org.glassfish.grizzly.utils.Charsets Maven / Gradle / Ivy
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package org.glassfish.grizzly.utils;
import java.nio.charset.Charset;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.UnsupportedCharsetException;
import java.util.Locale;
import java.util.Map;
import java.util.concurrent.ConcurrentMap;
import org.glassfish.grizzly.ThreadCache;
import org.glassfish.grizzly.ThreadCache.CachedTypeIndex;
/**
* Charset utility class.
*
* @author Alexey Stashok
*/
public final class Charsets {
static {
if (Boolean.getBoolean(Charsets.class.getName() + ".preloadAllCharsets")) {
preloadAllCharsets();
}
}
/**
* The default character encoding of this Java virtual machine.
*/
public static final String DEFAULT_CHARACTER_ENCODING =
Charset.defaultCharset().name();
private static final ConcurrentMap charsetAliasMap =
DataStructures.getConcurrentMap(8);
public static final Charset ASCII_CHARSET = lookupCharset("ASCII");
public static final Charset UTF8_CHARSET = lookupCharset("UTF-8");
/**
* Returns the default charset of this Java virtual machine.
* @see Charset#defaultCharset()
*/
public static final Charset DEFAULT_CHARSET = Charset.defaultCharset();
public static final int CODECS_CACHE_SIZE = 4;
private static final CharsetCodecResolver DECODER_RESOLVER =
new DecoderResolver();
private static final CharsetCodecResolver ENCODER_RESOLVER =
new EncoderResolver();
private static final CachedTypeIndex CODECS_CACHE =
ThreadCache.obtainIndex(CodecsCache.class, 1);
private static volatile boolean areCharsetsPreloaded;
/**
* Lookup a {@link Charset} by name.
* Fixes Charset concurrency issue (http://paul.vox.com/library/post/the-mysteries-of-java-character-set-performance.html)
*
* @param charsetName
* @return {@link Charset}
*/
public static Charset lookupCharset(final String charsetName) {
final String charsetLowerCase = charsetName.toLowerCase(Locale.US);
Charset charset = charsetAliasMap.get(charsetLowerCase);
if (charset == null) {
if (areCharsetsPreloaded) {
// if all charsets are preloaded - throw Exception right away
throw new UnsupportedCharsetException(charsetName);
}
final Charset newCharset = Charset.forName(charsetLowerCase);
final Charset prevCharset =
charsetAliasMap.putIfAbsent(charsetLowerCase, newCharset);
charset = prevCharset == null ? newCharset : prevCharset;
}
return charset;
}
/**
* Preloads all {@link Charset}s available to the JMV, which makes charset
* searching faster (at the cost of memory). The speed gain is most noticable
* in the case of non-existing charsets as it allows us to avoid an expensive
* call to {@link Charset#forName(java.lang.String)}.
*/
public static void preloadAllCharsets() {
synchronized (charsetAliasMap) {
final Map charsetsMap = Charset.availableCharsets();
for (Charset charset : charsetsMap.values()) {
charsetAliasMap.put(
charset.name().toLowerCase(Locale.US), charset);
for (String alias : charset.aliases()) {
charsetAliasMap.put(alias.toLowerCase(Locale.US), charset);
}
}
areCharsetsPreloaded = true;
}
}
/**
* Remove all preloaded charsets.
*/
public static void drainAllCharsets() {
synchronized (charsetAliasMap) {
areCharsetsPreloaded = false;
charsetAliasMap.clear();
}
}
/**
* Return the {@link Charset}'s {@link CharsetDecoder}.
* The Charsets class maintains the {@link CharsetDecoder} thread-local
* cache. Be aware - this shouldn't be used by multiple threads.
*
* @param charset {@link Charset}.
* @return the {@link Charset}'s {@link CharsetDecoder}.
*/
public static CharsetDecoder getCharsetDecoder(final Charset charset) {
if (charset == null) {
throw new IllegalArgumentException("Charset can not be null");
}
final CharsetDecoder decoder = obtainCodecsCache().getDecoder(charset);
decoder.reset();
return decoder;
}
/**
* Return the {@link Charset}'s {@link CharsetEncoder}.
* The Charsets class maintains the {@link CharsetEncoder} thread-local
* cache. Be aware - this shouldn't be used by multiple threads.
*
* @param charset {@link Charset}.
* @return the {@link Charset}'s {@link CharsetEncoder}.
*/
public static CharsetEncoder getCharsetEncoder(final Charset charset) {
if (charset == null) {
throw new IllegalArgumentException("Charset can not be null");
}
final CharsetEncoder encoder = obtainCodecsCache().getEncoder(charset);
encoder.reset();
return encoder;
}
private static CodecsCache obtainCodecsCache() {
CodecsCache cache = ThreadCache.getFromCache(CODECS_CACHE);
if (cache == null) {
cache = new CodecsCache();
ThreadCache.putToCache(CODECS_CACHE, cache);
}
return cache;
}
private static final class CodecsCache {
private final Object[] decoders =
new Object[CODECS_CACHE_SIZE];
private final Object[] encoders =
new Object[CODECS_CACHE_SIZE];
public CharsetDecoder getDecoder(final Charset charset) {
return (CharsetDecoder) obtainElementByCharset(
decoders, charset, DECODER_RESOLVER);
}
public CharsetEncoder getEncoder(final Charset charset) {
return (CharsetEncoder) obtainElementByCharset(
encoders, charset, ENCODER_RESOLVER);
}
private static Object obtainElementByCharset(final Object[] array,
final Charset charset, final CharsetCodecResolver resolver) {
int i = 0;
for (; i < array.length; i++) {
final Object currentElement = array[i];
if (currentElement == null) {
i++; // to make
break;
}
if (charset.equals(resolver.charset(currentElement))) {
makeFirst(array, i, currentElement);
return currentElement;
}
}
final Object newElement = resolver.newElement(charset);
makeFirst(array, i - 1, newElement);
return newElement;
}
private static void makeFirst(final Object[] array, final int offs,
final Object element) {
for (int i = offs - 1; i >= 0; i--) {
array[i + 1] = array[i];
}
array[0] = element;
}
}
private static interface CharsetCodecResolver {
Charset charset(Object element);
Object newElement(Charset charset);
}
private final static class DecoderResolver implements CharsetCodecResolver {
@Override
public Charset charset(final Object element) {
return ((CharsetDecoder) element).charset();
}
@Override
public Object newElement(final Charset charset) {
return charset.newDecoder();
}
}
private final static class EncoderResolver implements CharsetCodecResolver {
@Override
public Charset charset(final Object element) {
return ((CharsetEncoder) element).charset();
}
@Override
public Object newElement(final Charset charset) {
return charset.newEncoder();
}
}
}