88 lines
1.9 KiB
Go
88 lines
1.9 KiB
Go
// Copyright 2015 The Cayley Authors. All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package graph
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import (
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"encoding/json"
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"strconv"
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"sync"
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)
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// Defines the PrimaryKey interface, this abstracts the generation of IDs
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type primaryKeyType uint8
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const (
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none primaryKeyType = iota
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sequential
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)
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type PrimaryKey struct {
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keyType primaryKeyType
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mut sync.Mutex
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sequentialID int64
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}
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func NewSequentialKey(horizon int64) PrimaryKey {
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return PrimaryKey{
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keyType: sequential,
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sequentialID: horizon,
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}
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}
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func (p *PrimaryKey) Next() PrimaryKey {
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switch p.keyType {
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case sequential:
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p.mut.Lock()
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defer p.mut.Unlock()
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p.sequentialID++
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if p.sequentialID <= 0 {
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p.sequentialID = 1
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}
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return PrimaryKey{
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keyType: sequential,
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sequentialID: p.sequentialID,
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}
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case none:
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panic("Calling next() on a none PrimaryKey")
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}
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return PrimaryKey{}
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}
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func (p *PrimaryKey) Int() int64 {
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switch p.keyType {
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case sequential:
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return p.sequentialID
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}
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return -1
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}
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func (p *PrimaryKey) String() string {
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// More options for more keyTypes
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return strconv.FormatInt(p.sequentialID, 10)
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}
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func (p *PrimaryKey) MarshalJSON() ([]byte, error) {
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return json.Marshal(p.sequentialID)
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}
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func (p *PrimaryKey) UnmarshalJSON(bytes []byte) error {
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/* Careful special casing here. For example, string-related things might begin
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if bytes[0] == '"' {
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}
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*/
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p.keyType = sequential
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return json.Unmarshal(bytes, &p.sequentialID)
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}
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