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/* scoped_restore, a simple class for saving and restoring a value
Copyright (C) 2016-2020 Free Software Foundation, Inc.
This file is part of GDB.
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; either version 3 of the License, or
(at your option) any later version.
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 <http://www.gnu.org/licenses/>. */
#ifndef COMMON_SCOPED_RESTORE_H
#define COMMON_SCOPED_RESTORE_H
/* Base class for scoped_restore_tmpl. */
class scoped_restore_base
{
public:
/* This informs the (scoped_restore_tmpl<T>) dtor that you no longer
want the original value restored. */
void release () const
{ m_saved_var = NULL; }
protected:
scoped_restore_base (void *saved_var)
: m_saved_var (saved_var)
{}
/* The type-erased saved variable. This is here so that clients can
call release() on a "scoped_restore" local, which is a typedef to
a scoped_restore_base. See below. */
mutable void *m_saved_var;
};
/* A convenience typedef. Users of make_scoped_restore declare the
local RAII object as having this type. */
typedef const scoped_restore_base &scoped_restore;
/* An RAII-based object that saves a variable's value, and then
restores it again when this object is destroyed. */
template<typename T>
class scoped_restore_tmpl : public scoped_restore_base
{
public:
/* Create a new scoped_restore object that saves the current value
of *VAR. *VAR will be restored when this scoped_restore object
is destroyed. */
scoped_restore_tmpl (T *var)
: scoped_restore_base (var),
m_saved_value (*var)
{
}
/* Create a new scoped_restore object that saves the current value
of *VAR, and sets *VAR to VALUE. *VAR will be restored when this
scoped_restore object is destroyed. This is templated on T2 to
allow passing VALUEs of types convertible to T.
E.g.: T='base'; T2='derived'. */
template <typename T2>
scoped_restore_tmpl (T *var, T2 value)
: scoped_restore_base (var),
m_saved_value (*var)
{
*var = value;
}
scoped_restore_tmpl (const scoped_restore_tmpl<T> &other)
: scoped_restore_base {other.m_saved_var},
m_saved_value (other.m_saved_value)
{
other.m_saved_var = NULL;
}
~scoped_restore_tmpl ()
{
if (saved_var () != NULL)
*saved_var () = m_saved_value;
}
private:
/* Return a pointer to the saved variable with its type
restored. */
T *saved_var ()
{ return static_cast<T *> (m_saved_var); }
/* No need for this. It is intentionally not defined anywhere. */
scoped_restore_tmpl &operator= (const scoped_restore_tmpl &);
/* The saved value. */
const T m_saved_value;
};
/* Make a scoped_restore. This is useful because it lets template
argument deduction work. */
template<typename T>
scoped_restore_tmpl<T> make_scoped_restore (T *var)
{
return scoped_restore_tmpl<T> (var);
}
/* Make a scoped_restore. This is useful because it lets template
argument deduction work. */
template<typename T, typename T2>
scoped_restore_tmpl<T> make_scoped_restore (T *var, T2 value)
{
return scoped_restore_tmpl<T> (var, value);
}
#endif /* COMMON_SCOPED_RESTORE_H */
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