bigint

This repository implements a big integer library in C. The library supports many operations, such as basic arithmetic, comparison, fast modular exponentiation, prime number detection, square roots, and more.

Usage

To use the library, first include it in your C file.

#include "bigint.h"

To create a new big integer, use the bigint struct. You can initialize a big integer from a string, an integer, or another big integer.

int main() {
    // Initialize a big integer from a string
    bigint a = bigint_from_string("123456789012345678901234567890");

    // Initialize a big integer from an integer
    bigint b = bigint_from_int(1234567890);

    // Initialize a big integer from another big integer
    bigint c = bigint_copy(a);

    bigint_delete(a);
    bigint_delete(b);
    bigint_delete(c);

    return 0;
}

To perform arithmetic operations on big integers, use the provided functions.

int main() {
    // Initialize big integers
    bigint a = bigint_from_string("123456789012345678901234567890");
    bigint b = bigint_from_string("987654321098765432109876543210");

    // Perform arithmetic operations
    bigint c = bigint_add(a, b);
    bigint d = bigint_sub(a, b);
    bigint e = bigint_mul(a, b);
    bigint f = bigint_div(a, b);
    bigint g = bigint_mod(a, b);

    bigint_delete(a);
    bigint_delete(b);
    bigint_delete(c);
    bigint_delete(d);
    bigint_delete(e);
    bigint_delete(f);
    bigint_delete(g);

    return 0;
}

To compare big integers:

int main() {
    // Initialize big integers
    bigint a = bigint_from_string("123456789012345678901234567890");
    bigint b = bigint_from_string("987654321098765432109876543210");

    // Compare big integers
    if (bigint_eq(a, b)) {
        printf("a == b\n");
    } else if (bigint_lt(a, b)) {
        printf("a < b\n");
    } else if (bigint_gt(a, b)) {
        printf("a > b\n");
    }

    bigint_delete(a);
    bigint_delete(b);

    return 0;
}

To perform fast modular exponentiation:

int main() {
    // Initialize big integers
    bigint a = bigint_from_string("2");
    bigint b = bigint_from_string("1234");
    bigint m = bigint_from_string("10007");

    // Perform fast modular exponentiation
    bigint c = bigint_fast_pow(a, b, m);

    bigint_delete(a);
    bigint_delete(b);
    bigint_delete(c);
    bigint_delete(m);

    return 0;
}

To check if a big integer is prime:

int main() {
    // Initialize a big integer
    bigint a = bigint_from_string("123456789012345678901234567890");

    // Check if the big integer is prime
    if (bigint_is_prime(a)) {
        printf("a is prime\n");
    } else {
        printf("a is not prime\n");
    }

    bigint_delete(a);

    return 0;
}

To calculate the square root of a big integer:

int main() {
    // Initialize a big integer
    bigint a = bigint_from_string("123412341");

    // Calculate the square root
    bigint b = bigint_sqrt(a);

    bigint_delete(a);
    bigint_delete(b);

    return 0;
}

Building

To build your program with the big integer library, simply add it to your include path and link against the C standard library.

gcc -I path/to/bigint main.c -o main

CMake

To build with CMake, you can use a CMakeLists.txt file like the following:

cmake_minimum_required(VERSION 3.0)

# Create a new project
project(HelloWorld)

# Add an executable
add_executable(HelloWorld main.c)

include_directories(path/to/bigint)

Alternatively, you can use FetchContent to download the big integer repository and include it in your project.

# Import the library from the git repo
include(FetchContent)

FetchContent_Declare(
  bigint
  GIT_REPOSITORY https://github.com/adam-mcdaniel/bigint
  GIT_TAG        main
)

FetchContent_MakeAvailable(bigint)

# Include the header only library
include_directories(${bigint_SOURCE_DIR})

License

This project is licensed under the MIT License - see the LICENSE file for details.