beacon/engine, rpc: use json.Marshaler for direct result encoding

beacon/engine/gen_epe.go

@@ -12,31 +12,6 @@ import (
 
 var _ = (*executionPayloadEnvelopeMarshaling)(nil)
 
-// MarshalJSON marshals as JSON.
-func (e ExecutionPayloadEnvelope) MarshalJSON() ([]byte, error) {
-	type ExecutionPayloadEnvelope struct {
-		ExecutionPayload *ExecutableData `json:"executionPayload"  gencodec:"required"`
-		BlockValue       *hexutil.Big    `json:"blockValue"  gencodec:"required"`
-		BlobsBundle      *BlobsBundle    `json:"blobsBundle"`
-		Requests         []hexutil.Bytes `json:"executionRequests"`
-		Override         bool            `json:"shouldOverrideBuilder"`
-		Witness          *hexutil.Bytes  `json:"witness,omitempty"`
-	}
-	var enc ExecutionPayloadEnvelope
-	enc.ExecutionPayload = e.ExecutionPayload
-	enc.BlockValue = (*hexutil.Big)(e.BlockValue)
-	enc.BlobsBundle = e.BlobsBundle
-	if e.Requests != nil {
-		enc.Requests = make([]hexutil.Bytes, len(e.Requests))
-		for k, v := range e.Requests {
-			enc.Requests[k] = v
-		}
-	}
-	enc.Override = e.Override
-	enc.Witness = e.Witness
-	return json.Marshal(&enc)
-}
-
 // UnmarshalJSON unmarshals from JSON.
 func (e *ExecutionPayloadEnvelope) UnmarshalJSON(input []byte) error {
 	type ExecutionPayloadEnvelope struct {

beacon/engine/marshal_epe.go

@@ -68,9 +68,6 @@ func marshalHexBytesArray(buf []byte, items []hexutil.Bytes) []byte {
 }
 
 // writeHexBytes writes a hex-encoded byte slice as a JSON string ("0x...") to buf.
-// NOTE: This function avoids allocations by pre-allocating the buffer space needed;
-// otherwise, we would use hexutil.Encode() and append the result to the buffer.
-// hexutil.Encode() uses 64% more memory than writing to buffer directly.
 func writeHexBytes(buf []byte, data []byte) []byte {
 	buf = append(buf, '"', '0', 'x')
 	buf = slices.Grow(buf, len(data)*2+1)
@@ -81,10 +78,8 @@ func writeHexBytes(buf []byte, data []byte) []byte {
 	return buf
 }
 
-// PremarshaledJSON implements rpc.JSONPremarshaled. It returns pre-serialized
-// JSON by delegating small fields to their existing MarshalJSON methods and
-// hand-rolling only the BlobsBundle.
-func (e ExecutionPayloadEnvelope) PremarshaledJSON() ([]byte, error) {
+// MarshalJSON implements json.Marshaler.
+func (e ExecutionPayloadEnvelope) MarshalJSON() ([]byte, error) {
 	// Marshal the execution payload using its gencodec MarshalJSON.
 	payload, err := e.ExecutionPayload.MarshalJSON()
 	if err != nil {

eth/catalyst/api_benchmark_test.go

@@ -47,7 +47,7 @@ type encodingType int
 const (
 	encNone encodingType = iota
 	encJSON
-	encJSONPremarshaled
+	encJSONCustom
 	encRLP
 )
 
@@ -57,8 +57,8 @@ func (e encodingType) String() string {
 		return "none"
 	case encJSON:
 		return "json"
-	case encJSONPremarshaled:
-		return "json_premarshaled"
+	case encJSONCustom:
+		return "json_custom"
 	case encRLP:
 		return "rlp"
 	default:
@@ -66,7 +66,7 @@ func (e encodingType) String() string {
 	}
 }
 
-var encodingTypes = []encodingType{encNone, encJSON, encJSONPremarshaled, encRLP}
+var encodingTypes = []encodingType{encNone, encJSON, encJSONCustom, encRLP}
 
 // benchEncode encodes the value using the specified encoding type.
 // It fails the benchmark if encoding fails.
@@ -78,14 +78,14 @@ func benchEncode(b *testing.B, enc encodingType, v any) {
 		if err != nil {
 			b.Fatalf("JSON marshal failed: %v", err)
 		}
-	case encJSONPremarshaled:
-		if pm, ok := v.(rpc.JSONPremarshaled); ok {
-			_, err = pm.PremarshaledJSON()
+	case encJSONCustom:
+		if m, ok := v.(json.Marshaler); ok {
+			_, err = m.MarshalJSON()
 		} else {
 			_, err = json.Marshal(v)
 		}
 		if err != nil {
-			b.Fatalf("JSON premarshaled marshal failed: %v", err)
+			b.Fatalf("JSON MarshalJSON failed: %v", err)
 		}
 	case encRLP:
 		_, err = rlp.EncodeToBytes(v)

rpc/json.go

@@ -113,20 +113,13 @@ func (msg *jsonrpcMessage) errorResponse(err error) *jsonrpcMessage {
 	return resp
 }
 
-// JSONPremarshaled may be implemented by RPC return types that provide
-// pre-serialized JSON. This bypasses json.Marshal and its re-validation
-// pass. Implementors must ensure the returned bytes are valid JSON.
-type JSONPremarshaled interface {
-	PremarshaledJSON() ([]byte, error)
-}
-
 func (msg *jsonrpcMessage) response(result interface{}) *jsonrpcMessage {
 	var (
 		enc []byte
 		err error
 	)
-	if pm, ok := result.(JSONPremarshaled); ok {
-		enc, err = pm.PremarshaledJSON()
+	if m, ok := result.(json.Marshaler); ok {
+		enc, err = m.MarshalJSON()
 	} else {
 		enc, err = json.Marshal(result)
 	}