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 * Copyright (c) 2003, 2016, 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
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 */

package sun.instrument;

import java.lang.instrument.Instrumentation;
import java.lang.instrument.ClassFileTransformer;
import java.security.ProtectionDomain;

/*
 * Copyright 2003 Wily Technology, Inc.
 */

Support class for the InstrumentationImpl. Manages the list of registered transformers.
Keeps everything in the right order, deals with sync of the list,
and actually does the calling of the transformers.
/**
 * Support class for the InstrumentationImpl. Manages the list of registered transformers.
 * Keeps everything in the right order, deals with sync of the list,
 * and actually does the calling of the transformers.
 */
public class TransformerManager
{
    private class TransformerInfo {
        final ClassFileTransformer  mTransformer;
        String                      mPrefix;

        TransformerInfo(ClassFileTransformer transformer) {
            mTransformer = transformer;
            mPrefix = null;
        }

        ClassFileTransformer transformer() {
            return  mTransformer;
        }

        String getPrefix() {
            return mPrefix;
        }

        void setPrefix(String prefix) {
            mPrefix = prefix;
        }
    }

    
a given instance of this list is treated as immutable to simplify sync;
we pay copying overhead whenever the list is changed rather than every time
the list is referenced.
The array is kept in the order the transformers are added via addTransformer
(first added is 0, last added is length-1)
Use an array, not a List or other Collection. This keeps the set of classes
used by this code to a minimum. We want as few dependencies as possible in this
code, since it is used inside the class definition system. Any class referenced here
cannot be transformed by Java code.
/**
     * a given instance of this list is treated as immutable to simplify sync;
     * we pay copying overhead whenever the list is changed rather than every time
     * the list is referenced.
     * The array is kept in the order the transformers are added via addTransformer
     * (first added is 0, last added is length-1)
     * Use an array, not a List or other Collection. This keeps the set of classes
     * used by this code to a minimum. We want as few dependencies as possible in this
     * code, since it is used inside the class definition system. Any class referenced here
     * cannot be transformed by Java code.
     */
    private TransformerInfo[]  mTransformerList;

    
Is this TransformerManager for transformers capable of retransformation?
/***
     * Is this TransformerManager for transformers capable of retransformation?
     */
    private boolean            mIsRetransformable;

    TransformerManager(boolean isRetransformable) {
        mTransformerList    = new TransformerInfo[0];
        mIsRetransformable  = isRetransformable;
    }

    boolean isRetransformable() {
        return mIsRetransformable;
    }

    public synchronized void
    addTransformer( ClassFileTransformer    transformer) {
        TransformerInfo[] oldList = mTransformerList;
        TransformerInfo[] newList = new TransformerInfo[oldList.length + 1];
        System.arraycopy(   oldList,
                            0,
                            newList,
                            0,
                            oldList.length);
        newList[oldList.length] = new TransformerInfo(transformer);
        mTransformerList = newList;
    }

    public synchronized boolean
    removeTransformer(ClassFileTransformer  transformer) {
        boolean                 found           = false;
        TransformerInfo[]       oldList         = mTransformerList;
        int                     oldLength       = oldList.length;
        int                     newLength       = oldLength - 1;

        // look for it in the list, starting at the last added, and remember
        // where it was if we found it
        int matchingIndex   = 0;
        for ( int x = oldLength - 1; x >= 0; x-- ) {
            if ( oldList[x].transformer() == transformer ) {
                found           = true;
                matchingIndex   = x;
                break;
            }
        }

        // make a copy of the array without the matching element
        if ( found ) {
            TransformerInfo[]  newList = new TransformerInfo[newLength];

            // copy up to but not including the match
            if ( matchingIndex > 0 ) {
                System.arraycopy(   oldList,
                                    0,
                                    newList,
                                    0,
                                    matchingIndex);
            }

            // if there is anything after the match, copy it as well
            if ( matchingIndex < (newLength) ) {
                System.arraycopy(   oldList,
                                    matchingIndex + 1,
                                    newList,
                                    matchingIndex,
                                    (newLength) - matchingIndex);
            }
            mTransformerList = newList;
        }
        return found;
    }

    synchronized boolean
    includesTransformer(ClassFileTransformer transformer) {
        for (TransformerInfo info : mTransformerList) {
            if ( info.transformer() == transformer ) {
                return true;
            }
        }
        return false;
    }

    // This function doesn't actually snapshot anything, but should be
    // used to set a local variable, which will snapshot the transformer
    // list because of the copying semantics of mTransformerList (see
    // the comment for mTransformerList).
    private TransformerInfo[]
    getSnapshotTransformerList() {
        return mTransformerList;
    }

    public byte[]
    transform(  Module              module,
                ClassLoader         loader,
                String              classname,
                Class<?>            classBeingRedefined,
                ProtectionDomain    protectionDomain,
                byte[]              classfileBuffer) {
        boolean someoneTouchedTheBytecode = false;

        TransformerInfo[]  transformerList = getSnapshotTransformerList();

        byte[]  bufferToUse = classfileBuffer;

        // order matters, gotta run 'em in the order they were added
        for ( int x = 0; x < transformerList.length; x++ ) {
            TransformerInfo         transformerInfo = transformerList[x];
            ClassFileTransformer    transformer = transformerInfo.transformer();
            byte[]                  transformedBytes = null;

            try {
                transformedBytes = transformer.transform(   module,
                                                            loader,
                                                            classname,
                                                            classBeingRedefined,
                                                            protectionDomain,
                                                            bufferToUse);
            }
            catch (Throwable t) {
                // don't let any one transformer mess it up for the others.
                // This is where we need to put some logging. What should go here? FIXME
            }

            if ( transformedBytes != null ) {
                someoneTouchedTheBytecode = true;
                bufferToUse = transformedBytes;
            }
        }

        // if someone modified it, return the modified buffer.
        // otherwise return null to mean "no transforms occurred"
        byte [] result;
        if ( someoneTouchedTheBytecode ) {
            result = bufferToUse;
        }
        else {
            result = null;
        }

        return result;
    }


    int
    getTransformerCount() {
        TransformerInfo[]  transformerList = getSnapshotTransformerList();
        return transformerList.length;
    }

    boolean
    setNativeMethodPrefix(ClassFileTransformer transformer, String prefix) {
        TransformerInfo[]  transformerList = getSnapshotTransformerList();

        for ( int x = 0; x < transformerList.length; x++ ) {
            TransformerInfo         transformerInfo = transformerList[x];
            ClassFileTransformer    aTransformer = transformerInfo.transformer();

            if ( aTransformer == transformer ) {
                transformerInfo.setPrefix(prefix);
                return true;
            }
        }
        return false;
    }


    String[]
    getNativeMethodPrefixes() {
        TransformerInfo[]  transformerList = getSnapshotTransformerList();
        String[] prefixes                  = new String[transformerList.length];

        for ( int x = 0; x < transformerList.length; x++ ) {
            TransformerInfo         transformerInfo = transformerList[x];
            prefixes[x] = transformerInfo.getPrefix();
        }
        return prefixes;
    }
}