Overview
Description
Boost.Charconv converts character buffers to numbers, and numbers to character buffers. It is a small library of two overloaded functions to do the heavy lifting, plus several supporting enums, structures, templates, and constants, with a particular focus on performance and consistency across the supported development environments.
Why should I be interested in this Library? Charconv is locale-independent, non-allocating1, non-throwing and only requires a minimum of C++ 11.
It provides functionality similar to that found in std::printf
or std::strtod
with substantial performance increases.
This library can also be used in place of the standard library <charconv>
if unavailable with your toolchain.
Currently only GCC 11+ and MSVC 19.24+ support both integer and floating-point conversions in their implementation of <charconv>
.
If you are using either of those compilers, Boost.Charconv is at least as performant as <charconv>
, and can be up to several times faster.
See: Benchmarks
1 The one edge case where allocation may occur is you are parsing a string to an 80 or 128-bit long double
or __float128
, and the string is over 1024 bytes long.
Supported Compilers / OS
Boost.Charconv is tested on Ubuntu, macOS, and Windows with the following compilers:
-
GCC 5 or later
-
Clang 3.8 or later
-
Visual Studio 2015 (14.0) or later
Tested on GitHub Actions and Drone.
Getting Started
B2
Run the following commands to clone the latest versions of Boost and Charconv, prepare the Boost.Build system for use, and build the libraries with C++11 as the default standard:
git clone https://github.com/boostorg/boost
cd boost
git submodule update --init
cd ..
./bootstrap
./b2 cxxstd=11
To install the development environment, run:
sudo ./b2 install cxxstd=11
The value of cxxstd must be at least 11. See the b2 documentation under cxxstd
for all valid values.
__float128
and std::float128_t
Support
If using B2 or CMake the build system will automatically define BOOST_CHARCONV_HAS_QUADMATH
and link against it if the build system can successfully run a small test case.
If you are using another build system and you want support for these types you will have to define BOOST_CHARCONV_HAS_QUADMATH
, and link against libquadmath.
Important
|
libquadmath is only available on supported platforms (e.g. Linux with x86, x86_64, PPC64, and IA64). |
Dependencies
This library depends on: Boost.Assert, Boost.Config, Boost.Core, and optionally libquadmath (see above).
Basic Usage Examples
Usage Examples
#include <boost/charconv.hpp>
const char* buffer = "42";
int v = 0;
boost::charconv::from_chars_result r = boost::charconv::from_chars(buffer, buffer + std::strlen(buffer), v);
assert(r.ec == std::errc());
assert(v == 42);
char buffer[64];
int v = 123456;
boost::charconv::to_chars_result r = boost::charconv::to_chars(buffer, buffer + sizeof(buffer), v);
assert(r.ec == std::errc());
assert(!strncmp(buffer, "123456", 6)); // Strncmp returns 0 on match
API Reference
from_chars
from_chars overview
from_chars
is a set of functions that parse a string from [first, last)
in an attempt to convert the string into value
according to the chars_format
specified (if applicable).
The parsing of number is locale-independent (e.g. equivalent to the "C" locale).
The result of from_chars
is from_chars_result
which on success returns ptr == last
and ec == std::errc()
, and on failure returns ptr
equal to the last valid character parsed or last
on underflow/overflow, and ec == std::errc::invalid_argument
or std::errc::result_out_of_range
respectively. from_chars
does not require the character sequence to be null terminated.
