef CGAL_NEF_2_GENINFO_H
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#define CGAL_NEF_2_GENINFO_H
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#include <CGAL/license/Nef_2.h>
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#define CGAL_DEPRECATED_HEADER "<CGAL/Nef_2/geninfo.h>"
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#define CGAL_DEPRECATED_MESSAGE_DETAILS \
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"Something like boost::any or boost::variant should be used instead."
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#include <CGAL/internal/deprecation_warning.h>
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#include <CGAL/config.h>
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#include <memory>
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/*{\Moptions outfile=geninfo.man}*/
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/*{\Moptions constref=yes}*/
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/*{\Manpage {geninfo} {T} {Information association via GenPtr} {}}*/
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template <typename T>
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struct geninfo {
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typedef void* GenPtr;
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/*{\Mdefinition |\Mname| encapsulates information association via
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generic pointers of type |GenPtr (=void*)|. An object |t| of type |T|
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is stored directly in a variable |p| of type |GenPtr| if |sizeof(T)|
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is not larger than |sizeof(GenPtr)| (also called word size). Otherwise
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|t| is allocated on the heap and referenced via |p|. This class
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encapsulates the technicalities, however the user always has to obey
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the order of its usage: |create|-|access/const_access|-|clear|. On
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misuse memory problems occur.}*/
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/*{\Moperations 2 1}*/
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#ifdef CGAL_USE_FORMER_GENINFO
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static void create(GenPtr& p)
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/*{\Mstatic create a slot for an object of type |T| referenced
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via |p|.}*/
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{ if (sizeof(T) <= sizeof(GenPtr)) new((void*)(&p)) T;
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if (sizeof(T) > sizeof(GenPtr)) p = (GenPtr) new T;
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}
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static T& access(GenPtr& p)
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/*{\Mstatic access an object of type |T| via |p|.
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\precond |p| was initialized via |create| and was not cleared
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via |clear|.}*/
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{ if (sizeof(T) <= sizeof(GenPtr)) return *(T*)(&p);
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else return *(T*)p;
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}
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static const T& const_access(const GenPtr& p)
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/*{\Mstatic read-only access of an object of type |T| via |p|.
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\precond |p| was initialized via |create| and was not cleared
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via |clear|.}*/
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{ if (sizeof(T) <= sizeof(GenPtr)) return *(const T*)(&p);
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else return *(const T*)p;
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}
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static void clear(GenPtr& p)
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/*{\Mstatic clear the memory used for the object of type |T| via
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|p|. \precond |p| was initialized via |create|.}*/
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{ if (sizeof(T) <= sizeof(GenPtr)) ((T*)(&p))->~T();
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if (sizeof(T) > sizeof(GenPtr)) delete (T*) p;
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p=0;
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}
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#else //CGAL_USE_FORMER_GENINFO
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static void create(GenPtr& p) { p = (GenPtr) new T; }
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static T& access(GenPtr& p) { return *(T*)p; }
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static const T& const_access(const GenPtr& p)
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{ return *(const T*)p; }
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static void clear(GenPtr& p){
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delete (T*) p;
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p=0;
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}
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#endif //CGAL_USE_FORMER_GENINFO
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};
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/*{\Mexample In the first example we store a pair of boolean values
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which normally fit into one word. Thus there will no heap allocation
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take place.
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\begin{Mverb}
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struct A { bool a,b };
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GenPtr a;
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geninfo<A>::create(a);
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A& a_access = geninfo<A>::access(a);
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geninfo<A>::clear(a);
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\end{Mverb}
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The second example uses the heap scheme as two longs do not fit into
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one word.
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\begin{Mverb}
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struct B { long a,b };
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GenPtr b;
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geninfo<B>::create(b);
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B& b_access = geninfo<B>::access(b);
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geninfo<B>::clear(b);
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\end{Mverb}
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Note that usage of the scheme takes away with the actual check for the
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type size. Even more important this size might depend on the platform
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which is used to compile the code and thus the scheme enables platform
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independent programming.}*/
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#endif //GENINFO_H
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