path: root/libyul/YulString.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/>.
*/
/**
 * String abstraction that avoids copies.
 */

#pragma once

#include <boost/noncopyable.hpp>

#include <map>
#include <memory>
#include <vector>
#include <string>

namespace dev
{
namespace yul
{

class YulStringRepository: boost::noncopyable
{
public:
    YulStringRepository(): m_strings{std::make_shared<std::string>()}
    {
        m_ids[std::string{}] = 0;
    }
    static YulStringRepository& instance()
    {
        static YulStringRepository inst;
        return inst;
    }
    size_t stringToId(std::string const& _string)
    {
        if (_string.empty())
            return 0;
        size_t& id = m_ids[_string];
        if (id == 0)
        {
            m_strings.emplace_back(std::make_shared<std::string>(_string));
            id = m_strings.size() - 1;
        }
        return id;
    }
    std::string const& idToString(size_t _id) const
    {
        return *m_strings.at(_id);
    }

private:
    std::vector<std::shared_ptr<std::string>> m_strings;
    std::map<std::string, size_t> m_ids;
};

class YulString
{
public:
    YulString() = default;
    explicit YulString(std::string const& _s): m_id(YulStringRepository::instance().stringToId(_s)) {}
    YulString(YulString const&) = default;
    YulString(YulString&&) = default;
    YulString& operator=(YulString const&) = default;
    YulString& operator=(YulString&&) = default;

    /// This is not consistent with the string <-operator!
    bool operator<(YulString const& _other) const { return m_id < _other.m_id; }
    bool operator==(YulString const& _other) const { return m_id == _other.m_id; }
    bool operator!=(YulString const& _other) const { return m_id != _other.m_id; }

    bool empty() const { return m_id == 0; }
    std::string const& str() const
    {
        return YulStringRepository::instance().idToString(m_id);
    }

private:
    /// ID of the string. Assumes that the empty string has ID zero.
    size_t m_id = 0;
};

}
}