Definitions
namespace boost { namespace charconv {
struct from_chars_result
{
const char* ptr;
std::errc ec;
friend constexpr bool operator==(const from_chars_result& lhs, const from_chars_result& rhs) noexcept = default;
constexpr explicit operator bool() const noexcept { return ec == std::errc{}; }
}
template <typename Integral>
BOOST_CXX14_CONSTEXPR from_chars_result from_chars(const char* first, const char* last, Integral& value, int base = 10) noexcept;
template <typename Integral>
BOOST_CXX14_CONSTEXPR from_chars_result from_chars(boost::core::string_view sv, Integral& value, int base = 10) noexcept;
BOOST_CXX14_CONSTEXPR from_chars_result from_chars<bool>(const char* first, const char* last, bool& value, int base) = delete;
template <typename Real>
from_chars_result from_chars(const char* first, const char* last, Real& value, chars_format fmt = chars_format::general) noexcept;
template <typename Real>
from_chars_result from_chars(boost::core::string_view sv, Real& value, chars_format fmt = chars_format::general) noexcept;
// See note below Usage notes for from_chars for floating point types
template <typename Real>
from_chars_result from_chars_erange(const char* first, const char* last, Real& value, chars_format fmt = chars_format::general) noexcept;
template <typename Real>
from_chars_result from_chars_erange(boost::core::string_view sv, Real& value, chars_format fmt = chars_format::general) noexcept;
}} // Namespace boost::charconv
from_chars parameters
-
first
,last
- pointers to a valid range to parse -
sv
- string view of a valid range to parse. Compatible with boost::core::string_view, std::string, and std::string_view -
value
- where the output is stored upon successful parsing -
base
(integer only) - the integer base to use. Must be between 2 and 36 inclusive -
fmt
(floating point only) - The format of the buffer. See chars_format overview for description.
from_chars_result
-
ptr
- On return fromfrom_chars
it is a pointer to the first character not matching the pattern, or pointer tolast
if all characters are successfully parsed. -
ec
- the error code. Values returned byfrom_chars
are:
Return Value |
Description |
|
Successful Parsing |
|
1) Parsing a negative into an unsigned type 2) Leading 3) Leading space 4) Incompatible formatting (e.g. exponent on |
|
1) Overflow 2) Underflow |
-
operator==
- compares the values of ptr and ec for equality
Usage Notes
Usage notes for from_chars for integral types
-
All built-in integral types are allowed except bool which is deleted
-
These functions have been tested to support
__int128
andunsigned __int128
-
from_chars for integral types is constexpr when compiled using
-std=c++14
or newer-
One known exception is GCC 5 which does not support constexpr comparison of
const char*
.
-
-
A valid string must only contain the characters for numbers. Leading spaces are not ignored, and will return
std::errc::invalid_argument
.
Usage notes for from_chars for floating point types
-
On
std::errc::result_out_of_range
we return ±0 for small values (e.g. 1.0e-99999) or ±HUGE_VAL for large values (e.g. 1.0e+99999) to match the handling ofstd::strtod
. This is a divergence from the standard which states we should return thevalue
argument unmodified.-
from_chars
has an open issue with LWG here: https://cplusplus.github.io/LWG/lwg-active.html#3081. The standard for <charconv> does not distinguish between underflow and overflow like strtod does. Let’s say you are writing a JSON library, and you replacestd::strtod
withboost::charconv::from_chars
for performance reasons. Charconv returns std::errc::result_out_of_range on some conversion. You would then have to parse the string again yourself to figure out which of the four possible reasons you gotstd::errc::result_out_of_range
. Charconv can give you that information by usingboost::charconv::from_chars_erange
instead ofboost::charconv::from_chars
throughout the code base. By implementing the resolution to the LWG issue that matches the established strtod behavior I think we are providing the correct behavior without waiting on the committee’s decision.
-
-
These functions have been tested to support all built-in floating-point types and those from C++23’s
<stdfloat>
-
Long doubles can be 64, 80, or 128-bit, but must be IEEE 754 compliant. An example of a non-compliant, and therefore unsupported, format is
__ibm128
. -
Use of
__float128
orstd::float128_t
requires compiling with-std=gnu++xx
and linking GCC’slibquadmath
. This is done automatically when building with CMake.
