uint128

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Published: May 22, 2019 License: MIT Imports: 4 Imported by: 0

README

uint128

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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 embedding/aliasing uint128.Uint128 to give it a project-specific name.

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

Documentation

Index

Constants

This section is empty.

Variables

This section is empty.

Functions

This section is empty.

Types

type Uint128

type Uint128 struct {
	// contains filtered or unexported fields
}

A Uint128 is an unsigned 128-bit number.

var Zero Uint128

Zero is a zero-valued uint128.

func From64

func From64(v uint64) Uint128

From64 converts v to a Uint128 value.

func FromBig

func FromBig(i *big.Int) (u Uint128)

FromBig converts i to a Uint128 value. It panics if i is negative or overflows 128 bits.

func FromBytes

func FromBytes(b []byte) Uint128

FromBytes converts b to a Uint128 value.

func New

func New(lo, hi uint64) Uint128

New returns the Uint128 value (lo,hi).

func (Uint128) Add

func (u Uint128) Add(v Uint128) Uint128

Add returns u+v.

func (Uint128) Add64

func (u Uint128) Add64(v uint64) Uint128

Add64 returns u+v.

func (Uint128) And

func (u Uint128) And(v Uint128) Uint128

And returns u&v.

func (Uint128) And64

func (u Uint128) And64(v uint64) Uint128

And64 returns u&v.

func (Uint128) Big

func (u Uint128) Big() *big.Int

Big returns u as a *big.Int.

func (Uint128) Cmp

func (u Uint128) Cmp(v Uint128) int

Cmp compares two Uint128 values. The return value follows the convention of math/big.

func (Uint128) Cmp64

func (u Uint128) Cmp64(v uint64) int

Cmp64 compares u to v. The return value follows the convention of math/big.

func (Uint128) Div

func (u Uint128) Div(v Uint128) Uint128

Div returns u/v.

func (Uint128) Div64

func (u Uint128) Div64(v uint64) Uint128

Div64 returns u/v.

func (Uint128) Equals

func (u Uint128) Equals(v Uint128) bool

Equals returns true if u == v.

Uint128 values can be compared directly with ==, but use of the Equals method is preferred for consistency.

func (Uint128) Equals64

func (u Uint128) Equals64(v uint64) bool

Equals64 returns true if u == v.

func (Uint128) IsZero

func (u Uint128) IsZero() bool

IsZero returns true if u == 0.

func (Uint128) Lsh

func (u Uint128) Lsh(n uint) (s Uint128)

Lsh returns u<<n.

func (Uint128) Mul

func (u Uint128) Mul(v Uint128) Uint128

Mul returns u*v.

func (Uint128) Mul64

func (u Uint128) Mul64(v uint64) Uint128

Mul64 returns u*v.

func (Uint128) Or

func (u Uint128) Or(v Uint128) Uint128

Or returns u|v.

func (Uint128) Or64

func (u Uint128) Or64(v uint64) Uint128

Or64 returns u|v.

func (Uint128) PutBytes

func (u Uint128) PutBytes(b []byte)

PutBytes stores u in b in little-endian order. It panics if len(b) < 16.

func (Uint128) QuoRem

func (u Uint128) QuoRem(v Uint128) (q, r Uint128)

QuoRem returns q = u/v and r = u%v.

func (Uint128) QuoRem64

func (u Uint128) QuoRem64(v uint64) (q Uint128, r uint64)

QuoRem64 returns q = u/v and r = u%v.

func (Uint128) Rsh

func (u Uint128) Rsh(n uint) (s Uint128)

Rsh returns u>>n.

func (Uint128) String

func (u Uint128) String() string

String returns the base-10 representation of u as a string.

func (Uint128) Sub

func (u Uint128) Sub(v Uint128) Uint128

Sub returns u-v.

func (Uint128) Sub64

func (u Uint128) Sub64(v uint64) Uint128

Sub64 returns u-v.

func (Uint128) Xor

func (u Uint128) Xor(v Uint128) Uint128

Xor returns u^v.

func (Uint128) Xor64

func (u Uint128) Xor64(v uint64) Uint128

Xor64 returns u^v.

Source Files

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