Mercurial > hg > blitz_condensed
comparison src/EDU/oswego/cs/dl/util/concurrent/misc/PipedChannel.java @ 0:3dc0c5604566
Initial checkin of blitz 2.0 fcs - no installer yet.
author | Dan Creswell <dan.creswell@gmail.com> |
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date | Sat, 21 Mar 2009 11:00:06 +0000 |
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1 | |
2 package EDU.oswego.cs.dl.util.concurrent.misc; | |
3 import EDU.oswego.cs.dl.util.concurrent.*; | |
4 | |
5 import java.io.*; | |
6 | |
7 /** | |
8 * A channel based on a java.io.PipedInputStream and | |
9 * java.io.PipedOutputStream. Elements are serialized | |
10 * using ObjectInputStreams and ObjectOutputStreams | |
11 * upon insertion and extraction from the pipe. | |
12 * <p> | |
13 * IO Exceptions are transformed into Errors. This is | |
14 * in general not a good idea, but seems to be the most | |
15 * reasonable compromise for the intended usage contexts. | |
16 * <p> | |
17 * <b>Status</b> Uncertain. There are enough | |
18 * conceptual and implementation snags surrounding use | |
19 * of pipes as Channels to downplay use. However, | |
20 * without such bridges, people would have to | |
21 * duplicate code that should work the same way in both cases. | |
22 * | |
23 * <p>[<a href="http://gee.cs.oswego.edu/dl/classes/EDU/oswego/cs/dl/util/concurrent/intro.html"> Introduction to this package. </a>] | |
24 **/ | |
25 | |
26 public class PipedChannel extends SemaphoreControlledChannel { | |
27 protected ObjectInputStream in_; | |
28 protected ObjectOutputStream out_; | |
29 | |
30 protected final PipedOutputStream outp_; | |
31 protected final PipedInputStream inp_; | |
32 | |
33 | |
34 public PipedChannel() { | |
35 super(1); | |
36 | |
37 try { | |
38 outp_ = new PipedOutputStream(); | |
39 inp_ = new PipedInputStream(); | |
40 inp_.connect(outp_); | |
41 } | |
42 catch (IOException ex) { | |
43 ex.printStackTrace(); | |
44 throw new Error("Cannot construct Pipe?"); | |
45 } | |
46 } | |
47 | |
48 | |
49 /** | |
50 * Return input stream, first constructing if necessary. | |
51 * Needed because Object streams can block on open. | |
52 **/ | |
53 | |
54 protected synchronized ObjectInputStream in() { | |
55 try { | |
56 if (in_ == null) in_ = new ObjectInputStream(inp_); | |
57 return in_; | |
58 } | |
59 catch (IOException ex) { | |
60 ex.printStackTrace(); | |
61 throw new Error("IO exception during open"); | |
62 } | |
63 } | |
64 | |
65 /** | |
66 * Return output stream, first constructing if necessary. | |
67 * Needed because Object streams can block on open. | |
68 **/ | |
69 protected synchronized ObjectOutputStream out() { | |
70 try { | |
71 if (out_ == null) out_ = new ObjectOutputStream(outp_); | |
72 return out_; | |
73 } | |
74 catch (IOException ex) { | |
75 ex.printStackTrace(); | |
76 throw new Error("IO exception during open"); | |
77 } | |
78 } | |
79 | |
80 | |
81 /** Shared mechanics for put-based methods **/ | |
82 protected void insert(Object x) { | |
83 try { | |
84 out().writeObject(x); | |
85 } | |
86 catch (InterruptedIOException ex) { | |
87 Thread.currentThread().interrupt(); | |
88 } | |
89 catch (IOException ex) { | |
90 ex.printStackTrace(); | |
91 throw new Error("IO exception during put"); | |
92 } | |
93 } | |
94 | |
95 /** Shared mechanics for take-based methods **/ | |
96 protected Object extract() { | |
97 try { | |
98 return in().readObject(); | |
99 } | |
100 catch (InterruptedIOException ex) { | |
101 Thread.currentThread().interrupt(); | |
102 return null; | |
103 } | |
104 catch (IOException ex) { | |
105 ex.printStackTrace(); | |
106 throw new Error("IO exception during take"); | |
107 } | |
108 catch (ClassNotFoundException ex) { | |
109 ex.printStackTrace(); | |
110 throw new Error("Serialization exception during take"); | |
111 } | |
112 } | |
113 | |
114 /** Stubbed out for now **/ | |
115 public Object peek() { return null; } | |
116 } | |
117 |