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db.go
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db.go
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// Copyright (C) 2019-2024, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.
package prefixdb
import (
"context"
"slices"
"sync"
"github.com/ava-labs/avalanchego/database"
"github.com/ava-labs/avalanchego/utils"
"github.com/ava-labs/avalanchego/utils/hashing"
)
var (
_ database.Database = (*Database)(nil)
_ database.Batch = (*batch)(nil)
_ database.Iterator = (*iterator)(nil)
)
// Database partitions a database into a sub-database by prefixing all keys with
// a unique value.
type Database struct {
// All keys in this db begin with this byte slice
dbPrefix []byte
// Lexically one greater than dbPrefix, defining the end of this db's key range
dbLimit []byte
bufferPool *utils.BytesPool
// lock needs to be held during Close to guarantee db will not be set to nil
// concurrently with another operation. All other operations can hold RLock.
lock sync.RWMutex
// The underlying storage
db database.Database
closed bool
}
func newDB(prefix []byte, db database.Database) *Database {
return &Database{
dbPrefix: prefix,
dbLimit: incrementByteSlice(prefix),
db: db,
bufferPool: utils.NewBytesPool(),
}
}
func incrementByteSlice(orig []byte) []byte {
n := len(orig)
buf := make([]byte, n)
copy(buf, orig)
for i := n - 1; i >= 0; i-- {
buf[i]++
if buf[i] != 0 {
break
}
}
return buf
}
// New returns a new prefixed database
func New(prefix []byte, db database.Database) *Database {
if prefixDB, ok := db.(*Database); ok {
return newDB(
JoinPrefixes(prefixDB.dbPrefix, prefix),
prefixDB.db,
)
}
return newDB(
MakePrefix(prefix),
db,
)
}
// NewNested returns a new prefixed database without attempting to compress
// prefixes.
func NewNested(prefix []byte, db database.Database) *Database {
return newDB(
MakePrefix(prefix),
db,
)
}
func MakePrefix(prefix []byte) []byte {
return hashing.ComputeHash256(prefix)
}
func JoinPrefixes(firstPrefix, secondPrefix []byte) []byte {
simplePrefix := make([]byte, len(firstPrefix)+len(secondPrefix))
copy(simplePrefix, firstPrefix)
copy(simplePrefix[len(firstPrefix):], secondPrefix)
return MakePrefix(simplePrefix)
}
func PrefixKey(prefix, key []byte) []byte {
prefixedKey := make([]byte, len(prefix)+len(key))
copy(prefixedKey, prefix)
copy(prefixedKey[len(prefix):], key)
return prefixedKey
}
func (db *Database) Has(key []byte) (bool, error) {
db.lock.RLock()
defer db.lock.RUnlock()
if db.closed {
return false, database.ErrClosed
}
prefixedKey := db.prefix(key)
defer db.bufferPool.Put(prefixedKey)
return db.db.Has(*prefixedKey)
}
func (db *Database) Get(key []byte) ([]byte, error) {
db.lock.RLock()
defer db.lock.RUnlock()
if db.closed {
return nil, database.ErrClosed
}
prefixedKey := db.prefix(key)
defer db.bufferPool.Put(prefixedKey)
return db.db.Get(*prefixedKey)
}
func (db *Database) Put(key, value []byte) error {
db.lock.RLock()
defer db.lock.RUnlock()
if db.closed {
return database.ErrClosed
}
prefixedKey := db.prefix(key)
defer db.bufferPool.Put(prefixedKey)
return db.db.Put(*prefixedKey, value)
}
func (db *Database) Delete(key []byte) error {
db.lock.RLock()
defer db.lock.RUnlock()
if db.closed {
return database.ErrClosed
}
prefixedKey := db.prefix(key)
defer db.bufferPool.Put(prefixedKey)
return db.db.Delete(*prefixedKey)
}
func (db *Database) NewBatch() database.Batch {
return &batch{
Batch: db.db.NewBatch(),
db: db,
}
}
func (db *Database) NewIterator() database.Iterator {
return db.NewIteratorWithStartAndPrefix(nil, nil)
}
func (db *Database) NewIteratorWithStart(start []byte) database.Iterator {
return db.NewIteratorWithStartAndPrefix(start, nil)
}
func (db *Database) NewIteratorWithPrefix(prefix []byte) database.Iterator {
return db.NewIteratorWithStartAndPrefix(nil, prefix)
}
// Assumes it is safe to modify the arguments to db.db.NewIteratorWithStartAndPrefix after it returns.
