/*

 * 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.

 */

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.

     */

    private TransformerInfo[]  mTransformerList;

    /***

     * 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;

    }

}