Boost.CharConv

An implementation of <charconv> in C++11.

See more See less

/* Beats the global `[x-cloak] { display: none !important }` in styles.css. */ .hero__description-toggle[x-cloak] { display: inline-block !important; }

Documentation Source code Discuss in Slack GitHub Issues

About Boost.CharConv

Please check out the library's documentation to learn more.

View documentation

Quick Start

You are viewing the develop version of this library.

The master and develop pages are shown here to provide access to the newest in-development in-progress documentation. See the "Documentation" link on this page.

Other aspects of the page will reflect the previous official version, or not be available until the next release.

CharConv

This library is a C++11 compatible implementation of <charconv>. The full documentation can be found here: https://www.boost.org/doc/libs/master/libs/charconv/doc/html/charconv.html

Build Status

	Master	Develop
Github Actions
Drone
Codecov
Fuzzing

How to build the library

B2

git clone https://github.com/boostorg/boost
cd boost
git submodule update --init
cd ..
./bootstrap
./b2 cxxstd=11

This sets up a complete boost development and allows the tests to be run. To install the development environment run:

sudo ./b2 install cxxstd=11

Synopsis

Charconv is a collection of parsing functions that are locale-independent, non-allocating, and non-throwing.

namespace boost { namespace charconv {

enum class chars_format : unsigned
{
    scientific = 1 << 0,
    fixed = 1 << 1,
    hex = 1 << 2,
    general = fixed | scientific
};

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;
    friend constexpr bool operator!=(const from_chars_result& lhs, const from_chars_result& rhs) noexcept;
    constexpr explicit operator bool() const noexcept;
};

template <typename Integral>
BOOST_CXX14_CONSTEXPR from_chars_result from_chars(const char* first, const char* last, Integral& value, int base = 10) noexcept;

template <>
BOOST_CXX14_CONSTEXPR from_chars_result from_chars<bool>(const char* first, const char* last, bool& value, int base) noexcept = 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_erange(const char* first, const char* last, Real& value, chars_format fmt = chars_format::general) noexcept;

struct to_chars_result
{
    char* ptr;
    std::errc ec;

    friend constexpr bool operator==(const to_chars_result& lhs, const to_chars_result& rhs) noexcept;
    friend constexpr bool operator!=(const to_chars_result& lhs, const to_chars_result& rhs) noexcept;
    constexpr explicit operator bool() const noexcept;
};

template <typename Integral>
BOOST_CHARCONV_CONSTEXPR to_chars_result to_chars(char* first, char* last, Integral value, int base = 10) noexcept;

template <>
BOOST_CHARCONV_CONSTEXPR to_chars_result to_chars<bool>(char* first, char* last, bool 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

Notes

BOOST_CXX14_CONSTEXPR is defined as constexpr when compiling with C++14 or newer.
BOOST_CHARCONV_CONSTEXPR is defined as constexpr when compiling with C++14 or newer, and the compiler has __builtin_is_constant_evaluated
For explanation of from_chars_erange see docs under heading: Usage notes for from_chars for floating point types

Examples

`from_chars`

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); // Equivalent to the above
assert(v == 42);

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(v == 1.2345);

const char* buffer = "2a";
unsigned v = 0;
auto r = boost::charconv::from_chars(buffer, buffer + std::strlen(buffer), v, 16);
assert(r); // from_chars_result has operator bool()
assert(v == 42);

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);
assert(v == 8.0427e-18);

`to_chars`

char buffer[64] {};
int v = 42;
to_chars_result r = boost::charconv::to_chars(buffer, buffer + sizeof(buffer), v);
assert(r.ec == std::errc());
assert(!strcmp(buffer, "42")); // strcmp returns 0 on match

char buffer[64] {};
double v = 1e300;
to_chars_result r = boost::charconv::to_chars(buffer, buffer + sizeof(buffer), v);
assert(r.ec == std::errc());
assert(!strcmp(buffer, "1e+300"));

char buffer[64] {};
int v = 42;
to_chars_result r = boost::charconv::to_chars(buffer, buffer + sizeof(buffer), v, 16);
assert(r); // to_chars_result has operator bool()
assert(!strcmp(buffer, "2a")); // strcmp returns 0 on match