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/*
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 <tuple>
#include <libevmasm/ExpressionClasses.h>
#include <libevmasm/AssemblyItem.h>
namespace dev
{
namespace eth
{
class KnownState;
namespace GasCosts
{
static unsigned const stackLimit = 1024;
static unsigned const tier0Gas = 0;
static unsigned const tier1Gas = 2;
static unsigned const tier2Gas = 3;
static unsigned const tier3Gas = 5;
static unsigned const tier4Gas = 8;
static unsigned const tier5Gas = 10;
static unsigned const tier6Gas = 20;
static unsigned const tier7Gas = 0;
static unsigned const expGas = 10;
static unsigned const expByteGas = 10;
static unsigned const sha3Gas = 30;
static unsigned const sha3WordGas = 6;
static unsigned const sloadGas = 50;
static unsigned const sstoreSetGas = 20000;
static unsigned const sstoreResetGas = 5000;
static unsigned const sstoreRefundGas = 15000;
static unsigned const jumpdestGas = 1;
static unsigned const logGas = 375;
static unsigned const logDataGas = 8;
static unsigned const logTopicGas = 375;
static unsigned const createGas = 32000;
static unsigned const callGas = 40;
static unsigned const callStipend = 2300;
static unsigned const callValueTransferGas = 9000;
static unsigned const callNewAccountGas = 25000;
static unsigned const suicideRefundGas = 24000;
static unsigned const memoryGas = 3;
static unsigned const quadCoeffDiv = 512;
static unsigned const createDataGas = 200;
static unsigned const txGas = 21000;
static unsigned const txCreateGas = 53000;
static unsigned const txDataZeroGas = 4;
static unsigned const txDataNonZeroGas = 68;
static unsigned const copyGas = 3;
}
/**
* Class that helps computing the maximum gas consumption for instructions.
* Has to be initialized with a certain known state that will be automatically updated for
* each call to estimateMax. These calls have to supply strictly subsequent AssemblyItems.
* A new gas meter has to be constructed (with a new state) for control flow changes.
*/
class GasMeter
{
public:
struct GasConsumption
{
GasConsumption(unsigned _value = 0, bool _infinite = false): value(_value), isInfinite(_infinite) {}
GasConsumption(u256 _value, bool _infinite = false): value(_value), isInfinite(_infinite) {}
static GasConsumption infinite() { return GasConsumption(0, true); }
GasConsumption& operator+=(GasConsumption const& _other);
bool operator<(GasConsumption const& _other) const { return this->tuple() < _other.tuple(); }
std::tuple<bool const&, u256 const&> tuple() const { return std::tie(isInfinite, value); }
u256 value;
bool isInfinite;
};
/// Constructs a new gas meter given the current state.
explicit GasMeter(std::shared_ptr<KnownState> const& _state, u256 const& _largestMemoryAccess = 0):
m_state(_state), m_largestMemoryAccess(_largestMemoryAccess) {}
/// @returns an upper bound on the gas consumed by the given instruction and updates
/// the state.
GasConsumption estimateMax(AssemblyItem const& _item);
u256 const& largestMemoryAccess() const { return m_largestMemoryAccess; }
static unsigned runGas(Instruction _instruction);
private:
/// @returns _multiplier * (_value + 31) / 32, if _value is a known constant and infinite otherwise.
GasConsumption wordGas(u256 const& _multiplier, ExpressionClasses::Id _value);
/// @returns the gas needed to access the given memory position.
/// @todo this assumes that memory was never accessed before and thus over-estimates gas usage.
GasConsumption memoryGas(ExpressionClasses::Id _position);
/// @returns the memory gas for accessing the memory at a specific offset for a number of bytes
/// given as values on the stack at the given relative positions.
GasConsumption memoryGas(int _stackPosOffset, int _stackPosSize);
std::shared_ptr<KnownState> m_state;
/// Largest point where memory was accessed since the creation of this object.
u256 m_largestMemoryAccess;
};
inline std::ostream& operator<<(std::ostream& _str, GasMeter::GasConsumption const& _consumption)
{
if (_consumption.isInfinite)
return _str << "[???]";
else
return _str << std::dec << _consumption.value;
}
}
}
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