uint128

go get github.com/gaze-network/uint128

This project is a fork of lukechampine/uint128 with additional features and improvements:

1. Change overflow behavior from panicking to returning whether the operation overflowed.
   • Add AddOverflow, Add64Overflow, SubOverflow, Sub64Overflow, MulOverflow, Mul64Overflow functions which returns additional boolean indicating whether the operation overflowed. The original functions now ignores overflow instead of panicking.
   • Change FromBig function behaviour to return errors instead of panicking.
2. Add conversion functions Uint64(), Uint32(), Uint16(), Uint8() to convert Uint128 to native types.
3. Add functions IsUint64(), IsUint32(), IsUint16(), IsUint8() to check if Uint128 can be converted to native types without overflow.

uint128 provides a high-performance Uint128 type that supports standard arithmetic operations. Unlike math/big, operations on Uint128 values always produce new values instead of modifying a pointer receiver. A Uint128 value is therefore immutable, just like uint64 and friends.

The name uint128.Uint128 stutters, so I recommend either using a "dot import" or aliasing uint128.Uint128 to give it a project-specific name. Embedding the type is not recommended, because methods will still return uint128.Uint128; this means that, if you want to extend the type with new methods, your best bet is probably to copy the source code wholesale and rename the identifier. ¯\_(ツ)_/¯

Benchmarks

Addition, multiplication, and subtraction are on par with their native 64-bit equivalents. Division is slower: ~20x slower when dividing a Uint128 by a uint64, and ~100x slower when dividing by a Uint128. However, division is still faster than with big.Int (for the same operands), especially when dividing by a uint64.

BenchmarkArithmetic/Add-4              2000000000    0.45 ns/op    0 B/op      0 allocs/op
BenchmarkArithmetic/Sub-4              2000000000    0.67 ns/op    0 B/op      0 allocs/op
BenchmarkArithmetic/Mul-4              2000000000    0.42 ns/op    0 B/op      0 allocs/op
BenchmarkArithmetic/Lsh-4              2000000000    1.06 ns/op    0 B/op      0 allocs/op
BenchmarkArithmetic/Rsh-4              2000000000    1.06 ns/op    0 B/op      0 allocs/op

BenchmarkDivision/native_64/64-4       2000000000    0.39 ns/op    0 B/op      0 allocs/op
BenchmarkDivision/Div_128/64-4         2000000000    6.28 ns/op    0 B/op      0 allocs/op
BenchmarkDivision/Div_128/128-4        30000000      45.2 ns/op    0 B/op      0 allocs/op
BenchmarkDivision/big.Int_128/64-4     20000000      98.2 ns/op    8 B/op      1 allocs/op
BenchmarkDivision/big.Int_128/128-4    30000000      53.4 ns/op    48 B/op     1 allocs/op

BenchmarkString/Uint128-4              10000000      173 ns/op     48 B/op     1 allocs/op
BenchmarkString/big.Int-4              5000000       350 ns/op     144 B/op    3 allocs/op