/
sequence.go
73 lines (59 loc) · 1.81 KB
/
sequence.go
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package sequence
import (
"fmt"
"sync"
"sort"
)
var (
sequencesMu sync.RWMutex
sequences = map[string]Sequence{}
)
type Sequence interface {
// Open opens the sequence generator.
Open() (err error)
// NextSequence generates next sequence integer(unsigned 64bit).
// If some error happens, err will not be nil and seq will be 0.
// Else, err will be nil and next valid sequence integer will be in seq.
NextSequence() (seq uint64, err error)
// Close closes the sequence generator.
Close()
}
// GetSequence returns corresponding sequence instance with the specified
// sequenceType. If the specified sequenceType does not register itself, then
// err will be non nil and sequence will be nil. Else, err will be nil and
// sequence will be corresponding sequence instance.
func GetSequence(sequenceType string) (sequence Sequence, err error) {
sequencesMu.RLock()
defer sequencesMu.RUnlock()
if value, ok := sequences[sequenceType]; ok {
sequence = value
return sequence, nil
} else {
return nil, fmt.Errorf("%v is not registered.", sequenceType)
}
}
// Register makes a sequence generator available by the provided sequenceType.
// If Register is called twice with the same name or if driver is nil, it
// panics.
func MustRegister(sequenceType string, sequence Sequence) {
sequencesMu.Lock()
defer sequencesMu.Unlock()
if sequence == nil {
panic("sequence: Registered sequence is nil")
}
if _, dup := sequences[sequenceType]; dup {
panic("sequence: Register called twice for driver " + sequenceType)
}
sequences[sequenceType] = sequence
}
// Sequences returns a sorted list of the types of the registered sequences.
func Sequences() []string {
sequencesMu.RLock()
defer sequencesMu.RUnlock()
var list []string
for name := range sequences {
list = append(list, name)
}
sort.Strings(list)
return list
}