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gentime.go
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gentime.go
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package youyouayedee
import (
"encoding/binary"
"math/rand"
"sync"
"time"
"golang.org/x/crypto/blake2b"
)
// NewTimeGenerator constructs a new Generator that produces time-based UUIDs
// of the given version.
//
// Versions 1, 6, 7, and 8 are supported.
//
func NewTimeGenerator(version Version, o Options) (Generator, error) {
var err error
if version != 1 && version != 6 && version != 7 && version != 8 {
return nil, ErrVersionMismatch{Requested: version, Expected: []Version{1, 6, 7, 8}}
}
node := o.Node
if node.IsZero() {
node, err = GenerateNode(o)
if err != nil {
return nil, ErrOperationFailed{Operation: GenerateNodeOp, Err: err}
}
}
now := o.TimeSource
if now == nil {
now = time.Now
}
lsc := o.LeapSecondCalculator
if lsc == nil {
lsc = LeapSecondCalculatorDummy{}
}
cs := o.ClockStorage
if cs == nil {
cs = ClockStorageUnavailable{}
}
last, clock, err := cs.Load(node)
if err != nil {
if !isErrClockNotFound(err) {
return nil, ErrOperationFailed{Operation: ClockStorageLoadOp, Err: err}
}
last = now()
clock = rand.Uint32()
}
return &genTime{
node: node,
now: now,
lsc: lsc,
cs: cs,
ver: version,
last: last,
clock: clock,
}, nil
}
type genTime struct {
GeneratorBase
node Node
now func() time.Time
lsc LeapSecondCalculator
cs ClockStorage
ver Version
mu sync.Mutex
last time.Time
clock uint32
}
func (g *genTime) NewUUID() (UUID, error) {
g.mu.Lock()
defer g.mu.Unlock()
now := g.now()
if g.last.Before(now) {
g.last = now
} else {
now = g.last
g.clock++
}
err := g.cs.Store(g.node, g.last, g.clock)
if err != nil {
return Nil, ErrOperationFailed{Operation: ClockStorageStoreOp, Err: err}
}
var uuid UUID
var ticks uint64
if g.ver == 1 {
ticks = goTimeToGregorianTicks(g.lsc, now)
putV1Ticks(uuid[0:8], ticks)
putClock14(uuid[8:10], g.clock)
copy(uuid[10:16], g.node[0:6])
} else if g.ver == 6 {
ticks = goTimeToGregorianTicks(g.lsc, now)
putV6Ticks(uuid[0:8], ticks)
putClock14(uuid[8:10], g.clock)
copy(uuid[10:16], g.node[0:6])
} else {
ticks = goTimeToUnixTicks(now)
var hashInput [18]byte
binary.BigEndian.PutUint64(hashInput[0:8], ticks)
binary.BigEndian.PutUint32(hashInput[8:12], g.clock)
copy(hashInput[12:18], g.node[0:6])
sum := blake2b.Sum256(hashInput[:])
putUint48(uuid[0:6], ticks)
putClock32(uuid[6:11], g.clock)
copy(uuid[11:16], sum[0:5])
}
uuid[6] = (uuid[6] & 0x0f) | byte(g.ver<<4)
uuid[8] = (uuid[8] & 0x3f) | 0x80
return uuid, nil
}
var _ Generator = (*genTime)(nil)
func goTimeToGregorianTicks(lsc LeapSecondCalculator, now time.Time) uint64 {
s := now.Unix()
ns := now.Nanosecond()
if ns < 0 {
ns = nanosPerSecond - ns
s--
}
s += int64(lsc.LeapSecondsSinceUnixEpoch(s, false))
s += secondsFromGregorianEpochToUnixEpoch
if s < 0 {
s = 0
}
num := uint64(s*ticksPerSecond) + uint64(ns/nanosPerTick)
num &= tickMask
return num
}
func gregorianTicksToGoTime(lsc LeapSecondCalculator, num uint64) time.Time {
num &= tickMask
ns := int64(num%ticksPerSecond) * nanosPerTick
s := int64(num / ticksPerSecond)
s -= secondsFromGregorianEpochToUnixEpoch
s -= int64(lsc.LeapSecondsSinceUnixEpoch(s, true))
if s < 0 && ns > 0 {
ns = nanosPerSecond - ns
s++
}
return time.Unix(s, ns)
}
func goTimeToUnixTicks(now time.Time) uint64 {
s := now.Unix()
ns := now.Nanosecond()
if ns < 0 {
ns = nanosPerSecond - ns
s--
}
s64 := (s * millisPerSecond) + int64(ns/nanosPerMilli)
return uint64(s64) & milliMask
}
func signExtendUnixTicks(num uint64) int64 {
num &= milliMask
if (num & milliSignBit) == milliSignBit {
num |= ^uint64(milliMask)
}
return int64(num)
}
func unixTicksToGoTime(num int64) time.Time {
ns := (num % millisPerSecond) * nanosPerMilli
s := (num / millisPerSecond)
if s < 0 && ns > 0 {
ns = nanosPerSecond - ns
s++
}
return time.Unix(s, ns)
}