From a301c7502912165470aca1afa8163df5ea131c0f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?P=C3=A9ter=20Szil=C3=A1gyi?= <peterke@gmail.com>
Date: Tue, 4 Jul 2017 13:43:03 +0300
Subject: [PATCH] core: minor polishes to the Metropolis EIP 98 implementation

---
 core/state_processor.go |  3 ++-
 core/types/receipt.go   | 38 +++++++++++++++++++++++++++++---------
 2 files changed, 31 insertions(+), 10 deletions(-)

diff --git a/core/state_processor.go b/core/state_processor.go
index 158a9fa2df..4489cfce25 100644
--- a/core/state_processor.go
+++ b/core/state_processor.go
@@ -104,13 +104,14 @@ func ApplyTransaction(config *params.ChainConfig, bc *BlockChain, author *common
 	}
 
 	// Update the state with pending changes
-	usedGas.Add(usedGas, gas)
 	var root []byte
 	if config.IsMetropolis(header.Number) {
 		statedb.Finalise()
 	} else {
 		root = statedb.IntermediateRoot(config.IsEIP158(header.Number)).Bytes()
 	}
+	usedGas.Add(usedGas, gas)
+
 	// Create a new receipt for the transaction, storing the intermediate root and gas used by the tx
 	// based on the eip phase, we're passing wether the root touch-delete accounts.
 	receipt := types.NewReceipt(root, usedGas)
diff --git a/core/types/receipt.go b/core/types/receipt.go
index 46d2530bbc..a797da2e63 100644
--- a/core/types/receipt.go
+++ b/core/types/receipt.go
@@ -48,6 +48,8 @@ type receiptMarshaling struct {
 	GasUsed           *hexutil.Big
 }
 
+// homesteadReceiptRLP contains the receipt's Homestead consensus fields, used
+// during RLP serialization.
 type homesteadReceiptRLP struct {
 	PostState         []byte
 	CumulativeGasUsed *big.Int
@@ -55,6 +57,8 @@ type homesteadReceiptRLP struct {
 	Logs              []*Log
 }
 
+// metropolisReceiptRLP contains the receipt's Metropolis consensus fields, used
+// during RLP serialization.
 type metropolisReceiptRLP struct {
 	CumulativeGasUsed *big.Int
 	Bloom             Bloom
@@ -67,34 +71,50 @@ func NewReceipt(root []byte, cumulativeGasUsed *big.Int) *Receipt {
 }
 
 // EncodeRLP implements rlp.Encoder, and flattens the consensus fields of a receipt
-// into an RLP stream.
+// into an RLP stream. If no post state is present, metropolis fork is assumed.
 func (r *Receipt) EncodeRLP(w io.Writer) error {
 	if r.PostState == nil {
 		return rlp.Encode(w, &metropolisReceiptRLP{r.CumulativeGasUsed, r.Bloom, r.Logs})
-	} else {
-		return rlp.Encode(w, &homesteadReceiptRLP{r.PostState, r.CumulativeGasUsed, r.Bloom, r.Logs})
 	}
+	return rlp.Encode(w, &homesteadReceiptRLP{r.PostState, r.CumulativeGasUsed, r.Bloom, r.Logs})
 }
 
 // DecodeRLP implements rlp.Decoder, and loads the consensus fields of a receipt
 // from an RLP stream.
 func (r *Receipt) DecodeRLP(s *rlp.Stream) error {
+	// Load the raw bytes since we have multiple possible formats
 	raw, err := s.Raw()
 	if err != nil {
 		return err
 	}
-	var hr homesteadReceiptRLP
-	var mr metropolisReceiptRLP
-	if err = rlp.DecodeBytes(raw, &mr); err == nil {
-		r.CumulativeGasUsed, r.Bloom, r.Logs = mr.CumulativeGasUsed, mr.Bloom, mr.Logs
-	} else if err = rlp.DecodeBytes(raw, &hr); err == nil {
-		r.PostState, r.CumulativeGasUsed, r.Bloom, r.Logs = hr.PostState[:], hr.CumulativeGasUsed, hr.Bloom, hr.Logs
+	// Attempt to deserialize into a Metropolis format
+	var metro metropolisReceiptRLP
+	if err = rlp.DecodeBytes(raw, &metro); err == nil { // Keep the error in the outer scope!
+		r.CumulativeGasUsed = metro.CumulativeGasUsed
+		r.Bloom = metro.Bloom
+		r.Logs = metro.Logs
+
+		return nil
 	}
+	// Metropolis deserialization failed, attempt homestead
+	var home homesteadReceiptRLP
+	if err = rlp.DecodeBytes(raw, &home); err == nil { // Keep the error in the outer scope!
+		r.PostState = home.PostState[:]
+		r.CumulativeGasUsed = home.CumulativeGasUsed
+		r.Bloom = home.Bloom
+		r.Logs = home.Logs
+
+		return nil
+	}
+	// All decoders failed, return the last error
 	return err
 }
 
 // String implements the Stringer interface.
 func (r *Receipt) String() string {
+	if r.PostState == nil {
+		return fmt.Sprintf("receipt{cgas=%v bloom=%x logs=%v}", r.CumulativeGasUsed, r.Bloom, r.Logs)
+	}
 	return fmt.Sprintf("receipt{med=%x cgas=%v bloom=%x logs=%v}", r.PostState, r.CumulativeGasUsed, r.Bloom, r.Logs)
 }