comparison DEPENDENCIES/generic/include/boost/detail/lcast_precision.hpp @ 16:2665513ce2d3

Add boost headers

+// Copyright Alexander Nasonov & Paul A. Bristow 2006.
+
+// Use, modification and distribution are subject to 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_DETAIL_LCAST_PRECISION_HPP_INCLUDED
+#define BOOST_DETAIL_LCAST_PRECISION_HPP_INCLUDED
+
+#include <climits>
+#include <ios>
+#include <limits>
+
+#include <boost/config.hpp>
+#include <boost/integer_traits.hpp>
+
+#ifndef BOOST_NO_IS_ABSTRACT
+// Fix for SF:1358600 - lexical_cast & pure virtual functions & VC 8 STL
+#include <boost/mpl/if.hpp>
+#include <boost/type_traits/is_abstract.hpp>
+#endif
+
+#if defined(BOOST_NO_LIMITS_COMPILE_TIME_CONSTANTS) || \
+  (defined(BOOST_MSVC) && (BOOST_MSVC<1310))
+
+#define BOOST_LCAST_NO_COMPILE_TIME_PRECISION
+#endif
+
+#ifdef BOOST_LCAST_NO_COMPILE_TIME_PRECISION
+#include <boost/assert.hpp>
+#else
+#include <boost/static_assert.hpp>
+#endif
+
+namespace boost { namespace detail {
+
+class lcast_abstract_stub {};
+
+#ifndef BOOST_LCAST_NO_COMPILE_TIME_PRECISION
+// Calculate an argument to pass to std::ios_base::precision from
+// lexical_cast. See alternative implementation for broken standard
+// libraries in lcast_get_precision below. Keep them in sync, please.
+template<class T>
+struct lcast_precision
+{
+#ifdef BOOST_NO_IS_ABSTRACT
+    typedef std::numeric_limits<T> limits; // No fix for SF:1358600.
+#else
+    typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_<
+        boost::is_abstract<T>
+      , std::numeric_limits<lcast_abstract_stub>
+      , std::numeric_limits<T>
+      >::type limits;
+#endif
+
+    BOOST_STATIC_CONSTANT(bool, use_default_precision =
+            !limits::is_specialized || limits::is_exact
+        );
+
+    BOOST_STATIC_CONSTANT(bool, is_specialized_bin =
+            !use_default_precision &&
+            limits::radix == 2 && limits::digits > 0
+        );
+
+    BOOST_STATIC_CONSTANT(bool, is_specialized_dec =
+            !use_default_precision &&
+            limits::radix == 10 && limits::digits10 > 0
+        );
+
+    BOOST_STATIC_CONSTANT(std::streamsize, streamsize_max =
+            boost::integer_traits<std::streamsize>::const_max
+        );
+
+    BOOST_STATIC_CONSTANT(unsigned int, precision_dec = limits::digits10 + 1U);
+
+    BOOST_STATIC_ASSERT(!is_specialized_dec ||
+            precision_dec <= streamsize_max + 0UL
+        );
+
+    BOOST_STATIC_CONSTANT(unsigned long, precision_bin =
+            2UL + limits::digits * 30103UL / 100000UL
+        );
+
+    BOOST_STATIC_ASSERT(!is_specialized_bin ||
+            (limits::digits + 0UL < ULONG_MAX / 30103UL &&
+            precision_bin > limits::digits10 + 0UL &&
+            precision_bin <= streamsize_max + 0UL)
+        );
+
+    BOOST_STATIC_CONSTANT(std::streamsize, value =
+            is_specialized_bin ? precision_bin
+                               : is_specialized_dec ? precision_dec : 6
+        );
+};
+#endif
+
+template<class T>
+inline std::streamsize lcast_get_precision(T* = 0)
+{
+#ifndef BOOST_LCAST_NO_COMPILE_TIME_PRECISION
+    return lcast_precision<T>::value;
+#else // Follow lcast_precision algorithm at run-time:
+
+#ifdef BOOST_NO_IS_ABSTRACT
+    typedef std::numeric_limits<T> limits; // No fix for SF:1358600.
+#else
+    typedef BOOST_DEDUCED_TYPENAME boost::mpl::if_<
+        boost::is_abstract<T>
+      , std::numeric_limits<lcast_abstract_stub>
+      , std::numeric_limits<T>
+      >::type limits;
+#endif
+
+    bool const use_default_precision =
+        !limits::is_specialized || limits::is_exact;
+
+    if(!use_default_precision)
+    { // Includes all built-in floating-point types, float, double ...
+      // and UDT types for which digits (significand bits) is defined (not zero)
+
+        bool const is_specialized_bin =
+            limits::radix == 2 && limits::digits > 0;
+        bool const is_specialized_dec =
+            limits::radix == 10 && limits::digits10 > 0;
+        std::streamsize const streamsize_max =
+            (boost::integer_traits<std::streamsize>::max)();
+
+        if(is_specialized_bin)
+        { // Floating-point types with
+          // limits::digits defined by the specialization.
+
+            unsigned long const digits = limits::digits;
+            unsigned long const precision = 2UL + digits * 30103UL / 100000UL;
+            // unsigned long is selected because it is at least 32-bits
+            // and thus ULONG_MAX / 30103UL is big enough for all types.
+            BOOST_ASSERT(
+                    digits < ULONG_MAX / 30103UL &&
+                    precision > limits::digits10 + 0UL &&
+                    precision <= streamsize_max + 0UL
+                );
+            return precision;
+        }
+        else if(is_specialized_dec)
+        {   // Decimal Floating-point type, most likely a User Defined Type
+            // rather than a real floating-point hardware type.
+            unsigned int const precision = limits::digits10 + 1U;
+            BOOST_ASSERT(precision <= streamsize_max + 0UL);
+            return precision;
+        }
+    }
+
+    // Integral type (for which precision has no effect)
+    // or type T for which limits is NOT specialized,
+    // so assume stream precision remains the default 6 decimal digits.
+    // Warning: if your User-defined Floating-point type T is NOT specialized,
+    // then you may lose accuracy by only using 6 decimal digits.
+    // To avoid this, you need to specialize T with either
+    // radix == 2 and digits == the number of significand bits,
+    // OR
+    // radix = 10 and digits10 == the number of decimal digits.
+
+    return 6;
+#endif
+}
+
+template<class T>
+inline void lcast_set_precision(std::ios_base& stream, T*)
+{
+    stream.precision(lcast_get_precision<T>());
+}
+
+template<class Source, class Target>
+inline void lcast_set_precision(std::ios_base& stream, Source*, Target*)
+{
+    std::streamsize const s = lcast_get_precision(static_cast<Source*>(0));
+    std::streamsize const t = lcast_get_precision(static_cast<Target*>(0));
+    stream.precision(s > t ? s : t);
+}
+
+}}
+
+#endif //  BOOST_DETAIL_LCAST_PRECISION_HPP_INCLUDED
+