solidity/libsolidity/codegen/ir/IRLValue.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/>.
*/
/**
 * Generator for code that handles LValues.
 */

#pragma once

#include <libdevcore/Common.h>

#include <string>
#include <ostream>
#include <boost/variant.hpp>

namespace dev
{
namespace solidity
{

class VariableDeclaration;
class IRGenerationContext;
class Type;
class ArrayType;

/**
 * Abstract class used to retrieve, delete and store data in LValues.
 */
class IRLValue
{
protected:
	IRLValue(IRGenerationContext& _context, Type const* _type = nullptr):
		m_context(_context),
		m_type(_type)
	{}

public:
	virtual ~IRLValue() = default;
	/// @returns an expression to retrieve the value of the lvalue.
	virtual std::string retrieveValue() const = 0;
	/// Returns code that stores the value of @a _value (should be an identifier)
	/// of type @a _type in the lvalue. Might perform type conversion.
	virtual std::string storeValue(std::string const& _value, Type const& _type) const = 0;

	/// Returns code that will reset the stored value to zero
	virtual std::string setToZero() const = 0;
protected:
	IRGenerationContext& m_context;
	Type const* m_type;
};

class IRLocalVariable: public IRLValue
{
public:
	IRLocalVariable(
		IRGenerationContext& _context,
		VariableDeclaration const& _varDecl
	);
	std::string retrieveValue() const override { return m_variableName; }
	std::string storeValue(std::string const& _value, Type const& _type) const override;

	std::string setToZero() const override;
private:
	std::string m_variableName;
};

class IRStorageItem: public IRLValue
{
public:
	IRStorageItem(
		IRGenerationContext& _context,
		VariableDeclaration const& _varDecl
	);
	IRStorageItem(
		IRGenerationContext& _context,
		std::string _slot,
		boost::variant<std::string, unsigned> _offset,
		Type const& _type
	);
	std::string retrieveValue() const override;
	std::string storeValue(std::string const& _value, Type const& _type) const override;

	std::string setToZero() const override;
private:
	IRStorageItem(
		IRGenerationContext& _context,
		Type const& _type,
		std::pair<u256, unsigned> slot_offset
	);

	std::string const m_slot;
	/// unsigned: Used when the offset is known at compile time, uses optimized
	///           functions
	/// string: Used when the offset is determined at run time
	boost::variant<std::string, unsigned> const m_offset;
};

/**
 * Reference to the "length" member of a dynamically-sized storage array. This is an LValue with special
 * semantics since assignments to it might reduce its length and thus the array's members have to be
 * deleted.
 */
class IRStorageArrayLength: public IRLValue
{
public:
	IRStorageArrayLength(IRGenerationContext& _context, std::string _slot, Type const& _type, ArrayType const& _arrayType);

	std::string retrieveValue() const override;
	std::string storeValue(std::string const& _value, Type const& _type) const override;
	std::string setToZero() const override;

private:
	ArrayType const& m_arrayType;
	std::string const m_slot;
};

}
}