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/*
* Copyright (C) 2014 The Android Open Source Project
* Copyright (c) 2000, 2017, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*/
package java.nio.charset;
import com.android.icu.charset.CharsetFactory;
import java.io.UnsupportedEncodingException;
import jdk.internal.misc.VM;
import sun.misc.ASCIICaseInsensitiveComparator;
import sun.nio.cs.ThreadLocalCoders;
import sun.security.action.GetPropertyAction;
import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.charset.spi.CharsetProvider;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.AbstractMap;
import java.util.Arrays;
import java.util.Collections;
import java.util.HashMap;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Locale;
import java.util.Map;
import java.util.NoSuchElementException;
import java.util.Objects;
import java.util.ServiceConfigurationError;
import java.util.ServiceLoader;
import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;
// Android-changed: Docs to say UTF-8 is always the platform default charset.
/**
* A named mapping between sequences of sixteen-bit Unicode <a
* href="../../lang/Character.html#unicode">code units</a> and sequences of
* bytes. This class defines methods for creating decoders and encoders and
* for retrieving the various names associated with a charset. Instances of
* this class are immutable.
*
* <p> This class also defines static methods for testing whether a particular
* charset is supported, for locating charset instances by name, and for
* constructing a map that contains every charset for which support is
* available in the current Java virtual machine. Support for new charsets can
* be added via the service-provider interface defined in the {@link
* java.nio.charset.spi.CharsetProvider} class.
*
* <p> All of the methods defined in this class are safe for use by multiple
* concurrent threads.
*
*
* <a id="names"></a><a id="charenc"></a>
* <h2>Charset names</h2>
*
* <p> Charsets are named by strings composed of the following characters:
*
* <ul>
*
* <li> The uppercase letters {@code 'A'} through {@code 'Z'}
* (<code>'&#92;u0041'</code>&nbsp;through&nbsp;<code>'&#92;u005a'</code>),
*
* <li> The lowercase letters {@code 'a'} through {@code 'z'}
* (<code>'&#92;u0061'</code>&nbsp;through&nbsp;<code>'&#92;u007a'</code>),
*
* <li> The digits {@code '0'} through {@code '9'}
* (<code>'&#92;u0030'</code>&nbsp;through&nbsp;<code>'&#92;u0039'</code>),
*
* <li> The dash character {@code '-'}
* (<code>'&#92;u002d'</code>,&nbsp;<small>HYPHEN-MINUS</small>),
*
* <li> The plus character {@code '+'}
* (<code>'&#92;u002b'</code>,&nbsp;<small>PLUS SIGN</small>),
*
* <li> The period character {@code '.'}
* (<code>'&#92;u002e'</code>,&nbsp;<small>FULL STOP</small>),
*
* <li> The colon character {@code ':'}
* (<code>'&#92;u003a'</code>,&nbsp;<small>COLON</small>), and
*
* <li> The underscore character {@code '_'}
* (<code>'&#92;u005f'</code>,&nbsp;<small>LOW&nbsp;LINE</small>).
*
* </ul>
*
* A charset name must begin with either a letter or a digit. The empty string
* is not a legal charset name. Charset names are not case-sensitive; that is,
* case is always ignored when comparing charset names. Charset names
* generally follow the conventions documented in <a
* href="http://www.ietf.org/rfc/rfc2278.txt"><i>RFC&nbsp;2278:&nbsp;IANA Charset
* Registration Procedures</i></a>.
*
* <p> Every charset has a <i>canonical name</i> and may also have one or more
* <i>aliases</i>. The canonical name is returned by the {@link #name() name} method
* of this class. Canonical names are, by convention, usually in upper case.
* The aliases of a charset are returned by the {@link #aliases() aliases}
* method.