-
Examples
Basic usage
Integral
const char* buffer = "42";
int v = 0;
from_chars_result r = boost::charconv::from_chars(buffer, buffer + std::strlen(buffer), v);
assert(r.ec == std::errc());
assert(r); // Same as above but less verbose. Added in C++26.
assert(v == 42);
std::string str_buffer (buffer);
boost::core::string_view sv(str_buffer);
int v2;
auto r2 = boost::charconv::from_chars(sv, v2);
assert(r);
assert(v2 == v);
Floating Point
const char* buffer = "1.2345"
double v = 0;
auto r = boost::charconv::from_chars(buffer, buffer + std::strlen(buffer), v);
assert(r.ec == std::errc());
assert(r); // Same as above but less verbose. Added in C++26.
assert(v == 1.2345);
std::string str_buffer(buffer);
double v2;
auto r2 = boost::charconv::from_chars(buffer, v2);
assert(r2);
assert(v == v2);
Hexadecimal
Integral
const char* buffer = "2a";
unsigned v = 0;
auto r = boost::charconv::from_chars(buffer, buffer + std::strlen(buffer), v, 16);
assert(r.ec == std::errc());
assert(r); // Same as above but less verbose. Added in C++26.
assert(v == 42);
Floating Point
const char* buffer = "1.3a2bp-10";
double v = 0;
auto r = boost::charconv::from_chars(buffer, buffer + std::strlen(buffer), v, boost::charconv::chars_format::hex);
assert(r.ec == std::errc());
assert(r); // Same as above but less verbose. Added in C++26.
assert(v == 8.0427e-18);
std::errc::invalid_argument
The below is invalid because a negative value is being parsed into an unsigned integer.
const char* buffer = "-123";
unsigned v = 0;
auto r = boost::charconv::from_chars(buffer, buffer + std::strlen(buffer), v);
assert(r.ec == std::errc::invalid_argument);
assert(!r); // Same as above but less verbose. Added in C++26.
The below is invalid because a fixed format floating-point value can not have an exponent.
const char* buffer = "-1.573e-3";
double v = 0;
auto r = boost::charconv::from_chars(buffer, buffer + std::strlen(buffer), v, boost::charconv::chars_format::fixed);
assert(r.ec == std::errc::invalid_argument);
assert(!r); // Same as above but less verbose. Added in C++26.
Note: In the event of std::errc::invalid_argument
, v is not modified by from_chars
std::errc::result_out_of_range
const char* buffer = "1234";
unsigned char v = 0;
auto r = boost::charconv::from_chars(buffer, buffer + std::strlen(buffer), v);
assert(r.ec == std::errc::result_out_of_range);
assert(!r); // Same as above but less verbose. Added in C++26.
assert(v == 0)
Note: In the event of std::errc::result_out_of_range
, v is not modified by from_chars
to_chars
to_chars overview
to_chars
is a set of functions that attempts to convert value
into a character buffer specified by [first, last)
.
The result of to_chars
is to_chars_result
which on success returns ptr
equal to one-past-the-end of the characters written and ec == std::errc()
and on failure returns std::errc::value_too_large
and ptr == last
.
to_chars
does not null-terminate the returned characters.
