Clean up JSONCache

modules/ripple_data/utility/ripple_JSONCache.h

@@ -0,0 +1,92 @@
+#ifndef RIPPLE_JSCONCACHE_H
+#define RIPPLE_JSCONCACHE_H
+
+/** A simple cache for JSON.
+
+    @note All member functions are thread-safe.
+*/
+class JSONCache
+{
+public:
+    class Key
+    {
+    public:
+        Key (int op, const uint256& ledger, const uint160& object, int lastUse);
+        int compare(const Key& k) const;
+        bool operator<(const Key &k) const;
+        bool operator>(const Key &k) const;
+        bool operator<=(const Key &k) const;    
+        bool operator>=(const Key &k) const;
+        bool operator!=(const Key &k) const;
+        bool operator==(const Key &k) const;
+
+        void touch (Key const& key)    const;
+        bool isExpired (int expireTime) const;
+
+        std::size_t getHash () const;
+
+    private:
+        uint256            mLedger;
+        uint160            mObject;
+        int                mOperation;
+        mutable int        mLastUse;
+        std::size_t        mHash;
+    };
+
+public:
+    typedef boost::shared_ptr <Json::Value> data_t;
+
+public:
+    enum Kind
+    {
+        kindLines,
+        kindOffers
+    };
+
+    /** Construct the cache.
+
+        @param expirationTimeInSeconds The time until cached items expire, in seconds.
+    */
+    explicit JSONCache (int expirationTimeInSeconds);
+
+    /** Return the fraction of cache hits.
+    */
+    float getHitRate ();
+
+    /** Return the number of cached items.
+    */
+    int getNumberOfEntries ();
+
+    /** Retrieve a cached item.
+
+        @return The item, or a default constructed container if it was not found.
+    */
+    data_t getEntry (Kind kind, LedgerHash const& ledger, uint160 const& object);
+
+    /** Store an item in the cache.
+    */
+    void storeEntry (Kind kind, LedgerHash const& ledger, uint160 const& object, data_t const& data);
+
+    /** Purge expired items.
+
+        This must be called periodically.
+    */
+    void sweep ();
+
+private:
+    int getUptime () const;
+
+private:
+    int const m_expirationTime;
+    boost::unordered_map <Key, data_t> m_cache;
+    boost::recursive_mutex m_lock;
+    uint64 mHits;
+    uint64 mMisses;
+};
+
+inline std::size_t hash_value (JSONCache::Key const& key)
+{
+    return key.getHash ();
+}
+
+#endif