/* ====================================================================
* Trove - Copyright (c) 1999-2000 Walt Disney Internet Group
* ====================================================================
* The Tea Software License, Version 1.1
*
* Copyright (c) 2000 Walt Disney Internet Group. All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
*
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
*
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in
* the documentation and/or other materials provided with the
* distribution.
*
* 3. The end-user documentation included with the redistribution,
* if any, must include the following acknowledgment:
* "This product includes software developed by the
* Walt Disney Internet Group (http://opensource.go.com/)."
* Alternately, this acknowledgment may appear in the software itself,
* if and wherever such third-party acknowledgments normally appear.
*
* 4. The names "Tea", "TeaServlet", "Kettle", "Trove" and "BeanDoc" must
* not be used to endorse or promote products derived from this
* software without prior written permission. For written
* permission, please contact opensource@dig.com.
*
* 5. Products derived from this software may not be called "Tea",
* "TeaServlet", "Kettle" or "Trove", nor may "Tea", "TeaServlet",
* "Kettle", "Trove" or "BeanDoc" appear in their name, without prior
* written permission of the Walt Disney Internet Group.
*
* THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESSED OR IMPLIED
* WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
* DISCLAIMED. IN NO EVENT SHALL THE WALT DISNEY INTERNET GROUP OR ITS
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY
* OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
* ====================================================================
*
* For more information about Tea, please see http://opensource.go.com/.
*/
package com.go.trove.io;
import java.io.*;
import java.util.*;
import com.go.trove.util.IdentityMap;
/******************************************************************************
* A CharToByteBuffer that keeps track of interned strings (mainly string
* literals) and statically caches the results of those strings after applying
* a byte conversion. This can improve performance if many of the strings being
* passed to the append method have been converted before.
*
* @author Brian S O'Neill
* @version
* <!--$$Revision:--> 27 <!-- $-->, <!--$$JustDate:--> 7/31/01 <!-- $-->
*/
public class InternedCharToByteBuffer
implements CharToByteBuffer, Serializable
{
private static final int CACHES_PER_ENCODING = 11;
private static final int MIN_LENGTH = 4;
private static final Object MARKER = new Object();
private static Map cEncodings = new HashMap(7);
private static Random cLastRandom = new Random();
/**
* Returns several caches for the given encoding. A character in the
* string key is used to select the correct cache. By breaking up the
* cache in this way, the synchronization required to access the caches
* is distributed.
*/
private static Map[] getConvertedCaches(String encoding) {
synchronized (cEncodings) {
Map[] caches = (Map[])cEncodings.get(encoding);
if (caches == null) {
caches = new Map[CACHES_PER_ENCODING];
for (int i=0; i<CACHES_PER_ENCODING; i++) {
caches[i] = Collections.synchronizedMap(new IdentityMap());
}
cEncodings.put(encoding, caches);
}
return caches;
}
}
private static Random getRandom() {
synchronized (cLastRandom) {
return cLastRandom = new Random(cLastRandom.nextLong());
}
}
private CharToByteBuffer mBuffer;
private Random mRandom;
private transient Map[] mConvertedCaches;
public InternedCharToByteBuffer(CharToByteBuffer buffer)
throws IOException
{
mBuffer = buffer;
mConvertedCaches = getConvertedCaches(buffer.getEncoding());
}
public void setEncoding(String enc) throws IOException {
mBuffer.setEncoding(enc);
mConvertedCaches = getConvertedCaches(mBuffer.getEncoding());
}
public String getEncoding() throws IOException {
return mBuffer.getEncoding();
}
public long getBaseByteCount() throws IOException {
return mBuffer.getBaseByteCount();
}
public long getByteCount() throws IOException {
return mBuffer.getByteCount();
}
public void writeTo(OutputStream out) throws IOException {
mBuffer.writeTo(out);
}
public void append(byte b) throws IOException {
mBuffer.append(b);
}
public void append(byte[] bytes) throws IOException {
mBuffer.append(bytes);
}
public void append(byte[] bytes, int offset, int length)
throws IOException {
mBuffer.append(bytes, offset, length);
}
public void appendSurrogate(ByteData s) throws IOException {
mBuffer.appendSurrogate(s);
}
public void addCaptureBuffer(ByteBuffer buffer) throws IOException {
mBuffer.addCaptureBuffer(buffer);
}
public void removeCaptureBuffer(ByteBuffer buffer) throws IOException {
mBuffer.removeCaptureBuffer(buffer);
}
public void append(char c) throws IOException {
mBuffer.append(c);
}
public void append(char[] chars) throws IOException {
mBuffer.append(chars);
}
public void append(char[] chars, int offset, int length)
throws IOException {
mBuffer.append(chars, offset, length);
}
public void append(String str) throws IOException {
Map cache;
if ((cache = getConvertedCache(str)) == null) {
mBuffer.append(str);
return;
}
// Caching performed using a two pass technique. This is done to
// avoid the cost of String.getBytes() for strings that aren't
// actually interned.
Object value;
if ((value = cache.get(str)) != null) {
byte[] bytes;
if (value != MARKER) {
bytes = (byte[])value;
}
else {
// This is at least the second time the string has been seen,
// so assume it has been interned and call String.getBytes().
String enc = getEncoding();
if (enc != null) {
bytes = str.getBytes(enc);
}
else {
// no encoding specified so use default.
bytes = str.getBytes();
}
cache.put(str, bytes);
}
mBuffer.append(bytes);
}
else {
// Just put a marker at first to indicate that the string has been
// seen, but don't call String.getBytes() just yet.
if (mRandom == null) {
mRandom = getRandom();
}
if ((mRandom.nextInt() % 20) == 0) {
// Only mark sometimes in order to reduce the amount of times
// put is called for strings that will never be seen again.
// Calculating a random number is cheaper than putting into an
// IdentityMap because no objects are created. A consequence of
// this optimization is that it will take more iterations to
// discover the real string literals, but they will be
// discovered eventually.
cache.put(str, MARKER);
}
mBuffer.append(str);
}
}
public void append(String str, int offset, int length) throws IOException {
mBuffer.append(str, offset, length);
}
public void reset() throws IOException {
mBuffer.reset();
}
public void drain() throws IOException {
mBuffer.drain();
}
private Map getConvertedCache(String str) {
if (str.length() < MIN_LENGTH) {
return null;
}
return mConvertedCaches[str.charAt(1) % CACHES_PER_ENCODING];
}
private void readObject(ObjectInputStream in)
throws IOException, ClassNotFoundException
{
in.defaultReadObject();
mConvertedCaches = getConvertedCaches(mBuffer.getEncoding());
}
}