AsyncFortunaRandomSource: Refactor refiller for concurrent and shutdown

Add shutdown hook for FortunaRandomSource

core/java/src/net/i2p/util/FortunaRandomSource.java

@@ -44,6 +44,14 @@ public class FortunaRandomSource extends RandomSource implements EntropyHarveste
         _haveNextGaussian = false;
     }
     
+    /**
+     *  Note - methods may hang or NPE or throw IllegalStateExceptions after this
+     *  @since 0.8.8
+     */
+    public void shutdown() {
+        _fortuna.shutdown();
+    }
+
     @Override
     public synchronized void setSeed(byte buf[]) {
       _fortuna.addRandomBytes(buf);

core/java/src/net/i2p/util/RandomSource.java

@@ -28,6 +28,12 @@ public class RandomSource extends SecureRandom implements EntropyHarvester {
     private final EntropyHarvester _entropyHarvester;
     protected final I2PAppContext _context;
 
+    /**
+     *  Deprecated - do not instantiate this directly, as you won't get the
+     *  good one (Fortuna). Use getInstance() or
+     *  I2PAppContext.getGlobalContext().random() to get the FortunaRandomSource
+     *  instance.
+     */
     public RandomSource(I2PAppContext context) {
         super();
         _context = context;
@@ -202,10 +208,4 @@ public class RandomSource extends SecureRandom implements EntropyHarvester {
         rs.saveSeed();
         }
     }
-    
-    // noop
-    private static class DummyEntropyHarvester implements EntropyHarvester {
-        public void feedEntropy(String source, long data, int bitoffset, int bits) {}
-        public void feedEntropy(String source, byte[] data, int offset, int len) {}
-    }
 }