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VMID.java
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134 lines (122 loc) · 3.36 KB
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/*
* Copyright (c) 1996, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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*/
package java.rmi.dgc;
import java.rmi.server.UID;
import java.security.SecureRandom;
/**
* 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.
*
* @author Ann Wollrath
* @author Peter Jones
*/
public final class VMID implements java.io.Serializable {
/** Array of bytes uniquely identifying this host */
private static final byte[] randomBytes;
/**
* @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;
static {
// Generate 8 bytes of random data.
SecureRandom secureRandom = new SecureRandom();
byte bytes[] = new byte[8];
secureRandom.nextBytes(bytes);
randomBytes = bytes;
}
/**
* 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.
*/
public VMID() {
addr = randomBytes;
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 = addr[i] & 0xFF;
result.append((x < 0x10 ? "0" : "") +
Integer.toString(x, 16));
}
result.append(':');
result.append(uid.toString());
return result.toString();
}
}