| /* |
| * 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 java.nio.ByteBuffer; |
| import java.nio.CharBuffer; |
| import java.nio.charset.spi.CharsetProvider; |
| import java.security.AccessController; |
| import java.security.PrivilegedAction; |
| import java.util.Arrays; |
| import java.util.Collections; |
| 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.Set; |
| import java.util.ServiceLoader; |
| import java.util.ServiceConfigurationError; |
| import java.util.SortedMap; |
| import java.util.TreeMap; |
| import jdk.internal.misc.VM; |
| import sun.nio.cs.StandardCharsets; |
| import sun.nio.cs.ThreadLocalCoders; |
| import sun.security.action.GetPropertyAction; |
| |
| |
| /** |
| * 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>'\u0041'</code> through <code>'\u005a'</code>), |
| * |
| * <li> The lowercase letters {@code 'a'} through {@code 'z'} |
| * (<code>'\u0061'</code> through <code>'\u007a'</code>), |
| * |
| * <li> The digits {@code '0'} through {@code '9'} |
| * (<code>'\u0030'</code> through <code>'\u0039'</code>), |
| * |
| * <li> The dash character {@code '-'} |
| * (<code>'\u002d'</code>, <small>HYPHEN-MINUS</small>), |
| * |
| * <li> The plus character {@code '+'} |
| * (<code>'\u002b'</code>, <small>PLUS SIGN</small>), |
| * |
| * <li> The period character {@code '.'} |
| * (<code>'\u002e'</code>, <small>FULL STOP</small>), |
| * |
| * <li> The colon character {@code ':'} |
| * (<code>'\u003a'</code>, <small>COLON</small>), and |
| * |
| * <li> The underscore character {@code '_'} |
| * (<code>'\u005f'</code>, <small>LOW 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 2278: 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 style="text-align:left">Charset</th><th style="text-align:left">Description</th></tr> |
| * </thead> |
| * <tbody> |
| * <tr><td style="vertical-align:top">{@code US-ASCII}</td> |
| * <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><td style="vertical-align:top"><code>ISO-8859-1 </code></td> |
| * <td>ISO Latin Alphabet No. 1, a.k.a. {@code ISO-LATIN-1}</td></tr> |
| * <tr><td style="vertical-align:top">{@code UTF-8}</td> |
| * <td>Eight-bit UCS Transformation Format</td></tr> |
| * <tr><td style="vertical-align:top">{@code UTF-16BE}</td> |
| * <td>Sixteen-bit UCS Transformation Format, |
| * big-endian byte order</td></tr> |
| * <tr><td style="vertical-align:top">{@code UTF-16LE}</td> |
| * <td>Sixteen-bit UCS Transformation Format, |
| * little-endian byte order</td></tr> |
| * <tr><td style="vertical-align:top">{@code UTF-16}</td> |
| * <td>Sixteen-bit UCS Transformation Format, |
| * byte 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 2279</i></a>; the |
| * transformation format upon which it is based is specified in |
| * Amendment 2 of ISO 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 2781</i></a>; the |
| * transformation formats upon which they are based are specified in |
| * Amendment 1 of ISO 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>'\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> Every instance of the Java virtual machine has a default charset, which |
| * may or may not be one of the standard charsets. The default charset is |
| * determined during virtual-machine startup and typically depends upon the |
| * locale and charset being used by the underlying operating system. </p> |
| * |
| * <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 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 8859-1, |
| * JIS X 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 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 X 0201, JIS X 0208, and JIS X 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 -- */ |
| |
| private static volatile String bugLevel; |
| |
| static boolean atBugLevel(String bl) { // package-private |
| String level = bugLevel; |
| if (level == null) { |
| if (!VM.isBooted()) |
| return false; |
| bugLevel = level = GetPropertyAction |
| .privilegedGetProperty("sun.nio.cs.bugLevel", ""); |
| } |
| return level.equals(bl); |
| } |
| |
| /** |
| * 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 && !atBugLevel("1.4")) { |
| 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); |
| } |
| } |
| |
| /* The standard set of charsets */ |
| private static final CharsetProvider standardProvider = new 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 |
| // |
| private static volatile Object[] cache1; // "Level 1" cache |
| private static volatile Object[] cache2; // "Level 2" cache |
| |
| private static void cache(String charsetName, Charset cs) { |
| cache2 = cache1; |
| cache1 = new Object[] { 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<>() { |
| ClassLoader cl = ClassLoader.getSystemClassLoader(); |
| ServiceLoader<CharsetProvider> sl = |
| ServiceLoader.load(CharsetProvider.class, cl); |
| 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); |
| } |
| } |
| |
| /* 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; |
| } |
| |
| private static Charset lookup(String charsetName) { |
| if (charsetName == null) |
| throw new IllegalArgumentException("Null charset name"); |
| Object[] a; |
| if ((a = cache1) != null && charsetName.equals(a[0])) |
| return (Charset)a[1]; |
| // We expect most programs to use one Charset repeatedly. |
| // We convey a hint to this effect to the VM by putting the |
| // level 1 cache miss code in a separate method. |
| return lookup2(charsetName); |
| } |
| |
| private static Charset lookup2(String charsetName) { |
| Object[] a; |
| if ((a = cache2) != null && charsetName.equals(a[0])) { |
| cache2 = cache1; |
| cache1 = a; |
| return (Charset)a[1]; |
| } |
| Charset cs; |
| if ((cs = standardProvider.charsetForName(charsetName)) != null || |
| (cs = lookupExtendedCharset(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); |
| } |
| |
| // 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); |
| put(standardProvider.charsets(), m); |
| CharsetProvider[] ecps = ExtendedProviderHolder.extendedProviders; |
| for (CharsetProvider ecp :ecps) { |
| put(ecp.charsets(), m); |
| } |
| 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> The default charset is determined during virtual-machine startup and |
| * typically depends upon the locale and charset of the underlying |
| * operating system. |
| * |
| * @return A charset object for the default charset |
| * |
| * @since 1.5 |
| */ |
| public static Charset defaultCharset() { |
| if (defaultCharset == null) { |
| synchronized (Charset.class) { |
| String csn = GetPropertyAction |
| .privilegedGetProperty("file.encoding"); |
| Charset cs = lookup(csn); |
| if (cs != null) |
| defaultCharset = cs; |
| else |
| defaultCharset = forName("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) { |
| checkName(canonicalName); |
| String[] as = Objects.requireNonNullElse(aliases, zeroAliases); |
| 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(); |
| } |
| |
| } |
