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/*
* Copyright (c) 2014, 2018, 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.
*
* 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.
*/
package gc.g1.unloading.bytecode;
import java.util.*;
/**
* This utility class replaces peaces of bytes in bytecode by another peaces according to dictionary. This is useful for class redefenition.
*/
public class BytecodePatcher {
static private Map<byte[], byte[]> dictionary = new HashMap<>();
static {
dictionary.put("bytesToReplace0".getBytes(), "bytesToReplace1".getBytes());
dictionary.put("bytesToReplace2".getBytes(), "bytesToReplace3".getBytes());
}
public static void patch(byte[] bytecode) {
for (Map.Entry<byte[], byte[]> entry : dictionary.entrySet()) {
for (int i = 0; i + entry.getKey().length < bytecode.length; i++) {
boolean match = true;
for (int j = 0; j < entry.getKey().length; j++) {
if (bytecode[i + j] != entry.getKey()[j]) {
match = false;
break;
}
}
if (match) {
for (int j = 0; j < entry.getKey().length; j++)
bytecode[i + j] = entry.getValue()[j];
}
}
}
}
}
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