reimplemented random_access_index internal, cross-index splice in linear time

include/boost/multi_index/detail/rnd_index_node.hpp

@@ -1,4 +1,4 @@
-/* Copyright 2003-2018 Joaquin M Lopez Munoz.
+/* Copyright 2003-2021 Joaquin M Lopez Munoz.
  * Distributed under the Boost Software License, Version 1.0.
  * (See accompanying file LICENSE_1_0.txt or copy at
  * http://www.boost.org/LICENSE_1_0.txt)
@@ -169,6 +169,25 @@ struct random_access_index_node_impl
     }
   }
 
+  static ptr_pointer gather_nulls(
+    ptr_pointer pbegin,ptr_pointer pend,ptr_pointer x)
+  {
+    for(ptr_pointer p=pbegin;p!=x;++p){
+      if(*p){
+        *pbegin=*p;
+        (*pbegin)->up()=pbegin;
+        ++pbegin;
+      }
+    }
+    for(ptr_pointer p=pend;p!=x;){
+      if(*--p){
+        *--pend=*p;
+        (*pend)->up()=pend;
+      }
+    }
+    return pbegin;
+  }
+
 private:
   ptr_pointer up_;
 };

include/boost/multi_index/random_access_index.hpp

@@ -1140,9 +1140,21 @@ private:
   template<typename Iterator>
   void internal_splice(iterator position,Iterator first,Iterator last)
   {
-    index_node_type* pn=position.get_node();
+    /* null out [first, last) positions in ptrs array */
-    while(first!=last){
+
-      relocate(pn,static_cast<index_node_type*>((first++).get_node()));
+    for(Iterator it=first;it!=last;++it){ 
+      *(static_cast<index_node_type*>(it.get_node())->up())=0;
+    }
+
+    node_impl_ptr_pointer pp=node_impl_type::gather_nulls(
+      ptrs.begin(),ptrs.end(),
+      static_cast<index_node_type*>(position.get_node())->up());
+
+    /* relink [first, last) */
+
+    for(Iterator it=first;it!=last;++it,++pp){
+      *pp=static_cast<index_node_type*>(it.get_node());
+      (*pp)->up()=pp;
     }
   }