Ichthyostega
806db414dd
* Lumiera source code always was copyrighted by individual contributors * there is no entity "Lumiera.org" which holds any copyrights * Lumiera source code is provided under the GPL Version 2+ == Explanations == Lumiera as a whole is distributed under Copyleft, GNU General Public License Version 2 or above. For this to become legally effective, the ''File COPYING in the root directory is sufficient.'' The licensing header in each file is not strictly necessary, yet considered good practice; attaching a licence notice increases the likeliness that this information is retained in case someone extracts individual code files. However, it is not by the presence of some text, that legally binding licensing terms become effective; rather the fact matters that a given piece of code was provably copyrighted and published under a license. Even reformatting the code, renaming some variables or deleting parts of the code will not alter this legal situation, but rather creates a derivative work, which is likewise covered by the GPL! The most relevant information in the file header is the notice regarding the time of the first individual copyright claim. By virtue of this initial copyright, the first author is entitled to choose the terms of licensing. All further modifications are permitted and covered by the License. The specific wording or format of the copyright header is not legally relevant, as long as the intention to publish under the GPL remains clear. The extended wording was based on a recommendation by the FSF. It can be shortened, because the full terms of the license are provided alongside the distribution, in the file COPYING.
151 lines
3.4 KiB
C++
151 lines
3.4 KiB
C++
/*
|
||
OPTIONAL-REF.hpp - optional and switchable reference
|
||
|
||
Copyright (C)
|
||
2010, Hermann Vosseler <Ichthyostega@web.de>
|
||
|
||
**Lumiera** is free software; you can redistribute it and/or modify it
|
||
under the terms of the GNU General Public License as published by the
|
||
Free Software Foundation; either version 2 of the License, or (at your
|
||
option) any later version. See the file COPYING for further details.
|
||
|
||
*/
|
||
|
||
|
||
/** @file optional-ref.hpp
|
||
** a checked, switchable reference.
|
||
** Offers semantics similar to a pointer, but throws (not segfaults)
|
||
** on invalid dereferentiation
|
||
*/
|
||
|
||
|
||
#ifndef LIB_OPTIONAL_REF_H
|
||
#define LIB_OPTIONAL_REF_H
|
||
|
||
#include "lib/error.hpp"
|
||
|
||
|
||
namespace lib {
|
||
|
||
using LERR_(BOTTOM_VALUE);
|
||
|
||
|
||
|
||
|
||
|
||
/**
|
||
* Optional or switchable link to an existing object.
|
||
* This reference wrapper is accessed like a functor,
|
||
* but has the ability to be \em disabled. This disabled state
|
||
* is managed automatically by ctor and dtor, can be detected
|
||
* through \c bool check and -- contrary to a \c NULL pointer
|
||
* -- produces a real exception instead of crashing.
|
||
*
|
||
* @note \em not taking ownership of the pointee
|
||
*
|
||
* @see OptionalRef_test
|
||
* @see lib::AutoRegistered usage example
|
||
* @see SessionInterfaceModules::~SessionInterfaceModules()
|
||
*
|
||
*/
|
||
template<typename T>
|
||
class OptionalRef
|
||
{
|
||
T* ref_;
|
||
|
||
|
||
public:
|
||
OptionalRef()
|
||
: ref_(0)
|
||
{ }
|
||
|
||
~OptionalRef()
|
||
{
|
||
clear();
|
||
}
|
||
|
||
// using default copy operations...
|
||
|
||
explicit
|
||
OptionalRef(T& target) ///< ...\em not allowing implicit conversion from T&
|
||
: ref_(&target)
|
||
{ }
|
||
|
||
explicit operator bool() const { return isValid(); }
|
||
|
||
|
||
T&
|
||
operator() () const
|
||
{
|
||
if (!isValid())
|
||
throw lumiera::error::Logic ("access to this object is (not/yet) enabled"
|
||
, LERR_(BOTTOM_VALUE));
|
||
return *ref_;
|
||
}
|
||
|
||
|
||
/* === mutations ===*/
|
||
|
||
void
|
||
link_to (T& target)
|
||
{
|
||
ref_ = ⌖
|
||
}
|
||
|
||
void
|
||
clear()
|
||
{
|
||
ref_ = 0;
|
||
}
|
||
|
||
|
||
/* === comparison and diagnostics === */
|
||
|
||
bool
|
||
isValid() const
|
||
{
|
||
return bool(ref_);
|
||
}
|
||
|
||
bool
|
||
points_to (T const& target) const
|
||
{
|
||
return isValid()
|
||
&& ref_ == ⌖
|
||
}
|
||
|
||
friend bool
|
||
operator== (OptionalRef const& r1, OptionalRef const& r2)
|
||
{
|
||
return r1.ref_ == r2.ref_;
|
||
}
|
||
friend bool
|
||
operator!= (OptionalRef const& r1, OptionalRef const& r2)
|
||
{
|
||
return r1.ref_ != r2.ref_;
|
||
}
|
||
|
||
// mixed comparisons
|
||
friend bool
|
||
operator== (OptionalRef const& ref, T const& otherTarget) ///< @note might throw
|
||
{
|
||
return ref() == otherTarget;
|
||
}
|
||
|
||
friend bool operator== (T const& otherTarget, OptionalRef const& ref) { return ref == otherTarget; }
|
||
friend bool operator!= (T const& otherTarget, OptionalRef const& ref) { return !(ref == otherTarget); }
|
||
friend bool operator!= (OptionalRef const& ref, T const& otherTarget) { return !(ref == otherTarget); }
|
||
};
|
||
|
||
|
||
template<typename T>
|
||
OptionalRef<T>
|
||
optionalRefTo (T& target)
|
||
{
|
||
return OptionalRef<T> (target);
|
||
}
|
||
|
||
|
||
|
||
} // namespace lib
|
||
#endif
|