java/16 : java.base/jdk/internal/org/objectweb/asm/commons/SerialVersionUIDAdder.java

SerialVersionUIDAdder
https://openjdk.java.net/
GPLv2 + Classpath Exception
/*
 * 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.
 */

/*
 * 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:
 *
 * ASM: a very small and fast Java bytecode manipulation framework
 * Copyright (c) 2000-2011 INRIA, France Telecom
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. 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.
 * 3. Neither the name of the copyright holders nor the names of its
 *    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 THE COPYRIGHT OWNER OR CONTRIBUTORS BE
 * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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 * THE POSSIBILITY OF SUCH DAMAGE.
 */
package jdk.internal.org.objectweb.asm.commons;

import java.io.ByteArrayOutputStream;
import java.io.DataOutput;
import java.io.DataOutputStream;
import java.io.IOException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collection;
import jdk.internal.org.objectweb.asm.ClassVisitor;
import jdk.internal.org.objectweb.asm.FieldVisitor;
import jdk.internal.org.objectweb.asm.MethodVisitor;
import jdk.internal.org.objectweb.asm.Opcodes;

A ClassVisitor that adds a serial version unique identifier to a class if missing. A typical usage of this class is:   ClassWriter classWriter = new ClassWriter(...);
  ClassVisitor svuidAdder = new SerialVersionUIDAdder(classWriter);
  ClassVisitor classVisitor = new MyClassAdapter(svuidAdder);
  new ClassReader(orginalClass).accept(classVisitor, 0);

The SVUID algorithm can be found at https://docs.oracle.com/javase/10/docs/specs/serialization/class.html#stream-unique-identifiers:
The serialVersionUID is computed using the signature of a stream of bytes that reflect the
class definition. The National Institute of Standards and Technology (NIST) Secure Hash Algorithm
(SHA-1) is used to compute a signature for the stream. The first two 32-bit quantities are used
to form a 64-bit hash. A java.lang.DataOutputStream is used to convert primitive data types to a
sequence of bytes. The values input to the stream are defined by the Java Virtual Machine (VM)
specification for classes.
The sequence of items in the stream is as follows:

  The class name written using UTF encoding.
  
The class modifiers written as a 32-bit integer.
  
The name of each interface sorted by name written using UTF encoding.
  
For each field of the class sorted by field name (except private static and private
      transient fields):
      
        The name of the field in UTF encoding.
        
The modifiers of the field written as a 32-bit integer.
        
The descriptor of the field in UTF encoding
      
  
If a class initializer exists, write out the following:
      
        The name of the method, <clinit>, in UTF encoding.
        
The modifier of the method, STATIC, written as a 32-bit integer.
        
The descriptor of the method, ()V, in UTF encoding.
      
  
For each non-private constructor sorted by method name and signature:
      
        The name of the method, <init>, in UTF encoding.
        
The modifiers of the method written as a 32-bit integer.
        
The descriptor of the method in UTF encoding.
      
  
For each non-private method sorted by method name and signature:
      
        The name of the method in UTF encoding.
        
The modifiers of the method written as a 32-bit integer.
        
The descriptor of the method in UTF encoding.
      
  
The SHA-1 algorithm is executed on the stream of bytes produced by DataOutputStream and
      produces five 32-bit values sha[0..4].
  
The hash value is assembled from the first and second 32-bit values of the SHA-1 message
      digest. If the result of the message digest, the five 32-bit words H0 H1 H2 H3 H4, is in an
      array of five int values named sha, the hash value would be computed as follows: long hash
      = ((sha[0] >>> 24) & 0xFF) | ((sha[0] >>> 16) & 0xFF) << 8
      | ((sha[0] >>> 8) & 0xFF) << 16 | ((sha[0] >>> 0) & 0xFF)
      << 24 | ((sha[1] >>> 24) & 0xFF) << 32 | ((sha[1] >>> 16)
      & 0xFF) << 40 | ((sha[1] >>> 8) & 0xFF) << 48 | ((sha[1]
      >>> 0) & 0xFF) << 56;