Definitions
namespace boost { namespace charconv {
struct to_chars_result
{
char* ptr;
std::errc ec;
friend constexpr bool operator==(const to_chars_result& lhs, const to_chars_result& rhs) noexcept; = default;
constexpr explicit operator bool() const noexcept { return ec == std::errc{}; }
};
template <typename Integral>
BOOST_CHARCONV_CONSTEXPR to_chars_result to_chars(char* first, char* last, Integral value, int base = 10) noexcept;
template <typename Integral>
BOOST_CHARCONV_CONSTEXPR to_chars_result to_chars<bool>(char* first, char* last, Integral value, int base) noexcept = delete;
template <typename Real>
to_chars_result to_chars(char* first, char* last, Real value, chars_format fmt = chars_format::general, int precision) noexcept;
}} // Namespace boost::charconv
to_chars parameters
-
first, last
- pointers to the beginning and end of the character buffer -
value
- the value to be parsed into the buffer -
base
(integer only) - the integer base to use. Must be between 2 and 36 inclusive -
fmt
(float only) - the floating point format to use. See chars_format overview for description. -
precision
(float only) - the number of decimal places required
to_chars_result
-
ptr
- On return fromto_chars
points to one-past-the-end of the characters written on success orlast
on failure -
ec
- the error code. Values returned byto_chars
are:
Return Value |
Description |
|
Successful Parsing |
|
1) Overflow 2) Underflow |
-
operator==
- compares the value of ptr and ec for equality
Usage Notes
Usage notes for to_chars for integral types
-
All built-in integral types are allowed except bool which is deleted
-
from_chars for integral type is constexpr (BOOST_CHARCONV_CONSTEXPR is defined) when:
-
compiled using
-std=c++14
or newer -
using a compiler with
__builtin_ is_constant_evaluated
-
-
These functions have been tested to support
__int128
andunsigned __int128
Usage notes for to_chars for floating point types
-
The following will be returned when handling different values of
NaN
-
qNaN
returns "nan" -
-qNaN
returns "-nan(ind)" -
sNaN
returns "nan(snan)" -
-sNaN
returns "-nan(snan)"
-
-
These functions have been tested to support all built-in floating-point types and those from C++23’s
<stdfloat>
-
Long doubles can be 64, 80, or 128-bit, but must be IEEE 754 compliant. An example of a non-compliant, and therefore unsupported, format is
ibm128
. -
Use of
__float128
orstd::float128_t
requires compiling with-std=gnu++xx
and linking GCC’slibquadmath
. This is done automatically when building with CMake.
-
Examples
Basic Usage
Integral
char buffer[64] {};
int v = 42;
to_chars_result r = boost::charconv::to_chars(buffer, buffer + sizeof(buffer) - 1, v);
assert(r.ec == std::errc());
assert(!strcmp(buffer, "42")); // strcmp returns 0 on match
Floating Point
char buffer[64] {};
double v = 1e300;
to_chars_result r = boost::charconv::to_chars(buffer, buffer + sizeof(buffer) - 1, v);
assert(r.ec == std::errc());
assert(r); // Same as above but less verbose. Added in C++26.
assert(!strcmp(buffer, "1e+300"));
Hexadecimal
Integral
char buffer[64] {};
int v = 42;
to_chars_result r = boost::charconv::to_chars(buffer, buffer + sizeof(buffer) - 1, v, 16);
assert(r.ec == std::errc());
assert(r); // Same as above but less verbose. Added in C++26.
assert(!strcmp(buffer, "2a")); // strcmp returns 0 on match
Floating Point
char buffer_u[64] {};
double u = -1.08260383390082950e+20;
char buffer_v[64] {};
double v = -1.08260383390082946e+20;
to_chars(buffer_u, buffer_u + sizeof(buffer_u) - 1, u, chars_format::hex);
to_chars(buffer_v, buffer_v + sizeof(buffer_v) - 1, v, chars_format::hex);
std::cout << "U: " << buffer_u << "\nV: " << buffer_v << std::endl;
// U: -1.779a8946bb5fap+66
// V: -1.779a8946bb5f9p+66
//
// With hexfloats we can see the ULP distance between U and V is a - 9 == 1.
std::errc::value_too_large
Integral
char buffer[3] {};
int v = -1234;
to_chars_result r = boost::charconv::to_chars(buffer, buffer + sizeof(buffer) - 1, v, 16);
assert(r.ec == std::errc::value_too_large);
assert(!r); // Same as above but less verbose. Added in C++26.
Floating Point
char buffer[3] {};
double v = 1.2345;
auto r = boost::charconv::to_chars(buffer, buffer + sizeof(buffer) - 1, v);
assert(r.ec == std::errc::value_too_large);
assert(!r); // Same as above but less verbose. Added in C++26.
