From 4d62c463d143c93f7938db5b8f7d01d33aa1a698 Mon Sep 17 00:00:00 2001
From: chriseth <c@ethdev.com>
Date: Wed, 6 May 2015 10:43:59 +0200
Subject: Structural gas estimator.
---
GasMeter.cpp | 104 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
GasMeter.h | 67 ++++++++++++++++++++++++++++++++++++++
2 files changed, 171 insertions(+)
create mode 100644 GasMeter.cpp
create mode 100644 GasMeter.h
diff --git a/GasMeter.cpp b/GasMeter.cpp
new file mode 100644
index 00000000..e5fb0e09
--- /dev/null
+++ b/GasMeter.cpp
@@ -0,0 +1,104 @@
+/*
+ This file is part of cpp-ethereum.
+
+ cpp-ethereum is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ cpp-ethereum is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with cpp-ethereum. If not, see <http://www.gnu.org/licenses/>.
+*/
+/** @file GasMeter.cpp
+ * @author Christian <c@ethdev.com>
+ * @date 2015
+ */
+
+#include "GasMeter.h"
+#include <libevmcore/Params.h>
+
+using namespace std;
+using namespace dev;
+using namespace dev::eth;
+
+GasMeter::GasConsumption& GasMeter::GasConsumption::operator+=(GasConsumption const& _other)
+{
+ isInfinite = isInfinite || _other.isInfinite;
+ if (isInfinite)
+ return *this;
+ bigint v = bigint(value) + _other.value;
+ if (v > std::numeric_limits<u256>::max())
+ isInfinite = true;
+ else
+ value = u256(v);
+ return *this;
+}
+
+GasMeter::GasConsumption GasMeter::estimateMax(AssemblyItem const& _item)
+{
+ switch (_item.type()) {
+ case Push:
+ case PushTag:
+ return runGas(Instruction::PUSH1);
+ case Tag:
+ return runGas(Instruction::JUMPDEST);
+ case Operation:
+ {
+ GasConsumption gas = runGas(_item.instruction());
+ switch (_item.instruction())
+ {
+ case Instruction::SSTORE:
+ // @todo logic can be improved
+ gas += c_sstoreSetGas;
+ break;
+ case Instruction::SLOAD:
+ gas += c_sloadGas;
+ break;
+ case Instruction::MSTORE:
+ case Instruction::MSTORE8:
+ case Instruction::MLOAD:
+ case Instruction::RETURN:
+ case Instruction::SHA3:
+ case Instruction::CALLDATACOPY:
+ case Instruction::CODECOPY:
+ case Instruction::EXTCODECOPY:
+ case Instruction::LOG0:
+ case Instruction::LOG1:
+ case Instruction::LOG2:
+ case Instruction::LOG3:
+ case Instruction::LOG4:
+ case Instruction::CALL:
+ case Instruction::CALLCODE:
+ case Instruction::CREATE:
+ case Instruction::EXP:
+ // @todo logic can be improved
+ gas = GasConsumption::infinite();
+ break;
+ default:
+ break;
+ }
+ return gas;
+ break;
+ }
+ default:
+ break;
+ }
+
+ return GasConsumption::infinite();
+}
+
+GasMeter::GasConsumption GasMeter::runGas(Instruction _instruction)
+{
+ if (_instruction == Instruction::JUMPDEST)
+ return GasConsumption(1);
+
+ int tier = instructionInfo(_instruction).gasPriceTier;
+ return tier == InvalidTier ? GasConsumption::infinite() : c_tierStepGas[tier];
+}
+
+
diff --git a/GasMeter.h b/GasMeter.h
new file mode 100644
index 00000000..63dbc138
--- /dev/null
+++ b/GasMeter.h
@@ -0,0 +1,67 @@
+/*
+ This file is part of cpp-ethereum.
+
+ cpp-ethereum is free software: you can redistribute it and/or modify
+ it under the terms of the GNU General Public License as published by
+ the Free Software Foundation, either version 3 of the License, or
+ (at your option) any later version.
+
+ cpp-ethereum is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+ GNU General Public License for more details.
+
+ You should have received a copy of the GNU General Public License
+ along with cpp-ethereum. If not, see <http://www.gnu.org/licenses/>.
+*/
+/** @file GasMeter.cpp
+ * @author Christian <c@ethdev.com>
+ * @date 2015
+ */
+
+#pragma once
+
+#include <ostream>
+#include <libevmasm/AssemblyItem.h>
+
+namespace dev
+{
+namespace eth
+{
+
+/**
+ * Class that helps computing the maximum gas consumption for instructions.
+ */
+class GasMeter
+{
+public:
+ struct GasConsumption
+ {
+ GasConsumption(u256 _value = 0, bool _infinite = false): value(_value), isInfinite(_infinite) {}
+ static GasConsumption infinite() { return GasConsumption(0, true); }
+
+ GasConsumption& operator+=(GasConsumption const& _otherS);
+ std::ostream& operator<<(std::ostream& _str) const;
+
+ u256 value;
+ bool isInfinite;
+ };
+
+ /// Returns an upper bound on the gas consumed by the given instruction.
+ GasConsumption estimateMax(AssemblyItem const& _item);
+
+private:
+ static GasConsumption runGas(Instruction _instruction);
+};
+
+inline std::ostream& operator<<(std::ostream& _str, GasMeter::GasConsumption const& _consumption)
+{
+ if (_consumption.isInfinite)
+ return _str << "inf";
+ else
+ return _str << _consumption.value;
+}
+
+
+}
+}
--
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