Bit of tweaking of Variant 7 generation, update "Jug" helper class

Author: cowtowncoder

release-notes/CREDITS

@@ -118,6 +118,8 @@ Pascal Schumacher (PascalSchumacher@github)
 Hal Hildebrand (Hellblazer@github)
   * Contributed #41: Add support for Proposed type v6 (reordered timestamp)
   [4.1.0]
+  * Contributed #46: Add support for Proposed type v7 (epoch-based time uuid)
+  [4.1.0]
 
 Paul Galbraith (pgalbraith@github)
   * Contributed #52: Add `Generators.egressTimeBasedGenerator()` method that constructs

release-notes/VERSION

@@ -8,6 +8,8 @@ Releases
 
 #41: Add support for Proposed type v6 (reordered timestamp)
  (contributed by Hal H)
+#46: Add support for Proposed type v7 (epoch-based time uuid)
+ (contributed by Hal H)
 #52: Add `Generators.egressTimeBasedGenerator()` method that constructs `TimedBasedGenerator`
   with a sensible choice of interface
  (contributed by Paul G)

src/main/java/com/fasterxml/uuid/Jug.java

@@ -31,6 +31,8 @@ public class Jug
         TYPES.put("time-based", "t");
         TYPES.put("random-based", "r");
         TYPES.put("name-based", "n");
+        TYPES.put("reordered-time-based", "o"); // Variant 6
+        TYPES.put("epoch-time-based", "e"); // Variant 7
     }
 
     protected final static HashMap<String,String> OPTIONS = new HashMap<String,String>();
@@ -67,7 +69,9 @@ protected static void printUsage()
         System.err.println("And type is one of:");
         System.err.println("  time-based / t: generate UUID based on current time and optional\n    location information (defined with -e option)");
         System.err.println("  random-based / r: generate UUID based on the default secure random number generator");
-        System.err.println("  name-based / n: generate UUID based on the na the default secure random number generator");
+        System.err.println("  name-based / n: generate UUID based on MD5 hash of given String ('name')");
+        System.err.println("  reordered-time-based / o: generate UUID based on current time and optional\n    location information (defined with -e option)");
+        System.err.println("  epoch-based / e: generate UUID based on current time (as 'epoch') and random number");
     }
 
     private static void printMap(Map<String,String> m, PrintStream out, boolean option)
@@ -223,6 +227,9 @@ public static void main(String[] args)
 
         switch (typeC) {
         case 't': // time-based
+        case 'o': // reordered-time-based (Variant 6)
+            // 30-Jun-2022, tatu: Is this true? My former self must have had his
+            //    reasons so leaving as is but... odd.
             usesRnd = true;
             // No address specified? Need a dummy one...
             if (addr == null) {
@@ -235,7 +242,9 @@ public static void main(String[] args)
                     System.out.println(")");
                 }
             }
-            noArgGenerator = Generators.timeBasedGenerator(addr);
+            noArgGenerator = (typeC == 't')
+                    ? Generators.timeBasedGenerator(addr)
+                    : Generators.timeBasedReorderedGenerator(addr);
             break;
         case 'r': // random-based
             usesRnd = true;
@@ -247,6 +256,16 @@ public static void main(String[] args)
                 noArgGenerator = Generators.randomBasedGenerator(r);
             }
             break;
+        case 'e': // epoch-time-based
+            usesRnd = true;
+            {
+                SecureRandom r = new SecureRandom();
+                if (verbose) {
+                    System.out.print("(using secure random generator, info = '"+r.getProvider().getInfo()+"')");
+                }
+                noArgGenerator = Generators.timeBasedEpochGenerator(r);
+            }
+            break;
         case 'n': // name-based
             if (nameSpace == null) {
                 System.err.println("--name-space (-s) - argument missing when using method that requires it, exiting.");

src/main/java/com/fasterxml/uuid/impl/GeneratorImplBase.java

@@ -0,0 +1,17 @@
+package com.fasterxml.uuid.impl;
+
+import java.security.SecureRandom;
+
+/**
+ * Trivial helper class that uses class loading as synchronization
+ * mechanism for lazy instantiation of the shared secure random
+ * instance.
+ */
+public final class LazyRandom
+{
+    private final static SecureRandom shared = new SecureRandom();
+
+    public static SecureRandom sharedSecureRandom() {
+        return shared;
+    }
+}

src/main/java/com/fasterxml/uuid/impl/LazyRandom.java

@@ -76,9 +76,9 @@ public RandomBasedGenerator(Random rnd)
     @Override
     public UUID generate()
     {
-        /* 14-Oct-2010, tatu: Surprisingly, variant for reading byte array is
-         *   tad faster for SecureRandom... so let's use that then
-         */
+        // 14-Oct-2010, tatu: Surprisingly, variant for reading byte array is
+        //   tad faster for SecureRandom... so let's use that then
+
         long r1, r2;
 
         if (_secureRandom) {
@@ -114,24 +114,4 @@ private final static long _toInt(byte[] buffer, int offset)
             + ((buffer[++offset] & 0xFF) << 8)
             + (buffer[++offset] & 0xFF);
     }
-
-    /*
-    /**********************************************************************
-    /* Helper classes
-    /**********************************************************************
-     */
-
-    /**
-     * Trivial helper class that uses class loading as synchronization
-     * mechanism for lazy instantiation of the shared secure random
-     * instance.
-     */
-    protected final static class LazyRandom
-    {
-        private final static SecureRandom shared = new SecureRandom();
-
-        public static SecureRandom sharedSecureRandom() {
-            return shared;
-        }
-    }
 }

src/main/java/com/fasterxml/uuid/impl/RandomBasedGenerator.java

@@ -1,14 +1,11 @@
 package com.fasterxml.uuid.impl;
 
