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/* A safe iterator for GDB, the GNU debugger.
Copyright (C) 2018-2024 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_SAFE_ITERATOR_H
#define COMMON_SAFE_ITERATOR_H
#include <type_traits>
/* A forward iterator that wraps Iterator, such that when iterating
with iterator IT, it is possible to delete *IT without invalidating
IT. Suitably wrapped in a range type and used with range-for, this
allow convenient patterns like this:
// range_safe() returns a range type whose begin()/end() methods
// return safe iterators.
for (foo *f : range_safe ())
{
if (f->should_delete ())
{
// The ++it operation implicitly done by the range-for is
// still OK after this.
delete f;
}
}
*/
template<typename Iterator>
class basic_safe_iterator
{
public:
typedef basic_safe_iterator self_type;
typedef typename Iterator::value_type value_type;
typedef typename Iterator::reference reference;
typedef typename Iterator::pointer pointer;
typedef typename Iterator::iterator_category iterator_category;
typedef typename Iterator::difference_type difference_type;
/* Construct the begin iterator using the given arguments; the end iterator is
default constructed. */
template<typename... Args>
explicit basic_safe_iterator (Args &&...args)
: m_it (std::forward<Args> (args)...),
m_next (m_it)
{
if (m_it != m_end)
++m_next;
}
/* Construct the iterator using the first argument, and construct
the end iterator using the second argument. */
template<typename Arg>
explicit basic_safe_iterator (Arg &&arg, Arg &&arg2)
: m_it (std::forward<Arg> (arg)),
m_next (m_it),
m_end (std::forward<Arg> (arg2))
{
if (m_it != m_end)
++m_next;
}
/* Create a one-past-end iterator. */
basic_safe_iterator ()
{}
typename std::invoke_result<decltype(&Iterator::operator*), Iterator>::type
operator* () const
{ return *m_it; }
self_type &operator++ ()
{
m_it = m_next;
if (m_it != m_end)
++m_next;
return *this;
}
bool operator== (const self_type &other) const
{ return m_it == other.m_it; }
bool operator!= (const self_type &other) const
{ return m_it != other.m_it; }
private:
/* The current element. */
Iterator m_it {};
/* The next element. Always one element ahead of M_IT. */
Iterator m_next {};
/* A one-past-end iterator. */
Iterator m_end {};
};
/* A range adapter that wraps another range, and then returns safe
iterators wrapping the original range's iterators. */
template<typename Range>
class basic_safe_range
{
public:
typedef basic_safe_iterator<typename Range::iterator> iterator;
explicit basic_safe_range (Range range)
: m_range (range)
{
}
iterator begin ()
{
return iterator (m_range.begin (), m_range.end ());
}
iterator end ()
{
return iterator (m_range.end (), m_range.end ());
}
private:
Range m_range;
};
#endif /* COMMON_SAFE_ITERATOR_H */
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