added narrow_cast

include/boost/unordered/detail/foa.hpp

@@ -23,6 +23,7 @@
 #include <boost/predef.h>
 #include <boost/type_traits/has_trivial_copy.hpp>
 #include <boost/type_traits/is_nothrow_swappable.hpp>
+#include <boost/unordered/detail/narrow_cast.hpp>
 #include <boost/unordered/detail/xmx.hpp>
 #include <boost/unordered/hash_traits.hpp>
 #include <climits>
@@ -269,20 +270,12 @@ private:
       0xF8F8F8F8u,0xF9F9F9F9u,0xFAFAFAFAu,0xFBFBFBFBu,0xFCFCFCFCu,0xFDFDFDFDu,0xFEFEFEFEu,0xFFFFFFFFu,
     };
 
-#if defined(__MSVC_RUNTIME_CHECKS)
-    return (int)word[hash&0xffu];
-#else
-    return (int)word[(unsigned char)hash];
-#endif
+    return (int)word[narrow_cast<unsigned char>(hash)];
   }
 
   inline static unsigned char reduced_hash(std::size_t hash)
   {
-#if defined(__MSVC_RUNTIME_CHECKS)
-    return match_word(hash)&0xffu;
-#else
-    return (unsigned char)match_word(hash);
-#endif
+    return narrow_cast<unsigned char>(match_word(hash));
   }
 
   inline unsigned char& at(std::size_t pos)
@@ -533,11 +526,7 @@ struct group15
     std::size_t     pos=reinterpret_cast<uintptr_t>(pc)%sizeof(group15);
     group15        *pg=reinterpret_cast<group15*>(pc-pos);
     boost::uint64_t x=((pg->m[0])>>pos)&0x000100010001ull;
-#if defined(__MSVC_RUNTIME_CHECKS)
-    boost::uint32_t y=(x|(x>>15)|(x>>30))&0xffffffffu;
-#else
-    boost::uint32_t y=static_cast<boost::uint32_t>(x|(x>>15)|(x>>30));
-#endif
+    boost::uint32_t y=narrow_cast<boost::uint32_t>(x|(x>>15)|(x>>30));
     return !pg->is_not_overflowed(y);
   };
 
@@ -552,11 +541,7 @@ struct group15
   inline int match_occupied()const
   {
     boost::uint64_t x=m[0]|m[1];
-#if defined(__MSVC_RUNTIME_CHECKS)
-    boost::uint32_t y=(x|(x>>32))&0xffffffffu;
-#else
-    boost::uint32_t y=static_cast<boost::uint32_t>(x|(x>>32));
-#endif
+    boost::uint32_t y=narrow_cast<boost::uint32_t>(x|(x>>32));
     y|=y>>16;
     return y&0x7FFF;
   }
@@ -591,11 +576,7 @@ private:
       240,241,242,243,244,245,246,247,248,249,250,251,252,253,254,255,
     };
     
-#if defined(__MSVC_RUNTIME_CHECKS)
-  return table[hash&0xffu];
-#else
-    return table[(unsigned char)hash];
-#endif
+    return table[narrow_cast<unsigned char>(hash)];
   }
 
   inline void set_impl(std::size_t pos,std::size_t n)

include/boost/unordered/detail/narrow_cast.hpp

@@ -0,0 +1,44 @@
+/* Copyright 2022 Joaquin M Lopez Munoz.
+ * Distributed under the Boost Software License, Version 1.0.
+ * (See accompanying file LICENSE_1_0.txt or copy at
+ * http://www.boost.org/LICENSE_1_0.txt)
+ *
+ * See https://www.boost.org/libs/unordered for library home page.
+ */
+
+#ifndef BOOST_UNORDERED_DETAIL_NARROW_CAST_HPP
+#define BOOST_UNORDERED_DETAIL_NARROW_CAST_HPP
+
+#include <boost/config.hpp>
+#include <boost/static_assert.hpp>
+#include <boost/type_traits/is_integral.hpp>
+#include <boost/type_traits/make_unsigned.hpp>
+
+namespace boost{
+namespace unordered{
+namespace detail{
+
+template<typename To,typename From>
+BOOST_CONSTEXPR To narrow_cast(From x) BOOST_NOEXCEPT
+{
+  BOOST_STATIC_ASSERT(boost::is_integral<From>::value);
+  BOOST_STATIC_ASSERT(boost::is_integral<To>::value);
+  BOOST_STATIC_ASSERT(sizeof(From)>=sizeof(To));
+
+  return static_cast<To>(
+    x
+
+#if defined(__MSVC_RUNTIME_CHECKS)
+    /* Avoids VS's "Run-Time Check Failure #1 - A cast to a smaller data type
+     * has caused a loss of data."
+     */
+    &static_cast<typename boost::make_unsigned<To>::type>(~static_cast<To>(0))
+#endif
+  );
+}
+
+} /* namespace detail */
+} /* namespace unordered */
+} /* namespace boost */
+
+#endif

include/boost/unordered/detail/prime_fmod.hpp

@@ -11,6 +11,7 @@
 #include <boost/preprocessor/seq/enum.hpp>
 #include <boost/preprocessor/seq/for_each.hpp>
 #include <boost/preprocessor/seq/size.hpp>
+#include <boost/unordered/detail/narrow_cast.hpp>
 
 #include <boost/config.hpp>
 
@@ -117,15 +118,9 @@ namespace boost {
 #if defined(BOOST_UNORDERED_FCA_HAS_64B_SIZE_T)
           std::size_t sizes_under_32bit = inv_sizes32_len;
           if (BOOST_LIKELY(size_index < sizes_under_32bit)) {
-#if defined(__MSVC_RUNTIME_CHECKS)
             return fast_modulo(
-              boost::uint32_t(hash & 0xffffffffu) + boost::uint32_t(hash >> 32),
+              narrow_cast<boost::uint32_t>(hash) + narrow_cast<boost::uint32_t>(hash >> 32),
               inv_sizes32[size_index], boost::uint32_t(sizes[size_index]));
-#else
-            return fast_modulo(
-              boost::uint32_t(hash) + boost::uint32_t(hash >> 32),
-              inv_sizes32[size_index], boost::uint32_t(sizes[size_index]));
-#endif
           } else {
             return positions[size_index - sizes_under_32bit](hash);
           }