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Java > Open Source Codes > net > sf > saxon > sort > SortedTupleIterator


1 package net.sf.saxon.sort;
2
3 import net.sf.saxon.expr.XPathContext;
4 import net.sf.saxon.om.SequenceIterator;
5 import net.sf.saxon.trans.XPathException;
6 import net.sf.saxon.value.EmptySequence;
7 import net.sf.saxon.value.ObjectValue;
8 import net.sf.saxon.value.Value;
9
10 /**
11  * A SortedTupleIterator is a modified SortedIterator. Whereas the sorted iterator
12  * used by XSLT computes the sort key of each item in a sequence, using that item
13  * as the context item, the SortedTupleIterator used by XQuery precomputes the sort
14  * keys from scratch; they do not need to be a function of the item being sorted.
15  */
16
17 class SortedTupleIterator extends SortedIterator {
18
19     // Note, the sort key expression within the FixedSortKeyDefinition is not used
20 // in this subclass.
21
22     public SortedTupleIterator(XPathContext context, SequenceIterator base,
23                                FixedSortKeyDefinition[] sortKeys) throws XPathException {
24         super(context, base, sortKeys);
25     }
26
27     /**
28      * Override the method that builds the array of values and sort keys.
29      * @throws XPathException
30      */
31
32     protected void buildArray() throws XPathException {
33         int allocated = 100;
34         nodeKeys = new Object JavaDoc[allocated * recordSize];
35         count = 0;
36
37         // initialise the array with data
38
39         while (true) {
40             ObjectValue tupleObject = (ObjectValue)base.next();
41             if (tupleObject == null) {
42                 break;
43             }
44             Value[] tuple = (Value[])tupleObject.getObject();
45             if (count==allocated) {
46                 allocated *= 2;
47                 Object JavaDoc[] nk2 = new Object JavaDoc[allocated * recordSize];
48                 System.arraycopy(nodeKeys, 0, nk2, 0, count * recordSize);
49                 nodeKeys = nk2;
50             }
51             int k = count*recordSize;
52             nodeKeys[k] = new ObjectValue(tuple[0]);
53                 // this is the "item" that will be returned by the TupleIterator.
54 // In general it is actually a sequence, so we wrap it in an ObjectValue
55 // It subsequently gets unwrapped by the MappingFunction applied to the
56 // output of the SortedTupleIterator.
57 for (int n=1; n<=sortkeys.length; n++) {
58                 Value v = tuple[n].reduce();
59                 if (v instanceof EmptySequence) {
60                     nodeKeys[k+n] = null;
61                 } else {
62                     nodeKeys[k+n] = v;
63                 }
64             }
65             nodeKeys[k+sortkeys.length+1] = new Integer JavaDoc(count);
66             count++;
67         }
68     }
69 }
70
71
72 //
73 // The contents of this file are subject to the Mozilla Public License Version 1.0 (the "License");
74 // you may not use this file except in compliance with the License. You may obtain a copy of the
75 // License at http://www.mozilla.org/MPL/
76 //
77 // Software distributed under the License is distributed on an "AS IS" basis,
78 // WITHOUT WARRANTY OF ANY KIND, either express or implied.
79 // See the License for the specific language governing rights and limitations under the License.
80 //
81 // The Original Code is: all this file.
82 //
83 // The Initial Developer of the Original Code is Michael H. Kay
84 //
85 // Portions created by (your name) are Copyright (C) (your legal entity). All Rights Reserved.
86 //
87 // Contributor(s): none
88 //
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