*
* <p><a id="hn">Some charsets have an <i>historical name</i> that is defined for
* compatibility with previous versions of the Java platform.</a> A charset's
* historical name is either its canonical name or one of its aliases. The
* historical name is returned by the {@code getEncoding()} methods of the
* {@link java.io.InputStreamReader#getEncoding InputStreamReader} and {@link
* java.io.OutputStreamWriter#getEncoding OutputStreamWriter} classes.
*
* <p><a id="iana"> </a>If a charset listed in the <a
* href="http://www.iana.org/assignments/character-sets"><i>IANA Charset
* Registry</i></a> is supported by an implementation of the Java platform then
* its canonical name must be the name listed in the registry. Many charsets
* are given more than one name in the registry, in which case the registry
* identifies one of the names as <i>MIME-preferred</i>. If a charset has more
* than one registry name then its canonical name must be the MIME-preferred
* name and the other names in the registry must be valid aliases. If a
* supported charset is not listed in the IANA registry then its canonical name
* must begin with one of the strings {@code "X-"} or {@code "x-"}.
*
* <p> The IANA charset registry does change over time, and so the canonical
* name and the aliases of a particular charset may also change over time. To
* ensure compatibility it is recommended that no alias ever be removed from a
* charset, and that if the canonical name of a charset is changed then its
* previous canonical name be made into an alias.
*
*
* <h2>Standard charsets</h2>
*
*
*
* <p><a id="standard">Every implementation of the Java platform is required to support the
* following standard charsets.</a> Consult the release documentation for your
* implementation to see if any other charsets are supported. The behavior
* of such optional charsets may differ between implementations.
*
* <blockquote><table class="striped" style="width:80%">
* <caption style="display:none">Description of standard charsets</caption>
* <thead>
* <tr><th scope="col" style="text-align:left">Charset</th><th scope="col" style="text-align:left">Description</th></tr>
* </thead>
* <tbody>
* <tr><th scope="row" style="vertical-align:top">{@code US-ASCII}</th>
* <td>Seven-bit ASCII, a.k.a. {@code ISO646-US},
* a.k.a. the Basic Latin block of the Unicode character set</td></tr>
* <tr><th scope="row" style="vertical-align:top"><code>ISO-8859-1&nbsp;&nbsp;</code></th>
* <td>ISO Latin Alphabet No. 1, a.k.a. {@code ISO-LATIN-1}</td></tr>
* <tr><th scope="row" style="vertical-align:top">{@code UTF-8}</th>
* <td>Eight-bit UCS Transformation Format</td></tr>
* <tr><th scope="row" style="vertical-align:top">{@code UTF-16BE}</th>
* <td>Sixteen-bit UCS Transformation Format,
* big-endian byte&nbsp;order</td></tr>
* <tr><th scope="row" style="vertical-align:top">{@code UTF-16LE}</th>
* <td>Sixteen-bit UCS Transformation Format,
* little-endian byte&nbsp;order</td></tr>
* <tr><th scope="row" style="vertical-align:top">{@code UTF-16}</th>
* <td>Sixteen-bit UCS Transformation Format,
* byte&nbsp;order identified by an optional byte-order mark</td></tr>
* </tbody>
* </table></blockquote>
*
* <p> The {@code UTF-8} charset is specified by <a
* href="http://www.ietf.org/rfc/rfc2279.txt"><i>RFC&nbsp;2279</i></a>; the
* transformation format upon which it is based is specified in
* Amendment&nbsp;2 of ISO&nbsp;10646-1 and is also described in the <a
* href="http://www.unicode.org/unicode/standard/standard.html"><i>Unicode
* Standard</i></a>.
*
* <p> The {@code UTF-16} charsets are specified by <a
* href="http://www.ietf.org/rfc/rfc2781.txt"><i>RFC&nbsp;2781</i></a>; the
* transformation formats upon which they are based are specified in
* Amendment&nbsp;1 of ISO&nbsp;10646-1 and are also described in the <a
* href="http://www.unicode.org/unicode/standard/standard.html"><i>Unicode
* Standard</i></a>.
