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nlohmann::detail::dtoa_impl Namespace Reference

implements the Grisu2 algorithm for binary to decimal floating-point conversion. More...

Classes

struct  diyfp
 
struct  boundaries
 
struct  cached_power
 

Functions

template<typename Target , typename Source >
Target reinterpret_bits (const Source source)
 
template<typename FloatType >
boundaries compute_boundaries (FloatType value)
 
cached_power get_cached_power_for_binary_exponent (int e)
 
int find_largest_pow10 (const std::uint32_t n, std::uint32_t &pow10)
 
void grisu2_round (char *buf, int len, std::uint64_t dist, std::uint64_t delta, std::uint64_t rest, std::uint64_t ten_k)
 
void grisu2_digit_gen (char *buffer, int &length, int &decimal_exponent, diyfp M_minus, diyfp w, diyfp M_plus)
 
void grisu2 (char *buf, int &len, int &decimal_exponent, diyfp m_minus, diyfp v, diyfp m_plus)
 
template<typename FloatType >
void grisu2 (char *buf, int &len, int &decimal_exponent, FloatType value)
 
JSON_HEDLEY_RETURNS_NON_NULL char * append_exponent (char *buf, int e)
 appends a decimal representation of e to buf
 
JSON_HEDLEY_RETURNS_NON_NULL char * format_buffer (char *buf, int len, int decimal_exponent, int min_exp, int max_exp)
 prettify v = buf * 10^decimal_exponent
 

Variables

constexpr int kAlpha = -60
 
constexpr int kGamma = -32
 

Detailed Description

implements the Grisu2 algorithm for binary to decimal floating-point conversion.

This implementation is a slightly modified version of the reference implementation which may be obtained from http://florian.loitsch.com/publications (bench.tar.gz).

The code is distributed under the MIT license, Copyright (c) 2009 Florian Loitsch.

For a detailed description of the algorithm see:

[1] Loitsch, "Printing Floating-Point Numbers Quickly and Accurately with Integers", Proceedings of the ACM SIGPLAN 2010 Conference on Programming Language Design and Implementation, PLDI 2010 [2] Burger, Dybvig, "Printing Floating-Point Numbers Quickly and Accurately", Proceedings of the ACM SIGPLAN 1996 Conference on Programming Language Design and Implementation, PLDI 1996

Function Documentation

JSON_HEDLEY_RETURNS_NON_NULL char* nlohmann::detail::dtoa_impl::append_exponent ( char *  buf,
int  e 
)
inline

appends a decimal representation of e to buf

Returns
a pointer to the element following the exponent.
Precondition
-1000 < e < 1000

Definition at line 13572 of file json.hpp.

View newest version in sPHENIX GitHub at line 13572 of file json.hpp

References e, and k.

Referenced by format_buffer().

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template<typename FloatType >
boundaries nlohmann::detail::dtoa_impl::compute_boundaries ( FloatType  value)

Compute the (normalized) diyfp representing the input number 'value' and its boundaries.

Precondition
value must be finite and positive

Definition at line 12831 of file json.hpp.

View newest version in sPHENIX GitHub at line 12831 of file json.hpp

References E, nlohmann::detail::dtoa_impl::diyfp::e, F, nlohmann::detail::dtoa_impl::diyfp::f, isfinite, and v.

Referenced by grisu2().

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int nlohmann::detail::dtoa_impl::find_largest_pow10 ( const std::uint32_t  n,
std::uint32_t &  pow10 
)
inline

For n != 0, returns k, such that pow10 := 10^(k-1) <= n < 10^k. For n == 0, returns 1 and sets pow10 := 1.

Definition at line 13134 of file json.hpp.

View newest version in sPHENIX GitHub at line 13134 of file json.hpp

Referenced by grisu2_digit_gen().

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JSON_HEDLEY_RETURNS_NON_NULL char* nlohmann::detail::dtoa_impl::format_buffer ( char *  buf,
int  len,
int  decimal_exponent,
int  min_exp,
int  max_exp 
)
inline

prettify v = buf * 10^decimal_exponent

If v is in the range [10^min_exp, 10^max_exp) it will be printed in fixed-point notation. Otherwise it will be printed in exponential notation.

Precondition
min_exp < 0
max_exp > 0

Definition at line 13624 of file json.hpp.

