core/state, triedb/database: refactor state reader (#30712)

Co-authored-by: Martin HS <martin@swende.se>

core/state/database.go

@@ -186,9 +186,9 @@ func (db *CachingDB) Reader(stateRoot common.Hash) (Reader, error) {
 	// is optional and may be partially useful if it's not fully
 	// generated.
 	if db.snap != nil {
-		sr, err := newStateReader(stateRoot, db.snap)
+		snap := db.snap.Snapshot(stateRoot)
-		if err == nil {
+		if snap != nil {
-			readers = append(readers, sr) // snap reader is optional
+			readers = append(readers, newStateReader(snap)) // snap reader is optional
 		}
 	}
 	// Set up the trie reader, which is expected to always be available

core/state/reader.go

@@ -21,13 +21,13 @@ import (
 	"maps"
 
 	"github.com/ethereum/go-ethereum/common"
-	"github.com/ethereum/go-ethereum/core/state/snapshot"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/trie"
 	"github.com/ethereum/go-ethereum/trie/utils"
 	"github.com/ethereum/go-ethereum/triedb"
+	"github.com/ethereum/go-ethereum/triedb/database"
 )
 
 // Reader defines the interface for accessing accounts and storage slots
@@ -52,23 +52,18 @@ type Reader interface {
 	Copy() Reader
 }
 
-// stateReader is a wrapper over the state snapshot and implements the Reader
+// stateReader wraps a database state reader.
-// interface. It provides an efficient way to access flat state.
 type stateReader struct {
-	snap snapshot.Snapshot
+	reader database.StateReader
 	buff   crypto.KeccakState
 }
 
-// newStateReader constructs a flat state reader with on the specified state root.
+// newStateReader constructs a state reader with on the given state root.
-func newStateReader(root common.Hash, snaps *snapshot.Tree) (*stateReader, error) {
+func newStateReader(reader database.StateReader) *stateReader {
-	snap := snaps.Snapshot(root)
-	if snap == nil {
-		return nil, errors.New("snapshot is not available")
-	}
 	return &stateReader{
-		snap: snap,
+		reader: reader,
 		buff:   crypto.NewKeccakState(),
-	}, nil
+	}
 }
 
 // Account implements Reader, retrieving the account specified by the address.
@@ -78,18 +73,18 @@ func newStateReader(root common.Hash, snaps *snapshot.Tree) (*stateReader, error
 //
 // The returned account might be nil if it's not existent.
 func (r *stateReader) Account(addr common.Address) (*types.StateAccount, error) {
-	ret, err := r.snap.Account(crypto.HashData(r.buff, addr.Bytes()))
+	account, err := r.reader.Account(crypto.HashData(r.buff, addr.Bytes()))
 	if err != nil {
 		return nil, err
 	}
-	if ret == nil {
+	if account == nil {
 		return nil, nil
 	}
 	acct := &types.StateAccount{
-		Nonce:    ret.Nonce,
+		Nonce:    account.Nonce,
-		Balance:  ret.Balance,
+		Balance:  account.Balance,
-		CodeHash: ret.CodeHash,
+		CodeHash: account.CodeHash,
-		Root:     common.BytesToHash(ret.Root),
+		Root:     common.BytesToHash(account.Root),
 	}
 	if len(acct.CodeHash) == 0 {
 		acct.CodeHash = types.EmptyCodeHash.Bytes()
@@ -110,7 +105,7 @@ func (r *stateReader) Account(addr common.Address) (*types.StateAccount, error)
 func (r *stateReader) Storage(addr common.Address, key common.Hash) (common.Hash, error) {
 	addrHash := crypto.HashData(r.buff, addr.Bytes())
 	slotHash := crypto.HashData(r.buff, key.Bytes())
-	ret, err := r.snap.Storage(addrHash, slotHash)
+	ret, err := r.reader.Storage(addrHash, slotHash)
 	if err != nil {
 		return common.Hash{}, err
 	}
@@ -131,7 +126,7 @@ func (r *stateReader) Storage(addr common.Address, key common.Hash) (common.Hash
 // Copy implements Reader, returning a deep-copied snap reader.
 func (r *stateReader) Copy() Reader {
 	return &stateReader{
-		snap: r.snap,
+		reader: r.reader,
 		buff:   crypto.NewKeccakState(),
 	}
 }

triedb/database/database.go

@@ -18,6 +18,7 @@ package database
 
 import (
 	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/core/types"
 )
 
 // NodeReader wraps the Node method of a backing trie reader.
@@ -37,3 +38,31 @@ type NodeDatabase interface {
 	// An error will be returned if the specified state is not available.
 	NodeReader(stateRoot common.Hash) (NodeReader, error)
 }
+
+// StateReader wraps the Account and Storage method of a backing state reader.
+type StateReader interface {
+	// Account directly retrieves the account associated with a particular hash in
+	// the slim data format. An error will be returned if the read operation exits
+	// abnormally. Specifically, if the layer is already stale.
+	//
+	// Note:
+	// - the returned account object is safe to modify
+	// - no error will be returned if the requested account is not found in database
+	Account(hash common.Hash) (*types.SlimAccount, error)
+
+	// Storage directly retrieves the storage data associated with a particular hash,
+	// within a particular account. An error will be returned if the read operation
+	// exits abnormally.
+	//
+	// Note:
+	// - the returned storage data is not a copy, please don't modify it
+	// - no error will be returned if the requested slot is not found in database
+	Storage(accountHash, storageHash common.Hash) ([]byte, error)
+}
+
+// StateDatabase wraps the methods of a backing state store.
+type StateDatabase interface {
+	// StateReader returns a state reader associated with the specific state.
+	// An error will be returned if the specified state is not available.
+	StateReader(stateRoot common.Hash) (StateReader, error)
+}