*
* <p> The {@code UTF-16} charsets use sixteen-bit quantities and are
* therefore sensitive to byte order. In these encodings the byte order of a
* stream may be indicated by an initial <i>byte-order mark</i> represented by
* the Unicode character <code>'&#92;uFEFF'</code>. Byte-order marks are handled
* as follows:
*
* <ul>
*
* <li><p> When decoding, the {@code UTF-16BE} and {@code UTF-16LE}
* charsets interpret the initial byte-order marks as a <small>ZERO-WIDTH
* NON-BREAKING SPACE</small>; when encoding, they do not write
* byte-order marks. </p></li>
*
* <li><p> When decoding, the {@code UTF-16} charset interprets the
* byte-order mark at the beginning of the input stream to indicate the
* byte-order of the stream but defaults to big-endian if there is no
* byte-order mark; when encoding, it uses big-endian byte order and writes
* a big-endian byte-order mark. </p></li>
*
* </ul>
*
* In any case, byte order marks occurring after the first element of an
* input sequence are not omitted since the same code is used to represent
* <small>ZERO-WIDTH NON-BREAKING SPACE</small>.
*
* <p>Android note: The Android platform default is always UTF-8.
*
* <p>The {@link StandardCharsets} class defines constants for each of the
* standard charsets.
*
* <h2>Terminology</h2>
*
* <p> The name of this class is taken from the terms used in
* <a href="http://www.ietf.org/rfc/rfc2278.txt"><i>RFC&nbsp;2278</i></a>.
* In that document a <i>charset</i> is defined as the combination of
* one or more coded character sets and a character-encoding scheme.
* (This definition is confusing; some other software systems define
* <i>charset</i> as a synonym for <i>coded character set</i>.)
*
* <p> A <i>coded character set</i> is a mapping between a set of abstract
* characters and a set of integers. US-ASCII, ISO&nbsp;8859-1,
* JIS&nbsp;X&nbsp;0201, and Unicode are examples of coded character sets.
*
* <p> Some standards have defined a <i>character set</i> to be simply a
* set of abstract characters without an associated assigned numbering.
* An alphabet is an example of such a character set. However, the subtle
* distinction between <i>character set</i> and <i>coded character set</i>
* is rarely used in practice; the former has become a short form for the
* latter, including in the Java API specification.
*
* <p> A <i>character-encoding scheme</i> is a mapping between one or more
* coded character sets and a set of octet (eight-bit byte) sequences.
* UTF-8, UTF-16, ISO&nbsp;2022, and EUC are examples of
* character-encoding schemes. Encoding schemes are often associated with
* a particular coded character set; UTF-8, for example, is used only to
* encode Unicode. Some schemes, however, are associated with multiple
* coded character sets; EUC, for example, can be used to encode
* characters in a variety of Asian coded character sets.
*
* <p> When a coded character set is used exclusively with a single
* character-encoding scheme then the corresponding charset is usually
* named for the coded character set; otherwise a charset is usually named
* for the encoding scheme and, possibly, the locale of the coded
* character sets that it supports. Hence {@code US-ASCII} is both the
* name of a coded character set and of the charset that encodes it, while
* {@code EUC-JP} is the name of the charset that encodes the
* JIS&nbsp;X&nbsp;0201, JIS&nbsp;X&nbsp;0208, and JIS&nbsp;X&nbsp;0212
* coded character sets for the Japanese language.
