src/java.base/share/classes/sun/nio/cs/StandardCharsets.java.template

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 *
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * version 2 for more details (a copy is included in the LICENSE file that
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// -- This file was mechanically generated: Do not edit! -- //

package sun.nio.cs;

import java.nio.charset.Charset;
import java.nio.charset.spi.CharsetProvider;
import java.util.Iterator;
import java.util.Map;
import java.util.Set;
import jdk.internal.vm.annotation.Stable;

public class StandardCharsets extends CharsetProvider {

    _INCLUDE_ALIASES_TABLES_
    _INCLUDE_ALIASES_MAP_
    _INCLUDE_CLASSES_MAP_
    _INCLUDE_CACHE_MAP_

    // Maps canonical names to class names
    private @Stable Map<String,String> classMap;

    // Maps alias names to canonical names
    private @Stable Map<String,String> aliasMap;

    // Maps canonical names to cached instances
    private @Stable Map<String,Charset> cache;

    private static final String packagePrefix = "sun.nio.cs.";

    public StandardCharsets() {
    }

    private String canonicalize(String csn) {
        if (csn.startsWith("gb18030-")) {
            return csn.equals("gb18030-2022") && !GB18030.IS_2000 ||
                   csn.equals("gb18030-2000") && GB18030.IS_2000 ? "gb18030" : csn;
        } else {
            String acn = aliasMap().get(csn);
            return (acn != null) ? acn : csn;
        }
    }

    private Map<String,String> aliasMap() {
        Map<String,String> map = aliasMap;
        if (map == null) {
            aliasMap = map = new Aliases();
        }
        return map;
    }

    private Map<String,String> classMap() {
        Map<String,String> map = classMap;
        if (map == null) {
            classMap = map = new Classes();
        }
        return map;
    }

    private Map<String,Charset> cache() {
        Map<String,Charset> map = cache;
        if (map == null) {
            map = new Cache();
            map.put("utf-8", UTF_8.INSTANCE);
            map.put("iso-8859-1", ISO_8859_1.INSTANCE);
            map.put("us-ascii", US_ASCII.INSTANCE);
            map.put("utf-16", java.nio.charset.StandardCharsets.UTF_16);
            map.put("utf-16be", java.nio.charset.StandardCharsets.UTF_16BE);
            map.put("utf-16le", java.nio.charset.StandardCharsets.UTF_16LE);
            map.put("utf-32", java.nio.charset.StandardCharsets.UTF_32);
            map.put("utf-32be", java.nio.charset.StandardCharsets.UTF_32BE);
            map.put("utf-32le", java.nio.charset.StandardCharsets.UTF_32LE);
            cache = map;
        }
        return map;
    }

    // Private ASCII-only version, optimized for interpretation during startup
    //
    private static String toLower(String s) {
        int n = s.length();
        boolean allLower = true;
        for (int i = 0; i < n; i++) {
            int c = s.charAt(i);
            if (((c - 'A') | ('Z' - c)) >= 0) {
                allLower = false;
                break;
            }
        }
        if (allLower)
            return s;
        StringBuilder sb = new StringBuilder(n);
        for (int i = 0; i < n; i++) {
            int c = s.charAt(i);
            if (((c - 'A') | ('Z' - c)) >= 0)
                sb.append((char)(c + 0x20));
            else
                sb.append((char)c);
        }
        return sb.toString();
    }

    private Charset lookup(String charsetName) {
        // By checking these built-ins we can avoid initializing Aliases,
        // Classes and Cache eagerly during bootstrap.
        //
        // Initialization of java.nio.charset.StandardCharsets should be
        // avoided here to minimize time spent in System.initPhase1, as it
        // may delay initialization of performance critical VM subsystems.
        String csn;
        if (charsetName.equals("UTF-8")) {
            return UTF_8.INSTANCE;
        } else if (charsetName.equals("US-ASCII")) {
            return US_ASCII.INSTANCE;
        } else if (charsetName.equals("ISO-8859-1")) {
            return ISO_8859_1.INSTANCE;
        } else {
            csn = canonicalize(toLower(charsetName));
        }

        // Check cache first
        Charset cs = cache().get(csn);
        if (cs != null)
            return cs;

        // Do we even support this charset?
        String cln = classMap().get(csn);
        if (cln == null)
            return null;

        // Instantiate the charset and cache it
        try {
            @SuppressWarnings("deprecation")
            Object o = Class.forName(packagePrefix + cln,
                                     true,
                                     this.getClass().getClassLoader()).newInstance();
            return cache(csn, (Charset)o);
        } catch (ClassNotFoundException |
                 IllegalAccessException |
                 InstantiationException x) {
            return null;
        }
    }

    private Charset cache(String csn, Charset cs) {
        cache().put(csn, cs);
        return cs;
    }

    public final Charset charsetForName(String charsetName) {
        synchronized (this) {
            return lookup(charsetName);
        }
    }

    public final Iterator<Charset> charsets() {
        Set<String> charsetNames;
        synchronized (this) {
            // Ensure initialized in synchronized block
            charsetNames = classMap().keySet();
            aliasMap();
            cache();
        }
        return new Iterator<Charset>() {

                Iterator<String> i = charsetNames.iterator();

                public boolean hasNext() {
                    return i.hasNext();
                }

                public Charset next() {
                    String csn = i.next();
                    return lookup(csn);
                }

                public void remove() {
                    throw new UnsupportedOperationException();
                }

            };
    }
}