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140 lines
3.0 KiB
140 lines
3.0 KiB
package uuid
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/****************
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* Date: 21/06/15
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* Time: 5:48 PM
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***************/
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import (
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"encoding/gob"
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"log"
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"os"
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"time"
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)
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func init() {
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gob.Register(stateEntity{})
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}
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func SetupFileSystemStateSaver(pConfig StateSaverConfig) {
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saver := &FileSystemSaver{}
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saver.saveReport = pConfig.SaveReport
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saver.saveSchedule = int64(pConfig.SaveSchedule)
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SetupCustomStateSaver(saver)
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}
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// A wrapper for default setup of the FileSystemStateSaver
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type StateSaverConfig struct {
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// Print save log
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SaveReport bool
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// Save every x nanoseconds
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SaveSchedule time.Duration
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}
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// *********************************************** StateEntity
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// StateEntity acts as a marshaller struct for the state
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type stateEntity struct {
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Past Timestamp
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Node []byte
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Sequence uint16
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}
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// This implements the StateSaver interface for UUIDs
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type FileSystemSaver struct {
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cache *os.File
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saveState uint64
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saveReport bool
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saveSchedule int64
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}
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// Saves the current state of the generator
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// If the scheduled file save is reached then the file is synced
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func (o *FileSystemSaver) Save(pState *State) {
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if pState.past >= pState.next {
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err := o.open()
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defer o.cache.Close()
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if err != nil {
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log.Println("uuid.State.save:", err)
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return
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}
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// do the save
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o.encode(pState)
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// a tick is 100 nano seconds
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pState.next = pState.past + Timestamp(o.saveSchedule / 100)
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if o.saveReport {
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log.Printf("UUID STATE: SAVED %d", pState.past)
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}
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}
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}
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func (o *FileSystemSaver) Init(pState *State) {
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pState.saver = o
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err := o.open()
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defer o.cache.Close()
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if err != nil {
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if os.IsNotExist(err) {
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log.Printf("'%s' created\n", "uuid.SaveState")
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var err error
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o.cache, err = os.Create(os.TempDir() + "/state.unique")
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if err != nil {
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log.Println("uuid.State.init: SaveState error:", err)
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goto pastInit
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}
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o.encode(pState)
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} else {
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log.Println("uuid.State.init: SaveState error:", err)
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goto pastInit
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}
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}
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err = o.decode(pState)
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if err != nil {
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goto pastInit
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}
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pState.randomSequence = false
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pastInit:
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if timestamp() <= pState.past {
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pState.sequence++
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}
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pState.next = pState.past
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}
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func (o *FileSystemSaver) reset() {
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o.cache.Seek(0, 0)
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}
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func (o *FileSystemSaver) open() error {
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var err error
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o.cache, err = os.OpenFile(os.TempDir()+"/state.unique", os.O_RDWR, os.ModeExclusive)
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return err
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}
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// Encodes State generator data into a saved file
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func (o *FileSystemSaver) encode(pState *State) {
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// ensure reader state is ready for use
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o.reset()
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enc := gob.NewEncoder(o.cache)
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// Wrap private State data into the StateEntity
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err := enc.Encode(&stateEntity{pState.past, pState.node, pState.sequence})
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if err != nil {
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log.Panic("UUID.encode error:", err)
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}
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}
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// Decodes StateEntity data into the main State
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func (o *FileSystemSaver) decode(pState *State) error {
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o.reset()
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dec := gob.NewDecoder(o.cache)
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entity := stateEntity{}
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err := dec.Decode(&entity)
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if err != nil {
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log.Println("uuid.decode error:", err)
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return err
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}
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pState.past = entity.Past
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pState.node = entity.Node
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pState.sequence = entity.Sequence
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return nil
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}
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