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primarykey.go
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primarykey.go
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// Copyright 2015 The Cayley Authors. All rights reserved.
//
// 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 graph
import (
"code.google.com/p/go-uuid/uuid"
"encoding/json"
"errors"
"github.com/barakmich/glog"
"strconv"
"sync"
)
type primaryKeyType uint8
const (
none primaryKeyType = iota
sequential
unique
)
type PrimaryKey struct {
keyType primaryKeyType
mut sync.Mutex
sequentialID int64
uniqueID string
}
func NewSequentialKey(horizon int64) PrimaryKey {
return PrimaryKey{
keyType: sequential,
sequentialID: horizon,
}
}
func NewUniqueKey(horizon string) PrimaryKey {
id := uuid.Parse(horizon)
if id == nil {
id = uuid.NewUUID()
}
return PrimaryKey{
keyType: unique,
uniqueID: id.String(),
}
}
func (p *PrimaryKey) Next() PrimaryKey {
switch p.keyType {
case sequential:
p.mut.Lock()
defer p.mut.Unlock()
p.sequentialID++
if p.sequentialID <= 0 {
p.sequentialID = 1
}
return PrimaryKey{
keyType: sequential,
sequentialID: p.sequentialID,
}
case unique:
id := uuid.NewUUID()
p.uniqueID = id.String()
return *p
case none:
panic("Calling next() on a none PrimaryKey")
}
return PrimaryKey{}
}
func (p *PrimaryKey) Int() int64 {
switch p.keyType {
case sequential:
return p.sequentialID
case unique:
msg := "UUID cannot be converted to an int64"
glog.Errorln(msg)
panic(msg)
}
return -1
}
func (p *PrimaryKey) String() string {
switch p.keyType {
case sequential:
return strconv.FormatInt(p.sequentialID, 10)
case unique:
return p.uniqueID
case none:
panic("Calling String() on a none PrimaryKey")
}
return ""
}
func (p PrimaryKey) MarshalJSON() ([]byte, error) {
switch p.keyType {
case none:
return nil, errors.New("Cannot marshal PrimaryKey with KeyType of 'none'")
case sequential:
return json.Marshal(p.sequentialID)
case unique:
return []byte("\"u" + p.uniqueID + "\""), nil
default:
return nil, errors.New("Unknown PrimaryKey type")
}
}
//To avoid recursion in the implmentation of the UnmarshalJSON interface below
type primaryKey PrimaryKey
func (p *PrimaryKey) UnmarshalJSON(bytes []byte) error {
if bytes[0] == '"' {
switch bytes[1] {
case 'u':
p.keyType = unique
p.uniqueID = string(bytes[2 : len(bytes)-1])
return nil
default:
return errors.New("Unknown string-like PrimaryKey type")
}
}
p.keyType = sequential
return json.Unmarshal(bytes, &p.sequentialID)
}