package optint
Install
Dune Dependency
Authors
Maintainers
Sources
sha256=1dcbe0b6b6031f77db33028c87138fdb3bf90f92915e3b6629ddeb30a0d3000b
sha512=7d4b63c82b1dc1e363a892895c1a612bac3dcd33c27e2c27e8ea2e8868d659413226c7a0d7bdcac423f7fb016069d0de90c3eaa68986da6aea69e1f1ca583f18
README.md.html
Optint - Efficient integer types on 64-bit architectures
This library provides two new integer types, Optint.t
and Int63.t
, which guarantee efficient representation on 64-bit architectures and provide a best-effort boxed representation on 32-bit architectures.
Goal
The standard Int32.t
and Int64.t
types provided by the standard library have the same heap-allocated representation on all architectures. This consistent representation has costs in both memory and run-time performance.
On 64-bit architectures, it's often more efficient to use the native int
directly. This library provides types to do exactly this:
Optint.t
: an integer containing at least 32 bits. On 64-bit, this is an immediate integer; on 32-bit, it is a boxed 32-bit value. The overflow behaviour is platform-dependent.Int63.t
: an integer containing exactly 63 bits. On 64-bit, this is an immediate integer; on 32-bit, it is a boxed 64-bit integer that is wrapped to provide 63-bit two's complement semantics. The two implementations are observationally equivalent, modulo use ofMarshal
andObj
.
In summary:
Integer type | 32-bit representation | 64-bit representation | Semantics |
---|---|---|---|
Stdlib.Int.t |
31-bit immediate ✅ | 63-bit immediate ✅ | Always immediate |
Stdlib.Nativeint.t |
32-bit boxed ❌ | 64-bit boxed ❌ | Exactly word size |
Stdlib.Int32.t |
32-bit boxed ❌ | 32-bit boxed ❌ | Exactly 32 bits |
Stdlib.Int64.t |
64-bit boxed ❌ | 64-bit boxed ❌ | Exactly 64 bits |
Optint.t (new) |
32-bit boxed ❌ | 63-bit immediate ✅ | At least 32 bits |
Int63.t (new) |
64-bit boxed ❌ | 63-bit immediate ✅ | Exactly 63 bits |
These new types are safe and well-tested, but their architecture-dependent implementation makes them unsuitable for use with the Marshal
module. Use the provided encode and decode functions instead.