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| -rw-r--r-- | include/iprt/cpp/autores.h | 216 |
1 files changed, 216 insertions, 0 deletions
diff --git a/include/iprt/cpp/autores.h b/include/iprt/cpp/autores.h new file mode 100644 index 00000000..a620de7a --- /dev/null +++ b/include/iprt/cpp/autores.h @@ -0,0 +1,216 @@ +/** @file + * IPRT - C++ Resource Management. + */ + +/* + * Copyright (C) 2008-2022 Oracle and/or its affiliates. + * + * This file is part of VirtualBox base platform packages, as + * available from https://www.virtualbox.org. + * + * This program 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, in version 3 of the + * License. + * + * This program 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 + * General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, see <https://www.gnu.org/licenses>. + * + * The contents of this file may alternatively be used under the terms + * of the Common Development and Distribution License Version 1.0 + * (CDDL), a copy of it is provided in the "COPYING.CDDL" file included + * in the VirtualBox distribution, in which case the provisions of the + * CDDL are applicable instead of those of the GPL. + * + * You may elect to license modified versions of this file under the + * terms and conditions of either the GPL or the CDDL or both. + * + * SPDX-License-Identifier: GPL-3.0-only OR CDDL-1.0 + */ + +#ifndef IPRT_INCLUDED_cpp_autores_h +#define IPRT_INCLUDED_cpp_autores_h +#ifndef RT_WITHOUT_PRAGMA_ONCE +# pragma once +#endif + +#include <iprt/types.h> +#include <iprt/assert.h> +#include <iprt/cpp/utils.h> + + + +/** @defgroup grp_rt_cpp_autores C++ Resource Management + * @ingroup grp_rt_cpp + * @{ + */ + +/** + * A callable class template which returns the correct value against which an + * IPRT type must be compared to see if it is invalid. + * + * @warning This template *must* be specialised for the types it is to work with. + */ +template <class T> +inline T RTAutoResNil(void) +{ + AssertFatalMsgFailed(("Unspecialized template!\n")); + return (T)0; +} + +/** Specialisation of RTAutoResNil for RTFILE */ +template <> +inline RTFILE RTAutoResNil(void) +{ + return NIL_RTFILE; +} + +/** + * A function template which calls the correct destructor for an IPRT type. + * + * @warning This template *must* be specialised for the types it is to work with. + */ +template <class T> +inline void RTAutoResDestruct(T a_h) +{ + AssertFatalMsgFailed(("Unspecialized template!\n")); + NOREF(a_h); +} + +/** + * An auto pointer-type class for resources which take a C-style destructor + * (RTMemFree() or equivalent). + * + * The idea of this class is to manage resources which the current code is + * responsible for freeing. By wrapping the resource in an RTCAutoRes, you + * ensure that the resource will be freed when you leave the scope in which + * the RTCAutoRes is defined, unless you explicitly release the resource. + * + * A typical use case is when a function is allocating a number of resources. + * If any single allocation fails then all other resources must be freed. If + * all allocations succeed, then the resources should be returned to the + * caller. By placing all allocated resources in RTCAutoRes containers, you + * ensure that they will be freed on failure, and only have to take care of + * releasing them when you return them. + * + * @param T The type of the resource. + * @param Destruct The function to be used to free the resource. + * This parameter must be supplied if there is no + * specialisation of RTAutoDestruct available for @a T. + * @param NilRes The function returning the NIL value for T. Required. + * This parameter must be supplied if there is no + * specialisation of RTAutoResNil available for @a T. + * + * @note The class can not be initialised directly using assignment, due + * to the lack of a copy constructor. This is intentional. + */ +template <class T, void Destruct(T) = RTAutoResDestruct<T>, T NilRes(void) = RTAutoResNil<T> > +class RTCAutoRes + : public RTCNonCopyable +{ +protected: + /** The resource handle. */ + T m_hRes; + +public: + /** + * Constructor + * + * @param a_hRes The handle to resource to manage. Defaults to NIL. + */ + RTCAutoRes(T a_hRes = NilRes()) + : m_hRes(a_hRes) + { + } + + /** + * Destructor. + * + * This destroys any resource currently managed by the object. + */ + ~RTCAutoRes() + { + if (m_hRes != NilRes()) + Destruct(m_hRes); + } + + /** + * Assignment from a value. + * + * This destroys any resource currently managed by the object + * before taking on the new one. + * + * @param a_hRes The handle to the new resource. + */ + RTCAutoRes &operator=(T a_hRes) + { + if (m_hRes != NilRes()) + Destruct(m_hRes); + m_hRes = a_hRes; + return *this; + } + + /** + * Checks if the resource handle is NIL or not. + */ + bool operator!() + { + return m_hRes == NilRes(); + } + + /** + * Give up ownership the current resource, handing it to the caller. + * + * @returns The current resource handle. + * + * @note Nothing happens to the resource when the object goes out of scope. + */ + T release(void) + { + T Tmp = m_hRes; + m_hRes = NilRes(); + return Tmp; + } + + /** + * Deletes the current resources. + * + * @param a_hRes Handle to a new resource to manage. Defaults to NIL. + */ + void reset(T a_hRes = NilRes()) + { + if (a_hRes != m_hRes) + { + if (m_hRes != NilRes()) + Destruct(m_hRes); + m_hRes = a_hRes; + } + } + + /** + * Get the raw resource handle. + * + * Typically used passing the handle to some IPRT function while + * the object remains in scope. + * + * @returns The raw resource handle. + */ + T get(void) + { + return m_hRes; + } +}; + +/** @} */ + + +/* include after template definition */ +#include <iprt/mem.h> + +#endif /* !IPRT_INCLUDED_cpp_autores_h */ + |