In the event of std::errc::value_too_large
, to_chars_result.ptr is equal to last
chars_format
chars_format overview
boost::charconv::chars_format
is an enum class
used to define the format of floating point types with from_chars
and to_chars
.
Definition
namespace boost { namespace charconv {
enum class chars_format : unsigned
{
scientific = 1 << 0,
fixed = 1 << 1,
hex = 1 << 2,
general = fixed | scientific
};
}} // Namespace boost::charconv
Formats
Scientific Format
Scientific format will be of the form 1.3e+03
.
The integer part will be between 0 and 9 inclusive. The fraction and exponent will always appear.
The exponent will always have a minimum of 2 digits.
Fixed Format
Fixed format will be of the form 2.30
or 3090
. An exponent will not appear with this format.
If the precision of to_chars
exceeds that of the type (e.g. std::numeric_limits<double>::chars10
), 0s will be appended to the end of the significant digits.
Hex Format
Hex format will be of the form 1.0cp+05
. The integer part will always be 0 or 1.
The exponent will be with a p instead of an e as used with base 10 formats, because e is a valid hex value.
Note: Every binary floating-point number has a unique representation as a hexfloat, but not every hexfloat has a unique representation as a binary floating-point number.
This is due to the fact that the number of bits in the significand of an IEEE754 binary32 and binary64 are not divisible by 4.
Hexfloat Use Cases
For those unfamiliar with hexfloats, they are valuable in specific instances:
-
Precision control: Hexfloats can offer finer control over the precision of floating-point values. In hexadecimal notation, each digit represents four bits (one hexit), allowing you to directly manipulate the precision of the number by specifying a certain number of hexadecimal digits. This can be useful when you need to precisely control the level of accuracy required for your calculations.
-
Bit-level representation: Hexfloats provide a direct representation of the underlying bits of a floating-point number. Each hexadecimal digit corresponds to a specific group of bits, making it easier to visualize and understand the internal structure of the floating-point value. This can be helpful for debugging or analyzing floating-point arithmetic operations (e.g. Computing ULP distances).
General
General format will be the shortest representation of a number in either fixed or general format (e.g. 1234
instead of 1.234e+03
.
Limits
Limits overview
The contents of <boost/charconv/limits.hpp>
are designed to help the user optimize the size of the buffer required for to_chars
.
Definitions
namespace boost { namespace charconv {
template <typename T>
constexpr int limits<T>::max_chars10;
template <typename T>
constexpr int limits<T>::max_chars;
}} // Namespace boost::charconv
max_chars10
The minimum size of the buffer that needs to be
passed to to_chars
to guarantee successful conversion for all values of type T, when either no base is passed, or base 10 is passed.
max_chars
The minimum size of the buffer that needs to be passed to to_chars
to guarantee successful conversion for all values of type T, for any value of base.
Examples
The following two examples are for max_chars10
to optimize the buffer size with to_chars
for an integral type and a floating-point type respectively.
char buffer [boost::charconv::limits<std::int32_t>::max_chars10;
auto r = boost::charconv::to_chars(buffer, buffer + sizeof(buffer), std::numeric_limits<std::int32_t>::max());
assert(r.ec == std::errc());
assert(r); // Same as above but less verbose. Added in C++26.
assert(!strcmp(buffer, "2147483647")); // strcmp returns 0 on match
char buffer [boost::charconv::limits<float>::max_chars10;
auto r = boost::charconv::to_chars(buffer, buffer + sizeof(buffer), std::numeric_limits<float>::max());
assert(r.ec == std::errc());
assert(r); // Same as above but less verbose. Added in C++26.
assert(!strcmp(buffer, "3.40282347e+38")); // strcmp returns 0 on match
The following example is a usage of max_chars
when used to serialize an integer in binary (base = 2).
char buffer [boost::charconv::limits<std::uint16_t>::max_chars;
auto r = boost::charconv::to_chars(buffer, buffer + sizeof(buffer), std::numeric_limits<std::uint16_t>::max(), 2);
assert(r.ec == std::errc());
assert(r); // Same as above but less verbose. Added in C++26.
assert(!strcmp(buffer, "1111111111111111")); // strcmp returns 0 on match
Benchmarks
This section describes a range of performance benchmarks that have been run comparing this library with the standard library, and how to run your own benchmarks if required.