*
* <p> The native character encoding of the Java programming language is
* UTF-16. A charset in the Java platform therefore defines a mapping
* between sequences of sixteen-bit UTF-16 code units (that is, sequences
* of chars) and sequences of bytes. </p>
*
*
* @author Mark Reinhold
* @author JSR-51 Expert Group
* @since 1.4
*
* @see CharsetDecoder
* @see CharsetEncoder
* @see java.nio.charset.spi.CharsetProvider
* @see java.lang.Character
*/
public abstract class Charset
implements Comparable<Charset>
{
/* -- Static methods -- */
/**
* Checks that the given string is a legal charset name. </p>
*
* @param s
* A purported charset name
*
* @throws IllegalCharsetNameException
* If the given name is not a legal charset name
*/
private static void checkName(String s) {
int n = s.length();
if (n == 0) {
throw new IllegalCharsetNameException(s);
}
for (int i = 0; i < n; i++) {
char c = s.charAt(i);
if (c >= 'A' && c <= 'Z') continue;
if (c >= 'a' && c <= 'z') continue;
if (c >= '0' && c <= '9') continue;
if (c == '-' && i != 0) continue;
if (c == '+' && i != 0) continue;
if (c == ':' && i != 0) continue;
if (c == '_' && i != 0) continue;
if (c == '.' && i != 0) continue;
throw new IllegalCharsetNameException(s);
}
}
// Android-removed: We use ICU's list of standard charsets.
/* The standard set of charsets */
// private static final CharsetProvider standardProvider
// = new sun.nio.cs.StandardCharsets();
private static final String[] zeroAliases = new String[0];
// Cache of the most-recently-returned charsets,
// along with the names that were used to find them
//
// cache1/2 usage is explained in the lookup method
//
private static volatile Map.Entry<String, Charset> cache1 = null; // "Level 1" cache
private static final HashMap<String, Charset> cache2 = new HashMap<>(); // "Level 2" cache
private static void cache(String charsetName, Charset cs) {
synchronized(cache2) {
String canonicalName = cs.name();
Charset canonicalCharset = cache2.get(canonicalName);
if (canonicalCharset != null) {
cs = canonicalCharset;
} else {
cache2.put(canonicalName, cs);
for (String alias : cs.aliases()) {
cache2.put(alias, cs);
}
}
cache2.put(charsetName, cs);
}
cache1 = new AbstractMap.SimpleImmutableEntry<>(charsetName, cs);
}
// Creates an iterator that walks over the available providers, ignoring
// those whose lookup or instantiation causes a security exception to be
// thrown. Should be invoked with full privileges.
//
private static Iterator<CharsetProvider> providers() {
return new Iterator<>() {
ServiceLoader<CharsetProvider> sl =
ServiceLoader.load(CharsetProvider.class);
Iterator<CharsetProvider> i = sl.iterator();
CharsetProvider next = null;
private boolean getNext() {
while (next == null) {
try {
if (!i.hasNext())
return false;
next = i.next();
} catch (ServiceConfigurationError sce) {
if (sce.getCause() instanceof SecurityException) {
// Ignore security exceptions
continue;
}
throw sce;
}
}
return true;
}
public boolean hasNext() {
return getNext();
}
public CharsetProvider next() {
if (!getNext())
throw new NoSuchElementException();
CharsetProvider n = next;
next = null;
return n;
}
public void remove() {
throw new UnsupportedOperationException();
}
};
}
// Thread-local gate to prevent recursive provider lookups
private static ThreadLocal<ThreadLocal<?>> gate =
new ThreadLocal<ThreadLocal<?>>();
private static Charset lookupViaProviders(final String charsetName) {
// The runtime startup sequence looks up standard charsets as a
// consequence of the VM's invocation of System.initializeSystemClass
// in order to, e.g., set system properties and encode filenames. At
// that point the application class loader has not been initialized,
// however, so we can't look for providers because doing so will cause
// that loader to be prematurely initialized with incomplete
// information.
//
if (!VM.isBooted())
return null;
if (gate.get() != null)
// Avoid recursive provider lookups
return null;
try {
gate.set(gate);
return AccessController.doPrivileged(
new PrivilegedAction<>() {
public Charset run() {
for (Iterator<CharsetProvider> i = providers();
i.hasNext();) {
CharsetProvider cp = i.next();
Charset cs = cp.charsetForName(charsetName);
if (cs != null)
return cs;
}
return null;
}
});
} finally {
gate.set(null);
}
}
// Android-removed: Remove support for the extended charset provider.
