github.com/shabbyrobe/go-num

num: 128-bit signed and unsigned integers for Go

[!WARNING] This repo has moved to sourcehut (https://git.sr.ht/~shabbyrobe/go-num), and has also been placed into maintenance mode. This version will remain here for the time being but may be removed at a later date. You may also consider https://pkg.go.dev/lukechampine.com/uint128 for your use case as I am unlikely to spend much time on this in future unless a serious bug is found.

Fastish int128 (num.I128) and uint128 (num.U128) 128-bit integer types for Go, providing the majority of methods found in big.Int.

WARNING: Function execution times in this library almost always depend on the inputs. This library is inappropriate for use in any domain where it is important that the execution time does not reveal details about the inputs used.

I128 is a signed "two's complement" implementation that should behave the same way on overflow as int64.

U128 and I128 are immutable value types by default; operations always return a new value rather than mutating the existing one.

Simple usage:

a := num.U128From64(1234)
b := num.U128From64(5678)
b := a.Add(a)
fmt.Printf("%x", x)

Most operations that operate on 2 128-bit numbers have a variant that accepts a 64-bit number:

a := num.U128From64(1234)
b := a.Add64(5678)
fmt.Printf("%x", x)