// It is safe to modify [start] and [prefix] after this method returns.
func (db *Database) NewIteratorWithStartAndPrefix(start, prefix []byte) database.Iterator {
db.lock.RLock()
defer db.lock.RUnlock()
if db.closed {
return &database.IteratorError{
Err: database.ErrClosed,
}
}
prefixedStart := db.prefix(start)
defer db.bufferPool.Put(prefixedStart)
prefixedPrefix := db.prefix(prefix)
defer db.bufferPool.Put(prefixedPrefix)
return &iterator{
Iterator: db.db.NewIteratorWithStartAndPrefix(*prefixedStart, *prefixedPrefix),
db: db,
}
}
func (db *Database) Compact(start, limit []byte) error {
db.lock.RLock()
defer db.lock.RUnlock()
if db.closed {
return database.ErrClosed
}
prefixedStart := db.prefix(start)
defer db.bufferPool.Put(prefixedStart)
if limit == nil {
return db.db.Compact(*prefixedStart, db.dbLimit)
}
prefixedLimit := db.prefix(limit)
defer db.bufferPool.Put(prefixedLimit)
return db.db.Compact(*prefixedStart, *prefixedLimit)
}
func (db *Database) Close() error {
db.lock.Lock()
defer db.lock.Unlock()
if db.closed {
return database.ErrClosed
}
db.closed = true
return nil
}
func (db *Database) isClosed() bool {
db.lock.RLock()
defer db.lock.RUnlock()
return db.closed
}
func (db *Database) HealthCheck(ctx context.Context) (interface{}, error) {
db.lock.RLock()
defer db.lock.RUnlock()
if db.closed {
return nil, database.ErrClosed
}
return db.db.HealthCheck(ctx)
}
// Return a copy of [key], prepended with this db's prefix.
// The returned slice should be put back in the pool when it's done being used.
func (db *Database) prefix(key []byte) *[]byte {
keyLen := len(db.dbPrefix) + len(key)
prefixedKey := db.bufferPool.Get(keyLen)
copy(*prefixedKey, db.dbPrefix)
copy((*prefixedKey)[len(db.dbPrefix):], key)
return prefixedKey
}
// Batch of database operations
type batch struct {
database.Batch
db *Database
// Each key is prepended with the database's prefix.
// Each byte slice underlying a key should be returned to the pool
// when this batch is reset.
ops []batchOp
}
type batchOp struct {
Key *[]byte
Value []byte
Delete bool
}
func (b *batch) Put(key, value []byte) error {
prefixedKey := b.db.prefix(key)
copiedValue := slices.Clone(value)
b.ops = append(b.ops, batchOp{
Key: prefixedKey,
Value: copiedValue,
})
return b.Batch.Put(*prefixedKey, copiedValue)
}
func (b *batch) Delete(key []byte) error {
prefixedKey := b.db.prefix(key)
b.ops = append(b.ops, batchOp{
Key: prefixedKey,
Delete: true,
})
return b.Batch.Delete(*prefixedKey)
}
// Write flushes any accumulated data to the memory database.
func (b *batch) Write() error {
b.db.lock.RLock()
defer b.db.lock.RUnlock()
if b.db.closed {
return database.ErrClosed
}
return b.Batch.Write()
}
// Reset resets the batch for reuse.
func (b *batch) Reset() {
// Return the byte buffers underneath each key back to the pool.
// Don't return the byte buffers underneath each value back to the pool
// because we assume in batch.Replay that it's not safe to modify the
// value argument to w.Put.
for _, op := range b.ops {
b.db.bufferPool.Put(op.Key)
}
// Clear b.writes
if cap(b.ops) > len(b.ops)*database.MaxExcessCapacityFactor {
b.ops = make([]batchOp, 0, cap(b.ops)/database.CapacityReductionFactor)
} else {
clear(b.ops)
b.ops = b.ops[:0]
}
b.Batch.Reset()
}
// Replay the batch contents.
func (b *batch) Replay(w database.KeyValueWriterDeleter) error {
for _, op := range b.ops {
keyWithoutPrefix := (*op.Key)[len(b.db.dbPrefix):]
if op.Delete {
if err := w.Delete(keyWithoutPrefix); err != nil {
return err
}
} else {
if err := w.Put(keyWithoutPrefix, op.Value); err != nil {
return err
}
}
}
return nil
}
type iterator struct {
database.Iterator
db *Database
key, val []byte
err error
}
// Next calls the inner iterators Next() function and strips the keys prefix
func (it *iterator) Next() bool {
if it.db.isClosed() {
it.key = nil
it.val = nil
it.err = database.ErrClosed
return false
}
hasNext := it.Iterator.Next()
if hasNext {
key := it.Iterator.Key()
if prefixLen := len(it.db.dbPrefix); len(key) >= prefixLen {
key = key[prefixLen:]
}
it.key = key
it.val = it.Iterator.Value()
} else {
it.key = nil
it.val = nil
}
return hasNext
}
func (it *iterator) Key() []byte {
return it.key
}
func (it *iterator) Value() []byte {
return it.val
}
// Error returns [database.ErrClosed] if the underlying db was closed
// otherwise it returns the normal iterator error.
func (it *iterator) Error() error {
if it.err != nil {
return it.err
}
return it.Iterator.Error()
}