KickJava   Java API By Example, From Geeks To Geeks.

Java > Open Source Codes > com > sleepycat > bind > tuple > TupleBase


1 /*-
2  * See the file LICENSE for redistribution information.
3  *
4  * Copyright (c) 2000,2006 Oracle. All rights reserved.
5  *
6  * $Id: TupleBase.java,v 1.5 2006/10/30 21:14:08 bostic Exp $
7  */
8
9 package com.sleepycat.bind.tuple;
10
11 import com.sleepycat.je.DatabaseEntry;
12
13 /**
14  * A base class for tuple bindings and tuple key creators that provides control
15  * over the allocation of the output buffer.
16  *
17  * <p>Tuple bindings and key creators append data to a {@link TupleOutput}
18  * instance, which is also a {@link com.sleepycat.util.FastOutputStream}
19  * instance. This object has a byte array buffer that is resized when it is
20  * full. The reallocation of this buffer can be a performance factor for
21  * some applications using large objects. To manage this issue, the {@link
22  * #setTupleBufferSize} method may be used to control the initial size of the
23  * buffer, and the {@link #getTupleOutput} method may be overridden by
24  * subclasses to take over creation of the TupleOutput object.</p>
25  */
26 public class TupleBase {
27
28     private int outputBufferSize;
29
30     /**
31      * Initializes the initial output buffer size to zero.
32      *
33      * <p>Unless {@link #setTupleBufferSize} is called, the default {@link
34      * com.sleepycat.util.FastOutputStream#DEFAULT_INIT_SIZE} size will be
35      * used.</p>
36      */
37     public TupleBase() {
38         outputBufferSize = 0;
39     }
40
41     /**
42      * Sets the initial byte size of the output buffer that is allocated by the
43      * default implementation of {@link #getTupleOutput}.
44      *
45      * <p>If this property is zero (the default), the default {@link
46      * com.sleepycat.util.FastOutputStream#DEFAULT_INIT_SIZE} size is used.</p>
47      *
48      * @param byteSize the initial byte size of the output buffer, or zero to
49      * use the default size.
50      */
51     public void setTupleBufferSize(int byteSize) {
52         outputBufferSize = byteSize;
53     }
54
55     /**
56      * Returns the initial byte size of the output buffer.
57      *
58      * @return the initial byte size of the output buffer.
59      *
60      * @see #setTupleBufferSize
61      */
62     public int getTupleBufferSize() {
63         return outputBufferSize;
64     }
65
66     /**
67      * Returns an empty TupleOutput instance that will be used by the tuple
68      * binding or key creator.
69      *
70      * <p>The default implementation of this method creates a new TupleOutput
71      * with an initial buffer size that can be changed using the {@link
72      * #setTupleBufferSize} method.</p>
73      *
74      * <p>This method may be overridden to return a TupleOutput instance. For
75      * example, an instance per thread could be created and returned by this
76      * method. If a TupleOutput instance is reused, be sure to call its
77      * {@link com.sleepycat.util.FastOutputStream#reset} method before each
78      * use.</p>
79      *
80      * @param object is the object to be written to the tuple output, and may
81      * be used by subclasses to determine the size of the output buffer.
82      *
83      * @return an empty TupleOutput instance.
84      *
85      * @see #setTupleBufferSize
86      */
87     protected TupleOutput getTupleOutput(Object JavaDoc object) {
88         int byteSize = getTupleBufferSize();
89         if (byteSize != 0) {
90             return new TupleOutput(new byte[byteSize]);
91         } else {
92             return new TupleOutput();
93         }
94     }
95
96     /**
97      * Utility method to set the data in a entry buffer to the data in a tuple
98      * output object.
99      *
100      * @param output is the source tuple output object.
101      *
102      * @param entry is the destination entry buffer.
103      */
104     public static void outputToEntry(TupleOutput output, DatabaseEntry entry) {
105
106         entry.setData(output.getBufferBytes(), output.getBufferOffset(),
107                       output.getBufferLength());
108     }
109
110     /**
111      * Utility method to set the data in a entry buffer to the data in a tuple
112      * input object.
113      *
114      * @param input is the source tuple input object.
115      *
116      * @param entry is the destination entry buffer.
117      */
118     public static void inputToEntry(TupleInput input, DatabaseEntry entry) {
119
120         entry.setData(input.getBufferBytes(), input.getBufferOffset(),
121                       input.getBufferLength());
122     }
123
124     /**
125      * Utility method to create a new tuple input object for reading the data
126      * from a given buffer. If an existing input is reused, it is reset before
127      * returning it.
128      *
129      * @param entry is the source entry buffer.
130      *
131      * @return the new tuple input object.
132      */
133     public static TupleInput entryToInput(DatabaseEntry entry) {
134
135         return new TupleInput(entry.getData(), entry.getOffset(),
136                               entry.getSize());
137     }
138
139     /**
140      * Utility method for use by bindings to create a tuple output object.
141      *
142      * @return a new tuple output object.
143      *
144      * @deprecated replaced by {@link #getTupleOutput}
145      */
146     public static TupleOutput newOutput() {
147
148         return new TupleOutput();
149     }
150
151     /**
152      * Utility method for use by bindings to create a tuple output object
153      * with a specific starting size.
154      *
155      * @return a new tuple output object.
156      *
157      * @deprecated replaced by {@link #getTupleOutput}
158      */
159     public static TupleOutput newOutput(byte[] buffer) {
160
161         return new TupleOutput(buffer);
162     }
163 }
164
Popular Tags