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.io.*; 26 import java.nio.charset.*; 27 import java.util.*; 28 29 30 /** 31 * This BytecodeFactory produces bytecode that is golden bytecode with className substituted. 32 */ 33 public class BytecodeMutatorFactory implements BytecodeFactory { 34 35 private static final String FILLER_CHARACTER = "_"; 36 37 /** 38 * Utility method in this class 39 */ 40 public static String padName(String s, int length) { 41 int difference = length - s.length(); 42 StringBuilder sb = new StringBuilder(s); 43 for (int i = 0; i < difference; i++) { 44 sb.append(FILLER_CHARACTER); 45 } 46 return sb.toString(); 47 } 48 49 public String padName(String s) { 50 return padName(s, getNameLength()); 51 } 52 53 private final Charset CHARACTER_SET = StandardCharsets.UTF_8; 54 55 private List<Integer> offsets = new LinkedList<>(); 56 57 private byte[] templateBytecode; 58 59 private String templateClassName; 60 61 private byte[] templateClassNameAsBytes; 62 63 public BytecodeMutatorFactory() { 64 this(DefaultTemplateClass.class.getName()); 65 } 66 67 public BytecodeMutatorFactory(String templateClassName) { 68 this.templateClassName = templateClassName; 69 70 // Read bytecode to array 71 InputStream is = ClassLoader.getSystemResourceAsStream(templateClassName.replace('.', '/').concat(".class")); 72 try { 73 templateBytecode = new byte[is.available()]; 74 is.read(templateBytecode); 75 is.close(); 76 } catch (IOException e) { 77 throw new RuntimeException(e); 78 } 79 80 // Save offsets 81 templateClassNameAsBytes = templateClassName.replace('.', '/').getBytes(CHARACTER_SET); 82 for (int i = 0; i < templateBytecode.length; i++) { 83 boolean match = true; 84 for (int j = 0; j < templateClassNameAsBytes.length; j++) { 85 if (i + j >= templateBytecode.length || templateClassNameAsBytes[j] != templateBytecode[i + j]) { 86 match = false; 87 break; 88 } 89 } 90 if (match) { 91 offsets.add(i); 92 } 93 } 94 } 95 96 public byte[] getBytecode(String className) { 97 98 // Check size of name constraint 99 byte[] newClassNameAsBytes = className.replace('.', '/').getBytes(CHARACTER_SET); 100 if (newClassNameAsBytes.length != templateClassNameAsBytes.length) { 101 throw new RuntimeException("Can't produce bytecode with \"" + className + "\" substituted as class name. " + 102 "Length of this name differs from length of \"" + templateClassName + "\" which equals to " + templateClassName.length() + 103 ". Length of \"" + className + "\" is " + className.length() + "."); 104 } 105 106 // Prepare bytecode 107 byte[] result = Arrays.copyOf(templateBytecode, templateBytecode.length); 108 for (int offset : offsets) { 109 System.arraycopy(newClassNameAsBytes, 0, result, offset, newClassNameAsBytes.length); 110 } 111 return result; 112 } 113 114 public int getNameLength() { 115 return templateClassName.length(); 116 } 117 118 @Override 119 public Bytecode createBytecode(String className) { 120 String finalClassName = padName(className); 121 byte[] bytecode = getBytecode(finalClassName); 122 return new Bytecode(finalClassName, bytecode); 123 } 124 125 }