Allow configuration of target gas limit.

parity/main.rs

@@ -115,6 +115,7 @@ API and Console Options:
 
 Sealing/Mining Options:
   --gas-price WEI          Minimum amount of Wei to be paid for a transaction to be accepted for mining [default: 20000000000].
+  --gas-floor-target GAS   Amount of gas per block to target when sealing a new block [default: 4712388].
   --author ADDRESS         Specify the block author (aka "coinbase") address for sending block rewards
                            from sealed blocks [default: 0037a6b811ffeb6e072da21179d11b1406371c63].
   --extra-data STRING      Specify a custom extra-data for authored blocks, no more than 32 characters.
@@ -178,6 +179,7 @@ struct Args {
 	flag_jsonrpc_apis: String,
 	flag_author: String,
 	flag_gas_price: String,
+	flag_gas_floor_target: String,
 	flag_extra_data: Option<String>,
 	flag_logging: Option<String>,
 	flag_version: bool,
@@ -303,6 +305,13 @@ impl Configuration {
 		})
 	}
 
+	fn gas_floor_target(&self) -> U256 {
+		let d = &self.args.flag_gas_floor_target;
+		U256::from_dec_str(d).unwrap_or_else(|_| {
+			die!("{}: Invalid target gas floor given. Must be a decimal unsigned 256-bit number.", d)
+		})
+	}
+
 	fn gas_price(&self) -> U256 {
 		let d = self.args.flag_gasprice.as_ref().unwrap_or(&self.args.flag_gas_price);
 		U256::from_dec_str(d).unwrap_or_else(|_| {
@@ -485,6 +494,7 @@ impl Configuration {
 		// Miner
 		let miner = Miner::new();
 		miner.set_author(self.author());
+		miner.set_gas_floor_target(self.gas_floor_target());
 		miner.set_extra_data(self.extra_data());
 		miner.set_minimal_gas_price(self.gas_price());