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1: /* ObjID.java -- Unique object id with respect to the given host. 2: Copyright (c) 1996, 1997, 1998, 1999, 2004, 2006 3: Free Software Foundation, Inc. 4: 5: This file is part of GNU Classpath. 6: 7: GNU Classpath is free software; you can redistribute it and/or modify 8: it under the terms of the GNU General Public License as published by 9: the Free Software Foundation; either version 2, or (at your option) 10: any later version. 11: 12: GNU Classpath is distributed in the hope that it will be useful, but 13: WITHOUT ANY WARRANTY; without even the implied warranty of 14: MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU 15: General Public License for more details. 16: 17: You should have received a copy of the GNU General Public License 18: along with GNU Classpath; see the file COPYING. If not, write to the 19: Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 20: 02110-1301 USA. 21: 22: Linking this library statically or dynamically with other modules is 23: making a combined work based on this library. Thus, the terms and 24: conditions of the GNU General Public License cover the whole 25: combination. 26: 27: As a special exception, the copyright holders of this library give you 28: permission to link this library with independent modules to produce an 29: executable, regardless of the license terms of these independent 30: modules, and to copy and distribute the resulting executable under 31: terms of your choice, provided that you also meet, for each linked 32: independent module, the terms and conditions of the license of that 33: module. An independent module is a module which is not derived from 34: or based on this library. If you modify this library, you may extend 35: this exception to your version of the library, but you are not 36: obligated to do so. If you do not wish to do so, delete this 37: exception statement from your version. */ 38: 39: 40: package java.rmi.server; 41: 42: import java.io.DataInput; 43: import java.io.DataOutput; 44: import java.io.IOException; 45: import java.io.ObjectInput; 46: import java.io.ObjectOutput; 47: import java.io.Serializable; 48: 49: /** 50: * Represents the object identifier, unique for the host that generated it. 51: * The ObjID contains inside the integer object identifier that, if needed, 52: * may indicated that this is a reference to one of the well known objects 53: * on that host (registry, activator or dgc) and the {@link UID} that 54: * ensures uniqueness. 55: */ 56: public final class ObjID 57: implements Serializable 58: { 59: 60: /** 61: * Use serial version uid for interoperability. 62: */ 63: static final long serialVersionUID = - 6386392263968365220L; 64: 65: /** 66: * The object counter, which value is assigned when creating the ordinary 67: * objects without the known object id. The counter is incremented each time 68: * the new ObjID is constructed. 69: */ 70: private static long next = 0x8000000000000000L; 71: 72: /** 73: * The object to put the lock on when incrementing {@link #next} 74: */ 75: private static final Object lock = ObjID.class; 76: 77: /** 78: * Defines the ID of the naming service. 79: */ 80: public static final int REGISTRY_ID = 0; 81: 82: /** 83: * Defines the ID of the activator. 84: */ 85: public static final int ACTIVATOR_ID = 1; 86: 87: /** 88: * Defines the ID of the distributed garbage collector. 89: */ 90: public static final int DGC_ID = 2; 91: 92: /** 93: * The object Id (either well-known value or the value of the incrementing 94: * object counter. 95: */ 96: long objNum; 97: 98: /** 99: * The object unique identifier, generated individually for each object. 100: */ 101: UID space; 102: 103: /** 104: * Create the new object id, unique for this host. 105: */ 106: public ObjID() 107: { 108: synchronized (lock) 109: { 110: objNum = next++; 111: } 112: space = new UID(); 113: } 114: 115: /** 116: * Create the new object id defining the well known remotely accessible 117: * object, present in this host. The well - known objects are: 118: * <ul> 119: * <li>{@link #REGISTRY_ID} - RMI naming service.</li> 120: * <li>{@link #ACTIVATOR_ID} - activator</li> 121: * <li>{@link #DGC_ID} - distributed garbage collector (grants lease 122: * durations to keep the object before it is garbage collected.</li> 123: * </ul> 124: * 125: * @param id the well known object id, one of the above. 126: */ 127: public ObjID(int id) 128: { 129: objNum = (long) id; 130: space = new UID((short) 0); 131: } 132: 133: /** 134: * Write object id as long, then the object {@link UID}. 135: */ 136: public void write(ObjectOutput out) throws IOException 137: { 138: DataOutput dout = (DataOutput) out; 139: dout.writeLong(objNum); 140: space.write(dout); 141: } 142: 143: /** 144: * Read object id (as long), then the object {@link UID}. 145: */ 146: public static ObjID read(ObjectInput in) throws IOException 147: { 148: DataInput din = (DataInput) in; 149: ObjID id = new ObjID(); 150: id.objNum = din.readLong(); 151: id.space = UID.read(din); 152: return (id); 153: } 154: 155: /** 156: * Get the hashcode. 157: */ 158: public int hashCode() 159: { 160: return space == null ? (int) objNum : space.hashCode() ^ (int) objNum; 161: } 162: 163: /** 164: * Compare for equality. 165: */ 166: public boolean equals(Object obj) 167: { 168: if (obj instanceof ObjID) 169: { 170: ObjID that = (ObjID) obj; 171: return that.objNum == objNum && eq(that.space, space); 172: } 173: else 174: return false; 175: } 176: 177: /** 178: * Compare by .equals if both a and b are not null, compare directly if at 179: * least one of them is null. 180: */ 181: static final boolean eq(Object a, Object b) 182: { 183: if (a == null || b == null) 184: return a == b; 185: else 186: return a.equals(b); 187: } 188: 189: /** 190: * Get the string representation. 191: */ 192: public String toString() 193: { 194: return (objNum + ":" + space); 195: } 196: 197: }