111 lines
2.7 KiB
Go
111 lines
2.7 KiB
Go
// Copyright 2020 Andrew Thornton. All rights reserved.
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// Use of this source code is governed by a MIT-style
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// license that can be found in the LICENSE file.
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package levelqueue
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import (
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"sync"
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"github.com/syndtr/goleveldb/leveldb"
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"github.com/syndtr/goleveldb/leveldb/util"
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)
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const (
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setPrefixStr = "set"
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)
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// Set defines a set struct
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type Set struct {
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db *leveldb.DB
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closeUnderlyingDB bool
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lock sync.Mutex
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prefix []byte
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}
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// OpenSet opens a set from the db path or creates a set if it doesn't exist.
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// The keys will be prefixed with "set-" by default
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func OpenSet(dataDir string) (*Set, error) {
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db, err := leveldb.OpenFile(dataDir, nil)
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if err != nil {
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return nil, err
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}
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return NewSet(db, []byte(setPrefixStr), true)
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}
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// NewSet creates a set from a db. The keys will be prefixed with prefix
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// and at close the db will be closed as per closeUnderlyingDB
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func NewSet(db *leveldb.DB, prefix []byte, closeUnderlyingDB bool) (*Set, error) {
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set := &Set{
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db: db,
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closeUnderlyingDB: closeUnderlyingDB,
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}
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set.prefix = make([]byte, len(prefix))
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copy(set.prefix, prefix)
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return set, nil
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}
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// Add adds a member string to a key set, returns true if the member was not already present
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func (set *Set) Add(value []byte) (bool, error) {
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set.lock.Lock()
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defer set.lock.Unlock()
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setKey := withPrefix(set.prefix, value)
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has, err := set.db.Has(setKey, nil)
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if err != nil || has {
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return !has, err
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}
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return !has, set.db.Put(setKey, []byte(""), nil)
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}
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// Members returns the current members of the set
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func (set *Set) Members() ([][]byte, error) {
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set.lock.Lock()
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defer set.lock.Unlock()
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var members [][]byte
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prefix := withPrefix(set.prefix, []byte{})
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iter := set.db.NewIterator(util.BytesPrefix(prefix), nil)
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for iter.Next() {
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slice := iter.Key()[len(prefix):]
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value := make([]byte, len(slice))
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copy(value, slice)
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members = append(members, value)
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}
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iter.Release()
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return members, iter.Error()
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}
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// Has returns if the member is in the set
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func (set *Set) Has(value []byte) (bool, error) {
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set.lock.Lock()
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defer set.lock.Unlock()
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setKey := withPrefix(set.prefix, value)
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return set.db.Has(setKey, nil)
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}
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// Remove removes a member from the set, returns true if the member was present
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func (set *Set) Remove(value []byte) (bool, error) {
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set.lock.Lock()
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defer set.lock.Unlock()
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setKey := withPrefix(set.prefix, value)
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has, err := set.db.Has(setKey, nil)
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if err != nil || !has {
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return has, err
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}
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return has, set.db.Delete(setKey, nil)
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}
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// Close closes the set (and the underlying db if set to closeUnderlyingDB)
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func (set *Set) Close() error {
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if !set.closeUnderlyingDB {
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set.db = nil
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return nil
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}
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err := set.db.Close()
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set.db = nil
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return err
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}
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