View newest version in sPHENIX GitHub at line 13624 of file json.hpp

References append_exponent(), k, and n.

Referenced by nlohmann::detail::to_chars().

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cached_power nlohmann::detail::dtoa_impl::get_cached_power_for_binary_exponent ( int  e)
inline

For a normalized diyfp w = f * 2^e, this function returns a (normalized) cached power-of-ten c = f_c * 2^e_c, such that the exponent of the product w * c satisfies (Definition 3.2 from [1])

 alpha <= e_c + e + q <= gamma.

Definition at line 12970 of file json.hpp.

View newest version in sPHENIX GitHub at line 12970 of file json.hpp

References f, k, kAlpha, and kGamma.

Referenced by grisu2().

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void nlohmann::detail::dtoa_impl::grisu2 ( char *  buf,
int len,
int decimal_exponent,
diyfp  m_minus,
diyfp  v,
diyfp  m_plus 
)
inline

v = buf * 10^decimal_exponent len is the length of the buffer (number of decimal digits) The buffer must be large enough, i.e. >= max_digits10.

Definition at line 13472 of file json.hpp.

View newest version in sPHENIX GitHub at line 13472 of file json.hpp

References nlohmann::detail::dtoa_impl::diyfp::e, nlohmann::detail::dtoa_impl::cached_power::e, nlohmann::detail::dtoa_impl::diyfp::f, nlohmann::detail::dtoa_impl::cached_power::f, get_cached_power_for_binary_exponent(), grisu2_digit_gen(), nlohmann::detail::dtoa_impl::cached_power::k, and w.

Referenced by grisu2(), and nlohmann::detail::to_chars().

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template<typename FloatType >
void nlohmann::detail::dtoa_impl::grisu2 ( char *  buf,
int len,
int decimal_exponent,
FloatType  value 
)

v = buf * 10^decimal_exponent len is the length of the buffer (number of decimal digits) The buffer must be large enough, i.e. >= max_digits10.

Definition at line 13532 of file json.hpp.

View newest version in sPHENIX GitHub at line 13532 of file json.hpp

References compute_boundaries(), grisu2(), isfinite, nlohmann::detail::dtoa_impl::boundaries::minus, nlohmann::detail::dtoa_impl::boundaries::plus, w, and nlohmann::detail::dtoa_impl::boundaries::w.

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void nlohmann::detail::dtoa_impl::grisu2_digit_gen ( char *  buffer,
int length,
int decimal_exponent,
diyfp  M_minus,
diyfp  w,
diyfp  M_plus 
)
inline

Generates V = buffer * 10^decimal_exponent, such that M- <= V <= M+. M- and M+ must be normalized and share the same exponent -60 <= e <= -32.

Definition at line 13231 of file json.hpp.

View newest version in sPHENIX GitHub at line 13231 of file json.hpp

References d, Acts::Test::delta, nlohmann::detail::dtoa_impl::diyfp::e, nlohmann::detail::dtoa_impl::diyfp::f, find_largest_pow10(), grisu2_round(), k, kAlpha, kGamma, m, max, n, one, and r.

Referenced by grisu2().

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void nlohmann::detail::dtoa_impl::grisu2_round ( char *  buf,
int  len,
std::uint64_t  dist,
std::uint64_t  delta,
std::uint64_t  rest,
std::uint64_t  ten_k 
)
inline

Definition at line 13190 of file json.hpp.

View newest version in sPHENIX GitHub at line 13190 of file json.hpp

Referenced by grisu2_digit_gen().

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template<typename Target , typename Source >
Target nlohmann::detail::dtoa_impl::reinterpret_bits ( const Source  source)

Definition at line 12690 of file json.hpp.

View newest version in sPHENIX GitHub at line 12690 of file json.hpp

Variable Documentation

constexpr int nlohmann::detail::dtoa_impl::kAlpha = -60

Definition at line 12953 of file json.hpp.

View newest version in sPHENIX GitHub at line 12953 of file json.hpp

constexpr int nlohmann::detail::dtoa_impl::kGamma = -32

Definition at line 12954 of file json.hpp.

View newest version in sPHENIX GitHub at line 12954 of file json.hpp

Referenced by get_cached_power_for_binary_exponent(), and grisu2_digit_gen().