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1
4 package gnu.lists;
5
6 public class PositionManager
7 {
8 static final PositionManager manager = new PositionManager();
9
10 static public SeqPosition getPositionObject (int ipos)
11 {
12 PositionManager m = manager;
13 synchronized (m)
14 {
15 return m.positions[ipos];
16 }
17 }
18
19 SeqPosition[] positions = new SeqPosition[50];
20 int[] ivals = new int[50];
21 int freeListHead = -1;
22
23 private void addToFreeList(int[] ivals, int first, int end)
24 {
25 int head = freeListHead;
26 for (int i = first; i < end; i++)
27 {
28 ivals[i] = head;
29 head = i;
30 }
31 freeListHead = head;
32 }
33
34 private int getFreeSlot ()
35 {
36 int head = freeListHead;
37 if (head < 0)
38 {
39 int old_size = positions.length;
40 SeqPosition[] npositions = new SeqPosition[2 * old_size];
41 int[] nvals = new int[2 * old_size];
42 System.arraycopy(positions, 0, npositions, 0, old_size);
43 System.arraycopy(ivals, 0, nvals, 0, old_size);
44 positions = npositions;
45 ivals = nvals;
46 addToFreeList(nvals, old_size, 2 * old_size);
47 head = freeListHead;
48 }
49 freeListHead = ivals[head];
50 return head;
51 }
52
53 public PositionManager ()
54 {
55 addToFreeList(ivals, 1, ivals.length);
58 }
59
60 public synchronized int register(SeqPosition pos)
61 {
62 int i = getFreeSlot();
63 positions[i] = pos;
64 ivals[i] = -1;
65 return i;
66 }
67
68 public synchronized void release(int ipos)
69 {
70 SeqPosition pos = positions[ipos];
71 if (pos instanceof ExtPosition)
72 ((ExtPosition) pos).position = -1;
73 positions[ipos] = null;
74 ivals[ipos] = freeListHead;
75 freeListHead = ipos;
76 pos.release();
77 }
78 }
79 |
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