Merge pull request #644 from QuorumEngineering/estimategas-for-privatetransaction

EstimateGas to handle private transaction gas cost differences

internal/ethapi/api.go

@@ -55,6 +55,9 @@ import (
 
 const (
 	defaultGasPrice = 50 * params.Shannon
+
+	//Hex-encoded 64 byte array of "17" values
+	maxPrivateIntrinsicDataHex = "11111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111"
 )
 
 // PublicEthereumAPI provides an API to access Ethereum related information.
@@ -771,6 +774,33 @@ func (s *PublicBlockChainAPI) EstimateGas(ctx context.Context, args CallArgs) (h
 			return 0, fmt.Errorf("gas required exceeds allowance or always failing transaction")
 		}
 	}
+
+	//QUORUM
+
+	//We don't know if this is going to be a private or public transaction
+	//It is possible to have a data field that has a lower intrinsic value than the PTM hash
+	//so this checks that if we were to place a PTM hash (with all non-zero values) here then the transaction would
+	//still run
+	//This makes the return value a potential over-estimate of gas, rather than the exact cost to run right now
+
+	//if the transaction has a value then it cannot be private, so we can skip this check
+	if args.Value.ToInt().Cmp(big.NewInt(0)) == 0 {
+
+		isHomestead := s.b.ChainConfig().IsHomestead(new(big.Int).SetInt64(int64(rpc.PendingBlockNumber)))
+		intrinsicGasPublic, _ := core.IntrinsicGas(args.Data, args.To == nil, isHomestead)
+		intrinsicGasPrivate, _ := core.IntrinsicGas(common.Hex2Bytes(maxPrivateIntrinsicDataHex), args.To == nil, isHomestead)
+
+		if intrinsicGasPrivate > intrinsicGasPublic {
+			if math.MaxUint64 - hi < intrinsicGasPrivate - intrinsicGasPublic {
+				return 0, fmt.Errorf("private intrinsic gas addition exceeds allowance")
+			}
+			return hexutil.Uint64(hi + (intrinsicGasPrivate - intrinsicGasPublic)), nil
+		}
+
+	}
+
+	//END QUORUM
+
 	return hexutil.Uint64(hi), nil
 }