core/types: add legacy receipt deserialization (ethereum#28)

Receipts in `l2geth` are stored with L1 fee data to prevent
the need of having an archive node for historical L1 fee data.

https://github.com/ethereum-optimism/optimism/blob/91a80d287237032a47d68d8809b1dc67ad15293f/l2geth/core/types/receipt.go#L247

This ports the deserialization of the legacy `l2geth` style
serialization to `op-geth`. This is required for nodes that upgrade
using the db migration tool.

core/types/receipt.go

@@ -108,6 +108,72 @@ type storedReceiptRLP struct {
 	Logs              []*Log
 }
 
+// LegacyOptimismStoredReceiptRLP is the pre bedrock storage encoding of a
+// receipt. It will only exist in the database if it was migrated using the
+// migration tool. Nodes that sync using snap-sync will not have any of these
+// entries.
+type LegacyOptimismStoredReceiptRLP struct {
+	PostStateOrStatus []byte
+	CumulativeGasUsed uint64
+	Logs              []*LogForStorage
+	L1GasUsed         *big.Int
+	L1GasPrice        *big.Int
+	L1Fee             *big.Int
+	FeeScalar         string
+}
+
+// LogForStorage is a wrapper around a Log that handles
+// backward compatibility with prior storage formats.
+type LogForStorage Log
+
+// EncodeRLP implements rlp.Encoder.
+func (l *LogForStorage) EncodeRLP(w io.Writer) error {
+	rl := rlpLog{Address: l.Address, Topics: l.Topics, Data: l.Data}
+	return rlp.Encode(w, &rl)
+}
+
+type legacyRlpStorageLog struct {
+	Address     common.Address
+	Topics      []common.Hash
+	Data        []byte
+	BlockNumber uint64
+	TxHash      common.Hash
+	TxIndex     uint
+	BlockHash   common.Hash
+	Index       uint
+}
+
+// DecodeRLP implements rlp.Decoder.
+//
+// Note some redundant fields(e.g. block number, tx hash etc) will be assembled later.
+func (l *LogForStorage) DecodeRLP(s *rlp.Stream) error {
+	blob, err := s.Raw()
+	if err != nil {
+		return err
+	}
+	var dec rlpLog
+	err = rlp.DecodeBytes(blob, &dec)
+	if err == nil {
+		*l = LogForStorage{
+			Address: dec.Address,
+			Topics:  dec.Topics,
+			Data:    dec.Data,
+		}
+	} else {
+		// Try to decode log with previous definition.
+		var dec legacyRlpStorageLog
+		err = rlp.DecodeBytes(blob, &dec)
+		if err == nil {
+			*l = LogForStorage{
+				Address: dec.Address,
+				Topics:  dec.Topics,
+				Data:    dec.Data,
+			}
+		}
+	}
+	return err
+}
+
 // NewReceipt creates a barebone transaction receipt, copying the init fields.
 // Deprecated: create receipts using a struct literal instead.
 func NewReceipt(root []byte, failed bool, cumulativeGasUsed uint64) *Receipt {
@@ -283,8 +349,51 @@ func (r *ReceiptForStorage) EncodeRLP(_w io.Writer) error {
 // DecodeRLP implements rlp.Decoder, and loads both consensus and implementation
 // fields of a receipt from an RLP stream.
 func (r *ReceiptForStorage) DecodeRLP(s *rlp.Stream) error {
+	// Retrieve the entire receipt blob as we need to try multiple decoders
+	blob, err := s.Raw()
+	if err != nil {
+		return err
+	}
+	// First try to decode the latest receipt database format, try the pre-bedrock Optimism legacy format otherwise.
+	if err := decodeStoredReceiptRLP(r, blob); err == nil {
+		return nil
+	}
+	return decodeLegacyOptimismReceiptRLP(r, blob)
+}
+
+func decodeLegacyOptimismReceiptRLP(r *ReceiptForStorage, blob []byte) error {
+	var stored LegacyOptimismStoredReceiptRLP
+	if err := rlp.DecodeBytes(blob, &stored); err != nil {
+		return err
+	}
+	if err := (*Receipt)(r).setStatus(stored.PostStateOrStatus); err != nil {
+		return err
+	}
+	r.CumulativeGasUsed = stored.CumulativeGasUsed
+	r.Logs = make([]*Log, len(stored.Logs))
+	for i, log := range stored.Logs {
+		r.Logs[i] = (*Log)(log)
+	}
+	r.Bloom = CreateBloom(Receipts{(*Receipt)(r)})
+	// UsingOVM
+	scalar := new(big.Float)
+	if stored.FeeScalar != "" {
+		var ok bool
+		scalar, ok = scalar.SetString(stored.FeeScalar)
+		if !ok {
+			return errors.New("cannot parse fee scalar")
+		}
+	}
+	r.L1GasUsed = stored.L1GasUsed
+	r.L1GasPrice = stored.L1GasPrice
+	r.L1Fee = stored.L1Fee
+	r.FeeScalar = scalar
+	return nil
+}
+
+func decodeStoredReceiptRLP(r *ReceiptForStorage, blob []byte) error {
 	var stored storedReceiptRLP
-	if err := s.Decode(&stored); err != nil {
+	if err := rlp.DecodeBytes(blob, &stored); err != nil {
 		return err
 	}
 	if err := (*Receipt)(r).setStatus(stored.PostStateOrStatus); err != nil {