Add detail/reverse.hpp

include/boost/hash2/detail/reverse.hpp

@@ -0,0 +1,32 @@
+#ifndef BOOST_HASH2_DETAIL_REVERSE_HPP_INCLUDED
+#define BOOST_HASH2_DETAIL_REVERSE_HPP_INCLUDED
+
+// Copyright 2024 Peter Dimov.
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <cstdint>
+#include <cstring>
+
+namespace boost
+{
+namespace hash2
+{
+namespace detail
+{
+
+template<std::size_t N> void reverse( unsigned char (&d)[ N ], void const* s )
+{
+    unsigned char const* s2 = static_cast<unsigned char const*>( s );
+
+    for( std::size_t i = 0; i < N; ++i )
+    {
+        d[ i ] = s2[ N-1-i ];
+    }
+}
+
+} // namespace detail
+} // namespace hash2
+} // namespace boost
+
+#endif // #ifndef BOOST_HASH2_DETAIL_REVERSE_HPP_INCLUDED

include/boost/hash2/hash_append.hpp

@@ -15,6 +15,7 @@
 #include <boost/hash2/is_contiguously_hashable.hpp>
 #include <boost/hash2/get_integral_result.hpp>
 #include <boost/hash2/endian.hpp>
+#include <boost/hash2/detail/reverse.hpp>
 #include <boost/container_hash/is_range.hpp>
 #include <boost/container_hash/is_contiguous_range.hpp>
 #include <boost/container_hash/is_unordered_range.hpp>
@@ -153,9 +154,8 @@ template<class Hash, class Flavor, class T>
     constexpr auto N = sizeof(T);
 
     unsigned char tmp[ N ];
-    std::memcpy( tmp, &v, N );
 
-    std::reverse( tmp, tmp + N );
+    detail::reverse( tmp, &v );
 
     hash2::hash_append_range( h, f, tmp, tmp + N );
 }