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fifo.go
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fifo.go
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package gofifo
import (
"bytes"
"encoding/gob"
"errors"
"sync"
"time"
"github.com/streadway/simpleuuid"
"github.com/syndtr/goleveldb/leveldb"
)
var Empty = errors.New("fifo: empty")
type Fifo struct {
ldb *leveldb.DB
mux sync.Mutex
}
func NewFifo(datadir string) (*Fifo, error) {
fifo := &Fifo{}
var err error
fifo.ldb, err = leveldb.OpenFile(datadir, nil)
if err != nil {
return nil, err
}
return fifo, nil
}
func (fifo *Fifo) Close() {
if fifo.ldb != nil {
fifo.ldb.Close()
fifo.ldb = nil
}
}
func (fifo *Fifo) Register(t interface{}) {
gob.Register(t)
}
func (fifo *Fifo) nextId() (string, error) {
uuid, err := simpleuuid.NewTime(time.Now())
if err != nil {
return "", err
}
return uuid.String(), nil
}
func (fifo *Fifo) Enqueue(obj interface{}) (err error) {
uuid, err := fifo.nextId()
if err != nil {
return
}
mCache := new(bytes.Buffer)
encCache := gob.NewEncoder(mCache)
encCache.Encode(obj)
err = fifo.ldb.Put([]byte(uuid), mCache.Bytes(), nil)
return
}
func (fifo *Fifo) Dequeue(obj interface{}) (err error) {
fifo.mux.Lock()
defer fifo.mux.Unlock()
err = Empty
iter := fifo.ldb.NewIterator(nil, nil)
defer iter.Release()
for iter.Next() {
var key = string(iter.Key())
value := iter.Value()
pCache := bytes.NewBuffer(value)
decCache := gob.NewDecoder(pCache)
err = decCache.Decode(obj)
if err != nil {
return
}
fifo.ldb.Delete([]byte(key), nil)
return
}
return
}