/usr/include/boost/detail/lcast_precision.hpp is in libboost1.55-dev 1.55.0+dfsg-3.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 | // 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
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