Add boost::core::memory_resource

include/boost/core/memory_resource.hpp

@@ -0,0 +1,76 @@
+#ifndef BOOST_CORE_MEMORY_RESOURCE_HPP_INCLUDED
+#define BOOST_CORE_MEMORY_RESOURCE_HPP_INCLUDED
+
+// MS compatible compilers support #pragma once
+
+#if defined(_MSC_VER) && (_MSC_VER >= 1020)
+# pragma once
+#endif
+
+//  Copyright 2023 Peter Dimov
+//  Distributed under the Boost Software License, Version 1.0.
+//  https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/core/max_align.hpp>
+#include <boost/config.hpp>
+#include <cstddef>
+#include <new>
+
+namespace boost
+{
+namespace core
+{
+
+class memory_resource
+{
+public:
+
+#if defined(BOOST_NO_CXX11_DEFAULTED_FUNCTIONS)
+
+    virtual ~memory_resource() {}
+
+#else
+
+    virtual ~memory_resource() = default;
+
+#endif
+
+    BOOST_ATTRIBUTE_NODISCARD void* allocate( std::size_t bytes, std::size_t alignment = max_align )
+    {
+        // https://github.com/boostorg/container/issues/199
+        // https://cplusplus.github.io/LWG/issue3471
+        return ::operator new( bytes, do_allocate( bytes, alignment ) );
+    }
+
+    void deallocate( void* p, std::size_t bytes, std::size_t alignment = max_align )
+    {
+        do_deallocate( p, bytes, alignment );
+    }
+
+    bool is_equal( memory_resource const & other ) const BOOST_NOEXCEPT
+    {
+        return do_is_equal( other );
+    }
+
+private:
+
+    virtual void* do_allocate( std::size_t bytes, std::size_t alignment ) = 0;
+    virtual void do_deallocate( void* p, std::size_t bytes, std::size_t alignment ) = 0;
+
+    virtual bool do_is_equal( memory_resource const & other ) const BOOST_NOEXCEPT = 0;
+};
+
+inline bool operator==( memory_resource const& a, memory_resource const& b ) BOOST_NOEXCEPT
+{
+    return &a == &b || a.is_equal( b );
+}
+
+inline bool operator!=( memory_resource const& a, memory_resource const& b ) BOOST_NOEXCEPT
+{
+    return !( a == b );
+}
+
+} // namespace core
+} // namespace boost
+
+#endif  // #ifndef BOOST_CORE_MEMORY_RESOURCE_HPP_INCLUDED