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Java > Open Source Codes > com > db4o > cs > messages > MsgQuery


1 /* Copyright (C) 2004 - 2006 db4objects Inc. http://www.db4o.com
2
3 This file is part of the db4o open source object database.
4
5 db4o is free software; you can redistribute it and/or modify it under
6 the terms of version 2 of the GNU General Public License as published
7 by the Free Software Foundation and as clarified by db4objects' GPL
8 interpretation policy, available at
9 http://www.db4o.com/about/company/legalpolicies/gplinterpretation/
10 Alternatively you can write to db4objects, Inc., 1900 S Norfolk Street,
11 Suite 350, San Mateo, CA 94403, USA.
12
13 db4o is distributed in the hope that it will be useful, but WITHOUT ANY
14 WARRANTY; without even the implied warranty of MERCHANTABILITY or
15 FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
16 for more details.
17
18 You should have received a copy of the GNU General Public License along
19 with this program; if not, write to the Free Software Foundation, Inc.,
20 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */
21 package com.db4o.cs.messages;
22
23 import com.db4o.*;
24 import com.db4o.config.*;
25 import com.db4o.cs.*;
26 import com.db4o.foundation.*;
27 import com.db4o.inside.query.*;
28
29 public abstract class MsgQuery extends MsgObject {
30     
31     private static final int ID_AND_SIZE = 2;
32     
33     private static int nextID;
34     
35     protected final void writeQueryResult(AbstractQueryResult queryResult, YapServerThread serverThread, QueryEvaluationMode evaluationMode) {
36         
37         int queryResultId = 0;
38         int maxCount = 0;
39         
40         if(evaluationMode == QueryEvaluationMode.IMMEDIATE){
41             maxCount = queryResult.size();
42         } else{
43             queryResultId = generateID();
44             maxCount = config().prefetchObjectCount();
45         }
46         
47         MsgD message = QUERY_RESULT.getWriterForLength(transaction(), bufferLength(maxCount));
48         YapWriter writer = message.payLoad();
49         writer.writeInt(queryResultId);
50         
51         IntIterator4 idIterator = queryResult.iterateIDs();
52         
53         writer.writeIDs(idIterator, maxCount);
54         
55         if(queryResultId > 0){
56             serverThread.mapQueryResultToID(new LazyClientObjectSetStub(queryResult, idIterator), queryResultId);
57         }
58         
59         serverThread.write(message);
60     }
61
62     private int bufferLength(int maxCount) {
63         return YapConst.INT_LENGTH * (maxCount + ID_AND_SIZE);
64     }
65     
66     private static synchronized int generateID(){
67         nextID ++;
68         if(nextID < 0){
69             nextID = 1;
70         }
71         return nextID;
72     }
73     
74     protected AbstractQueryResult newQueryResult(QueryEvaluationMode mode){
75         return stream().newQueryResult(transaction(), mode);
76     }
77
78 }
79
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