subclass java Random so we can save/restore state more easily

Author: timfel

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/random/PRandom.java

@@ -6,7 +6,17 @@
 import com.oracle.graal.python.builtins.objects.type.PythonClass;
 
 public class PRandom extends PythonBuiltinObject {
-    private Random javaRandom = new Random();
+    private static class PythonRandom extends Random {
+        private static final long serialVersionUID = 1L;
+
+        long getSeed() {
+            int nextseed = this.next(48); // 48 magic number of bits shifted away in superclass
+            this.setSeed(nextseed);
+            return nextseed;
+        }
+    }
+
+    private PythonRandom javaRandom = new PythonRandom();
 
     public PRandom(PythonClass cls) {
         super(cls);
@@ -16,6 +26,10 @@ public void setSeed(long seed) {
         javaRandom.setSeed(seed);
     }
 
+    public long getSeed() {
+        return javaRandom.getSeed();
+    }
+
     public long nextLong() {
         return javaRandom.nextLong();
     }
@@ -28,7 +42,7 @@ public Random getJavaRandom() {
         return javaRandom;
     }
 
-    public void setJavaRandom(Random random) {
-        javaRandom = random;
+    public void resetJavaRandom() {
+        javaRandom = new PythonRandom();
     }
 }

graalpython/com.oracle.graal.python/src/com/oracle/graal/python/builtins/objects/random/RandomBuiltins.java

@@ -2,7 +2,6 @@
 
 import java.math.BigInteger;
 import java.util.List;
-import java.util.Random;
 
 import com.oracle.graal.python.builtins.Builtin;
 import com.oracle.graal.python.builtins.CoreFunctions;
@@ -73,7 +72,8 @@ public PNone setstate(PRandom random, PTuple tuple) {
             if (arr.length == 1) {
                 Object object = arr[0];
                 if (object instanceof Long) {
-                    random.setJavaRandom(new Random((Long) object));
+                    random.resetJavaRandom();
+                    random.setSeed((Long) object);
                     return PNone.NONE;
                 }
             }
@@ -88,7 +88,7 @@ public abstract static class GetStateNode extends PythonBuiltinNode {
         @Specialization
         @TruffleBoundary
         public PTuple getstate(PRandom random) {
-            return factory().createTuple(new Object[]{random.nextLong()});
+            return factory().createTuple(new Object[]{random.getSeed()});
         }
     }