CodeSizeCache.h

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/*
        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/>.
*/
#pragma once

#include <map>
#include <libdevcore/FixedHash.h>
#include <libdevcore/Guards.h>

namespace dev
{
namespace eth
{

class CodeSizeCache
{
public:
        void store(h256 const& _hash, size_t size)
        {
                UniqueGuard g(x_cache);
                if (m_cache.size() >= c_maxSize)
                        removeRandomElement();
                m_cache[_hash] = size;
        }
        bool contains(h256 const& _hash) const
        {
                UniqueGuard g(x_cache);
                return m_cache.count(_hash);
        }
        size_t get(h256 const& _hash) const
        {
                UniqueGuard g(x_cache);
                return m_cache.at(_hash);
        }

        static CodeSizeCache& instance() { static CodeSizeCache cache; return cache; }

private:
        void removeRandomElement()
        {
                if (!m_cache.empty())
                {
                        auto it = m_cache.lower_bound(h256::random());
                        if (it == m_cache.end())
                                it = m_cache.begin();
                        m_cache.erase(it);
                }
        }

        static const size_t c_maxSize = 50000;
        mutable Mutex x_cache;
        std::map<h256, size_t> m_cache;
};

}
}