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Better UUID documentation + more tests.

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Harald Kuhr
2012-03-12 10:53:13 +01:00
parent 9cb21dbfc9
commit 07a5c62a28
2 changed files with 239 additions and 57 deletions
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83
sandbox/sandbox-common/src/main/java/com/twelvemonkeys/util/UUIDFactory.java
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@@ -35,16 +35,25 @@ import java.net.SocketException;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.security.SecureRandom;
import java.util.ArrayList;
import java.util.Enumeration;
import java.util.List;
import java.util.UUID;
import java.util.*;
/**
* A factory for creating UUIDs not directly supported by {@link java.util.UUID}.
* <p>
* This class can create
* version 1 (time based, using either MAC aka IEEE 802 address or Random "node" value)
* and version 5 (SHA1 hash based) UUIDs.
* version 1 time based, using either IEEE 802 (mac) address or random "node" value
* and version 5 SHA1 hash based UUIDs.
* </p>
* <p>
* The node value for version 1 UUIDs will, by default, reflect the IEEE 802 (mac) address of one of
* the network interfaces of the local computer.
* This node value can be manually overridden by setting
* the system property {@code "com.twelvemonkeys.util.UUID.node"} to a valid IEEE 802 address, on the form
* {@code 12:34:56:78:9a:bc} or {@code 12-34-45-78-9a-bc}.
* </p>
* <p>
* The node value for the random "node" based version 1 UUIDs will be stable for the lifetime of the VM.
* </p>
*
* @author <a href="mailto:harald.kuhr@gmail.com">Harald Kuhr</a>
* @author last modified by $Author: haraldk$
@@ -54,14 +63,14 @@ import java.util.UUID;
* @see <a href="http://en.wikipedia.org/wiki/Universally_unique_identifier">Wikipedia</a>
* @see java.util.UUID
*/
public class UUIDFactory {
public final class UUIDFactory {
private static final String NODE_PROPERTY = "com.twelvemonkeys.util.UUID.node";
/**
* Nil UUID: {@code "00000000-0000-0000-0000-000000000000"}.
*
* The nil UUID is special form of UUID that is specified to have all
* 128 bits set to zero.
* 128 bits set to zero. Not particularly useful.
*
* @see <a href="http://tools.ietf.org/html/rfc4122#section-4.1.7">RFC 4122</a>
*/
@@ -69,8 +78,9 @@ public class UUIDFactory {
private static final SecureRandom SECURE_RANDOM = new SecureRandom();
// Assumes MAC address is constant, which it may not be on clients moving from ethernet to wifi etc...
// TODO: Update at some interval
private static final Comparator<UUID> COMPARATOR = new UUIDComparator();
// Assumes MAC address is constant, which it may not be if a network card is replaced
static final long MAC_ADDRESS_NODE = getMacAddressNode();
static final long SECURE_RANDOM_NODE = getSecureRandomNode();
@@ -134,7 +144,7 @@ public class UUIDFactory {
String nodesString = nodesStrings[i];
try {
String[] nodes = nodesString.split("(?<=(^|\\W)[0-9a-fA-F]{2})\\W(?=[0-9a-fA-F]{2}($|\\W))", 6);
String[] nodes = nodesString.split("(?<=(^|\\W)[0-9a-fA-F]{2})\\W(?=[0-9a-fA-F]{2}(\\W|$))", 6);
long nodeAddress = 0;
@@ -159,6 +169,8 @@ public class UUIDFactory {
return addressNodes;
}
private UUIDFactory() {}
// See also http://tools.ietf.org/html/rfc4122#appendix-B
// See http://tools.ietf.org/html/rfc4122: 4.3. Algorithm for Creating a Name-Based UUID
// TODO: Naming (of the method)
@@ -213,6 +225,7 @@ public class UUIDFactory {
// See http://tools.ietf.org/html/rfc4122#appendix-B
// TODO: Naming (of the method)
// TODO: Document that these can never clash with node based v1 UUIDs due to unicast/multicast bit
// However, no uniqueness between multiple mavhines/vms/nodes can be guaranteed.
static UUID timeRandomBasedV1() {
return new UUID(createTimeAndVersion(), createClockSeqAndNode(SECURE_RANDOM_NODE));
}
@@ -241,8 +254,52 @@ public class UUIDFactory {
return time;
}
// TODO: Implement compare as spec'ed, see http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7025832
// - Probably create a comparator
/**
* Returns a comparator that compares UUIDs as 128 bit unsigned entities, as mentioned in RFC 4122.
* This is different than {@link UUID#compareTo(Object)} that compares the UUIDs as signed entities.
*
* @return a comparator that compares UUIDs as 128 bit unsigned entities.
*
* @see <a href="http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7025832">java.lang.UUID compareTo() does not do an unsigned compare</a>
* @see
*/
public static Comparator<UUID> comparator() {
return COMPARATOR;
}
static final class UUIDComparator implements Comparator<UUID> {
public int compare(UUID left, UUID right) {
// The ordering is intentionally set up so that the UUIDs
// can simply be numerically compared as two *UNSIGNED* numbers
if (left.getMostSignificantBits() >>> 32 < right.getMostSignificantBits() >>> 32) {
return -1;
}
else if (left.getMostSignificantBits() >>> 32 > right.getMostSignificantBits() >>> 32) {
return 1;
}
else if ((left.getMostSignificantBits() & 0xffffffffl) < (right.getMostSignificantBits() & 0xffffffffl)) {
return -1;
}
else if ((left.getMostSignificantBits() & 0xffffffffl) > (right.getMostSignificantBits() & 0xffffffffl)) {
return 1;
}
else if (left.getLeastSignificantBits() >>> 32 < right.getLeastSignificantBits() >>> 32) {
return -1;
}
else if (left.getLeastSignificantBits() >>> 32 > right.getLeastSignificantBits() >>> 32) {
return 1;
}
else if ((left.getLeastSignificantBits() & 0xffffffffl) < (right.getLeastSignificantBits() & 0xffffffffl)) {
return -1;
}
else if ((left.getLeastSignificantBits() & 0xffffffffl) > (right.getLeastSignificantBits() & 0xffffffffl)) {
return 1;
}
return 0;
}
}
/**
* A high-resolution timer for use in creating version 1 UUIDs.