Author: Rajendra Inamdar, Vishal Vishnoi/**
 * A {@link ClassVisitor} that adds a serial version unique identifier to a class if missing. A
 * typical usage of this class is:
 *
 * <pre>
 *   ClassWriter classWriter = new ClassWriter(...);
 *   ClassVisitor svuidAdder = new SerialVersionUIDAdder(classWriter);
 *   ClassVisitor classVisitor = new MyClassAdapter(svuidAdder);
 *   new ClassReader(orginalClass).accept(classVisitor, 0);
 * </pre>
 *
 * <p>The SVUID algorithm can be found at <a href=
 * "https://docs.oracle.com/javase/10/docs/specs/serialization/class.html#stream-unique-identifiers"
 * >https://docs.oracle.com/javase/10/docs/specs/serialization/class.html#stream-unique-identifiers</a>:
 *
 * <p>The serialVersionUID is computed using the signature of a stream of bytes that reflect the
 * class definition. The National Institute of Standards and Technology (NIST) Secure Hash Algorithm
 * (SHA-1) is used to compute a signature for the stream. The first two 32-bit quantities are used
 * to form a 64-bit hash. A java.lang.DataOutputStream is used to convert primitive data types to a
 * sequence of bytes. The values input to the stream are defined by the Java Virtual Machine (VM)
 * specification for classes.
 *
 * <p>The sequence of items in the stream is as follows:
 *
 * <ol>
 *   <li>The class name written using UTF encoding.
 *   <li>The class modifiers written as a 32-bit integer.
 *   <li>The name of each interface sorted by name written using UTF encoding.
 *   <li>For each field of the class sorted by field name (except private static and private
 *       transient fields):
 *       <ol>
 *         <li>The name of the field in UTF encoding.
 *         <li>The modifiers of the field written as a 32-bit integer.
 *         <li>The descriptor of the field in UTF encoding
 *       </ol>
 *   <li>If a class initializer exists, write out the following:
 *       <ol>
 *         <li>The name of the method, &lt;clinit&gt;, in UTF encoding.
 *         <li>The modifier of the method, STATIC, written as a 32-bit integer.
 *         <li>The descriptor of the method, ()V, in UTF encoding.
 *       </ol>
 *   <li>For each non-private constructor sorted by method name and signature:
 *       <ol>
 *         <li>The name of the method, &lt;init&gt;, in UTF encoding.
 *         <li>The modifiers of the method written as a 32-bit integer.
 *         <li>The descriptor of the method in UTF encoding.
 *       </ol>
 *   <li>For each non-private method sorted by method name and signature:
 *       <ol>
 *         <li>The name of the method in UTF encoding.
 *         <li>The modifiers of the method written as a 32-bit integer.
 *         <li>The descriptor of the method in UTF encoding.
 *       </ol>
 *   <li>The SHA-1 algorithm is executed on the stream of bytes produced by DataOutputStream and
 *       produces five 32-bit values sha[0..4].
 *   <li>The hash value is assembled from the first and second 32-bit values of the SHA-1 message
 *       digest. If the result of the message digest, the five 32-bit words H0 H1 H2 H3 H4, is in an
 *       array of five int values named sha, the hash value would be computed as follows: long hash
 *       = ((sha[0] &gt;&gt;&gt; 24) &amp; 0xFF) | ((sha[0] &gt;&gt;&gt; 16) &amp; 0xFF) &lt;&lt; 8
 *       | ((sha[0] &gt;&gt;&gt; 8) &amp; 0xFF) &lt;&lt; 16 | ((sha[0] &gt;&gt;&gt; 0) &amp; 0xFF)
 *       &lt;&lt; 24 | ((sha[1] &gt;&gt;&gt; 24) &amp; 0xFF) &lt;&lt; 32 | ((sha[1] &gt;&gt;&gt; 16)
 *       &amp; 0xFF) &lt;&lt; 40 | ((sha[1] &gt;&gt;&gt; 8) &amp; 0xFF) &lt;&lt; 48 | ((sha[1]
 *       &gt;&gt;&gt; 0) &amp; 0xFF) &lt;&lt; 56;
 * </ol>
 *
 * @author Rajendra Inamdar, Vishal Vishnoi
 */
// DontCheck(AbbreviationAsWordInName): can't be renamed (for backward binary compatibility).
public class SerialVersionUIDAdder extends ClassVisitor {

