zkint

A high-performance, header-only multi-precision integer library for C99+ and C++11+. It implements signed and unsigned integers of sizes 128, 256, 512, and 1024 bits.

Features

• Header-Only: Simple integration without pre-compilation.
• Portability: Compatible with GCC, Clang, MSVC, and ICC.
• Standards Compliant: Works with C99 and later, and C++11 and later.
• Type Promotion: Full C++ template-based type promotion rules matching standard behaviors.
• Overloaded Operators: Native arithmetic, logical, and bitwise operators in C++.
• Generic Macros: C11 _Generic macros for generic arithmetic in C.

Installation

CMake FetchContent

To include zkint in your CMake project:

include(FetchContent)

FetchContent_Declare(
    zkint
    GIT_REPOSITORY https://github.com/kvzidev/zkint.h.git
    GIT_TAG        master
)
FetchContent_MakeAvailable(zkint)

# Link your target
target_link_libraries(your_target PRIVATE zk::zkint)

Usage

C++ Example

#include <zkint.h>
#include <iostream>

int main() {
    zk::uint256_t a("0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF");
    zk::uint256_t b = 1;
    zk::uint256_t c = a + b; // Automatic promotion and overflow handling
    std::cout << c.to_string() << std::endl;
    return 0;
}

C Example

#include <zkint.h>
#include <stdio.h>

int main() {
    zk_uint256_t a = zk_uint256_from_string("0xFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF");
    zk_uint256_t b = zk_uint256_from_uint64(1);
    zk_uint256_t c = zk_uint256_add(a, b);
    
    char buf[128];
    zk_uint256_to_string(c, buf, sizeof(buf));
    printf("%s\n", buf);
    return 0;
}

Running Tests

Use the helper scripts:

• ./build.sh to compile tests.
• ./test.sh to execute tests.

Compiler Compatibility

The library is verified and fully supported under the following compiler configurations:

Compiler	Operating System	C++ Standard
GCC	Linux (Ubuntu)	C++11, C++17, C++20
Clang	Linux (Ubuntu)	C++11, C++17, C++20
Intel oneAPI (icx)	Linux (Ubuntu)	C++11, C++17, C++20
MSVC (cl)	Windows	C++14, C++17, C++20

License

Copyright (c) 2026 Kevin Zanzi. Please see the LICENSE.