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-rw-r--r--3rdParty/Boost/src/boost/integer/integer_log2.hpp112
1 files changed, 112 insertions, 0 deletions
diff --git a/3rdParty/Boost/src/boost/integer/integer_log2.hpp b/3rdParty/Boost/src/boost/integer/integer_log2.hpp
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+// -----------------------------------------------------------
+// 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
+//
+// 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)
+//
+// -----------------------------------------------------------
+
+#ifndef BOOST_INTEGER_INTEGER_LOG2_HPP
+#define BOOST_INTEGER_INTEGER_LOG2_HPP
+
+#include <assert.h>
+#ifdef __BORLANDC__
+#include <climits>
+#endif
+#include <boost/limits.hpp>
+#include <boost/config.hpp>
+
+
+namespace boost {
+ namespace detail {
+
+ template <typename T>
+ int integer_log2_impl(T x, int n) {
+
+ int result = 0;
+
+ while (x != 1) {
+
+ const T t = static_cast<T>(x >> n);
+ if (t) {
+ result += n;
+ x = t;
+ }
+ n /= 2;
+
+ }
+
+ return result;
+ }
+
+
+
+ // helper to find the maximum power of two
+ // less than p (more involved than necessary,
+ // to avoid PTS)
+ //
+ template <int p, int n>
+ struct max_pow2_less {
+
+ enum { c = 2*n < p };
+
+ BOOST_STATIC_CONSTANT(int, value =
+ c ? (max_pow2_less< c*p, 2*c*n>::value) : n);
+
+ };
+
+ template <>
+ struct max_pow2_less<0, 0> {
+
+ BOOST_STATIC_CONSTANT(int, value = 0);
+ };
+
+ // this template is here just for Borland :(
+ // 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
+ template <typename T>
+ struct width {
+
+#ifdef __BORLANDC__
+ BOOST_STATIC_CONSTANT(int, value = sizeof(T) * CHAR_BIT);
+#else
+ BOOST_STATIC_CONSTANT(int, value = (std::numeric_limits<T>::digits));
+#endif
+
+ };
+
+ } // detail
+
+
+ // ---------
+ // integer_log2
+ // ---------------
+ //
+ template <typename T>
+ int integer_log2(T x) {
+
+ assert(x > 0);
+
+ const int n = detail::max_pow2_less<
+ detail::width<T> :: value, 4
+ > :: value;
+
+ return detail::integer_log2_impl(x, n);
+
+ }
+
+
+
+}
+
+
+
+#endif // include guard