Move gdbsupport to the top level

[deliverable/binutils-gdb.git] / gdbsupport / scoped_restore.h

diff --git a/gdbsupport/scoped_restore.h b/gdbsupport/scoped_restore.h
new file mode 100644 (file)
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+++ b/gdbsupport/scoped_restore.h
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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 */