[master] Merge branch 'trac2821'

src/lib/dhcpsrv/mysql_lease_mgr.h

@@ -19,6 +19,7 @@
 #include <dhcpsrv/lease_mgr.h>
 
 #include <boost/scoped_ptr.hpp>
+#include <boost/utility.hpp>
 #include <mysql/mysql.h>
 
 #include <time.h>
@@ -26,6 +27,54 @@
 namespace isc {
 namespace dhcp {
 
+/// @brief MySQL Handle Holder
+///
+/// Small RAII object for safer initialization, will close the database
+/// connection upon destruction.  This means that if an exception is thrown
+/// during database initialization, resources allocated to the database are
+/// guaranteed to be freed.
+///
+/// It makes no sense to copy an object of this class.  After the copy, both
+/// objects would contain pointers to the same MySql context object.  The
+/// destruction of one would invalid the context in the remaining object.
+/// For this reason, the class is declared noncopyable.
+class MySqlHolder : public boost::noncopyable {
+public:
+
+    /// @brief Constructor
+    ///
+    /// Initialize MySql and store the associated context object.
+    ///
+    /// @throw DbOpenError Unable to initialize MySql handle.
+    MySqlHolder() : mysql_(mysql_init(NULL)) {
+        if (mysql_ == NULL) {
+            isc_throw(DbOpenError, "unable to initialize MySQL");
+        }
+    }
+
+    /// @brief Destructor
+    ///
+    /// Frees up resources allocated by the initialization of MySql.
+    ~MySqlHolder() {
+        if (mysql_ != NULL) {
+            mysql_close(mysql_);
+        }
+        // The library itself shouldn't be needed anymore
+        mysql_library_end();
+    }
+
+    /// @brief Conversion Operator
+    ///
+    /// Allows the MySqlHolder object to be passed as the context argument to
+    /// mysql_xxx functions.
+    operator MYSQL*() const {
+        return (mysql_);
+    }
+
+private:
+    MYSQL* mysql_;      ///< Initialization context
+};
+
 // Define the current database schema values
 
 const uint32_t CURRENT_VERSION_VERSION = 1;
@@ -379,7 +428,7 @@ public:
     /// @param cltt Reference to location where client last transmit time
     ///        is put.
     static
-    void convertFromDatabaseTime(const MYSQL_TIME& expire, 
+    void convertFromDatabaseTime(const MYSQL_TIME& expire,
                                  uint32_t valid_lifetime, time_t& cltt);
     ///@}
 
@@ -616,7 +665,7 @@ private:
     /// declare them as "mutable".)
     boost::scoped_ptr<MySqlLease4Exchange> exchange4_; ///< Exchange object
     boost::scoped_ptr<MySqlLease6Exchange> exchange6_; ///< Exchange object
-    MYSQL*              mysql_;                 ///< MySQL context object
+    MySqlHolder mysql_;
     std::vector<MYSQL_STMT*> statements_;       ///< Prepared statements
     std::vector<std::string> text_statements_;  ///< Raw text of statements
 };