uint128.go

package ksuid

import (
	"encoding/binary"
	"fmt"
	"math/bits"
)

// uint128 represents an unsigned 128 bits little endian integer.
type uint128 [2]uint64

func uint128Payload(ksuid KSUID) uint128 {
	return makeUint128FromPayload(ksuid[timestampLengthInBytes:])
}

func makeUint128(high uint64, low uint64) uint128 {
	return uint128{low, high}
}

func makeUint128FromPayload(payload []byte) uint128 {
	return uint128{
		binary.BigEndian.Uint64(payload[8:]), // low
		binary.BigEndian.Uint64(payload[:8]), // high
	}
}

func (v uint128) ksuid(timestamp uint32) (out KSUID) {
	binary.BigEndian.PutUint32(out[:4], timestamp) // time
	binary.BigEndian.PutUint64(out[4:12], v[1])    // high
	binary.BigEndian.PutUint64(out[12:], v[0])     // low
	return
}

func (v uint128) bytes() (out [16]byte) {
	binary.BigEndian.PutUint64(out[:8], v[1])
	binary.BigEndian.PutUint64(out[8:], v[0])
	return
}

func (v uint128) String() string {
	return fmt.Sprintf("0x%016X%016X", v[0], v[1])
}

func cmp128(x, y uint128) int {
	if x[1] < y[1] {
		return -1
	}
	if x[1] > y[1] {
		return 1
	}
	if x[0] < y[0] {
		return -1
	}
	if x[0] > y[0] {
		return 1
	}
	return 0
}

func add128(x, y uint128) (z uint128) {
	var c uint64
	z[0], c = bits.Add64(x[0], y[0], 0)
	z[1], _ = bits.Add64(x[1], y[1], c)
	return
}

func sub128(x, y uint128) (z uint128) {
	var b uint64
	z[0], b = bits.Sub64(x[0], y[0], 0)
	z[1], _ = bits.Sub64(x[1], y[1], b)
	return
}

func incr128(x uint128) (z uint128) {
	var c uint64
	z[0], c = bits.Add64(x[0], 1, 0)
	z[1] = x[1] + c
	return
}