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comparison src/com/go/trove/io/InternedCharToByteBuffer.java @ 0:3dc0c5604566

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Initial checkin of blitz 2.0 fcs - no installer yet.
author Dan Creswell <dan.creswell@gmail.com>
date Sat, 21 Mar 2009 11:00:06 +0000
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-1:000000000000 0:3dc0c5604566
1 /* ====================================================================
2 * Trove - Copyright (c) 1999-2000 Walt Disney Internet Group
3 * ====================================================================
4 * The Tea Software License, Version 1.1
5 *
6 * Copyright (c) 2000 Walt Disney Internet Group. All rights reserved.
7 *
8 * Redistribution and use in source and binary forms, with or without
9 * modification, are permitted provided that the following conditions
10 * are met:
11 *
12 * 1. Redistributions of source code must retain the above copyright
13 * notice, this list of conditions and the following disclaimer.
14 *
15 * 2. Redistributions in binary form must reproduce the above copyright
16 * notice, this list of conditions and the following disclaimer in
17 * the documentation and/or other materials provided with the
18 * distribution.
19 *
20 * 3. The end-user documentation included with the redistribution,
21 * if any, must include the following acknowledgment:
22 * "This product includes software developed by the
23 * Walt Disney Internet Group (http://opensource.go.com/)."
24 * Alternately, this acknowledgment may appear in the software itself,
25 * if and wherever such third-party acknowledgments normally appear.
26 *
27 * 4. The names "Tea", "TeaServlet", "Kettle", "Trove" and "BeanDoc" must
28 * not be used to endorse or promote products derived from this
29 * software without prior written permission. For written
30 * permission, please contact opensource@dig.com.
31 *
32 * 5. Products derived from this software may not be called "Tea",
33 * "TeaServlet", "Kettle" or "Trove", nor may "Tea", "TeaServlet",
34 * "Kettle", "Trove" or "BeanDoc" appear in their name, without prior
35 * written permission of the Walt Disney Internet Group.
36 *
37 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
38 * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
39 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
40 * DISCLAIMED. IN NO EVENT SHALL THE WALT DISNEY INTERNET GROUP OR ITS
41 * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
42 * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
43 * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
44 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
45 * OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
46 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
47 * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
48 * ====================================================================
49 *
50 * For more information about Tea, please see http://opensource.go.com/.
51 */
52
53 package com.go.trove.io;
54
55 import java.io.*;
56 import java.util.*;
57 import com.go.trove.util.IdentityMap;
58
59 /******************************************************************************
60 * A CharToByteBuffer that keeps track of interned strings (mainly string
61 * literals) and statically caches the results of those strings after applying
62 * a byte conversion. This can improve performance if many of the strings being
63 * passed to the append method have been converted before.
64 *
65 * @author Brian S O'Neill
66 * @version
67 * <!--$$Revision: 1.1 $-->, <!--$$JustDate:--> 7/31/01 <!-- $-->
68 */
69 public class InternedCharToByteBuffer
70 implements CharToByteBuffer, Serializable
71 {
72 private static final int CACHES_PER_ENCODING = 11;
73 private static final int MIN_LENGTH = 4;
74
75 private static final Object MARKER = new Object();
76
77 private static Map cEncodings = new HashMap(7);
78
79 private static Random cLastRandom = new Random();
80
81 /**
82 * Returns several caches for the given encoding. A character in the
83 * string key is used to select the correct cache. By breaking up the
84 * cache in this way, the synchronization required to access the caches
85 * is distributed.
