/*
* @(#)VMID.java 1.21 05/11/17
*
* Copyright 2006 Sun Microsystems, Inc. All rights reserved.
* SUN PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*/
package java.rmi.dgc;
import java.io.*;
import java.net.*;
import java.rmi.server.UID;
import java.security.*;
/**
* A VMID is a identifier that is unique across all Java virtual
* machines. VMIDs are used by the distributed garbage collector
* to identify client VMs.
*
* @version 1.21, 11/17/05
* @author Ann Wollrath
* @author Peter Jones
*/
public final class VMID implements java.io.Serializable {
/** array of bytes uniquely identifying this host */
private static byte[] localAddr = computeAddressHash();
/**
* @serial array of bytes uniquely identifying host created on
*/
private byte[] addr;
/**
* @serial unique identifier with respect to host created on
*/
private UID uid;
/** indicate compatibility with JDK 1.1.x version of class */
private static final long serialVersionUID = -538642295484486218L;
/**
* Create a new VMID. Each new VMID returned from this constructor
* is unique for all Java virtual machines under the following
* conditions: a) the conditions for uniqueness for objects of
* the class <code>java.rmi.server.UID</code> are satisfied, and b) an
* address can be obtained for this host that is unique and constant
* for the lifetime of this object. <p>
*/
public VMID() {
addr = localAddr;
uid = new UID();
}
/**
* Return true if an accurate address can be determined for this
* host. If false, reliable VMID cannot be generated from this host
* @return true if host address can be determined, false otherwise
* @deprecated
*/
@Deprecated
public static boolean isUnique() {
return true;
}
/**
* Compute hash code for this VMID.
*/
public int hashCode() {
return uid.hashCode();
}
/**
* Compare this VMID to another, and return true if they are the
* same identifier.
*/
public boolean equals(Object obj) {
if (obj instanceof VMID) {
VMID vmid = (VMID) obj;
if (!uid.equals(vmid.uid))
return false;
if ((addr == null) ^ (vmid.addr == null))
return false;
if (addr != null) {
if (addr.length != vmid.addr.length)
return false;
for (int i = 0; i < addr.length; ++ i)
if (addr[i] != vmid.addr[i])
return false;
}
return true;
} else {
return false;
}
}
/**
* Return string representation of this VMID.
*/
public String toString() {
StringBuffer result = new StringBuffer();
if (addr != null)
for (int i = 0; i < addr.length; ++ i) {
int x = (int) (addr[i] & 0xFF);
result.append((x < 0x10 ? "0" : "") +
Integer.toString(x, 16));
}
result.append(':');
result.append(uid.toString());
return result.toString();
}
/**
* Compute the hash an IP address. The hash is the first 8 bytes
* of the SHA digest of the IP address.
*/
private static byte[] computeAddressHash() {
/*
* Get the local host's IP address.
*/
byte[] addr = (byte[]) java.security.AccessController.doPrivileged(
new PrivilegedAction() {
public Object run() {
try {
return InetAddress.getLocalHost().getAddress();
} catch (Exception e) {
}
return new byte[] { 0, 0, 0, 0 };
}
});
byte[] addrHash;
final int ADDR_HASH_LENGTH = 8;
try {
/*
* Calculate message digest of IP address using SHA.
*/
MessageDigest md = MessageDigest.getInstance("SHA");
ByteArrayOutputStream sink = new ByteArrayOutputStream(64);
DataOutputStream out = new DataOutputStream(
new DigestOutputStream(sink, md));
out.write(addr, 0, addr.length);
out.flush();
byte digest[] = md.digest();
int hashlength = Math.min(ADDR_HASH_LENGTH, digest.length);
addrHash = new byte[hashlength];
System.arraycopy(digest, 0, addrHash, 0, hashlength);
} catch (IOException ignore) {
/* can't happen, but be deterministic anyway. */
addrHash = new byte[0];
} catch (NoSuchAlgorithmException complain) {
throw new InternalError(complain.toString());
}
return addrHash;
}
}