    The JVM name of static initializer methods. /** The JVM name of static initializer methods. */
    private static final String CLINIT = "<clinit>";

    A flag that indicates if we need to compute SVUID. /** A flag that indicates if we need to compute SVUID. */
    private boolean computeSvuid;

    Whether the class already has a SVUID. /** Whether the class already has a SVUID. */
    private boolean hasSvuid;

    The class access flags. /** The class access flags. */
    private int access;

    The internal name of the class. /** The internal name of the class. */
    private String name;

    The interfaces implemented by the class. /** The interfaces implemented by the class. */
    private String[] interfaces;

    The fields of the class that are needed to compute the SVUID. /** The fields of the class that are needed to compute the SVUID. */
    private Collection<Item> svuidFields;

    Whether the class has a static initializer. /** Whether the class has a static initializer. */
    private boolean hasStaticInitializer;

    The constructors of the class that are needed to compute the SVUID. /** The constructors of the class that are needed to compute the SVUID. */
    private Collection<Item> svuidConstructors;

    The methods of the class that are needed to compute the SVUID. /** The methods of the class that are needed to compute the SVUID. */
    private Collection<Item> svuidMethods;

    Constructs a new SerialVersionUIDAdder. Subclasses must not use this
constructor. Instead, they must use the SerialVersionUIDAdder(int, ClassVisitor) version. 
Params: classVisitor – a ClassVisitor to which this visitor will delegate calls.
Throws: IllegalStateException – If a subclass calls this constructor./**
      * Constructs a new {@link SerialVersionUIDAdder}. <i>Subclasses must not use this
      * constructor</i>. Instead, they must use the {@link #SerialVersionUIDAdder(int, ClassVisitor)}
      * version.
      *
      * @param classVisitor a {@link ClassVisitor} to which this visitor will delegate calls.
      * @throws IllegalStateException If a subclass calls this constructor.
      */
    public SerialVersionUIDAdder(final ClassVisitor classVisitor) {
        this(/* latest api = */ Opcodes.ASM8, classVisitor);
        if (getClass() != SerialVersionUIDAdder.class) {
            throw new IllegalStateException();
        }
    }

    Constructs a new SerialVersionUIDAdder. 
Params: api – the ASM API version implemented by this visitor. Must be one of Opcodes.ASM4, Opcodes.ASM5, Opcodes.ASM6, Opcodes.ASM7 or Opcodes.ASM8.
classVisitor – a ClassVisitor to which this visitor will delegate calls./**
      * Constructs a new {@link SerialVersionUIDAdder}.
      *
      * @param api the ASM API version implemented by this visitor. Must be one of {@link
      *     Opcodes#ASM4}, {@link Opcodes#ASM5}, {@link Opcodes#ASM6}, {@link Opcodes#ASM7} or {@link
      *     Opcodes#ASM8}.
      * @param classVisitor a {@link ClassVisitor} to which this visitor will delegate calls.
      */
    protected SerialVersionUIDAdder(final int api, final ClassVisitor classVisitor) {
        super(api, classVisitor);
    }

    // -----------------------------------------------------------------------------------------------
    // Overridden methods
    // -----------------------------------------------------------------------------------------------

