memcache.h

Go to the documentation of this file.

 
#ifndef CPPCOMMON_CACHE_MEMCACHE_H
#define CPPCOMMON_CACHE_MEMCACHE_H
 
#include "time/timespan.h"
#include "time/timestamp.h"
 
#include <mutex>
#include <map>
#include <shared_mutex>
#include <unordered_map>
 
namespace CppCommon {
 
 
template <typename TKey, typename TValue>
class MemCache
{
public:
    MemCache() = default;
    MemCache(const MemCache&) = delete;
    MemCache(MemCache&&) = delete;
    ~MemCache() = default;
 
    MemCache& operator=(const MemCache&) = delete;
    MemCache& operator=(MemCache&&) = delete;
 
    explicit operator bool() const { return !empty(); }
 
    bool empty() const;
 
    size_t size() const;
 
 
    bool emplace(TKey&& key, TValue&& value, const Timespan& timeout = Timespan(0));
 
 
    bool insert(const TKey& key, const TValue& value, const Timespan& timeout = Timespan(0));
 
 
    bool find(const TKey& key);
 
    bool find(const TKey& key, TValue& value);
 
    bool find(const TKey& key, TValue& value, Timestamp& timeout);
 
 
    bool remove(const TKey& key);
 
    void clear();
 
    void watchdog(const UtcTimestamp& utc = UtcTimestamp());
 
    void swap(MemCache& cache) noexcept;
    template <typename UKey, typename UValue>
    friend void swap(MemCache<UKey, UValue>& cache1, MemCache<UKey, UValue>& cache2) noexcept;
 
private:
    mutable std::shared_mutex _lock;
    Timestamp _timestamp;
 
    struct MemCacheEntry
    {
        TValue value;
        Timestamp timestamp;
        Timespan timespan;
 
        MemCacheEntry() = default;
        MemCacheEntry(const TValue& v, const Timestamp& ts = Timestamp(), const Timespan& tp = Timespan()) : value(v), timestamp(ts), timespan(tp) {}
        MemCacheEntry(TValue&& v, const Timestamp& ts = Timestamp(), const Timespan& tp = Timespan()) : value(v), timestamp(ts), timespan(tp) {}
    };
 
    std::unordered_map<TKey, MemCacheEntry> _entries_by_key;
    std::map<Timestamp, TKey> _entries_by_timestamp;
 
    bool remove_internal(const TKey& key);
};
 
} // namespace CppCommon
 
#include "memcache.inl"
 
#endif // CPPCOMMON_CACHE_MEMCACHE_H