//
/* The extended set of charsets */
/*
private static class ExtendedProviderHolder {
static final CharsetProvider[] extendedProviders = extendedProviders();
// returns ExtendedProvider, if installed
private static CharsetProvider[] extendedProviders() {
return AccessController.doPrivileged(new PrivilegedAction<>() {
public CharsetProvider[] run() {
CharsetProvider[] cps = new CharsetProvider[1];
int n = 0;
ServiceLoader<CharsetProvider> sl =
ServiceLoader.loadInstalled(CharsetProvider.class);
for (CharsetProvider cp : sl) {
if (n + 1 > cps.length) {
cps = Arrays.copyOf(cps, cps.length << 1);
}
cps[n++] = cp;
}
return n == cps.length ? cps : Arrays.copyOf(cps, n);
}});
}
}
private static Charset lookupExtendedCharset(String charsetName) {
if (!VM.isBooted()) // see lookupViaProviders()
return null;
CharsetProvider[] ecps = ExtendedProviderHolder.extendedProviders;
for (CharsetProvider cp : ecps) {
Charset cs = cp.charsetForName(charsetName);
if (cs != null)
return cs;
}
return null;
}
*/
// We expect most programs to use one Charset repeatedly, so the most recently used Charset
// instance is stored in the level 1 cache. We convey a hint to this effect to the VM by putting
// the level 1 cache miss code in a separate method. Since charsetName is not necessarily in
// canonical form, we store the mapping from both the canonical name and the aliases to the
// instance in a map for level 2 cache.
private static Charset lookup(String charsetName) {
if (charsetName == null)
throw new IllegalArgumentException("Null charset name");
final Map.Entry<String, Charset> cached = cache1;
if (cached != null && charsetName.equals(cached.getKey()))
return cached.getValue();
return lookup2(charsetName);
}
private static Charset lookup2(String charsetName) {
Charset cs;
synchronized (cache2) {
if ((cs = cache2.get(charsetName)) != null) {
cache1 = new AbstractMap.SimpleImmutableEntry<>(charsetName, cs);
return cs;
}
}
// Android-changed: Drop support for "standard" and "extended"
// providers.
if ((cs = CharsetFactory.create(charsetName)) != null ||
(cs = lookupViaProviders(charsetName)) != null)
{
cache(charsetName, cs);
return cs;
}
/* Only need to check the name if we didn't find a charset for it */
checkName(charsetName);
return null;
}
/**
* Tells whether the named charset is supported.
*
* @param charsetName
* The name of the requested charset; may be either
* a canonical name or an alias
*
* @return {@code true} if, and only if, support for the named charset
* is available in the current Java virtual machine
*
* @throws IllegalCharsetNameException
* If the given charset name is illegal
*
* @throws IllegalArgumentException
* If the given {@code charsetName} is null
*/
public static boolean isSupported(String charsetName) {
return (lookup(charsetName) != null);
}
/**
* Returns a charset object for the named charset.
*
* @param charsetName
* The name of the requested charset; may be either
* a canonical name or an alias
*
* @return A charset object for the named charset
*
* @throws IllegalCharsetNameException
* If the given charset name is illegal
*
* @throws IllegalArgumentException
* If the given {@code charsetName} is null
*
* @throws UnsupportedCharsetException
* If no support for the named charset is available
* in this instance of the Java virtual machine
*/
public static Charset forName(String charsetName) {
Charset cs = lookup(charsetName);
if (cs != null)
return cs;
throw new UnsupportedCharsetException(charsetName);
}
// BEGIN Android-added: forNameUEE(String) method.
/**
* Equivalent to {@code forName} but only throws {@code UnsupportedEncodingException},
* which is all pre-nio code claims to throw.
