trie/triedb: add Reader to backend interface (ethereum#29988)

triedb/database.go

@@ -74,6 +74,10 @@ type backend interface {
 
 	// Close closes the trie database backend and releases all held resources.
 	Close() error
+
+	// Reader returns a reader for accessing all trie nodes with provided state
+	// root. An error will be returned if the requested state is not available.
+	Reader(root common.Hash) (database.Reader, error)
 }
 
 // Database is the wrapper of the underlying backend which is shared by different
@@ -123,13 +127,7 @@ func NewDatabase(diskdb ethdb.Database, config *Config) *Database {
 // Reader returns a reader for accessing all trie nodes with provided state root.
 // An error will be returned if the requested state is not available.
 func (db *Database) Reader(blockRoot common.Hash) (database.Reader, error) {
-	switch b := db.backend.(type) {
-	case *hashdb.Database:
-		return b.Reader(blockRoot)
-	case *pathdb.Database:
-		return b.Reader(blockRoot)
-	}
-	return nil, errors.New("unknown backend")
+	return db.backend.Reader(blockRoot)
 }
 
 // Update performs a state transition by committing dirty nodes contained in the

triedb/hashdb/database.go

@@ -33,6 +33,7 @@ import (
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/trie/trienode"
 	"github.com/ethereum/go-ethereum/trie/triestate"
+	"github.com/ethereum/go-ethereum/triedb/database"
 )
 
 var (
@@ -625,7 +626,7 @@ func (db *Database) Close() error {
 
 // Reader retrieves a node reader belonging to the given state root.
 // An error will be returned if the requested state is not available.
-func (db *Database) Reader(root common.Hash) (*reader, error) {
+func (db *Database) Reader(root common.Hash) (database.Reader, error) {
 	if _, err := db.node(root); err != nil {
 		return nil, fmt.Errorf("state %#x is not available, %v", root, err)
 	}