From bd8c8b03279f6bf41f959ad8c2f20cad51836f3e Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Ion=20Gazta=C3=B1aga?= <igaztanaga@gmail.com>
Date: Mon, 9 Sep 2024 00:37:47 +0200
Subject: [PATCH] Add unused_storage optimization function

---
 include/boost/container/devector.hpp | 22 ++++++++++++++++++++++
 include/boost/container/vector.hpp   |  8 ++++++++
 2 files changed, 30 insertions(+)

diff --git a/include/boost/container/devector.hpp b/include/boost/container/devector.hpp
index 9b1f643..e7fe1df 100644
--- a/include/boost/container/devector.hpp
+++ b/include/boost/container/devector.hpp
@@ -2170,6 +2170,28 @@ class devector
                                  || allocator_traits_type::is_always_equal::value)
    {   x.swap(y);   }
 
+   #ifndef BOOST_CONTAINER_DOXYGEN_INVOKED
+
+   //Functions for optimizations, not for users
+   T *unused_storage(size_type &size)
+   {
+      T *const storage_addr = boost::movelib::to_raw_pointer(m_.buffer);
+      if(this->empty()){
+         size = m_.capacity;
+         return storage_addr;
+      }
+      else if(this->back_free_capacity() > this->front_free_capacity()){
+         size = this->back_free_capacity();
+         return storage_addr + m_.back_idx;
+      }
+      else{
+         size = this->front_free_capacity();
+         return storage_addr;
+      }
+   }
+
+   #endif
+
    private:
 
    void priv_move_assign(BOOST_RV_REF(devector) x, dtl::bool_<true> /*steal_resources*/)
diff --git a/include/boost/container/vector.hpp b/include/boost/container/vector.hpp
index b6fe317..0f683c2 100644
--- a/include/boost/container/vector.hpp
+++ b/include/boost/container/vector.hpp
@@ -2394,6 +2394,14 @@ private:
       boost::movelib::adaptive_merge( this->begin(), pos, e, comp
                                     , this->priv_raw_end(), this->capacity() - this->size());
    }
+
+   //Function for optimizations, not for users
+   T *unused_storage(size_type &size)
+   {
+      size = static_cast<size_type>(this->capacity() - this->size());
+      return this->priv_raw_end();
+   }
+  
    #endif
 
    private: