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state.go
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state.go
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// (c) 2019-2020, Ava Labs, Inc. All rights reserved.
// See the file LICENSE for licensing terms.
package atomic
import (
"bytes"
"errors"
"github.com/ava-labs/avalanchego/codec"
"github.com/ava-labs/avalanchego/database"
"github.com/ava-labs/avalanchego/database/linkeddb"
"github.com/ava-labs/avalanchego/database/prefixdb"
"github.com/ava-labs/avalanchego/ids"
"github.com/ava-labs/avalanchego/utils"
"github.com/ava-labs/avalanchego/utils/hashing"
)
var errDuplicatedOperation = errors.New("duplicated operation on provided value")
type dbElement struct {
// Present indicates the value was removed before existing.
// If set to false, when this element is added to the shared memory, it will
// be immediately removed.
// If set to true, then this element will be removed normally when remove is
// called.
Present bool `serialize:"true"`
// Value is the body of this element.
Value []byte `serialize:"true"`
// Traits are a collection of features that can be used to lookup this
// element.
Traits [][]byte `serialize:"true"`
}
type state struct {
c codec.Manager
valueDB database.Database
indexDB database.Database
}
func (s *state) Value(key []byte) (*Element, error) {
value, err := s.loadValue(key)
if err != nil {
return nil, err
}
if !value.Present {
return nil, database.ErrNotFound
}
return &Element{
Key: key,
Value: value.Value,
Traits: value.Traits,
}, nil
}
func (s *state) SetValue(e *Element) error {
value, err := s.loadValue(e.Key)
if err == nil {
// The key was already registered with the state.
if !value.Present {
// This was previously optimistically deleted from the database, so
// it should be immediately removed.
return s.valueDB.Delete(e.Key)
}
// This key was written twice, which is invalid
return errDuplicatedOperation
}
if err != database.ErrNotFound {
// An unexpected error occurred, so we should propagate that error
return err
}
for _, trait := range e.Traits {
traitDB := prefixdb.New(trait, s.indexDB)
traitList := linkeddb.NewDefault(traitDB)
if err := traitList.Put(e.Key, nil); err != nil {
return err
}
}
dbElem := dbElement{
Present: true,
Value: e.Value,
Traits: e.Traits,
}
valueBytes, err := s.c.Marshal(codecVersion, &dbElem)
if err != nil {
return err
}
return s.valueDB.Put(e.Key, valueBytes)
}
func (s *state) RemoveValue(key []byte) error {
value, err := s.loadValue(key)
if err != nil {
if err != database.ErrNotFound {
// An unexpected error occurred, so we should propagate that error
return err
}
// The value doesn't exist, so we should optimistically deleted it
dbElem := dbElement{Present: false}
valueBytes, err := s.c.Marshal(codecVersion, &dbElem)
if err != nil {
return err
}
return s.valueDB.Put(key, valueBytes)
}
// Don't allow the removal of something that was already removed.
if !value.Present {
return errDuplicatedOperation
}
for _, trait := range value.Traits {
traitDB := prefixdb.New(trait, s.indexDB)
traitList := linkeddb.NewDefault(traitDB)
if err := traitList.Delete(key); err != nil {
return err
}
}
return s.valueDB.Delete(key)
}
func (s *state) loadValue(key []byte) (*dbElement, error) {
valueBytes, err := s.valueDB.Get(key)
if err != nil {
return nil, err
}
// The key was in the database
value := &dbElement{}
_, err = s.c.Unmarshal(valueBytes, value)
return value, err
}
func (s *state) getKeys(traits [][]byte, startTrait, startKey []byte, limit int) ([][]byte, []byte, []byte, error) {
tracked := ids.Set{}
keys := [][]byte(nil)
lastTrait := startTrait
lastKey := startKey
utils.Sort2DBytes(traits)
for _, trait := range traits {
switch bytes.Compare(trait, startTrait) {
case -1:
continue
case 1:
startKey = nil
}
lastTrait = trait
var err error
lastKey, err = s.appendTraitKeys(&keys, &tracked, &limit, trait, startKey)
if err != nil {
return nil, nil, nil, err
}
if limit == 0 {
break
}
}
return keys, lastTrait, lastKey, nil
}
func (s *state) appendTraitKeys(keys *[][]byte, tracked *ids.Set, limit *int, trait, startKey []byte) ([]byte, error) {
lastKey := startKey
traitDB := prefixdb.New(trait, s.indexDB)
traitList := linkeddb.NewDefault(traitDB)
iter := traitList.NewIteratorWithStart(startKey)
defer iter.Release()
for iter.Next() && *limit > 0 {
key := iter.Key()
lastKey = key
id := hashing.ComputeHash256Array(key)
if tracked.Contains(id) {
continue
}
tracked.Add(id)
*keys = append(*keys, key)
*limit--
}
return lastKey, iter.Error()
}