-
-import java.nio.ByteBuffer;
 import java.security.SecureRandom;
 import java.util.Random;
 import java.util.UUID;
 
 import com.fasterxml.uuid.NoArgGenerator; 
 import com.fasterxml.uuid.UUIDType;
-import com.fasterxml.uuid.impl.RandomBasedGenerator.LazyRandom;
 
 /**
  * Implementation of UUID generator that uses time/location based generation
@@ -21,29 +18,27 @@
  * {@link com.fasterxml.uuid.ext.FileBasedTimestampSynchronizer} (or
  * equivalent).
  *
- * @since 3.1
+ * @since 4.1
  */
 public class TimeBasedEpochGenerator extends NoArgGenerator
 {
-    
     /*
     /**********************************************************************
     /* Configuration
     /**********************************************************************
      */
 
-
     /**
      * Random number generator that this generator uses.
      */
     protected final Random _random;
-    
+
     /*
     /**********************************************************************
     /* Construction
     /**********************************************************************
      */
-    
+
     /**
      * @param rnd Random number generator to use for generating UUIDs; if null,
      *   shared default generator is used. Note that it is strongly recommend to
@@ -58,7 +53,7 @@ public TimeBasedEpochGenerator(Random rnd)
         }
         _random = rnd;
     }
-    
+
     /*
     /**********************************************************************
     /* Access to config
@@ -67,25 +62,58 @@ public TimeBasedEpochGenerator(Random rnd)
 
     @Override
     public UUIDType getType() { return UUIDType.TIME_BASED_EPOCH; }
-    
+
     /*
     /**********************************************************************
     /* UUID generation
     /**********************************************************************
      */
-    
+
     @Override
     public UUID generate()
     {
-        ByteBuffer buff = ByteBuffer.allocate(2 * 8);
         final long rawTimestamp = System.currentTimeMillis();
-        final byte[] buffer = new byte[10];
-        _random.nextBytes(buffer);
-        buff.position(6);
-        buff.put(buffer);
-        buff.position(0);
-        buff.putLong(rawTimestamp << 16);
-        buff.flip();
-        return UUIDUtil.constructUUID(UUIDType.TIME_BASED_EPOCH, buff.array());
+        final byte[] rnd = new byte[10];
+        _random.nextBytes(rnd);
+
+        // Use only 48 lowest bits as per spec, next 16 bit from random
+        // (note: UUIDUtil.constuctUUID will add "version" so it's only 12
+        // actual random bits)
+        long l1 = (rawTimestamp << 16) | _toShort(rnd, 8);
+
+        // And then the other 64 bits of random; likewise UUIDUtil.constructUUID
+        // will overwrite first 2 random bits so it's "only" 62 bits
+        long l2 = _toLong(rnd, 0);
+
+        // and as per above, this call fills in "variant" and "version" bits
+        return UUIDUtil.constructUUID(UUIDType.TIME_BASED_EPOCH, l1, l2);
+    }
+
+    /*
+    /**********************************************************************
+    /* Internal methods
+    /**********************************************************************
+     */
+
+    protected final static long _toLong(byte[] buffer, int offset)
+    {
+        long l1 = _toInt(buffer, offset);
+        long l2 = _toInt(buffer, offset+4);
+        long l = (l1 << 32) + ((l2 << 32) >>> 32);
+        return l;
+    }
+
+    private final static long _toInt(byte[] buffer, int offset)
+    {
+        return (buffer[offset] << 24)
+            + ((buffer[++offset] & 0xFF) << 16)
+            + ((buffer[++offset] & 0xFF) << 8)
+            + (buffer[++offset] & 0xFF);
+    }
+
+    private final static long _toShort(byte[] buffer, int offset)
+    {
+        return ((buffer[offset] & 0xFF) << 8)
+            + (buffer[++offset] & 0xFF);
     }
 }

src/main/java/com/fasterxml/uuid/impl/TimeBasedEpochGenerator.java

@@ -15,15 +15,14 @@
  * {@link com.fasterxml.uuid.ext.FileBasedTimestampSynchronizer} (or
  * equivalent).
  *
- * @since 3.1
+ * @since 4.1
  */
 public class TimeBasedReorderedGenerator extends NoArgGenerator
 {
-    
     public static int BYTE_OFFSET_TIME_HIGH = 0;
     public static int BYTE_OFFSET_TIME_MID = 4;
     public static int BYTE_OFFSET_TIME_LOW = 7;
-    
+
     /*
     /**********************************************************************
     /* Configuration