From 771943e291bb64764d24aef0832f2908b7160cc0 Mon Sep 17 00:00:00 2001
From: Christian Mazakas <christian.mazakas@gmail.com>
Date: Thu, 7 Sep 2023 08:33:33 -0700
Subject: [PATCH] Add `to_pointer` helper for converting raw pointers to fancy

This helps us avoid an unconditional nullptr check when the user's pointer type is fancy
---
 include/boost/unordered/detail/foa/table.hpp | 32 ++++++++++++--------
 1 file changed, 19 insertions(+), 13 deletions(-)

diff --git a/include/boost/unordered/detail/foa/table.hpp b/include/boost/unordered/detail/foa/table.hpp
index f82586a5..1afcc7a2 100644
--- a/include/boost/unordered/detail/foa/table.hpp
+++ b/include/boost/unordered/detail/foa/table.hpp
@@ -133,22 +133,28 @@ private:
   template<typename> friend class table_erase_return_type;
   template<typename,typename,typename,typename> friend class table;
 
-  table_iterator(group_type* pg,std::size_t n,const table_element_type* p_)
+  template<
+    typename Ptr,typename Ptr2,
+    typename std::enable_if<!std::is_same<Ptr,Ptr2>::value>::type* = nullptr
+  >
+  static Ptr to_pointer(Ptr2 p)
   {
-    if(pg)
-    {
-      using pointer_traits=boost::pointer_traits<char_pointer>;
-      pc=pointer_traits::pointer_to(
-        reinterpret_cast<unsigned char*>(const_cast<group_type*>(pg))[n]);
-    }
-
-    if(p_)
-    {
-      using pointer_traits=boost::pointer_traits<table_element_pointer>;
-      p=pointer_traits::pointer_to(*const_cast<table_element_type*>(p_));
-    }
+    if(!p){return nullptr;}
+    return boost::pointer_traits<Ptr>::pointer_to(*p);
   }
 
+  template<typename Ptr>
+  static Ptr to_pointer(Ptr p)
+  {
+    return p;
+  }
+
+  table_iterator(group_type* pg,std::size_t n,const table_element_type* p_):
+    pc{to_pointer<char_pointer>(
+      reinterpret_cast<unsigned char*>(const_cast<group_type*>(pg))+n)},
+    p{to_pointer<table_element_pointer>(const_cast<table_element_type*>(p_))}
+  {}
+
   inline void increment()noexcept
   {
     BOOST_ASSERT(p!=nullptr);