go get lukechampine.com/uint128
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)_/¯
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