NameCodec.java

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 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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 * This code is free software; you can redistribute it and/or modify it
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 * 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
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 * accompanied this code).
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/*
 * This file is available under and governed by the GNU General Public
 * License version 2 only, as published by the Free Software Foundation.
 * However, the following notice accompanied the original version of this
 * file, and Oracle licenses the original version of this file under the BSD
 * license:
 */
/*
   Copyright 2009-2013 Attila Szegedi

   Licensed under both the Apache License, Version 2.0 (the "Apache License")
   and the BSD License (the "BSD License"), with licensee being free to
   choose either of the two at their discretion.

   You may not use this file except in compliance with either the Apache
   License or the BSD License.

   If you choose to use this file in compliance with the Apache License, the
   following notice applies to you:

       You may obtain a copy of the Apache License at

           http://www.apache.org/licenses/LICENSE-2.0

       Unless required by applicable law or agreed to in writing, software
       distributed under the License is distributed on an "AS IS" BASIS,
       WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
       implied. See the License for the specific language governing
       permissions and limitations under the License.

   If you choose to use this file in compliance with the BSD License, the
   following notice applies to you:

       Redistribution and use in source and binary forms, with or without
       modification, are permitted provided that the following conditions are
       met:
       * Redistributions of source code must retain the above copyright
         notice, this list of conditions and the following disclaimer.
       * 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.
       * Neither the name of the copyright holder nor the names of
         contributors may be used to endorse or promote products derived from
         this software without specific prior written permission.

       THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
       IS" AND ANY EXPRESS 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 COPYRIGHT HOLDER
       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.
*/

package jdk.internal.dynalink.support;

import jdk.internal.dynalink.CallSiteDescriptor;

/**
 * Implements the name mangling and demangling as specified by John Rose's
 * <a href="https://blogs.oracle.com/jrose/entry/symbolic_freedom_in_the_vm" target="_blank">"Symbolic Freedom in the
 * VM"</a> article. It is recommended that implementers of languages on the JVM uniformly adopt this for symbolic
 * interoperability between languages. Normally, you would mangle the names as you're generating bytecode, and then
 * demangle them when you're creating {@link CallSiteDescriptor} objects. Note that you are expected to mangle
 * individual tokens, and not the whole name at the call site, i.e. the colon character normally separating the tokens
 * is never mangled. I.e. you wouldn't mangle {@code dyn:getProp:color} into {@code dyn\!getProp\!color}, but you would
 * mangle {@code dyn:getProp:color$} into {@code dyn:getProp:\=color\%} (only mangling the individual token containing
 * the symbol {@code color$}). {@link CallSiteDescriptorFactory#tokenizeName(String)} (and by implication, all call site
 * descriptors it creates) will automatically perform demangling on the passed names. If you use this factory, or you
 * have your own way of creating call site descriptors, but you still delegate to this method of the default factory
 * (it is recommended that you do), then you have demangling handled for you already, and only need to ensure that you
 * mangle the names when you're emitting them in the bytecode.
 *
 * @author Attila Szegedi
 */
public class NameCodec {
    private static final char ESCAPE_CHAR = '\\';
    private static final char EMPTY_ESCAPE = '=';
    private static final String EMPTY_NAME = new String(new char[] { ESCAPE_CHAR, EMPTY_ESCAPE });
    private static final char EMPTY_CHAR = 0xFEFF;

    private static final int MIN_ENCODING = '$';
    private static final int MAX_ENCODING = ']';
    private static final char[] ENCODING = new char[MAX_ENCODING - MIN_ENCODING + 1];
    private static final int MIN_DECODING = '!';
    private static final int MAX_DECODING = '}';
    private static final char[] DECODING = new char[MAX_DECODING - MIN_DECODING + 1];

    static {
        addEncoding('/', '|');
        addEncoding('.', ',');
        addEncoding(';', '?');
        addEncoding('$', '%');
        addEncoding('<', '^');
        addEncoding('>', '_');
        addEncoding('[', '{');
        addEncoding(']', '}');
        addEncoding(':', '!');
        addEncoding('\\', '-');
        DECODING[EMPTY_ESCAPE - MIN_DECODING] = EMPTY_CHAR;
    }

    private NameCodec() {
    }

    /**
     * Encodes ("mangles") an unencoded symbolic name.
     * @param name the symbolic name to mangle
     * @return the mangled form of the symbolic name.
     */
    public static String encode(final String name) {
        final int l = name.length();
        if(l == 0) {
            return EMPTY_NAME;
        }
        StringBuilder b = null;
        int lastEscape = -1;
        for(int i = 0; i < l; ++i) {
            final int encodeIndex = name.charAt(i) - MIN_ENCODING;
            if(encodeIndex >= 0 && encodeIndex < ENCODING.length) {
                final char e = ENCODING[encodeIndex];
                if(e != 0) {
                    if(b == null) {
                        b = new StringBuilder(name.length() + 3);
                        if(name.charAt(0) != ESCAPE_CHAR && i > 0) {
                            b.append(EMPTY_NAME);
                        }
                        b.append(name, 0, i);
                    } else {
                        b.append(name, lastEscape + 1, i);
                    }
                    b.append(ESCAPE_CHAR).append(e);
                    lastEscape = i;
                }
            }
        }
        if(b == null) {
            return name.toString();
        }
        assert lastEscape != -1;
        b.append(name, lastEscape + 1, l);
        return b.toString();
    }

    /**
     * Decodes ("demangles") an encoded symbolic name.
     * @param name the symbolic name to demangle
     * @return the demangled form of the symbolic name.
     */
    public static String decode(final String name) {
        if(name.charAt(0) != ESCAPE_CHAR) {
            return name;
        }
        final int l = name.length();
        if(l == 2 && name.charAt(1) == EMPTY_CHAR) {
            return "";
        }
        final StringBuilder b = new StringBuilder(name.length());
        int lastEscape = -2;
        int lastBackslash = -1;
        for(;;) {
            final int nextBackslash = name.indexOf(ESCAPE_CHAR, lastBackslash + 1);
            if(nextBackslash == -1 || nextBackslash == l - 1) {
                break;
            }
            final int decodeIndex = name.charAt(nextBackslash + 1) - MIN_DECODING;
            if(decodeIndex >= 0 && decodeIndex < DECODING.length) {
                final char d = DECODING[decodeIndex];
                if(d == EMPTY_CHAR) {
                    // "\=" is only valid at the beginning of a mangled string
                    if(nextBackslash == 0) {
                        lastEscape = 0;
                    }
                } else if(d != 0) {
                    b.append(name, lastEscape + 2, nextBackslash).append(d);
                    lastEscape = nextBackslash;
                }
            }
            lastBackslash = nextBackslash;
        }
        b.append(name, lastEscape + 2, l);
        return b.toString();
    }

    private static void addEncoding(final char from, final char to) {
        ENCODING[from - MIN_ENCODING] = to;
        DECODING[to - MIN_DECODING] = from;
    }
}