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mborland merged 2 commits into from
Feb 26, 2026
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Improve Overview and Readme #336

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Improve the overview
mborland Feb 26, 2026
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Small update to README
mborland Feb 26, 2026
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3 changes: 2 additions & 1 deletion README.md
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Expand Up @@ -16,6 +16,7 @@ int128 is under active development and is not an official boost library.

This library is header only. It contains no other dependencies.
Simply `#include` it and use it.
With C++20 and greater you can instead `import boost.int128`.

## CMake

Expand Down Expand Up @@ -64,7 +65,7 @@ struct int128_t;

These types operate like built-in integer types.
They have their own implementations of the Standard-Library functions
(e.g. like those found in `<limits>`, `<iostream>`, `<bit>` etc.).
(e.g., like those found in `<limits>`, `<iostream>`, `<bit>` etc.).

The entire library can be conveniently included with `#include <boost/int128.hpp>`

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14 changes: 10 additions & 4 deletions doc/modules/ROOT/pages/overview.adoc
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Expand Up @@ -15,16 +15,22 @@ Matt Borland
Boost.Int128 is a portable implementation of a signed, and an unsigned 128-bit integer and related functionality (i.e. `<bit>`, `<iostream>`, etc).
Importantly, on all platforms, the `sizeof` the types provided in this library are exactly 128-bits.

The library is header-only, has no dependencies, and requires only C++14.
The library is header-only, has no dependencies, and requires only pass:[C++14].
When using pass:[C++20] or newer, the library can be consumed as a module `import boost.int128`.

== Motivation

128-bit integers are remarkably useful in a number of domains, but portability is often an issue.
An example is a 64-bit machine running Linux (say Ubuntu 24.04) has `__int128`, but the same exact machine running Windows does not have this type.
128-bit integers are useful across many domains, but pass:[C++] provides no portable way to use them.
GCC and Clang offer `__int128` as a non-standard extension on 64-bit targets, but it lacks `std::numeric_limits` specializations, `<iostream>` support, and is absent entirely on MSVC.
Multiprecision libraries can fill the gap, but typically at the cost of a larger `sizeof` and additional overhead.
Boost.Int128 solves this by providing types that are exactly 128-bits on every platform.
Operation implementations rely on compiler intrinsic where available for native performance, and optimized software implementations elsewhere.

== Use Cases

Anywhere 128-bit integers are needed.
* **Networking** — IPv6 addresses are 128 bits wide; a single integer makes masking, comparison, and arithmetic straightforward.
* **Unique identifiers** — UUIDs / GUIDs are 128-bit values commonly used as database keys and distributed system identifiers.
* **Scientific and Financial computing** — Extended-range accumulators, large combinatorial values, and algorithms that need overflow-free 64×64 multiplication.

== Supported Compilers

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