*
* @hide internal use only
*/
public static Charset forNameUEE(String charsetName) throws UnsupportedEncodingException {
try {
return Charset.forName(charsetName);
} catch (Exception cause) {
UnsupportedEncodingException ex = new UnsupportedEncodingException(charsetName);
ex.initCause(cause);
throw ex;
}
}
// END Android-added: forNameUEE(String) method.
// Fold charsets from the given iterator into the given map, ignoring
// charsets whose names already have entries in the map.
//
private static void put(Iterator<Charset> i, Map<String,Charset> m) {
while (i.hasNext()) {
Charset cs = i.next();
if (!m.containsKey(cs.name()))
m.put(cs.name(), cs);
}
}
/**
* Constructs a sorted map from canonical charset names to charset objects.
*
* <p> The map returned by this method will have one entry for each charset
* for which support is available in the current Java virtual machine. If
* two or more supported charsets have the same canonical name then the
* resulting map will contain just one of them; which one it will contain
* is not specified. </p>
*
* <p> The invocation of this method, and the subsequent use of the
* resulting map, may cause time-consuming disk or network I/O operations
* to occur. This method is provided for applications that need to
* enumerate all of the available charsets, for example to allow user
* charset selection. This method is not used by the {@link #forName
* forName} method, which instead employs an efficient incremental lookup
* algorithm.
*
* <p> This method may return different results at different times if new
* charset providers are dynamically made available to the current Java
* virtual machine. In the absence of such changes, the charsets returned
* by this method are exactly those that can be retrieved via the {@link
* #forName forName} method. </p>
*
* @return An immutable, case-insensitive map from canonical charset names
* to charset objects
*/
public static SortedMap<String,Charset> availableCharsets() {
return AccessController.doPrivileged(
new PrivilegedAction<>() {
public SortedMap<String,Charset> run() {
TreeMap<String,Charset> m =
new TreeMap<>(
String.CASE_INSENSITIVE_ORDER);
// Android-changed: No more "standard" and extended provider.
// put(standardProvider.charsets(), m);
// CharsetProvider[] ecps = ExtendedProviderHolder.extendedProviders;
// for (CharsetProvider ecp :ecps) {
// put(ecp.charsets(), m);
// }
for (String charsetName : CharsetFactory.getAvailableCharsetNames()) {
Charset charset = CharsetFactory.create(charsetName);
m.put(charset.name(), charset);
}
for (Iterator<CharsetProvider> i = providers(); i.hasNext();) {
CharsetProvider cp = i.next();
put(cp.charsets(), m);
}
return Collections.unmodifiableSortedMap(m);
}
});
}
private static volatile Charset defaultCharset;
/**
* Returns the default charset of this Java virtual machine.
*
* <p>Android note: The Android platform default is always UTF-8.
*
* @return A charset object for the default charset
*
* @since 1.5
*/
public static Charset defaultCharset() {
// Android-changed: Use UTF_8 unconditionally.
/*
if (defaultCharset == null) {
synchronized (Charset.class) {
String csn = GetPropertyAction
.privilegedGetProperty("file.encoding");
Charset cs = lookup(csn);
if (cs != null)
defaultCharset = cs;
else
defaultCharset = sun.nio.cs.UTF_8.INSTANCE;
}
}
*/
if (defaultCharset == null) {
synchronized (Charset.class) {
defaultCharset = java.nio.charset.StandardCharsets.UTF_8;
}
}
return defaultCharset;
}
/* -- Instance fields and methods -- */
private final String name; // tickles a bug in oldjavac
private final String[] aliases; // tickles a bug in oldjavac
private Set<String> aliasSet = null;
/**
* Initializes a new charset with the given canonical name and alias
* set.
