Boost C++ Libraries

...one of the most highly regarded and expertly designed C++ library projects in the world. — Herb Sutter and Andrei Alexandrescu, C++ Coding Standards

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.

vcpkg

Run the following commands to clone the latest version of Charconv and install it using vcpkg:

git clone https://github.com/boostorg/charconv
cd charconv
vcpkg install charconv --overlay-ports=ports/charconv

Any required Boost packages not currently installed in your development environment will be installed automatically.

Conan

Run the following commands to clone the latest version of Charconv and build a boost_charconv package using your default profile:

git clone https://github.com/boostorg/charconv
conan create charconv/conan --build missing

The package will be put in the local Conan cache along with all direct and transitive dependencies.

Tip
 Since Charconv only depends on a few header-only Boost libraries, you can save time by requesting header-only Boost: 
conan create charconv/conan -o 'boost*:header_only=True' --build missing

After the package is built, you can use it in your own projects. For example, using a conanfile.txt:

[requires]
boost_charconv/1.0.0

Dependencies

This library depends on: Boost.Assert, Boost.Config, Boost.Core, and libquadmath on supported platforms (e.g. Linux with x86, x86_64, PPC64, and IA64).

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

Functions

Structures

Enums

Constants

Macros

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 from from_chars it is a pointer to the first character not matching the pattern, or pointer to last if all characters are successfully parsed.

  • ec - the error code. Values returned by from_chars are:

Return Value

Description

std::errc()

Successful Parsing

std::errc::invalid_argument

1) Parsing a negative into an unsigned type

2) Leading + sign

3) Leading space

4) Incompatible formatting (e.g. exponent on chars_format::fixed, or p as exponent on value that is not chars_format::hex) See chars_format overview

std::errc::result_out_of_range

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 and unsigned __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 of std::strtod. This is a divergence from the standard which states we should return the value 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 replace std::strtod with boost::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 got std::errc::result_out_of_range. Charconv can give you that information by using boost::charconv::from_chars_erange instead of boost::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 or std::float128_t requires compiling with -std=gnu++xx and linking GCC’s libquadmath. 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 from to_chars points to one-past-the-end of the characters written on success or last on failure

  • ec - the error code. Values returned by to_chars are:

Return Value

Description

std::errc()

Successful Parsing

std::errc::value_too_large

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 and unsigned __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 or std::float128_t requires compiling with -std=gnu++xx and linking GCC’s libquadmath. 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

#include::charconv/reference.adoc[]

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:

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
Table 1. to_chars floating point with the shortest representation
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
Table 2. from_chars floating point with scientific formatting
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
Table 3. to_chars base 10 integers
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
Table 4. from_chars base 10 integers
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
Table 5. to_chars floating point with the shortest representation
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
Table 6. from_chars floating point with scientific formatting
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
Table 7. to_chars base 10 integers
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
Table 8. from_chars base 10 integers
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
Table 9. to_chars floating point with the shortest representation
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
Table 10. from_chars floating point with scientific formatting
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
Table 11. to_chars base 10 integers
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
Table 12. from_chars base 10 integers
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:

Acknowledgments

Special thanks to the following people (non-inclusive list):

  • Peter Dimov for providing technical guidance and contributing to the library throughout development.

  • Junekey Jeon for developing and answering my questions about his integer-formatting, Dragonbox, and Floff.

  • Chris Kormanyos for serving as the library review manager.

  • Stephan T. Lavavej for providing the basis for the benchmarks.

  • All that reviewed the library and provided feedback to make it better.

This documentation is copyright 2022-2023 Peter Dimov and Matt Borland and is distributed under the Boost Software License, Version 1.0.