Added thirdparty: boost library

thirdparty/include/boost/integer/integer_log2.hpp

@@ -0,0 +1,117 @@
+// -----------------------------------------------------------
+// integer_log2.hpp
+//
+//   Gives the integer part of the logarithm, in base 2, of a
+// given number. Behavior is undefined if the argument is <= 0.
+//
+//        Copyright (c) 2003-2004, 2008 Gennaro Prota
+//            Copyright (c) 2022 Andrey Semashev
+//
+// Distributed under the Boost Software License, Version 1.0.
+//    (See accompanying file LICENSE_1_0.txt or copy at
+//          https://www.boost.org/LICENSE_1_0.txt)
+//
+// -----------------------------------------------------------
+
+#ifndef BOOST_INTEGER_INTEGER_LOG2_HPP
+#define BOOST_INTEGER_INTEGER_LOG2_HPP
+
+#include <climits>
+#include <limits>
+#include <boost/config.hpp>
+#include <boost/assert.hpp>
+#include <boost/cstdint.hpp>
+#include <boost/core/bit.hpp>
+#include <boost/core/enable_if.hpp>
+#include <boost/type_traits/is_integral.hpp>
+#include <boost/type_traits/make_unsigned.hpp>
+
+namespace boost {
+namespace detail {
+
+// helper to find the maximum power of two
+// less than p
+template< unsigned int p, unsigned int n, bool = ((2u * n) < p) >
+struct max_pow2_less :
+    public max_pow2_less< p, 2u * n >
+{
+};
+
+template< unsigned int p, unsigned int n >
+struct max_pow2_less< p, n, false >
+{
+    BOOST_STATIC_CONSTANT(unsigned int, value = n);
+};
+
+template< typename T >
+inline typename boost::disable_if< boost::is_integral< T >, int >::type integer_log2_impl(T x)
+{
+    unsigned int n = detail::max_pow2_less<
+        std::numeric_limits< T >::digits,
+        CHAR_BIT / 2u
+    >::value;
+
+    int result = 0;
+    while (x != 1)
+    {
+        T t(x >> n);
+        if (t)
+        {
+            result += static_cast< int >(n);
+#if !defined(BOOST_NO_CXX11_RVALUE_REFERENCES)
+            x = static_cast< T&& >(t);
+#else
+            x = t;
+#endif
+        }
+        n >>= 1u;
+    }
+
+    return result;
+}
+
+template< typename T >
+inline typename boost::enable_if< boost::is_integral< T >, int >::type integer_log2_impl(T x)
+{
+    // We could simply rely on numeric_limits but sometimes
+    // Borland tries to use numeric_limits<const T>, because
+    // of its usual const-related problems in argument deduction
+    // - gps
+    return static_cast< int >((sizeof(T) * CHAR_BIT - 1u) -
+        boost::core::countl_zero(static_cast< typename boost::make_unsigned< T >::type >(x)));
+}
+
+#if defined(BOOST_HAS_INT128)
+// We need to provide explicit overloads for __int128 because (a) boost/core/bit.hpp currently does not support it and
+// (b) std::numeric_limits are not specialized for __int128 in some standard libraries.
+inline int integer_log2_impl(boost::uint128_type x)
+{
+    const boost::uint64_t x_hi = static_cast< boost::uint64_t >(x >> 64u);
+    if (x_hi != 0u)
+        return 127 - boost::core::countl_zero(x_hi);
+    else
+        return 63 - boost::core::countl_zero(static_cast< boost::uint64_t >(x));
+}
+
+inline int integer_log2_impl(boost::int128_type x)
+{
+    return detail::integer_log2_impl(static_cast< boost::uint128_type >(x));
+}
+#endif // defined(BOOST_HAS_INT128)
+
+} // namespace detail
+
+
+// ------------
+// integer_log2
+// ------------
+template< typename T >
+inline int integer_log2(T x)
+{
+    BOOST_ASSERT(x > 0);
+    return detail::integer_log2_impl(x);
+}
+
+} // namespace boost
+
+#endif // BOOST_INTEGER_INTEGER_LOG2_HPP