How to Represent 128-bit Numbers in C ?

Representing 128-bit Numbers in C

When dealing with large numbers beyond the scope of native data types, efficient and standardized representation becomes crucial. For 128-bit numbers, C bietet several approaches, primarily involving leveraging libraries or creating custom implementations.

Custom Implementations

One approach is to construct a class containing multiple 64-bit or 32-bit numbers, or to allocate a 128-bit memory block and handle operations manually. However, this approach is prone to implementation errors and lacks built-in operator support.

Boost Multiprecision Library

Boost provides the boost::multiprecision::uint128_t type, which offers a robust solution for representing 128-bit numbers. It supports all essential arithmetic operators, ensuring compatibility with native numeric types.

Example Usage

The following code snippet demonstrates the use of the Boost multiprecision library:

#include <boost/multiprecision/uint128.hpp>

using namespace boost::multiprecision;

uint128_t x("12345678901234567890");
uint128_t y(U128_C(98765432109876543210));

auto z = x + y;

In this example, the uint128_t data type is utilized to perform arithmetic operations on large 128-bit numbers.

Extending to Larger Numbers

The Boost multiprecision library also provides __int256 and __int512 types for 256-bit and 512-bit integers. This enables easy extension of the representation to even larger numbers.

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