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db.go
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db.go
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// (c) 2019-2020, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.
package prefixdb
import (
"sync"
"github.com/ava-labs/gecko/database"
"github.com/ava-labs/gecko/database/nodb"
"github.com/ava-labs/gecko/utils/hashing"
)
// Database partitions a database into a sub-database by prefixing all keys with
// a unique value.
type Database struct {
lock sync.RWMutex
dbPrefix []byte
db database.Database
}
// New returns a new prefixed database
func New(prefix []byte, db database.Database) *Database {
if prefixDB, ok := db.(*Database); ok {
simplePrefix := make([]byte, len(prefixDB.dbPrefix)+len(prefix))
copy(simplePrefix, prefixDB.dbPrefix)
copy(simplePrefix[len(prefixDB.dbPrefix):], prefix)
return NewNested(simplePrefix, prefixDB.db)
}
return NewNested(prefix, db)
}
// NewNested returns a new prefixed database without attempting to compress
// prefixes.
func NewNested(prefix []byte, db database.Database) *Database {
return &Database{
dbPrefix: hashing.ComputeHash256(prefix),
db: db,
}
}
// Has implements the Database interface
func (db *Database) Has(key []byte) (bool, error) {
db.lock.RLock()
defer db.lock.RUnlock()
if db.db == nil {
return false, database.ErrClosed
}
return db.db.Has(db.prefix(key))
}
// Get implements the Database interface
func (db *Database) Get(key []byte) ([]byte, error) {
db.lock.RLock()
defer db.lock.RUnlock()
if db.db == nil {
return nil, database.ErrClosed
}
return db.db.Get(db.prefix(key))
}
// Put implements the Database interface
func (db *Database) Put(key, value []byte) error {
db.lock.Lock()
defer db.lock.Unlock()
if db.db == nil {
return database.ErrClosed
}
return db.db.Put(db.prefix(key), value)
}
// Delete implements the Database interface
func (db *Database) Delete(key []byte) error {
db.lock.Lock()
defer db.lock.Unlock()
if db.db == nil {
return database.ErrClosed
}
return db.db.Delete(db.prefix(key))
}
// NewBatch implements the Database interface
func (db *Database) NewBatch() database.Batch {
return &batch{
Batch: db.db.NewBatch(),
db: db,
}
}
// NewIterator implements the Database interface
func (db *Database) NewIterator() database.Iterator { return db.NewIteratorWithStartAndPrefix(nil, nil) }
// NewIteratorWithStart implements the Database interface
func (db *Database) NewIteratorWithStart(start []byte) database.Iterator {
return db.NewIteratorWithStartAndPrefix(start, nil)
}
// NewIteratorWithPrefix implements the Database interface
func (db *Database) NewIteratorWithPrefix(prefix []byte) database.Iterator {
return db.NewIteratorWithStartAndPrefix(nil, prefix)
}
// NewIteratorWithStartAndPrefix implements the Database interface
func (db *Database) NewIteratorWithStartAndPrefix(start, prefix []byte) database.Iterator {
db.lock.RLock()
defer db.lock.RUnlock()
if db.db == nil {
return &nodb.Iterator{Err: database.ErrClosed}
}
return &iterator{
Iterator: db.db.NewIteratorWithStartAndPrefix(db.prefix(start), db.prefix(prefix)),
db: db,
}
}
// Stat implements the Database interface
func (db *Database) Stat(stat string) (string, error) {
db.lock.RLock()
defer db.lock.RUnlock()
if db.db == nil {
return "", database.ErrClosed
}
return db.db.Stat(stat)
}
// Compact implements the Database interface
func (db *Database) Compact(start, limit []byte) error {
db.lock.Lock()
defer db.lock.Unlock()
if db.db == nil {
return database.ErrClosed
}
return db.db.Compact(db.prefix(start), db.prefix(limit))
}
// Close implements the Database interface
func (db *Database) Close() error {
db.lock.Lock()
defer db.lock.Unlock()
if db.db == nil {
return database.ErrClosed
}
db.db = nil
return nil
}
func (db *Database) prefix(key []byte) []byte {
prefixedKey := make([]byte, len(db.dbPrefix)+len(key))
copy(prefixedKey, db.dbPrefix)
copy(prefixedKey[len(db.dbPrefix):], key)
return prefixedKey
}
type keyValue struct {
key []byte
value []byte
delete bool
}
type batch struct {
database.Batch
db *Database
writes []keyValue
}
// Put implements the Batch interface
func (b *batch) Put(key, value []byte) error {
b.writes = append(b.writes, keyValue{copyBytes(key), copyBytes(value), false})
return b.Batch.Put(b.db.prefix(key), value)
}
// Delete implements the Batch interface
func (b *batch) Delete(key []byte) error {
b.writes = append(b.writes, keyValue{copyBytes(key), nil, true})
return b.Batch.Delete(b.db.prefix(key))
}
// Write flushes any accumulated data to the memory database.
func (b *batch) Write() error {
b.db.lock.Lock()
defer b.db.lock.Unlock()
if b.db.db == nil {
return database.ErrClosed
}
return b.Batch.Write()
}
// Reset resets the batch for reuse.
func (b *batch) Reset() {
b.writes = b.writes[:0]
b.Batch.Reset()
}
// Replay replays the batch contents.
func (b *batch) Replay(w database.KeyValueWriter) error {
for _, keyvalue := range b.writes {
if keyvalue.delete {
if err := w.Delete(keyvalue.key); err != nil {
return err
}
} else if err := w.Put(keyvalue.key, keyvalue.value); err != nil {
return err
}
}
return nil
}
type iterator struct {
database.Iterator
db *Database
}
// Key calls the inner iterators Key and strips the prefix
func (it *iterator) Key() []byte {
key := it.Iterator.Key()
if prefixLen := len(it.db.dbPrefix); len(key) >= prefixLen {
return key[prefixLen:]
}
return key
}
func copyBytes(bytes []byte) []byte {
copiedBytes := make([]byte, len(bytes))
copy(copiedBytes, bytes)
return copiedBytes
}