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authorRemko Tronçon <git@el-tramo.be>2009-06-01 08:48:42 (GMT)
committerRemko Tronçon <git@el-tramo.be>2009-06-01 09:24:28 (GMT)
commit2812bddd81f8a1b804c7460f4e14cd0aa393d129 (patch)
treed46294f35150c4f0f43deaf2d31fceaf945ae715 /3rdParty/Boost/boost/detail/lcast_precision.hpp
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+// 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((Source*)0);
+ std::streamsize const t = lcast_get_precision((Target*)0);
+ stream.precision(s > t ? s : t);
+}
+
+}}
+
+#endif // BOOST_DETAIL_LCAST_PRECISION_HPP_INCLUDED
+