Add connection_pool_factory, use it as the default

1 files changed, 90 insertions, 0 deletions

diff --git a/odb/mysql/connection-factory.hxx b/odb/mysql/connection-factory.hxx
index ef86224..bb439a8 100644
--- a/odb/mysql/connection-factory.hxx
+++ b/odb/mysql/connection-factory.hxx
@@ -6,12 +6,18 @@
 #ifndef ODB_MYSQL_CONNECTION_FACTORY_HXX
 #define ODB_MYSQL_CONNECTION_FACTORY_HXX
 
+#include <vector>
+#include <cstddef> // std::size_t
+
 #include <odb/shared-ptr.hxx>
 
 #include <odb/mysql/version.hxx>
 #include <odb/mysql/forward.hxx>
 #include <odb/mysql/connection.hxx>
 
+#include <odb/details/mutex.hxx>
+#include <odb/details/condition.hxx>
+
 namespace odb
 {
   namespace mysql
@@ -47,8 +53,92 @@ namespace odb
       database (database_type&);
 
     private:
+      new_connection_factory (const new_connection_factory&);
+      new_connection_factory& operator= (const new_connection_factory&);
+
+    private:
       database_type* db_;
     };
+
+    class connection_pool_factory: public connection_factory
+    {
+    public:
+      // The max_connections argument specifies the maximum number of
+      // concurrent connections this pool will maintain. If this value
+      // is 0 then the pool will create a new connection every time all
+      // of the existing connections are in use.
+      //
+      // The min_connections argument specifies the minimum number of
+      // connections that should be maintained by the pool. If the
+      // number of connections maintained by the pool exceeds this
+      // number and there are no active waiters for a new connection,
+      // then the pool will release the excess connections. If this
+      // value is 0 then the pool will maintain all the connections
+      // that were ever created.
+      //
+      connection_pool_factory (std::size_t max_connections = 0,
+                               std::size_t min_connections = 0)
+          : max_ (max_connections),
+            min_ (min_connections),
+            in_use_ (0),
+            waiters_ (0),
+            db_ (0),
+            cond_ (mutex_)
+      {
+      }
+
+      virtual shared_ptr<connection>
+      connect ();
+
+      virtual void
+      database (database_type&);
+
+      virtual
+      ~connection_pool_factory ();
+
+    private:
+      connection_pool_factory (const connection_pool_factory&);
+      connection_pool_factory& operator= (const connection_pool_factory&);
+
+    private:
+      class pooled_connection: public connection
+      {
+      public:
+        // NULL pool value indicates that the connection is not in use.
+        //
+        pooled_connection (database_type&, connection_pool_factory*);
+
+      private:
+        static void
+        zero_counter (void*);
+
+      private:
+        friend class connection_pool_factory;
+
+        shared_base::refcount_callback callback_;
+        connection_pool_factory* pool_;
+      };
+
+      friend class pooled_connection;
+      typedef std::vector<shared_ptr<pooled_connection> > connections;
+
+    private:
+      void
+      release (pooled_connection*);
+
+    private:
+      const std::size_t max_;
+      const std::size_t min_;
+
+      std::size_t in_use_;  // Number of connections currently in use.
+      std::size_t waiters_; // Number of threads waiting for a connection.
+
+      database_type* db_;
+      connections connections_;
+
+      details::mutex mutex_;
+      details::condition cond_;
+    };
   }
 }