The values are relative to the performance of std::printf
and std::strtoX
.
Larger numbers are more performant (e.g. 2.00 means twice as fast, and 0.50 means it takes twice as long).
std::printf
and std::strtoX
are always listed first as they will be the reference value.
How to run the Benchmarks
To run the benchmarks yourself, navigate to the test folder and define BOOST_CHARCONV_RUN_BENCHMARKS
when running the tests.
An example on Linux with b2: ../../../b2 cxxstd=20 toolset=gcc-13 define=BOOST_CHARCONV_RUN_BENCHMARKS STL_benchmark linkflags="-lfmt" -a release
.
Additionally, you will need the following:
-
A compiler with full
<charconv>
support:-
GCC 11 or newer
-
MSVC 19.24 or newer
-
Results
x86_64 Linux
Data in tables 1 - 4 were run on Ubuntu 23.04 with x86_64 architecture using GCC 13.1.0 with libstdc++.
Floating Point
Function | Relative Performance (float / double) |
---|---|
std::printf |
1.00 / 1.00 |
Boost.lexical_cast |
0.56 / 0.49 |
Boost.spirit.karma |
1.70 / 2.62 |
std::to_chars |
4.01 / 6.03 |
Boost.Charconv.to_chars |
4.46 / 6.20 |
Google double-conversion |
1.26 / 1.91 |
{fmt} |
2.52 / 3.63 |
Function | Relative Performance (float / double) |
---|---|
std::strto(f/d) |
1.00 / 1.00 |
Boost.lexical_cast |
0.33 / 0.42 |
Boost.spirit.qi |
3.17 / 4.65 |
std::from_chars |
3.23 / 5.77 |
Boost.Charconv.from_chars |
3.28 / 5.75 |
Google double-conversion |
1.16 / 1.30 |
Integral
Function | Relative Performance (uint32_t / uint64_t) |
---|---|
std::printf |
1.00 / 1.00 |
Boost.lexical_cast |
1.80 / 1.38 |
Boost.spirit.karma |
2.81 / 1.62 |
std::to_chars |
4.06 / 2.45 |
Boost.Charconv.to_chars |
4.13 / 2.48 |
{fmt} |
2.88 / 2.21 |
Function | Relative Performance (uint32_t / uint64_t) |
---|---|
std::strto(ul,ull) |
1.00 / 1.00 |
Boost.lexical_cast |
0.53 / 0.52 |
Boost.spirit.qi |
2.24 / 1.49 |
std::from_chars |
1.97 / 1.68 |
Boost.Charconv.from_chars |
2.54 / 1.78 |
x86_64 Windows
Data in tables 5 - 8 were run on Windows 11 with x86_64 architecture using MSVC 14.3 (V17.7.0).
Floating Point
Function | Relative Performance (float / double) |
---|---|
std::printf |
1.00 / 1.00 |
Boost.lexical_cast |
0.50 / 0.70 |
Boost.spirit.karma |
2.23 / 7.58 |
std::to_chars |
5.58 / 15.77 |
Boost.Charconv.to_chars |
5.62 / 15.26 |
Function | Relative Performance (float / double) |
---|---|
std::strto(f/d) |
1.00 / 1.00 |
Boost.lexical_cast |
0.14 / 0.20 |
Boost.spirit.qi |
2.03 / 4.58 |
std::from_chars |
1.01 / 1.23 |
Boost.Charconv.from_chars |
2.06 / 5.21 |
Integral
Function | Relative Performance (uint32_t / uint64_t) |
---|---|
std::printf |
1.00 / 1.00 |
Boost.lexical_cast |
0.68 / 0.68 |
Boost.spirit.karma |
2.75 / 1.67 |
std::to_chars |
2.75 / 2.10 |
Boost.Charconv.to_chars |
2.75 / 2.06 |
Function | Relative Performance (uint32_t / uint64_t) |
---|---|
std::strto(ul,ull) |
1.00 / 1.00 |
Boost.lexical_cast |
0.46 / 0.39 |
Boost.spirit.qi |
1.94 / 1.63 |
std::from_chars |
2.43 / 2.18 |
Boost.Charconv.from_chars |
2.68 / 2.27 |
ARM MacOS
Data in tables 9-12 were run on MacOS Ventura 13.5.2 with M1 Pro architecture using Homebrew GCC 13.2.0 with libstdc++.
