1 /* 2 * Copyright (c) 2014, 2018, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 */ 23 package gc.g1.unloading.bytecode; 24 25 import java.util.*; 26 27 28 /** 29 * This utility class replaces peaces of bytes in bytecode by another peaces according to dictionary. This is useful for class redefenition. 30 */ 31 public class BytecodePatcher { 32 33 static private Map<byte[], byte[]> dictionary = new HashMap<>(); 34 35 static { 36 dictionary.put("bytesToReplace0".getBytes(), "bytesToReplace1".getBytes()); 37 dictionary.put("bytesToReplace2".getBytes(), "bytesToReplace3".getBytes()); 38 } 39 patch(byte[] bytecode)40 public static void patch(byte[] bytecode) { 41 for (Map.Entry<byte[], byte[]> entry : dictionary.entrySet()) { 42 for (int i = 0; i + entry.getKey().length < bytecode.length; i++) { 43 boolean match = true; 44 for (int j = 0; j < entry.getKey().length; j++) { 45 if (bytecode[i + j] != entry.getKey()[j]) { 46 match = false; 47 break; 48 } 49 } 50 if (match) { 51 for (int j = 0; j < entry.getKey().length; j++) 52 bytecode[i + j] = entry.getValue()[j]; 53 } 54 } 55 } 56 } 57 58 } 59