[PATCH][Hashtable 4/6] Clean local_iterator implementation
Jonathan Wakely
jwakely@redhat.com
Fri Jul 17 10:45:40 GMT 2020
On 17/11/19 22:03 +0100, François Dumont wrote:
>Simplify local_iterator implementation. It makes local_iterator and
>iterator comparable which is used in debug containers.
>
>Â Â Â * include/bits/hashtable_policy.h (_Node_iterator_base()): New.
>Â Â Â (operator==(const _Node_iterator_base&, const _Node_iterator_base&)):
>Â Â Â Make hidden friend.
>Â Â Â (operator!=(const _Node_iterator_base&, const _Node_iterator_base&)):
>Â Â Â Make hidden friend.
>Â Â Â (_Local_iterator_base<>): Inherits _Node_iterator_base.
>Â Â Â (_Local_iterator_base<>::_M_cur): Remove.
>Â Â Â (_Local_iterator_base<>::_M_curr()): Remove.
>Â Â Â (operator==(const _Local_iterator_base&, const _Local_iterator_base&)):
>Â Â Â Remove.
>Â Â Â (operator!=(const _Local_iterator_base&, const _Local_iterator_base&)):
>Â Â Â Remove.
>Â Â Â * include/debug/unordered_map (unordered_map<>::_M_invalidate): Adapt.
>Â Â Â (unordered_multimap<>::_M_invalidate): Adapt.
>Â Â Â * include/debug/unordered_set (unordered_set<>::_M_invalidate): Adapt.
>Â Â Â (unordered_multiset<>::_M_invalidate): Adapt.
>
>Tested under Linux x86_64.
OK for master, with one (non-essential) change mentioned below ...
>diff --git a/libstdc++-v3/include/bits/hashtable_policy.h b/libstdc++-v3/include/bits/hashtable_policy.h
>index f330f7f811b..5cc943b3d22 100644
>--- a/libstdc++-v3/include/bits/hashtable_policy.h
>+++ b/libstdc++-v3/include/bits/hashtable_policy.h
>@@ -301,27 +301,24 @@ namespace __detail
>
> __node_type* _M_cur;
>
>+ _Node_iterator_base() = default;
> _Node_iterator_base(__node_type* __p) noexcept
> : _M_cur(__p) { }
>
> void
> _M_incr() noexcept
> { _M_cur = _M_cur->_M_next(); }
>- };
>
>- template<typename _Value, typename _Cache_hash_code>
>- inline bool
>- operator==(const _Node_iterator_base<_Value, _Cache_hash_code>& __x,
>- const _Node_iterator_base<_Value, _Cache_hash_code >& __y)
>- noexcept
>- { return __x._M_cur == __y._M_cur; }
>+ friend bool
>+ operator==(const _Node_iterator_base& __x, const _Node_iterator_base& __y)
>+ noexcept
>+ { return __x._M_cur == __y._M_cur; }
>
>- template<typename _Value, typename _Cache_hash_code>
>- inline bool
>- operator!=(const _Node_iterator_base<_Value, _Cache_hash_code>& __x,
>- const _Node_iterator_base<_Value, _Cache_hash_code>& __y)
>- noexcept
>- { return __x._M_cur != __y._M_cur; }
>+ friend bool
>+ operator!=(const _Node_iterator_base& __x, const _Node_iterator_base& __y)
>+ noexcept
>+ { return __x._M_cur != __y._M_cur; }
This operator!= can be surrounded by:
#if __cpp_impl_three_way_comparison < 201907L
...
#endif
because when three-way comparisons are supported (i.e. C++20 and
later) the operator!= can be generated by the compiler.
>+ };
>
> /// Node iterators, used to iterate through all the hashtable.
> template<typename _Value, typename _Constant_iterators,
>@@ -345,7 +342,7 @@ namespace __detail
> const _Value&, _Value&>::type;
>
> _Node_iterator() noexcept
>- : __base_type(0) { }
>+ : __base_type(nullptr) { }
>
> explicit
> _Node_iterator(__node_type* __p) noexcept
>@@ -394,7 +391,7 @@ namespace __detail
> typedef const _Value& reference;
>
> _Node_const_iterator() noexcept
>- : __base_type(0) { }
>+ : __base_type(nullptr) { }
>
> explicit
> _Node_const_iterator(__node_type* __p) noexcept
>@@ -1426,9 +1423,11 @@ namespace __detail
> struct _Local_iterator_base<_Key, _Value, _ExtractKey,
> _H1, _H2, _Hash, __hash_cached_t>
> : private _Hashtable_ebo_helper<0, _H2>
>+ , _Node_iterator_base<_Value, __hash_cached_t>
I was initially worried this is an ABI break, but it just moves the
_M_cur member into a new base class, which will be at the same offset
into the class, and won't change the sie or alignment. So I think it's
OK.
>@@ -1576,33 +1572,10 @@ namespace __detail
> _M_destroy() { this->_M_h()->~__hash_code_base(); }
>
> public:
>- const void*
>- _M_curr() const { return _M_cur; } // for equality ops and debug mode
>-
> std::size_t
> _M_get_bucket() const { return _M_bucket; } // for debug mode
> };
>
>- template<typename _Key, typename _Value, typename _ExtractKey,
>- typename _H1, typename _H2, typename _Hash,
>- typename _Cache_hash_code>
>- inline bool
>- operator==(const _Local_iterator_base<_Key, _Value, _ExtractKey,
>- _H1, _H2, _Hash, _Cache_hash_code>& __x,
>- const _Local_iterator_base<_Key, _Value, _ExtractKey,
>- _H1, _H2, _Hash, _Cache_hash_code>& __y)
>- { return __x._M_curr() == __y._M_curr(); }
>-
>- template<typename _Key, typename _Value, typename _ExtractKey,
>- typename _H1, typename _H2, typename _Hash,
>- typename _Cache_hash_code>
>- inline bool
>- operator!=(const _Local_iterator_base<_Key, _Value, _ExtractKey,
>- _H1, _H2, _Hash, _Cache_hash_code>& __x,
>- const _Local_iterator_base<_Key, _Value, _ExtractKey,
>- _H1, _H2, _Hash, _Cache_hash_code>& __y)
>- { return __x._M_curr() != __y._M_curr(); }
>-
Removing these operators (and making the ones for the base hidden
friends) is a nice improvement.
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