/**
* 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;
}
/** Utility routine for setting the context class loader. Returns previous class loader. */
public static ClassLoader setContextClassLoader(ClassLoader newClassLoader) {
// Can only reference final local variables from dopriveleged block
final ClassLoader classLoaderToSet = newClassLoader;
final Thread currentThread = Thread.currentThread();
ClassLoader originalClassLoader = currentThread.getContextClassLoader();
if (classLoaderToSet != originalClassLoader) {
if (System.getSecurityManager() == null) {
currentThread.setContextClassLoader(classLoaderToSet);
} else {
java.security.AccessController.doPrivileged(
new java.security.PrivilegedAction() {
public java.lang.Object run() {
currentThread.setContextClassLoader(classLoaderToSet);
return null;
}
});
}
}
return originalClassLoader;
}