C++ Dbt::get_flags方法代码示例

bool
Freeze::IteratorHelperI::find(const Dbt& key) const
{
    assert((key.get_flags() & DB_DBT_USERMEM) != 0);
    Dbt dbKey(key);

#if (DB_VERSION_MAJOR <= 4) || (DB_VERSION_MAJOR == 5 && DB_VERSION_MINOR <= 1)
    //
    // When we have a custom-comparison function, Berkeley DB returns
    // the key on-disk (when it finds one). We disable this behavior:
    // (ref Oracle SR 5925672.992)
    //
    dbKey.set_flags(dbKey.get_flags() | DB_DBT_PARTIAL);
#else
    //
    // In DB > 5.1 we can not set DB_DBT_PARTIAL in the key Dbt,
    // when using DB_SET, we must resize the Dbt key param to hold enough
    // space or Dbc::get fails with DB_BUFFER_SMALL.
    //
    dbKey.set_ulen(dbKey.get_size());
#endif

    //
    // Keep 0 length since we're not interested in the data.
    //
    Dbt dbValue;
    dbValue.set_flags(DB_DBT_USERMEM | DB_DBT_PARTIAL);

    for(;;)
    {
        try
        {
            return _dbc->get(&dbKey, &dbValue, DB_SET) == 0;
        }
        catch(const ::DbDeadlockException& dx)
        {
            if(_tx != 0)
            {
                _tx->dead();
            }

            DeadlockException ex(__FILE__, __LINE__);
            ex.message = dx.what();
            throw ex;
        }
        catch(const ::DbException& dx)
        {
            DatabaseException ex(__FILE__, __LINE__);
            ex.message = dx.what();
            throw ex;
        }
    }
}

void test_dbt(void) {
    u_int32_t size  = 3;
    u_int32_t flags = 5;
    u_int32_t ulen  = 7;
    void*     data  = &size;
    Dbt dbt;

    dbt.set_size(size);
    dbt.set_flags(flags);
    dbt.set_data(data);
    dbt.set_ulen(ulen);
    assert(dbt.get_size()  == size);
    assert(dbt.get_flags() == flags);
    assert(dbt.get_data()  == data);
    assert(dbt.get_ulen()  == ulen);
}

void BtRecExample::run()
{
	db_recno_t recno;
	int ret;
	char buf[1024];

	// Acquire a cursor for the database.
	dbp->cursor(NULL, &dbcp, 0);

	//
	// Prompt the user for a record number, then retrieve and display
	// that record.
	//
	for (;;) {
		// Get a record number.
		cout << "recno #> ";
		cout.flush();
		if (fgets(buf, sizeof(buf), stdin) == NULL)
			break;
		recno = atoi(buf);

		//
		// Start with a fresh key each time,
		// the dbp->get() routine returns
		// the key and data pair, not just the key!
		//
		Dbt key(&recno, sizeof(recno));
		Dbt data;

		if ((ret = dbcp->get(&key, &data, DB_SET_RECNO)) != 0) {
			dbp->err(ret, "DBcursor->get");
			throw DbException(ret);
		}

		// Display the key and data.
		show("k/d\t", &key, &data);

		// Move the cursor a record forward.
		if ((ret = dbcp->get(&key, &data, DB_NEXT)) != 0) {
			dbp->err(ret, "DBcursor->get");
			throw DbException(ret);
		}

		// Display the key and data.
		show("next\t", &key, &data);

		//
		// Retrieve the record number for the following record into
		// local memory.
		//
		data.set_data(&recno);
		data.set_size(sizeof(recno));
		data.set_ulen(sizeof(recno));
		data.set_flags(data.get_flags() | DB_DBT_USERMEM);

		if ((ret = dbcp->get(&key, &data, DB_GET_RECNO)) != 0) {
			if (ret != DB_NOTFOUND && ret != DB_KEYEMPTY) {
				dbp->err(ret, "DBcursor->get");
				throw DbException(ret);
			}
		}
		else {
			cout << "retrieved recno: " << (u_long)recno << "\n";
		}
	}

	dbcp->close();
	dbcp = NULL;
}