    @Override
    public void visit(
            final int version,
            final int access,
            final String name,
            final String signature,
            final String superName,
            final String[] interfaces) {
        // Get the class name, access flags, and interfaces information (step 1, 2 and 3) for SVUID
        // computation.
        computeSvuid = (access & Opcodes.ACC_ENUM) == 0;

        if (computeSvuid) {
            this.name = name;
            this.access = access;
            this.interfaces = interfaces.clone();
            this.svuidFields = new ArrayList<>();
            this.svuidConstructors = new ArrayList<>();
            this.svuidMethods = new ArrayList<>();
        }

        super.visit(version, access, name, signature, superName, interfaces);
    }

    @Override
    public MethodVisitor visitMethod(
            final int access,
            final String name,
            final String descriptor,
            final String signature,
            final String[] exceptions) {
        // Get constructor and method information (step 5 and 7). Also determine if there is a class
        // initializer (step 6).
        if (computeSvuid) {
            if (CLINIT.equals(name)) {
                hasStaticInitializer = true;
            }
            // Collect the non private constructors and methods. Only the ACC_PUBLIC, ACC_PRIVATE,
            // ACC_PROTECTED, ACC_STATIC, ACC_FINAL, ACC_SYNCHRONIZED, ACC_NATIVE, ACC_ABSTRACT and
            // ACC_STRICT flags are used.
            int mods =
                    access
                            & (Opcodes.ACC_PUBLIC
                                    | Opcodes.ACC_PRIVATE
                                    | Opcodes.ACC_PROTECTED
                                    | Opcodes.ACC_STATIC
                                    | Opcodes.ACC_FINAL
                                    | Opcodes.ACC_SYNCHRONIZED
                                    | Opcodes.ACC_NATIVE
                                    | Opcodes.ACC_ABSTRACT
                                    | Opcodes.ACC_STRICT);

            if ((access & Opcodes.ACC_PRIVATE) == 0) {
                if ("<init>".equals(name)) {
                    svuidConstructors.add(new Item(name, mods, descriptor));
                } else if (!CLINIT.equals(name)) {
                    svuidMethods.add(new Item(name, mods, descriptor));
                }
            }
        }

        return super.visitMethod(access, name, descriptor, signature, exceptions);
    }

    @Override
    public FieldVisitor visitField(
            final int access,
            final String name,
            final String desc,
            final String signature,
            final Object value) {
        // Get the class field information for step 4 of the algorithm. Also determine if the class
        // already has a SVUID.
        if (computeSvuid) {
            if ("serialVersionUID".equals(name)) {
                // Since the class already has SVUID, we won't be computing it.
                computeSvuid = false;
                hasSvuid = true;
            }
            // Collect the non private fields. Only the ACC_PUBLIC, ACC_PRIVATE, ACC_PROTECTED,
            // ACC_STATIC, ACC_FINAL, ACC_VOLATILE, and ACC_TRANSIENT flags are used when computing
            // serialVersionUID values.
            if ((access & Opcodes.ACC_PRIVATE) == 0
                    || (access & (Opcodes.ACC_STATIC | Opcodes.ACC_TRANSIENT)) == 0) {
                int mods =
                        access
                                & (Opcodes.ACC_PUBLIC
                                        | Opcodes.ACC_PRIVATE
                                        | Opcodes.ACC_PROTECTED
                                        | Opcodes.ACC_STATIC
                                        | Opcodes.ACC_FINAL
                                        | Opcodes.ACC_VOLATILE
                                        | Opcodes.ACC_TRANSIENT);
                svuidFields.add(new Item(name, mods, desc));
            }
        }

        return super.visitField(access, name, desc, signature, value);
    }

    @Override
    public void visitInnerClass(
            final String innerClassName,
            final String outerName,
            final String innerName,
            final int innerClassAccess) {
        // Handles a bizarre special case. Nested classes (static classes declared inside another class)
        // that are protected have their access bit set to public in their class files to deal with some
        // odd reflection situation. Our SVUID computation must do as the JVM does and ignore access
        // bits in the class file in favor of the access bits of the InnerClass attribute.
        if ((name != null) && name.equals(innerClassName)) {
            this.access = innerClassAccess;
        }
        super.visitInnerClass(innerClassName, outerName, innerName, innerClassAccess);
    }

    @Override
    public void visitEnd() {
        // Add the SVUID field to the class if it doesn't have one.
        if (computeSvuid && !hasSvuid) {
            try {
                addSVUID(computeSVUID());
            } catch (IOException e) {
                throw new IllegalStateException("Error while computing SVUID for " + name, e);
            }
        }

        super.visitEnd();
    }

    // -----------------------------------------------------------------------------------------------
    // Utility methods
    // -----------------------------------------------------------------------------------------------

    Returns true if the class already has a SVUID field. The result of this method is only valid
when visitEnd has been called.
Returns: true if the class already has a SVUID field./**
      * Returns true if the class already has a SVUID field. The result of this method is only valid
      * when visitEnd has been called.
      *
      * @return true if the class already has a SVUID field.
      */
    // DontCheck(AbbreviationAsWordInName): can't be renamed (for backward binary compatibility).
    public boolean hasSVUID() {
        return hasSvuid;
    }

    Adds a final static serialVersionUID field to the class, with the given value.
Params: svuid – the serialVersionUID field value./**
      * Adds a final static serialVersionUID field to the class, with the given value.
      *
      * @param svuid the serialVersionUID field value.
      */
    // DontCheck(AbbreviationAsWordInName): can't be renamed (for backward binary compatibility).
    protected void addSVUID(final long svuid) {
        FieldVisitor fieldVisitor =
                super.visitField(
                        Opcodes.ACC_FINAL + Opcodes.ACC_STATIC, "serialVersionUID", "J", null, svuid);
        if (fieldVisitor != null) {
            fieldVisitor.visitEnd();
        }
    }

    Computes and returns the value of SVUID.
Throws: IOException – if an I/O error occurs.
Returns: the serial version UID./**
      * Computes and returns the value of SVUID.
      *
      * @return the serial version UID.
      * @throws IOException if an I/O error occurs.
      */
    // DontCheck(AbbreviationAsWordInName): can't be renamed (for backward binary compatibility).
    protected long computeSVUID() throws IOException {
        long svuid = 0;

        try (ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
                DataOutputStream dataOutputStream = new DataOutputStream(byteArrayOutputStream)) {

            // 1. The class name written using UTF encoding.
            dataOutputStream.writeUTF(name.replace('/', '.'));

            // 2. The class modifiers written as a 32-bit integer.
            int mods = access;
            if ((mods & Opcodes.ACC_INTERFACE) != 0) {
                mods =
                        svuidMethods.isEmpty() ? (mods & ~Opcodes.ACC_ABSTRACT) : (mods | Opcodes.ACC_ABSTRACT);
            }
            dataOutputStream.writeInt(
                    mods
                            & (Opcodes.ACC_PUBLIC
                                    | Opcodes.ACC_FINAL
                                    | Opcodes.ACC_INTERFACE
                                    | Opcodes.ACC_ABSTRACT));

            // 3. The name of each interface sorted by name written using UTF encoding.
            Arrays.sort(interfaces);
            for (String interfaceName : interfaces) {
                dataOutputStream.writeUTF(interfaceName.replace('/', '.'));
            }

            // 4. For each field of the class sorted by field name (except private static and private
            // transient fields):
            //   1. The name of the field in UTF encoding.
            //   2. The modifiers of the field written as a 32-bit integer.
            //   3. The descriptor of the field in UTF encoding.
            // Note that field signatures are not dot separated. Method and constructor signatures are dot
            // separated. Go figure...
            writeItems(svuidFields, dataOutputStream, false);

            // 5. If a class initializer exists, write out the following:
            //   1. The name of the method, <clinit>, in UTF encoding.
            //   2. The modifier of the method, ACC_STATIC, written as a 32-bit integer.
            //   3. The descriptor of the method, ()V, in UTF encoding.
            if (hasStaticInitializer) {
                dataOutputStream.writeUTF(CLINIT);
                dataOutputStream.writeInt(Opcodes.ACC_STATIC);
                dataOutputStream.writeUTF("()V");
            }

            // 6. For each non-private constructor sorted by method name and signature:
            //   1. The name of the method, <init>, in UTF encoding.
            //   2. The modifiers of the method written as a 32-bit integer.
            //   3. The descriptor of the method in UTF encoding.
            writeItems(svuidConstructors, dataOutputStream, true);

