1/* 2 * Copyright (c) 2000, 2016, 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 */ 24 25package sun.jvm.hotspot.oops; 26 27import java.io.*; 28import java.util.*; 29import sun.jvm.hotspot.debugger.*; 30import sun.jvm.hotspot.runtime.*; 31import sun.jvm.hotspot.types.*; 32import sun.jvm.hotspot.utilities.*; 33 34// A Symbol is a canonicalized string. 35// All Symbols reside in global symbolTable. 36 37public class Symbol extends VMObject { 38 static { 39 VM.registerVMInitializedObserver(new Observer() { 40 public void update(Observable o, Object data) { 41 initialize(VM.getVM().getTypeDataBase()); 42 } 43 }); 44 } 45 46 private static synchronized void initialize(TypeDataBase db) throws WrongTypeException { 47 Type type = db.lookupType("Symbol"); 48 length = type.getCIntegerField("_length"); 49 baseOffset = type.getField("_body").getOffset(); 50 idHash = type.getCIntegerField("_identity_hash"); 51 } 52 53 // Format: 54 // [header] 55 // [klass ] 56 // [length] byte size of uft8 string 57 // ..body.. 58 59 public static Symbol create(Address addr) { 60 if (addr == null) { 61 return null; 62 } 63 return new Symbol(addr); 64 } 65 66 Symbol(Address addr) { 67 super(addr); 68 } 69 70 public boolean isSymbol() { return true; } 71 72 private static long baseOffset; // tells where the array part starts 73 74 // Fields 75 private static CIntegerField length; 76 77 // Accessors for declared fields 78 public long getLength() { return length.getValue(this.addr); } 79 80 public byte getByteAt(long index) { 81 return addr.getJByteAt(baseOffset + index); 82 } 83 // _identity_hash is a short 84 private static CIntegerField idHash; 85 86 public int identityHash() { 87 long addr_value = getAddress().asLongValue(); 88 int addr_bits = (int)(addr_value >> (VM.getVM().getLogMinObjAlignmentInBytes() + 3)); 89 int length = (int)getLength(); 90 int byte0 = getByteAt(0); 91 int byte1 = getByteAt(1); 92 int id_hash = (int)(0xffff & idHash.getValue(this.addr)); 93 return id_hash | 94 ((addr_bits ^ (length << 8) ^ ((byte0 << 8) | byte1)) << 16); 95 } 96 97 public boolean equals(byte[] modUTF8Chars) { 98 int l = (int) getLength(); 99 if (l != modUTF8Chars.length) return false; 100 while (l-- > 0) { 101 if (modUTF8Chars[l] != getByteAt(l)) return false; 102 } 103 if (Assert.ASSERTS_ENABLED) { 104 Assert.that(l == -1, "we should be at the beginning"); 105 } 106 return true; 107 } 108 109 public byte[] asByteArray() { 110 int length = (int) getLength(); 111 byte [] result = new byte [length]; 112 for (int index = 0; index < length; index++) { 113 result[index] = getByteAt(index); 114 } 115 return result; 116 } 117 118 public String asString() { 119 // Decode the byte array and return the string. 120 try { 121 return readModifiedUTF8(asByteArray()); 122 } catch(Exception e) { 123 System.err.println(addr); 124 e.printStackTrace(); 125 return null; 126 } 127 } 128 129 public boolean startsWith(String str) { 130 return asString().startsWith(str); 131 } 132 133 public void printValueOn(PrintStream tty) { 134 tty.print("#" + asString()); 135 } 136 137 /** Note: this comparison is used for vtable sorting only; it 138 doesn't matter what order it defines, as long as it is a total, 139 time-invariant order Since Symbol* are in C_HEAP, their 140 relative order in memory never changes, so use address 141 comparison for speed. */ 142 public long fastCompare(Symbol other) { 143 return addr.minus(other.addr); 144 } 145 146 private static String readModifiedUTF8(byte[] buf) throws IOException { 147 final int len = buf.length; 148 byte[] tmp = new byte[len + 2]; 149 // write modified UTF-8 length as short in big endian 150 tmp[0] = (byte) ((len >>> 8) & 0xFF); 151 tmp[1] = (byte) ((len >>> 0) & 0xFF); 152 // copy the data 153 System.arraycopy(buf, 0, tmp, 2, len); 154 DataInputStream dis = new DataInputStream(new ByteArrayInputStream(tmp)); 155 return dis.readUTF(); 156 } 157} 158