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119 lines
3.5 KiB
C++
119 lines
3.5 KiB
C++
/* scoped_restore, a simple class for saving and restoring a value
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Copyright (C) 2016-2018 Free Software Foundation, Inc.
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This file is part of GDB.
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>. */
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#ifndef SCOPED_RESTORE_H
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#define SCOPED_RESTORE_H
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/* Base class for scoped_restore_tmpl. */
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class scoped_restore_base
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{
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public:
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/* This informs the (scoped_restore_tmpl<T>) dtor that you no longer
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want the original value restored. */
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void release () const
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{ m_saved_var = NULL; }
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protected:
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scoped_restore_base (void *saved_var)
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: m_saved_var (saved_var)
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{}
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/* The type-erased saved variable. This is here so that clients can
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call release() on a "scoped_restore" local, which is a typedef to
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a scoped_restore_base. See below. */
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mutable void *m_saved_var;
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};
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/* A convenience typedef. Users of make_scoped_restore declare the
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local RAII object as having this type. */
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typedef const scoped_restore_base &scoped_restore;
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/* An RAII-based object that saves a variable's value, and then
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restores it again when this object is destroyed. */
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template<typename T>
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class scoped_restore_tmpl : public scoped_restore_base
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{
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public:
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/* Create a new scoped_restore object that saves the current value
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of *VAR. *VAR will be restored when this scoped_restore object
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is destroyed. */
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scoped_restore_tmpl (T *var)
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: scoped_restore_base (var),
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m_saved_value (*var)
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{
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}
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/* Create a new scoped_restore object that saves the current value
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of *VAR, and sets *VAR to VALUE. *VAR will be restored when this
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scoped_restore object is destroyed. This is templated on T2 to
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allow passing VALUEs of types convertible to T.
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E.g.: T='base'; T2='derived'. */
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template <typename T2>
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scoped_restore_tmpl (T *var, T2 value)
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: scoped_restore_base (var),
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m_saved_value (*var)
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{
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*var = value;
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}
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scoped_restore_tmpl (const scoped_restore_tmpl<T> &other)
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: scoped_restore_base {other.m_saved_var},
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m_saved_value (other.m_saved_value)
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{
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other.m_saved_var = NULL;
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}
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~scoped_restore_tmpl ()
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{
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if (saved_var () != NULL)
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*saved_var () = m_saved_value;
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}
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private:
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/* Return a pointer to the saved variable with its type
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restored. */
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T *saved_var ()
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{ return static_cast<T *> (m_saved_var); }
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/* No need for this. It is intentionally not defined anywhere. */
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scoped_restore_tmpl &operator= (const scoped_restore_tmpl &);
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/* The saved value. */
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const T m_saved_value;
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};
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/* Make a scoped_restore. This is useful because it lets template
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argument deduction work. */
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template<typename T>
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scoped_restore_tmpl<T> make_scoped_restore (T *var)
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{
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return scoped_restore_tmpl<T> (var);
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}
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/* Make a scoped_restore. This is useful because it lets template
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argument deduction work. */
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template<typename T, typename T2>
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scoped_restore_tmpl<T> make_scoped_restore (T *var, T2 value)
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{
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return scoped_restore_tmpl<T> (var, value);
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}
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#endif /* SCOPED_RESTORE_H */
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