How can I represent 128-bit numbers efficiently in C ?

Representing 128-bit Numbers in C

In C , the best approach to representing 128-bit numbers largely depends on the desired functionality and preferences. Several methods are available, each with its own advantages and drawbacks.

One option involves creating a class with multiple internal members. For instance, one could implement a class containing two 64-bit numbers or four 32-bit numbers, providing the desired 128-bit representation.

Alternatively, one might consider directly allocating a 128-bit block of memory and manipulating it manually. However, this approach requires careful handling of bit operations and can be prone to implementation errors.

Boost Multiprecision Library

For a more robust and standardized solution, consider utilizing the Boost Multiprecision Library. This library provides efficient and flexible multi-precision arithmetic types, including support for 128-bit unsigned integers:

boost::multiprecision::uint128_t my_large_number = boost::multiprecision::uint128_t(12345678901234567890);

With Boost Multiprecision, one gains access to a comprehensive set of arithmetic operators, allowing operations on 128-bit numbers in a manner similar to built-in numeric types. It also supports convenient initialization using strings and C99-style constants.

Extending to Larger Integers

The Boost Multiprecision Library further enables representing integers with arbitrary precision. If one needs to represent larger integers, such as 256-bit or 512-bit, simply instantiate the corresponding type provided by the library. For instance, boost::multiprecision::uint256_t represents a 256-bit unsigned integer.

In summary, while manual memory allocation and bitwise manipulation offer flexibility, the Boost Multiprecision Library provides a well-established and comprehensive solution for representing and manipulating large integers in C . Its wide range of features and potential for representing numbers of any size make it a preferred choice for handling 128-bit and larger integers in C .

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