mscharconv

<charconv> from Microsoft STL, but multi-platform.

Tested with MSVC, gcc, and clang on Windows, Linux, and macOS (will likely work on other platforms supported by any of these compilers)

Usage

The library is header only. You can clone the repo or copy the contents of the include directory in your project.

Alternatively you can use with CMake. The provided CMakeLists.txt defines an INTERFACE target mscharconv and its alias msstl::charconv.

To use the library in your code simply include <msstl/charconv.hpp> and use to_chars and from_chars from the namespace msstl.

C++17 or later is needed.

Example

#include <msstl/charconv.hpp>
#include <iostream>
#include <string_view>

int main() {
    std::string_view pi_str = "3.14159 is pi";
    double pi;
    auto [p, ec] = msstl::from_chars(pi_str.data(), pi_str.data() + pi_str.length(), pi);
    if (ec != std::errc{}) {
        std::cerr << "Error converting \"" << pi_str << "\" to double\n";
        return 1;
    }
    std::cout << "Got double " << pi << ". The rest is \"" << p << "\".\n";

    return 0;
}

Additional Utilities

An additional header util.hpp is provided with the library with non-standard util functions in namespace msstl::util. Note that util.hpp is NOT self contained. You must include it after including charconv.hpp.

The utility functions are:

• bool from_string(std::string_view str, INTEGER& out, int base = 10); - convert string to integral number with a given base. Will return true if the conversion is successful. The string must be an integer and nothing more. Even though from_chars supports inputs like "123 and some text" and will stop at the first non-integer character, from_string will consider this to be an invalid input and return false.
• bool from_string(std::string_view str, FLOATING_POINT_NUM& out); - convert a string to a floating point number. Return true is successful. Same restrictions as above apply.

Advanced usage

For the basic usage of the library one needs to include charconv.hpp which is quite big. It contains a lot of code and huge helper arrays. If you include charconv in many places of your code, it may lead to long compilation times. The advanced usage of the library allows the functions to be compiled separately and only once per project. To enable this, instead of including charconv.hpp include charconv_fwd.hpp and in a single place of your code define MSCHARCONV_IMPLEMENT and then include charconv.hpp.

Additionally if you want to provide a shared library interface to the functions, define MSCHARCONV_API to your import/export symbols, before including charconv_fwd.hpp

Development

The library is created by automatically converting headers from a clone of Microsoft STL with the Ruby script convert-msstl-files.rb. Additionally support functions and macros are provided in charconv_impl.inl.

License

Copyright (c) Microsoft Corporation, Borislav Stanimirov, and contributors.

SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception