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service.go
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service.go
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// Copyright 2019-present Open Networking Foundation.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package counter
import (
"github.com/atomix/atomix-api/go/atomix/primitive/counter"
"github.com/atomix/atomix-go-framework/pkg/atomix/errors"
)
func init() {
registerServiceFunc(newService)
}
func newService(context ServiceContext) Service {
return &counterService{
ServiceContext: context,
}
}
// counterService is a state machine for a counter primitive
type counterService struct {
ServiceContext
value int64
}
func (c *counterService) Backup(writer SnapshotWriter) error {
return writer.WriteState(&CounterState{
Value: c.value,
})
}
func (c *counterService) Restore(reader SnapshotReader) error {
state, err := reader.ReadState()
if err != nil {
return err
}
c.value = state.Value
return nil
}
func (c *counterService) Set(set SetProposal) error {
if err := checkPreconditions(c.value, set.Request().Preconditions); err != nil {
return err
}
c.value = set.Request().Value
return set.Reply(&counter.SetResponse{
Value: c.value,
})
}
func (c *counterService) Get(get GetProposal) error {
return get.Reply(&counter.GetResponse{
Value: c.value,
})
}
func (c *counterService) Increment(increment IncrementProposal) error {
c.value += increment.Request().Delta
return increment.Reply(&counter.IncrementResponse{
Value: c.value,
})
}
func (c *counterService) Decrement(decrement DecrementProposal) error {
c.value -= decrement.Request().Delta
return decrement.Reply(&counter.DecrementResponse{
Value: c.value,
})
}
func checkPreconditions(value int64, preconditions []counter.Precondition) error {
for _, precondition := range preconditions {
switch p := precondition.Precondition.(type) {
case *counter.Precondition_Value:
if value != p.Value {
return errors.NewConflict("value precondition failed")
}
}
}
return nil
}