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serial.go
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serial.go
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package model
import (
"encoding/gob"
"errors"
"os"
"sync"
)
var (
Err_PrefixNotFound = errors.New("prefix_not_found")
Err_PrefixExist = errors.New("prefix_exist")
)
type SerialMgr interface {
CreateSerial(prefix string, startNumber int64) error
UpdateSerial(prefix string, startNumber int64) error
GetSerial(prefix string) (int64, error)
ClearSerial(prefix string) error
Persistance() error
}
type serial struct {
serialMap map[string]int64
persistFile string
sync.Mutex
}
func NewSerial(cfg *Config) SerialMgr {
// check if file exists
mgr := &serial{
persistFile: cfg.PersistanceFile,
serialMap: make(map[string]int64),
}
if FileExists(cfg.PersistanceFile) {
// if file exists, load from file
f, err := os.Open(cfg.PersistanceFile)
if err != nil {
return nil
}
defer f.Close()
dec := gob.NewDecoder(f)
dec.Decode(&mgr.serialMap)
}
return mgr
}
func (s *serial) CreateSerial(prefix string, startNumber int64) error {
if _, ok := s.serialMap[prefix]; ok {
return Err_PrefixExist
}
s.Lock()
s.serialMap[prefix] = startNumber
s.Unlock()
return nil
}
func (s *serial) UpdateSerial(prefix string, startNumber int64) error {
if _, ok := s.serialMap[prefix]; !ok {
return Err_PrefixNotFound
}
s.Lock()
s.serialMap[prefix] = startNumber
s.Unlock()
return nil
}
func (s *serial) GetSerial(prefix string) (int64, error) {
if _, ok := s.serialMap[prefix]; !ok {
return 0, Err_PrefixNotFound
}
s.Lock()
defer s.Unlock()
result := s.serialMap[prefix] + 1
s.serialMap[prefix] = result
return result, nil
}
func (s *serial) ClearSerial(prefix string) error {
if _, ok := s.serialMap[prefix]; !ok {
return Err_PrefixNotFound
}
s.Lock()
delete(s.serialMap, prefix)
s.Unlock()
return nil
}
func (s *serial) Persistance() error {
// save map to file
f, err := os.Create(s.persistFile)
if err != nil {
return err
}
defer f.Close()
enc := gob.NewEncoder(f)
s.Lock()
defer s.Unlock()
if err := enc.Encode(s.serialMap); err != nil {
return err
}
return nil
}