Floating Point
Function | Relative Performance (float / double) |
---|---|
std::printf |
1.00 / 1.00 |
Boost.lexical_cast |
0.58 / 0.16 |
Boost.spirit.karma |
1.39 / 1.22 |
std::to_chars |
6.78 / 6.47 |
Boost.Charconv.to_chars |
7.25 / 6.86 |
Google double-conversion |
2.26 / 2.16 |
{fmt} |
3.78 / 3.38 |
Function | Relative Performance (float / double) |
---|---|
std::strto(f/d) |
1.00 / 1.00 |
Boost.lexical_cast |
0.06 / 0.06 |
Boost.spirit.qi |
1.12 / 1.06 |
std::from_chars |
1.32 / 1.65 |
Boost.Charconv.from_chars |
1.28 / 1.63 |
Google double-conversion |
0.45 / 0.32 |
Integral
Function | Relative Performance (uint32_t / uint64_t) |
---|---|
std::printf |
1.00 / 1.00 |
Boost.lexical_cast |
2.08 / 1.75 |
Boost.spirit.karma |
4.17 / 2.06 |
std::to_chars |
6.25 / 4.12 |
Boost.Charconv.to_chars |
6.25 / 4.12 |
{fmt} |
5.29 / 3.47 |
Function | Relative Performance (uint32_t / uint64_t) |
---|---|
std::strto(ul,ull) |
1.00 / 1.00 |
Boost.lexical_cast |
0.56 / 0.54 |
Boost.spirit.qi |
1.39 / 1.33 |
std::from_chars |
1.92 / 1.65 |
Boost.Charconv.from_chars |
2.27 / 1.65 |
Sources
The following papers and blog posts serve as the basis for the algorithms used in the library:
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J.R. Parker A General Character to Integer Conversion Method, Software: Practice and Experience 15 (8), 1985.
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Junekey Jeon, Faster integer formatting - James Anhalt (jeaiii)’s algorithm
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Junekey Jeon, Dragonbox: A New Floating-Point Binary-to-Decimal Conversion Algorithm
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Junekey Jeon, Fixed-precision formatting of floating-point numbers
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William D. Clinger, How to Read Floating Point Numbers Accurately, 1990
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Daniel Lemire, Number Parsing at a Gigabyte per Second, Software: Practice and Experience 51 (8), 2021.
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Noble Mushtak, Daniel Lemire, Fast Number Parsing Without Fallback, Software: Practice and Experience (to appear)
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Ulf Adams, Ryū revisited: printf floating point conversion, Proceedings of the ACM on Programming Languages Volume 3, 2019
Acknowledgments
Special thanks to the following people (non-inclusive list):
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Peter Dimov for providing technical guidance and contributing to the library throughout development.
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Junekey Jeon for developing and answering my questions about his integer-formatting, Dragonbox, and Floff.
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Chris Kormanyos for serving as the library review manager.
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Stephan T. Lavavej for providing the basis for the benchmarks.
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All that reviewed the library and provided feedback to make it better.
Copyright and License
This documentation is copyright 2022-2023 Peter Dimov and Matt Borland and is distributed under the Boost Software License, Version 1.0.