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25 
26 package java.nio.channels;
27 
28 import java.io.IOException;
29 import java.nio.channels.spi.*;
30 
31 
32 /**
33  * A pair of channels that implements a unidirectional pipe.
34  *
35  * <p> A pipe consists of a pair of channels: A writable {@link
36  * Pipe.SinkChannel sink} channel and a readable {@link Pipe.SourceChannel source}
37  * channel.  Once some bytes are written to the sink channel they can be read
38  * from the source channel in exactly the order in which they were written.
39  *
40  * <p> Whether or not a thread writing bytes to a pipe will block until another
41  * thread reads those bytes, or some previously-written bytes, from the pipe is
42  * system-dependent and therefore unspecified.  Many pipe implementations will
43  * buffer up to a certain number of bytes between the sink and source channels,
44  * but such buffering should not be assumed.  </p>
45  *
46  *
47  * @author Mark Reinhold
48  * @author JSR-51 Expert Group
49  * @since 1.4
50  */
51 
52 public abstract class Pipe {
53 
54     /**
55      * A channel representing the readable end of a {@link Pipe}.
56      *
57      * @since 1.4
58      */
59     public abstract static class SourceChannel
60         extends AbstractSelectableChannel
61         implements ReadableByteChannel, ScatteringByteChannel
62     {
63         /**
64          * Constructs a new instance of this class.
65          *
66          * @param  provider
67          *         The selector provider
68          */
SourceChannel(SelectorProvider provider)69         protected SourceChannel(SelectorProvider provider) {
70             super(provider);
71         }
72 
73         /**
74          * Returns an operation set identifying this channel's supported
75          * operations.
76          *
77          * <p> Pipe-source channels only support reading, so this method
78          * returns {@link SelectionKey#OP_READ}.  </p>
79          *
80          * @return  The valid-operation set
81          */
validOps()82         public final int validOps() {
83             return SelectionKey.OP_READ;
84         }
85 
86     }
87 
88     /**
89      * A channel representing the writable end of a {@link Pipe}.
90      *
91      * @since 1.4
92      */
93     public abstract static class SinkChannel
94         extends AbstractSelectableChannel
95         implements WritableByteChannel, GatheringByteChannel
96     {
97         /**
98          * Initializes a new instance of this class.
99          *
100          * @param  provider
101          *         The selector provider
102          */
SinkChannel(SelectorProvider provider)103         protected SinkChannel(SelectorProvider provider) {
104             super(provider);
105         }
106 
107         /**
108          * Returns an operation set identifying this channel's supported
109          * operations.
110          *
111          * <p> Pipe-sink channels only support writing, so this method returns
112          * {@link SelectionKey#OP_WRITE}.  </p>
113          *
114          * @return  The valid-operation set
115          */
validOps()116         public final int validOps() {
117             return SelectionKey.OP_WRITE;
118         }
119 
120     }
121 
122     /**
123      * Initializes a new instance of this class.
124      */
Pipe()125     protected Pipe() { }
126 
127     /**
128      * Returns this pipe's source channel.
129      *
130      * @return  This pipe's source channel
131      */
source()132     public abstract SourceChannel source();
133 
134     /**
135      * Returns this pipe's sink channel.
136      *
137      * @return  This pipe's sink channel
138      */
sink()139     public abstract SinkChannel sink();
140 
141     /**
142      * Opens a pipe.
143      *
144      * <p> The new pipe is created by invoking the {@link
145      * java.nio.channels.spi.SelectorProvider#openPipe openPipe} method of the
146      * system-wide default {@link java.nio.channels.spi.SelectorProvider}
147      * object.  </p>
148      *
149      * @return  A new pipe
150      *
151      * @throws  IOException
152      *          If an I/O error occurs
153      */
open()154     public static Pipe open() throws IOException {
155         return SelectorProvider.provider().openPipe();
156     }
157 
158 }
159