*
* @param canonicalName
* The canonical name of this charset
*
* @param aliases
* An array of this charset's aliases, or null if it has no aliases
*
* @throws IllegalCharsetNameException
* If the canonical name or any of the aliases are illegal
*/
protected Charset(String canonicalName, String[] aliases) {
String[] as = Objects.requireNonNullElse(aliases, zeroAliases);
// Skip checks for the standard, built-in Charsets we always load
// during initialization.
if (canonicalName != "ISO-8859-1"
&& canonicalName != "US-ASCII"
&& canonicalName != "UTF-8") {
checkName(canonicalName);
for (int i = 0; i < as.length; i++) {
checkName(as[i]);
}
}
this.name = canonicalName;
this.aliases = as;
}
/**
* Returns this charset's canonical name.
*
* @return The canonical name of this charset
*/
public final String name() {
return name;
}
/**
* Returns a set containing this charset's aliases.
*
* @return An immutable set of this charset's aliases
*/
public final Set<String> aliases() {
if (aliasSet != null)
return aliasSet;
int n = aliases.length;
HashSet<String> hs = new HashSet<>(n);
for (int i = 0; i < n; i++)
hs.add(aliases[i]);
aliasSet = Collections.unmodifiableSet(hs);
return aliasSet;
}
/**
* Returns this charset's human-readable name for the default locale.
*
* <p> The default implementation of this method simply returns this
* charset's canonical name. Concrete subclasses of this class may
* override this method in order to provide a localized display name. </p>
*
* @return The display name of this charset in the default locale
*/
public String displayName() {
return name;
}
/**
* Tells whether or not this charset is registered in the <a
* href="http://www.iana.org/assignments/character-sets">IANA Charset
* Registry</a>.
*
* @return {@code true} if, and only if, this charset is known by its
* implementor to be registered with the IANA
*/
public final boolean isRegistered() {
return !name.startsWith("X-") && !name.startsWith("x-");
}
/**
* Returns this charset's human-readable name for the given locale.
*
* <p> The default implementation of this method simply returns this
* charset's canonical name. Concrete subclasses of this class may
* override this method in order to provide a localized display name. </p>
*
* @param locale
* The locale for which the display name is to be retrieved
*
* @return The display name of this charset in the given locale
*/
public String displayName(Locale locale) {
return name;
}
/**
* Tells whether or not this charset contains the given charset.
*
* <p> A charset <i>C</i> is said to <i>contain</i> a charset <i>D</i> if,
* and only if, every character representable in <i>D</i> is also
* representable in <i>C</i>. If this relationship holds then it is
* guaranteed that every string that can be encoded in <i>D</i> can also be
* encoded in <i>C</i> without performing any replacements.
*
* <p> That <i>C</i> contains <i>D</i> does not imply that each character
* representable in <i>C</i> by a particular byte sequence is represented
* in <i>D</i> by the same byte sequence, although sometimes this is the
* case.
*
* <p> Every charset contains itself.
*
* <p> This method computes an approximation of the containment relation:
* If it returns {@code true} then the given charset is known to be
* contained by this charset; if it returns {@code false}, however, then
* it is not necessarily the case that the given charset is not contained
* in this charset.
*
* @param cs
* The given charset
*
* @return {@code true} if the given charset is contained in this charset
*/
public abstract boolean contains(Charset cs);
/**
* Constructs a new decoder for this charset.
*
* @return A new decoder for this charset
*/
public abstract CharsetDecoder newDecoder();
/**
* Constructs a new encoder for this charset.
*
* @return A new encoder for this charset
*
* @throws UnsupportedOperationException
* If this charset does not support encoding
*/
public abstract CharsetEncoder newEncoder();
/**
* Tells whether or not this charset supports encoding.
*
* <p> Nearly all charsets support encoding. The primary exceptions are
* special-purpose <i>auto-detect</i> charsets whose decoders can determine
* which of several possible encoding schemes is in use by examining the
* input byte sequence. Such charsets do not support encoding because
* there is no way to determine which encoding should be used on output.
