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1
21 package com.db4o.cs;
22
23 import com.db4o.foundation.*;
24 import com.db4o.inside.query.*;
25
26
29 class ClientQueryResultIterator implements Iterator4 {
30
31 private Object  [] _prefetchedObjects;
32 private int _remainingObjects;
33 private int _prefetchRight;
34 private final AbstractQueryResult _client;
35 private final IntIterator4 _ids;
36
37 public ClientQueryResultIterator(AbstractQueryResult client) {
38 _client = client;
39 _ids = client.iterateIDs();
40 }
41
42 public Object current() {
43 synchronized (streamLock()) {
44 return _client.activate(prefetchedCurrent());
45 }
46 }
47
48 private Object streamLock() {
49 return _client.streamLock();
50 }
51
52 public void reset() {
53 _remainingObjects = 0;
54 _ids.reset();
55 }
56
57 public boolean moveNext() {
58 synchronized (streamLock()) {
59 if (_remainingObjects > 0) {
60 --_remainingObjects;
61 return skipNulls();
62 }
63
64 prefetch();
65
66 --_remainingObjects;
67 if(_remainingObjects < 0){
68 return false;
69 }
70 return skipNulls();
71 }
72 }
73
74 private boolean skipNulls() {
75 if (prefetchedCurrent() == null){
77 return moveNext();
78 }
79 return true;
80 }
81
82 private void prefetch() {
83 ensureObjectCacheAllocated(prefetchCount());
84 _remainingObjects = stream().prefetchObjects(_ids, _prefetchedObjects, prefetchCount());
85 _prefetchRight=_remainingObjects;
86 }
87
88 private int prefetchCount() {
89 return stream().config().prefetchObjectCount();
90 }
91
92 private YapClient stream() {
93 return (YapClient) _client.stream();
94 }
95
96 private Object prefetchedCurrent() {
97 return _prefetchedObjects[_prefetchRight-_remainingObjects-1];
98 }
99
100
102
116 private void ensureObjectCacheAllocated(int prefetchObjectCount) {
117 if(_prefetchedObjects==null) {
118 _prefetchedObjects = new Object [prefetchObjectCount];
119 return;
120 }
121 if(prefetchObjectCount>_prefetchedObjects.length) {
122 Object [] newPrefetchedObjects=new Object [prefetchObjectCount];
123 System.arraycopy(_prefetchedObjects, 0, newPrefetchedObjects, 0, _prefetchedObjects.length);
124 _prefetchedObjects=newPrefetchedObjects;
125 }
126 }
127
128
129 }
130 |
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