From 33c3d22bf8516bd504af9ecde5333ab4df34e349 Mon Sep 17 00:00:00 2001
From: Laurent Rineau <laurent.rineau@cgal.org>
Date: Thu, 22 Feb 2024 13:40:58 +0100
Subject: [PATCH] simpler timestamp system

---
 STL_Extension/include/CGAL/Compact_container.h | 16 ++++++++--------
 STL_Extension/include/CGAL/Time_stamper.h      | 11 +----------
 2 files changed, 9 insertions(+), 18 deletions(-)

diff --git a/STL_Extension/include/CGAL/Compact_container.h b/STL_Extension/include/CGAL/Compact_container.h
index e82a33412d9..6778f94e041 100644
--- a/STL_Extension/include/CGAL/Compact_container.h
+++ b/STL_Extension/include/CGAL/Compact_container.h
@@ -403,10 +403,17 @@ public:
 
     pointer ret = free_list;
     free_list = clean_pointee(ret);
+    std::size_t ts;
+    if constexpr (Time_stamper::has_timestamp) {
+      ts = ret->time_stamp();
+    }
     std::allocator_traits<allocator_type>::construct(alloc, ret, t);
+    if constexpr (Time_stamper::has_timestamp) {
+      ret->set_time_stamp(ts);
+    }
+    Time_stamper::set_time_stamp(ret, time_stamp);
     CGAL_assertion(type(ret) == USED);
     ++size_;
-    Time_stamper::set_time_stamp(ret, time_stamp);
     return iterator(ret, 0);
   }
 
@@ -652,9 +659,6 @@ private:
   // Get the type of the pointee.
   static Type type(const_pointer ptr)
   {
-    if constexpr (Time_stamper::has_timestamp) {
-      return (Type)(ptr->time_stamp() >> Time_stamper::time_stamp_shift);
-    }
     char * p = (char *) Traits::pointer(*ptr);
     return (Type) (reinterpret_cast<std::ptrdiff_t>(p) -
                    reinterpret_cast<std::ptrdiff_t>(clean_pointer(p)));
@@ -663,10 +667,6 @@ private:
   // Sets the pointer part and the type of the pointee.
   static void set_type(pointer ptr, void * p, Type t)
   {
-    if constexpr (Time_stamper::has_timestamp) {
-      const auto ts = ptr->time_stamp() & ~(Time_stamper::time_stamp_mask);
-      ptr->set_time_stamp(ts | (static_cast<std::size_t>(t) << Time_stamper::time_stamp_shift));
-    }
     // This out of range compare is always true and causes lots of
     // unnecessary warnings.
     // CGAL_precondition(0 <= t && t < 4);
diff --git a/STL_Extension/include/CGAL/Time_stamper.h b/STL_Extension/include/CGAL/Time_stamper.h
index 7afe7160eee..645900760eb 100644
--- a/STL_Extension/include/CGAL/Time_stamper.h
+++ b/STL_Extension/include/CGAL/Time_stamper.h
@@ -29,27 +29,18 @@ template <typename T>
 struct Time_stamper
 {
   static constexpr bool has_timestamp = true;
-  static constexpr int time_stamp_shift = sizeof(std::size_t) * CHAR_BIT - 2;
-  static constexpr std::size_t time_stamp_mask = std::size_t(0b11) << time_stamp_shift;
-  static constexpr std::size_t time_stamp_is_free_mask = std::size_t(0b001) << (time_stamp_shift - 1);
 
   static void initialize_time_stamp(T* pt) {
     pt->set_time_stamp(std::size_t(-1));
   }
 
-  static bool is_free(const T* pt)
-  {
-    return ( pt->time_stamp() & time_stamp_is_free_mask )!= 0;
-  }
-
   template <typename time_stamp_t>
   static void set_time_stamp(T* pt, time_stamp_t& time_stamp_) {
-    if(is_free(pt)) {
+    if(pt->time_stamp() == std::size_t(-1)) {
       const std::size_t new_ts = time_stamp_++;
       pt->set_time_stamp(new_ts);
     }
     else {
-      pt->set_time_stamp(pt->time_stamp() & ~time_stamp_mask);
       // else: the time stamp is re-used
 
       // Enforces that the time stamp is greater than the current value.