86 */
87 private static Map[] getConvertedCaches(String encoding) {
88 synchronized (cEncodings) {
89 Map[] caches = (Map[])cEncodings.get(encoding);
90 if (caches == null) {
91 caches = new Map[CACHES_PER_ENCODING];
92 for (int i=0; i<CACHES_PER_ENCODING; i++) {
93 caches[i] = Collections.synchronizedMap(new IdentityMap());
94 }
95 cEncodings.put(encoding, caches);
96 }
97 return caches;
98 }
99 }
100
101 private static Random getRandom() {
102 synchronized (cLastRandom) {
103 return cLastRandom = new Random(cLastRandom.nextLong());
104 }
105 }
106
107 private CharToByteBuffer mBuffer;
108 private Random mRandom;
109 private transient Map[] mConvertedCaches;
110
111 public InternedCharToByteBuffer(CharToByteBuffer buffer)
112 throws IOException
113 {
114 mBuffer = buffer;
115 mConvertedCaches = getConvertedCaches(buffer.getEncoding());
116 }
117
118 public void setEncoding(String enc) throws IOException {
119 mBuffer.setEncoding(enc);
120 mConvertedCaches = getConvertedCaches(mBuffer.getEncoding());
121 }
122
123 public String getEncoding() throws IOException {
124 return mBuffer.getEncoding();
125 }
126
127 public long getBaseByteCount() throws IOException {
128 return mBuffer.getBaseByteCount();
129 }
130
131 public long getByteCount() throws IOException {
132 return mBuffer.getByteCount();
133 }
134
135 public void writeTo(OutputStream out) throws IOException {
136 mBuffer.writeTo(out);
137 }
138
139 public void append(byte b) throws IOException {
140 mBuffer.append(b);
141 }
142
143 public void append(byte[] bytes) throws IOException {
144 mBuffer.append(bytes);
145 }
146
147 public void append(byte[] bytes, int offset, int length)
148 throws IOException {
149
150 mBuffer.append(bytes, offset, length);
151 }
152
153 public void appendSurrogate(ByteData s) throws IOException {
154 mBuffer.appendSurrogate(s);
155 }
156
157 public void addCaptureBuffer(ByteBuffer buffer) throws IOException {
158 mBuffer.addCaptureBuffer(buffer);
159 }
160
161 public void removeCaptureBuffer(ByteBuffer buffer) throws IOException {
162 mBuffer.removeCaptureBuffer(buffer);
163 }
164
165 public void append(char c) throws IOException {
166 mBuffer.append(c);
167 }
168
169 public void append(char[] chars) throws IOException {
170 mBuffer.append(chars);
171 }
172
173 public void append(char[] chars, int offset, int length)
174 throws IOException {
175
176 mBuffer.append(chars, offset, length);
177 }
178
179 public void append(String str) throws IOException {
180 Map cache;
181 if ((cache = getConvertedCache(str)) == null) {
182 mBuffer.append(str);
183 return;
184 }
185
186 // Caching performed using a two pass technique. This is done to
187 // avoid the cost of String.getBytes() for strings that aren't
188 // actually interned.
189
190 Object value;
191
192 if ((value = cache.get(str)) != null) {
193 byte[] bytes;
194 if (value != MARKER) {
195 bytes = (byte[])value;
196 }
197 else {
198 // This is at least the second time the string has been seen,
199 // so assume it has been interned and call String.getBytes().
200 String enc = getEncoding();
201 if (enc != null) {
202 bytes = str.getBytes(enc);
203 }
204 else {
205 // no encoding specified so use default.
206 bytes = str.getBytes();
207 }
208 cache.put(str, bytes);
209 }
210
211 mBuffer.append(bytes);
212 }
213 else {
214 // Just put a marker at first to indicate that the string has been
215 // seen, but don't call String.getBytes() just yet.
216 if (mRandom == null) {
217 mRandom = getRandom();
218 }
219 if ((mRandom.nextInt() % 20) == 0) {
220 // Only mark sometimes in order to reduce the amount of times
221 // put is called for strings that will never be seen again.
222 // Calculating a random number is cheaper than putting into an
223 // IdentityMap because no objects are created. A consequence of
224 // this optimization is that it will take more iterations to
225 // discover the real string literals, but they will be
226 // discovered eventually.
227 cache.put(str, MARKER);
228 }
229 mBuffer.append(str);
230 }
231 }
232
233 public void append(String str, int offset, int length) throws IOException {
234 mBuffer.append(str, offset, length);
235 }
236
237 public void reset() throws IOException {
238 mBuffer.reset();
239 }
240
241 public void drain() throws IOException {
242 mBuffer.drain();
243 }
244
245 private Map getConvertedCache(String str) {
246 if (str.length() < MIN_LENGTH) {
247 return null;
248 }
249 return mConvertedCaches[str.charAt(1) % CACHES_PER_ENCODING];
250 }
251
252 private void readObject(ObjectInputStream in)
253 throws IOException, ClassNotFoundException
254 {
255 in.defaultReadObject();
256 mConvertedCaches = getConvertedCaches(mBuffer.getEncoding());
257 }
258 }