Start optimising time-based UUID.

[lgpl/argeo-commons.git] / org.argeo.util / src / org / argeo / util / UuidUtils.java

diff --git a/org.argeo.util/src/org/argeo/util/UuidUtils.java b/org.argeo.util/src/org/argeo/util/UuidUtils.java
index 54e6b2cb363a6004c16812dbd82e6c26d770f9bb..d0537a555c87106e9cc4fc6ee1d307a3920e203a 100644 (file)
--- a/org.argeo.util/src/org/argeo/util/UuidUtils.java
+++ b/org.argeo.util/src/org/argeo/util/UuidUtils.java
@@ -20,6 +20,7 @@ import java.util.concurrent.atomic.AtomicInteger;
 public class UuidUtils {
        /** Nil UUID (00000000-0000-0000-0000-000000000000). */
        public final static UUID NIL_UUID = UUID.fromString("00000000-0000-0000-0000-000000000000");
+       public final static LocalDateTime GREGORIAN_START = LocalDateTime.of(1582, 10, 15, 0, 0, 0);
 
        private final static SecureRandom RANDOM;
        private final static AtomicInteger CLOCK_SEQUENCE;
@@ -77,8 +78,7 @@ public class UuidUtils {
 
        public static UUID timeBasedUUID(LocalDateTime time, BitSet node) {
                // most significant
-               LocalDateTime start = LocalDateTime.of(1582, 10, 15, 0, 0, 0);
-               Duration duration = Duration.between(start, time);
+               Duration duration = Duration.between(GREGORIAN_START, time);
 
                // Number of 100 ns intervals in one second: 1000000000 / 100 = 10000000
                long timeNanos = duration.getSeconds() * 10000000 + duration.getNano() / 100;
@@ -240,24 +240,34 @@ public class UuidUtils {
        public final static void main(String[] args) {
                UUID uuid;
 
-//             uuid= compactToUuid("996b1f5122de4b2f94e49168d32f22d1");
-//             System.out.println(uuid.toString() + ", isRandom=" + isRandom(uuid));
+               uuid = compactToUuid("996b1f5122de4b2f94e49168d32f22d1");
+               System.out.println(uuid.toString() + ", isRandom=" + isRandom(uuid));
+
+               // warm up
+               for (int i = 0; i < 10; i++) {
+                       UUID.randomUUID();
+                       timeBasedRandomUUID();
+                       timeBasedUUID();
+               }
 
                long begin;
                long duration;
+
                begin = System.nanoTime();
                uuid = UUID.randomUUID();
                duration = System.nanoTime() - begin;
                System.out.println(uuid.toString() + " in " + duration + " ns, isRandom=" + isRandom(uuid));
+
                begin = System.nanoTime();
-               uuid = timeBasedRandomUUID();
+               uuid = timeBasedUUID();
                duration = System.nanoTime() - begin;
                System.out.println(uuid.toString() + " in " + duration + " ns, isTimeBasedRandom=" + isTimeBasedRandom(uuid));
-//             System.out.println(toBinaryString(uuid, 8, ' '));
-//             System.out.println(toBinaryString(uuid, 16, '\n'));
+
                begin = System.nanoTime();
-               uuid = timeBasedUUID();
+               uuid = timeBasedRandomUUID();
                duration = System.nanoTime() - begin;
                System.out.println(uuid.toString() + " in " + duration + " ns, isTimeBasedRandom=" + isTimeBasedRandom(uuid));
+//             System.out.println(toBinaryString(uuid, 8, ' '));
+//             System.out.println(toBinaryString(uuid, 16, '\n'));
        }
 }