GasEstimator.h

/*
	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/>.
*/
/**
 * @author Christian <c@ethdev.com>
 * @date 2015
 * Gas consumption estimator working alongside the AST.
 */

#pragma once

#include <vector>
#include <map>
#include <array>
#include <libevmasm/GasMeter.h>
#include <libevmasm/Assembly.h>

namespace dev
{
namespace solidity
{

class ASTNode;
class FunctionDefinition;

struct GasEstimator
{
public:
	using GasConsumption = eth::GasMeter::GasConsumption;
	using ASTGasConsumption = std::map<ASTNode const*, GasConsumption>;
	using ASTGasConsumptionSelfAccumulated =
		std::map<ASTNode const*, std::array<GasConsumption, 2>>;

	/// Estimates the gas consumption for every assembly item in the given assembly and stores
	/// it by source location.
	/// @returns a mapping from each AST node to a pair of its particular and syntactically accumulated gas costs.
	static ASTGasConsumptionSelfAccumulated structuralEstimation(
		eth::AssemblyItems const& _items,
		std::vector<ASTNode const*> const& _ast
	);
	/// @returns a mapping from nodes with non-overlapping source locations to gas consumptions such that
	/// the following source locations are part of the mapping:
	/// 1. source locations of statements that do not contain other statements
	/// 2. maximal source locations that do not overlap locations coming from the first rule
	static ASTGasConsumption breakToStatementLevel(
		ASTGasConsumptionSelfAccumulated const& _gasCosts,
		std::vector<ASTNode const*> const& _roots
	);

	/// @returns the estimated gas consumption by the (public or external) function with the
	/// given signature. If no signature is given, estimates the maximum gas usage.
	static GasConsumption functionalEstimation(
		eth::AssemblyItems const& _items,
		std::string const& _signature = ""
	);

	/// @returns the estimated gas consumption by the given function which starts at the given
	/// offset into the list of assembly items.
	/// @note this does not work correctly for recursive functions.
	static GasConsumption functionalEstimation(
		eth::AssemblyItems const& _items,
		size_t const& _offset,
		FunctionDefinition const& _function
	);

private:
	/// @returns the set of AST nodes which are the finest nodes at their location.
	static std::set<ASTNode const*> finestNodesAtLocation(std::vector<ASTNode const*> const& _roots);
};

}
}