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c# big integer implementation on C++ (portable format desired)

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csBigInteger.cpp

csBigInteger for C++

This project is part of the csBigInteger macro project, a C# BigInteger implementation on C++ (portable format desired)

This project is an ongoing port of csBigInteger.js project: https://github.com/neoresearch/csBigInteger.js

Why chosing C/C++ language for that?

Existing frameworks use high-level languages that may not be suitable for very lightweight architectures, such as microcontrollers with very limited computing capabilities.

C/C++ is interoperable with nearly all existing languages, so the idea is to provide modules that can be reused on other projects (on other languages too).

Build Instructions

There are currently two implementations for BigInteger.h: BigIntegerGMP.cpp or BigIntegerMono.cpp.

GNU MP implementation

On debian-based systems (or ubuntu), just type make vendor (it will install libgmp-dev package).

Mono implementation

Mono implementation will generate a csbiginteger_dotnet.dll and load it through csbiginteger_mono.so. It is much more complex process, but it guarantees that original BigInteger C# library is being used. Right now, tests are passing for both gmp and mono implementations, so gmp C++ native implementation is much preferred (and more lightweight) on practice.

If you want to go this way, you will need mono:

sudo apt-key adv --keyserver hkp://keyserver.ubuntu.com:80 --recv-keys 3FA7E0328081BFF6A14DA29AA6A19B38D3D831EF
sudo apt install apt-transport-https ca-certificates
echo "deb https://download.mono-project.com/repo/ubuntu stable-xenial main" | sudo tee /etc/apt/sources.list.d/mono-official-stable.list
sudo apt update
sudo apt install mono-complete

tests

It will also configure test library (as long as you cloned this project with --submodules too). To test, just run make test.

C++ Standard

Currently, C++11 is adopted, in order to keep the best compatibility between conversors and compilers. However, it is recommended to migrate to C++17 as soon as possible, if this does not break compatibility with any existing modules and tools.

Let's please follow the CppCoreGuidelines.

vscode IDE

If using vscode IDE, it is recommended to install the following extensions:

  • C/C++ (currently 0.23.0-insiders2)
  • C++ Intellisense (currently 0.2.2)
  • GoogleTest Adapter (currently 1.8.3)

C++ Format Style

The currently adopted style for C++ is Mozilla, with indentation level set to 3. Recommended configuration for vscode:

{
    "[cpp]": {
        "editor.tabSize" : 3,
        "editor.detectIndentation": false
    },
    "C_Cpp.clang_format_fallbackStyle": "{ BasedOnStyle : Mozilla , ColumnLimit : 0, IndentWidth: 3, AccessModifierOffset: -3}"
}

Variable Naming Style

The naming style for variables and methods is based on C# language. So, CamelCase is used and public variables start with upper-case letters, while private and local variables start with lower-case. The idea is to preseve maximum compatibility with reference project (which is on C#).

Anything that is beyond the scope of the reference project can use classic CamelCase C++ naming (for example, starting variables with lower-case).

License

Code follows MIT License.

Implementation BigIntegerGMP.cpp (class implementation of standard BigInteger.h) is LGPLv3. The reason is that this implementation depends on GNU MP Bignum Library (licensed LGPLv3 since version 6), what means that all modifications of BigIntegerGMP.cpp, or usage of its code (even partially) on other projects should also adopt LGPLv3 (not MIT License).

Implementation BigIntegerMono.cpp depends on Mono license, which is also MIT License.

The binaries generated by this project (csbiginteger_gmp.so or csbiginteger_mono.so) can be freely used on other projects, regardless of license.