Implement boost::core::endian

include/boost/core/bit.hpp

@@ -506,13 +506,43 @@ BOOST_CXX14_CONSTEXPR T bit_ceil( T x ) BOOST_NOEXCEPT
 
 // endian
 
+#if defined(__BYTE_ORDER__) && defined(__ORDER_LITTLE_ENDIAN__) && __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+
+# define BOOST_CORE_BIT_NATIVE_INITIALIZER =little
+
+#elif defined(__BYTE_ORDER__) && defined(__ORDER_BIG_ENDIAN__) && __BYTE_ORDER__ == __ORDER_BIG_ENDIAN__
+
+# define BOOST_CORE_BIT_NATIVE_INITIALIZER =big
+
+#elif defined(__BYTE_ORDER__) && defined(__ORDER_PDP_ENDIAN__) && __BYTE_ORDER__ == __ORDER_PDP_ENDIAN__
+
+# define BOOST_CORE_BIT_NATIVE_INITIALIZER
+
+#elif defined(__LITTLE_ENDIAN__)
+
+# define BOOST_CORE_BIT_NATIVE_INITIALIZER =little
+
+#elif defined(__BIG_ENDIAN__)
+
+# define BOOST_CORE_BIT_NATIVE_INITIALIZER =big
+
+#elif defined(_MSC_VER) || defined(__i386__) || defined(__x86_64__)
+
+# define BOOST_CORE_BIT_NATIVE_INITIALIZER =little
+
+#else
+
+# define BOOST_CORE_BIT_NATIVE_INITIALIZER
+
+#endif
+
 #if !defined(BOOST_NO_CXX11_SCOPED_ENUMS)
 
 enum class endian
 {
-    little,
     big,
-    // native = /* see description */
+    little,
+    native BOOST_CORE_BIT_NATIVE_INITIALIZER
 };
 
 typedef endian endian_type;
@@ -524,9 +554,9 @@ namespace endian
 
 enum type
 {
-    little,
     big,
-    // native = /* see description */
+    little,
+    native BOOST_CORE_BIT_NATIVE_INITIALIZER
 };
 
 } // namespace endian
@@ -535,6 +565,8 @@ typedef endian::type endian_type;
 
 #endif
 
+#undef BOOST_CORE_BIT_NATIVE_INITIALIZER
+
 } // namespace core
 } // namespace boost
 

test/Jamfile.v2

@@ -231,6 +231,7 @@ run has_single_bit_test.cpp ;
 run bit_floor_test.cpp ;
 run bit_ceil_test.cpp ;
 run bit_popcount_test.cpp ;
+run bit_endian_test.cpp ;
 
 use-project /boost/core/swap : ./swap ;
 build-project ./swap ;

test/bit_endian_test.cpp

@@ -0,0 +1,36 @@
+// Test for boost/core/bit.hpp (bit_ceil)
+//
+// Copyright 2020 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/core/bit.hpp>
+#include <boost/core/lightweight_test.hpp>
+#include <boost/cstdint.hpp>
+#include <cstring>
+
+int main()
+{
+    boost::uint64_t v = static_cast<boost::uint64_t>( 0x0102030405060708ull );
+
+    if( boost::core::endian::native == boost::core::endian::little )
+    {
+        unsigned char w[] = { 8, 7, 6, 5, 4, 3, 2, 1 };
+        BOOST_TEST( std::memcmp( &v, w, 8 ) == 0 );
+    }
+    else if( boost::core::endian::native == boost::core::endian::big )
+    {
+        unsigned char w[] = { 1, 2, 3, 4, 5, 6, 7, 8 };
+        BOOST_TEST( std::memcmp( &v, w, 8 ) == 0 );
+    }
+    else
+    {
+        unsigned char w1[] = { 8, 7, 6, 5, 4, 3, 2, 1 };
+        BOOST_TEST( std::memcmp( &v, w1, 8 ) != 0 );
+
+        unsigned char w2[] = { 1, 2, 3, 4, 5, 6, 7, 8 };
+        BOOST_TEST( std::memcmp( &v, w2, 8 ) != 0 );
+    }
+
+    return boost::report_errors();
+}