            // 7. For each non-private method sorted by method name and signature:
            //   1. The name of the method in UTF encoding.
            //   2. The modifiers of the method written as a 32-bit integer.
            //   3. The descriptor of the method in UTF encoding.
            writeItems(svuidMethods, dataOutputStream, true);

            dataOutputStream.flush();

            // 8. The SHA-1 algorithm is executed on the stream of bytes produced by DataOutputStream and
            // produces five 32-bit values sha[0..4].
            byte[] hashBytes = computeSHAdigest(byteArrayOutputStream.toByteArray());

            // 9. The hash value is assembled from the first and second 32-bit values of the SHA-1 message
            // digest. If the result of the message digest, the five 32-bit words H0 H1 H2 H3 H4, is in an
            // array of five int values named sha, the hash value would be computed as follows:
            for (int i = Math.min(hashBytes.length, 8) - 1; i >= 0; i--) {
                svuid = (svuid << 8) | (hashBytes[i] & 0xFF);
            }
        }

        return svuid;
    }

    Returns the SHA-1 message digest of the given value.
Params: value – the value whose SHA message digest must be computed.
Returns: the SHA-1 message digest of the given value./**
      * Returns the SHA-1 message digest of the given value.
      *
      * @param value the value whose SHA message digest must be computed.
      * @return the SHA-1 message digest of the given value.
      */
    // DontCheck(AbbreviationAsWordInName): can't be renamed (for backward binary compatibility).
    protected byte[] computeSHAdigest(final byte[] value) {
        try {
            return MessageDigest.getInstance("SHA").digest(value);
        } catch (NoSuchAlgorithmException e) {
            throw new UnsupportedOperationException(e);
        }
    }

    Sorts the items in the collection and writes it to the given output stream.
Params: itemCollection – a collection of items.
dataOutputStream – where the items must be written.
dotted – whether package names must use dots, instead of slashes.
Throws: IOException – if an error occurs./**
      * Sorts the items in the collection and writes it to the given output stream.
      *
      * @param itemCollection a collection of items.
      * @param dataOutputStream where the items must be written.
      * @param dotted whether package names must use dots, instead of slashes.
      * @exception IOException if an error occurs.
      */
    private static void writeItems(
            final Collection<Item> itemCollection,
            final DataOutput dataOutputStream,
            final boolean dotted)
            throws IOException {
        Item[] items = itemCollection.toArray(new Item[0]);
        Arrays.sort(items);
        for (Item item : items) {
            dataOutputStream.writeUTF(item.name);
            dataOutputStream.writeInt(item.access);
            dataOutputStream.writeUTF(dotted ? item.descriptor.replace('/', '.') : item.descriptor);
        }
    }

    // -----------------------------------------------------------------------------------------------
    // Inner classes
    // -----------------------------------------------------------------------------------------------

    private static final class Item implements Comparable<Item> {

        final String name;
        final int access;
        final String descriptor;

        Item(final String name, final int access, final String descriptor) {
            this.name = name;
            this.access = access;
            this.descriptor = descriptor;
        }

        @Override
        public int compareTo(final Item item) {
            int result = name.compareTo(item.name);
            if (result == 0) {
                result = descriptor.compareTo(item.descriptor);
            }
            return result;
        }

        @Override
        public boolean equals(final Object other) {
            if (other instanceof Item) {
                return compareTo((Item) other) == 0;
            }
            return false;
        }

        @Override
        public int hashCode() {
            return name.hashCode() ^ descriptor.hashCode();
        }
    }
}
Params:	classVisitor – a `ClassVisitor` to which this visitor will delegate calls.
Throws:	IllegalStateException – If a subclass calls this constructor.
Throws:	IOException – if an I/O error occurs.
Returns:	the serial version UID.
Params:	value – the value whose SHA message digest must be computed.
Returns:	the SHA-1 message digest of the given value.
Params:	itemCollection – a collection of items. dataOutputStream – where the items must be written. dotted – whether package names must use dots, instead of slashes.
Throws:	IOException – if an error occurs.
/

java/ 16/ java.base/jdk/internal/org/objectweb/asm/commons/SerialVersionUIDAdder.java
