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/*
This file is part of solidity.
solidity 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.
solidity 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 solidity. If not, see <http://www.gnu.org/licenses/>.
*/
/** @file PathGasMeter.cpp
* @author Christian <c@ethdev.com>
* @date 2015
*/
#pragma once
#include <libevmasm/GasMeter.h>
#include <liblangutil/EVMVersion.h>
#include <set>
#include <vector>
#include <memory>
namespace dev
{
namespace eth
{
class KnownState;
struct GasPath
{
size_t index = 0;
std::shared_ptr<KnownState> state;
u256 largestMemoryAccess;
GasMeter::GasConsumption gas;
std::set<size_t> visitedJumpdests;
};
/**
* Computes an upper bound on the gas usage of a computation starting at a certain position in
* a list of AssemblyItems in a given state until the computation stops.
* Can be used to estimate the gas usage of functions on any given input.
*/
class PathGasMeter
{
public:
explicit PathGasMeter(AssemblyItems const& _items, solidity::EVMVersion _evmVersion);
GasMeter::GasConsumption estimateMax(size_t _startIndex, std::shared_ptr<KnownState> const& _state);
static GasMeter::GasConsumption estimateMax(
AssemblyItems const& _items,
solidity::EVMVersion _evmVersion,
size_t _startIndex,
std::shared_ptr<KnownState> const& _state
)
{
return PathGasMeter(_items, _evmVersion).estimateMax(_startIndex, _state);
}
private:
/// Adds a new path item to the queue, but only if we do not already have
/// a higher gas usage at that point.
/// This is not exact as different state might influence higher gas costs at a later
/// point in time, but it greatly reduces computational overhead.
void queue(std::unique_ptr<GasPath>&& _newPath);
GasMeter::GasConsumption handleQueueItem();
/// Map of jumpdest -> gas path, so not really a queue. We only have one queued up
/// item per jumpdest, because of the behaviour of `queue` above.
std::map<size_t, std::unique_ptr<GasPath>> m_queue;
std::map<size_t, GasMeter::GasConsumption> m_highestGasUsagePerJumpdest;
std::map<u256, size_t> m_tagPositions;
AssemblyItems const& m_items;
solidity::EVMVersion m_evmVersion;
};
}
}
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