From 91e78fd746a9eddabf42e2f2ae5ad2f015a7403b Mon Sep 17 00:00:00 2001
From: Christian Mazakas <christian.mazakas@gmail.com>
Date: Mon, 25 Jul 2022 11:35:23 -0700
Subject: [PATCH 1/2] Add `erase_node()` function to table, creating an
 optimizer-friendly function

---
 .../boost/unordered/detail/implementation.hpp   | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/include/boost/unordered/detail/implementation.hpp b/include/boost/unordered/detail/implementation.hpp
index cec99c79..2cc27c5d 100644
--- a/include/boost/unordered/detail/implementation.hpp
+++ b/include/boost/unordered/detail/implementation.hpp
@@ -2928,6 +2928,23 @@ namespace boost {
           return 1;
         }
 
+        iterator erase_node(c_iterator pos) {
+          c_iterator next = pos;
+          ++next;
+          
+          bucket_iterator itb = pos.itb;
+          node_pointer* pp = boost::addressof(itb->next);
+          while (*pp != pos.p) {
+            pp = boost::addressof((*pp)->next);
+          }
+
+          buckets_.extract_node_after(itb, pp);
+          this->delete_node(pos.p);
+          --size_;
+
+          return iterator(next.p, next.itb);
+        }
+
         iterator erase_nodes_range(c_iterator first, c_iterator last)
         {
           if (first == last) {

From a31e894411c7f0504c1fe3279d08af07f35dd1e8 Mon Sep 17 00:00:00 2001
From: Christian Mazakas <christian.mazakas@gmail.com>
Date: Mon, 25 Jul 2022 11:35:38 -0700
Subject: [PATCH 2/2] Update implementation to use `erase_node()` where
 applicable

---
 include/boost/unordered/unordered_map.hpp | 16 ++++------------
 include/boost/unordered/unordered_set.hpp |  9 ++-------
 2 files changed, 6 insertions(+), 19 deletions(-)

diff --git a/include/boost/unordered/unordered_map.hpp b/include/boost/unordered/unordered_map.hpp
index 02fe1f9f..97908fb6 100644
--- a/include/boost/unordered/unordered_map.hpp
+++ b/include/boost/unordered/unordered_map.hpp
@@ -1856,18 +1856,14 @@ namespace boost {
     typename unordered_map<K, T, H, P, A>::iterator
     unordered_map<K, T, H, P, A>::erase(iterator position)
     {
-      const_iterator last = position;
-      ++last;
-      return table_.erase_nodes_range(position, last);
+      return table_.erase_node(position);
     }
 
     template <class K, class T, class H, class P, class A>
     typename unordered_map<K, T, H, P, A>::iterator
     unordered_map<K, T, H, P, A>::erase(const_iterator position)
     {
-      const_iterator last = position;
-      ++last;
-      return table_.erase_nodes_range(position, last);
+      return table_.erase_node(position);
     }
 
     template <class K, class T, class H, class P, class A>
@@ -2340,9 +2336,7 @@ namespace boost {
     unordered_multimap<K, T, H, P, A>::erase(iterator position)
     {
       BOOST_ASSERT(position != this->end());
-      iterator next = position;
-      ++next;
-      return table_.erase_nodes_range(position, next);
+      return table_.erase_node(position);
     }
 
     template <class K, class T, class H, class P, class A>
@@ -2350,9 +2344,7 @@ namespace boost {
     unordered_multimap<K, T, H, P, A>::erase(const_iterator position)
     {
       BOOST_ASSERT(position != this->end());
-      const_iterator next = position;
-      ++next;
-      return table_.erase_nodes_range(position, next);
+      return table_.erase_node(position);
     }
 
     template <class K, class T, class H, class P, class A>
diff --git a/include/boost/unordered/unordered_set.hpp b/include/boost/unordered/unordered_set.hpp
index d1ddc347..8721a68a 100644
--- a/include/boost/unordered/unordered_set.hpp
+++ b/include/boost/unordered/unordered_set.hpp
@@ -1457,9 +1457,7 @@ namespace boost {
     typename unordered_set<T, H, P, A>::iterator
     unordered_set<T, H, P, A>::erase(const_iterator position)
     {
-      const_iterator last = position;
-      ++last;
-      return table_.erase_nodes_range(position, last);
+      return table_.erase_node(position);
     }
 
     template <class T, class H, class P, class A>
@@ -1853,10 +1851,7 @@ namespace boost {
     unordered_multiset<T, H, P, A>::erase(const_iterator position)
     {
       BOOST_ASSERT(position != this->end());
-      iterator next = position;
-      ++next;
-      table_.erase_nodes_range(position, next);
-      return next;
+      return table_.erase_node(position);
     }
 
     template <class T, class H, class P, class A>