LiXiaoqi/libcarla
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
master
libcarla/include/system/boost/multiprecision/detail/float_string_cvt.hpp
LiXiaoqi 220ecf68c6 init
2024-10-18 13:19:59 +08:00

334 lines
8.9 KiB
C++
Raw Permalink Blame History

///////////////////////////////////////////////////////////////
// Copyright 2013 John Maddock. 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
//
// Generic routines for converting floating point values to and from decimal strings.
// Note that these use "naive" algorithms which result in rounding error - so they
// do not round trip to and from the string representation (but should only be out
// in the last bit).
//
#ifndef BOOST_MP_FLOAT_STRING_CVT_HPP
#define BOOST_MP_FLOAT_STRING_CVT_HPP
#include <string>
#include <cctype>
#include <boost/multiprecision/detail/no_exceptions_support.hpp>
#include <boost/multiprecision/detail/assert.hpp>
namespace boost { namespace multiprecision { namespace detail {
template <class I>
inline void round_string_up_at(std::string& s, std::ptrdiff_t pos, I& expon)
{
//
// Rounds up a string representation of a number at pos:
//
if (pos < 0)
{
s.insert(static_cast<std::string::size_type>(0), 1, '1');
s.erase(s.size() - 1);
++expon;
}
else if (s[static_cast<std::size_t>(pos)] == '9')
{
s[static_cast<std::size_t>(pos)] = '0';
round_string_up_at(s, pos - 1, expon);
}
else
{
if ((pos == 0) && (s[static_cast<std::size_t>(pos)] == '0') && (s.size() == 1))
++expon;
++s[static_cast<std::size_t>(pos)];
}
}
template <class Backend>
std::string convert_to_string(Backend b, std::streamsize digits, std::ios_base::fmtflags f)
{
using default_ops::eval_convert_to;
using default_ops::eval_divide;
using default_ops::eval_floor;
using default_ops::eval_fpclassify;
using default_ops::eval_log10;
using default_ops::eval_multiply;
using default_ops::eval_pow;
using default_ops::eval_subtract;
using ui_type = typename std::tuple_element<0, typename Backend::unsigned_types>::type;
using exponent_type = typename Backend::exponent_type ;
std::string result;
bool iszero = false;
bool isneg = false;
exponent_type expon = 0;
std::streamsize org_digits = digits;
BOOST_MP_ASSERT(digits > 0);
int fpt = eval_fpclassify(b);
if (fpt == static_cast<int>(FP_ZERO))
{
result = "0";
iszero = true;
}
else if (fpt == static_cast<int>(FP_INFINITE))
{
if (b.compare(ui_type(0)) < 0)
return "-inf";
else
return ((f & std::ios_base::showpos) == std::ios_base::showpos) ? "+inf" : "inf";
}
else if (fpt == static_cast<int>(FP_NAN))
{
return "nan";
}
else
{
//
// Start by figuring out the exponent:
//
isneg = b.compare(ui_type(0)) < 0;
if (isneg)
b.negate();
Backend t;
Backend ten;
ten = ui_type(10);
eval_log10(t, b);
eval_floor(t, t);
eval_convert_to(&expon, t);
if (-expon > std::numeric_limits<number<Backend> >::max_exponent10 - 3)
{
int e = -expon / 2;
Backend t2;
eval_pow(t2, ten, e);
eval_multiply(t, t2, b);
eval_multiply(t, t2);
if (expon & 1)
eval_multiply(t, ten);
}
else
{
eval_pow(t, ten, -expon);
eval_multiply(t, b);
}
//
// Make sure we're between [1,10) and adjust if not:
//
if (t.compare(ui_type(1)) < 0)
{
eval_multiply(t, ui_type(10));
--expon;
}
else if (t.compare(ui_type(10)) >= 0)
{
eval_divide(t, ui_type(10));
++expon;
}
Backend digit;
ui_type cdigit;
//
// Adjust the number of digits required based on formatting options:
//
if (((f & std::ios_base::fixed) == std::ios_base::fixed) && (expon != -1))
digits += expon + 1;
if ((f & std::ios_base::scientific) == std::ios_base::scientific)
++digits;
//
// Extract the digits one at a time:
//
for (unsigned i = 0; i < digits; ++i)
{
eval_floor(digit, t);
eval_convert_to(&cdigit, digit);
result += static_cast<char>('0' + cdigit);
eval_subtract(t, digit);
eval_multiply(t, ten);
}
//
// Possibly round result:
//
if (digits >= 0)
{
eval_floor(digit, t);
eval_convert_to(&cdigit, digit);
eval_subtract(t, digit);
if ((cdigit == 5) && (t.compare(ui_type(0)) == 0))
{
// Bankers rounding:
if ((*result.rbegin() - '0') & 1)
{
round_string_up_at(result, result.size() - 1, expon);
}
}
else if (cdigit >= 5)
{
round_string_up_at(result, result.size() - 1, expon);
}
}
eval_floor(t, b);
if ((t.compare(b) == 0) && (static_cast<std::size_t>(expon + 1) < result.size()))
{
// Input is an integer, sometimes we get a result which is not an integer here as a result of printing too
// many digits, so lets round if required:
round_string_up_at(result, expon + 1, expon);
result.erase(expon + 1);
}
}
while ((static_cast<std::streamsize>(result.size()) > digits) && (result.size() != 0U))
{
// We may get here as a result of rounding...
