path: root/LValue.h

/*
    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/>.
*/
/**
 * @author Christian <c@ethdev.com>
 * @date 2015
 * LValues for use in the expresison compiler.
 */

#pragma once

#include <memory>
#include <libevmcore/SourceLocation.h>

namespace dev
{
namespace solidity
{

class Declaration;
class Type;
class CompilerContext;

/**
 * Abstract class used to retrieve, delete and store data in lvalues/variables.
 */
class LValue
{
protected:
    LValue(CompilerContext& _compilerContext, std::shared_ptr<Type const> const& _dataType):
        m_context(_compilerContext), m_dataType(_dataType) {}

public:
    /// @returns true if this lvalue reference type occupies a slot on the stack.
    virtual bool storesReferenceOnStack() const = 0;
    /// Copies the value of the current lvalue to the top of the stack and, if @a _remove is true,
    /// also removes the reference from the stack.
    /// @a _location source location of the current expression, used for error reporting.
    virtual void retrieveValue(SourceLocation const& _location, bool _remove = false) const = 0;
    /// Moves a value from the stack to the lvalue. Removes the value if @a _move is true.
    /// @a _location is the source location of the expression that caused this operation.
    /// Stack pre: value [lvalue_ref]
    /// Stack post if !_move: value_of(lvalue_ref)
    virtual void storeValue(Type const& _sourceType,
        SourceLocation const& _location = SourceLocation(), bool _move = false) const = 0;
    /// Stores zero in the lvalue.
    /// @a _location is the source location of the requested operation
    virtual void setToZero(SourceLocation const& _location = SourceLocation()) const = 0;

protected:
    CompilerContext& m_context;
    std::shared_ptr<Type const> m_dataType;
};

/**
 * Local variable that is completely stored on the stack.
 */
class StackVariable: public LValue
{
public:
    explicit StackVariable(CompilerContext& _compilerContext, Declaration const& _declaration);

    virtual bool storesReferenceOnStack() const { return false; }
    virtual void retrieveValue(SourceLocation const& _location, bool _remove = false) const override;
    virtual void storeValue(Type const& _sourceType,
        SourceLocation const& _location = SourceLocation(), bool _move = false) const override;
    virtual void setToZero(SourceLocation const& _location = SourceLocation()) const override;

private:
    /// Base stack offset (@see CompilerContext::getBaseStackOffsetOfVariable) of the local variable.
    unsigned m_baseStackOffset;
    /// Number of stack elements occupied by the value (not the reference).
    unsigned m_size;
};

/**
 * Reference to some item in storage. The (starting) position of the item is stored on the stack.
 */
class StorageItem: public LValue
{
public:
    /// Constructs the LValue and pushes the location of @a _declaration onto the stack.
    explicit StorageItem(CompilerContext& _compilerContext, Declaration const& _declaration);
    /// Constructs the LValue and assumes that the storage reference is already on the stack.
    explicit StorageItem(CompilerContext& _compilerContext, std::shared_ptr<Type const> const& _type);
    virtual bool storesReferenceOnStack() const { return true; }
    virtual void retrieveValue(SourceLocation const& _location, bool _remove = false) const override;
    virtual void storeValue(Type const& _sourceType,
        SourceLocation const& _location = SourceLocation(), bool _move = false) const override;
    virtual void setToZero(SourceLocation const& _location = SourceLocation()) const override;

private:
    /// Number of stack elements occupied by the value (not the reference).
    /// Only used for value types.
    unsigned m_size;
};

}
}