01: /*
02: (c) Copyright 2002, 2003, 2004, 2005, 2006, 2007, 2008 Hewlett-Packard Development Company, LP
03: [See end of file]
04: $Id: Stage.java,v 1.13 2008/01/02 12:07:57 andy_seaborne Exp $
05: */
06:
07: package com.hp.hpl.jena.graph.query;
08:
09: /**
10: a processing stage in the query pipeline. Each stage
11: gets connected to its predecessor in the pipeline, and
12: mangles the contents before handing them on to the next
13: stage.
14:
15: @author hedgehog
16: */
17:
18: public abstract class Stage {
19: /** the previous stage of the pipeline, once connected */
20: protected Stage previous;
21:
22: public volatile boolean stillOpen = true;
23:
24: /** construct a new initial stage for the pipeline */
25: public static Stage initial(int count) {
26: return new InitialStage(count);
27: }
28:
29: /** connect this stage to its supplier; return this for chaining. */
30: public Stage connectFrom(Stage s) {
31: previous = s;
32: return this ;
33: }
34:
35: public boolean isClosed() {
36: return !stillOpen;
37: }
38:
39: protected final void markClosed() {
40: stillOpen = false;
41: }
42:
43: public void close() {
44: previous.close();
45: markClosed();
46: }
47:
48: /**
49: execute the pipeline and pump the results into _sink_; this is asynchronous.
50: deliver that same _sink_ as our result. (This allows the sink to be created
51: as the argument to _deliver_.)
52: */
53: public abstract Pipe deliver(Pipe sink);
54: }
55:
56: /*
57: (c) Copyright 2002, 2003, 2004, 2005, 2006, 2007, 2008 Hewlett-Packard Development Company, LP
58: All rights reserved.
59:
60: Redistribution and use in source and binary forms, with or without
61: modification, are permitted provided that the following conditions
62: are met:
63:
64: 1. Redistributions of source code must retain the above copyright
65: notice, this list of conditions and the following disclaimer.
66:
67: 2. Redistributions in binary form must reproduce the above copyright
68: notice, this list of conditions and the following disclaimer in the
69: documentation and/or other materials provided with the distribution.
70:
71: 3. The name of the author may not be used to endorse or promote products
72: derived from this software without specific prior written permission.
73:
74: THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
75: IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
76: OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
77: IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
78: INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
79: NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
80: DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
81: THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
82: (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
83: THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
84: */
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