if (result.size() > 1)
result.erase(result.size() - 1);
else
{
if (expon > 0)
--expon; // so we put less padding in the result.
else
++expon;
++digits;
}
}
BOOST_MP_ASSERT(org_digits >= 0);
if (isneg)
result.insert(static_cast<std::string::size_type>(0), 1, '-');
format_float_string(result, expon, org_digits, f, iszero);
return result;
}
template <class Backend>
void convert_from_string(Backend& b, const char* p)
{
using default_ops::eval_add;
using default_ops::eval_divide;
using default_ops::eval_multiply;
using default_ops::eval_pow;
using ui_type = typename std::tuple_element<0, typename Backend::unsigned_types>::type;
b = ui_type(0);
if (!p || (*p == 0))
return;
bool is_neg = false;
bool is_neg_expon = false;
constexpr ui_type ten = ui_type(10);
typename Backend::exponent_type expon = 0;
int digits_seen = 0;
using limits = std::numeric_limits<number<Backend, et_off>>;
constexpr int max_digits = limits::is_specialized ? limits::max_digits10 + 1 : INT_MAX;
if (*p == '+')
++p;
else if (*p == '-')
{
is_neg = true;
++p;
}
if ((std::strcmp(p, "nan") == 0) || (std::strcmp(p, "NaN") == 0) || (std::strcmp(p, "NAN") == 0))
{
eval_divide(b, ui_type(0));
if (is_neg)
b.negate();
return;
}
if ((std::strcmp(p, "inf") == 0) || (std::strcmp(p, "Inf") == 0) || (std::strcmp(p, "INF") == 0))
{
b = ui_type(1);
eval_divide(b, ui_type(0));
if (is_neg)
b.negate();
return;
}
//
// Grab all the leading digits before the decimal point:
//
while (std::isdigit(*p))
{
eval_multiply(b, ten);
eval_add(b, ui_type(*p - '0'));
++p;
++digits_seen;
}
if (*p == '.')
{
//
// Grab everything after the point, stop when we've seen
// enough digits, even if there are actually more available:
//
++p;
while (std::isdigit(*p))
{
eval_multiply(b, ten);
eval_add(b, ui_type(*p - '0'));
++p;
--expon;
if (++digits_seen > max_digits)
break;
}
while (std::isdigit(*p))
++p;
}
//
// Parse the exponent:
//
if ((*p == 'e') || (*p == 'E'))
{
++p;
if (*p == '+')
++p;
else if (*p == '-')
{
is_neg_expon = true;
++p;
}
typename Backend::exponent_type e2 = 0;
while (std::isdigit(*p))
{
e2 *= 10;
e2 += (*p - '0');
++p;
}
if (is_neg_expon)
e2 = -e2;
expon += e2;
}
if (expon)
{
// Scale by 10^expon, note that 10^expon can be
// outside the range of our number type, even though the
// result is within range, if that looks likely, then split
// the calculation in two:
Backend t;
t = ten;
if (expon > limits::min_exponent10 + 2)
{
eval_pow(t, t, expon);
eval_multiply(b, t);
}
else
{
eval_pow(t, t, expon + digits_seen + 1);
eval_multiply(b, t);
t = ten;
eval_pow(t, t, -digits_seen - 1);
eval_multiply(b, t);
}
}
if (is_neg)
b.negate();
if (*p)
{
// Unexpected input in string:
BOOST_MP_THROW_EXCEPTION(std::runtime_error("Unexpected characters in string being interpreted as a float128."));
}
}
}}} // namespace boost::multiprecision::detail
#endif
Reference in New Issue View Git Blame Copy Permalink