* Implementations of such charsets should override this method to return
* {@code false}. </p>
*
* @return {@code true} if, and only if, this charset supports encoding
*/
public boolean canEncode() {
return true;
}
/**
* Convenience method that decodes bytes in this charset into Unicode
* characters.
*
* <p> An invocation of this method upon a charset {@code cs} returns the
* same result as the expression
*
* <pre>
* cs.newDecoder()
* .onMalformedInput(CodingErrorAction.REPLACE)
* .onUnmappableCharacter(CodingErrorAction.REPLACE)
* .decode(bb); </pre>
*
* except that it is potentially more efficient because it can cache
* decoders between successive invocations.
*
* <p> This method always replaces malformed-input and unmappable-character
* sequences with this charset's default replacement byte array. In order
* to detect such sequences, use the {@link
* CharsetDecoder#decode(java.nio.ByteBuffer)} method directly. </p>
*
* @param bb The byte buffer to be decoded
*
* @return A char buffer containing the decoded characters
*/
public final CharBuffer decode(ByteBuffer bb) {
try {
return ThreadLocalCoders.decoderFor(this)
.onMalformedInput(CodingErrorAction.REPLACE)
.onUnmappableCharacter(CodingErrorAction.REPLACE)
.decode(bb);
} catch (CharacterCodingException x) {
throw new Error(x); // Can't happen
}
}
/**
* Convenience method that encodes Unicode characters into bytes in this
* charset.
*
* <p> An invocation of this method upon a charset {@code cs} returns the
* same result as the expression
*
* <pre>
* cs.newEncoder()
* .onMalformedInput(CodingErrorAction.REPLACE)
* .onUnmappableCharacter(CodingErrorAction.REPLACE)
* .encode(bb); </pre>
*
* except that it is potentially more efficient because it can cache
* encoders between successive invocations.
*
* <p> This method always replaces malformed-input and unmappable-character
* sequences with this charset's default replacement string. In order to
* detect such sequences, use the {@link
* CharsetEncoder#encode(java.nio.CharBuffer)} method directly. </p>
*
* @param cb The char buffer to be encoded
*
* @return A byte buffer containing the encoded characters
*/
public final ByteBuffer encode(CharBuffer cb) {
try {
return ThreadLocalCoders.encoderFor(this)
.onMalformedInput(CodingErrorAction.REPLACE)
.onUnmappableCharacter(CodingErrorAction.REPLACE)
.encode(cb);
} catch (CharacterCodingException x) {
throw new Error(x); // Can't happen
}
}
/**
* Convenience method that encodes a string into bytes in this charset.
*
* <p> An invocation of this method upon a charset {@code cs} returns the
* same result as the expression
*
* <pre>
* cs.encode(CharBuffer.wrap(s)); </pre>
*
* @param str The string to be encoded
*
* @return A byte buffer containing the encoded characters
*/
public final ByteBuffer encode(String str) {
return encode(CharBuffer.wrap(str));
}
/**
* Compares this charset to another.
*
* <p> Charsets are ordered by their canonical names, without regard to
* case. </p>
*
* @param that
* The charset to which this charset is to be compared
*
* @return A negative integer, zero, or a positive integer as this charset
* is less than, equal to, or greater than the specified charset
*/
public final int compareTo(Charset that) {
return (name().compareToIgnoreCase(that.name()));
}
/**
* Computes a hashcode for this charset.
*
* @return An integer hashcode
*/
public final int hashCode() {
return name().hashCode();
}
/**
* Tells whether or not this object is equal to another.
*
* <p> Two charsets are equal if, and only if, they have the same canonical
* names. A charset is never equal to any other type of object. </p>
*
* @return {@code true} if, and only if, this charset is equal to the
* given object
*/
public final boolean equals(Object ob) {
if (!(ob instanceof Charset))
return false;
if (this == ob)
return true;
return name.equals(((Charset)ob).name());
}
/**
* Returns a string describing this charset.
*
* @return A string describing this charset
*/
public final String toString() {
return name();
}
}
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