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#pragma once
#include "base/logging.hpp"
#include <cstddef>
#include <string>
#include <unordered_map>
#include <utility>
namespace search
{
template <class Key, class Value>
class Cache
{
std::unordered_map<Key, Value> m_map;
/// query statistics
size_t m_accesses;
size_t m_misses;
size_t m_emptyQueriesCount; /// empty queries count at a row
std::string m_name; /// cache name for print functions
public:
explicit Cache(std::string const & name)
: m_accesses(0), m_misses(0), m_emptyQueriesCount(0), m_name(name)
{
}
std::pair<Value &, bool> Get(Key const & key)
{
auto r = m_map.insert(std::make_pair(key, Value()));
++m_accesses;
if (r.second)
++m_misses;
return std::pair<Value &, bool>(r.first->second, r.second);
}
void Clear()
{
m_map.clear();
m_accesses = m_misses = 0;
m_emptyQueriesCount = 0;
}
/// Called at the end of every search query.
void ClearIfNeeded()
{
if (m_accesses != 0)
{
LOG(LDEBUG, ("Cache", m_name, "Queries =", m_accesses, "From cache =", m_accesses - m_misses,
"Added =", m_misses));
m_accesses = m_misses = 0;
m_emptyQueriesCount = 0;
}
else if (++m_emptyQueriesCount > 5)
{
LOG(LDEBUG, ("Clearing cache", m_name));
Clear();
}
}
};
} // namespace search
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