refactoring of the trace aliasing

Author: lexicalscope

README.md

@@ -1,7 +1,7 @@
 Java Bytecode Snapshot Vm and Symbolic Executor [![Build Status](https://travis-ci.org/lexicalscope/svm.png?branch=master)](https://travis-ci.org/lexicalscope/svm)
 =========================================
 
-If you would like to help out, please contact me or just fork and get going.
+If you would like to help out, please contact me or just fork and get going. You will need to use maven 3 to build things, and I have put eclipse config files in the repo so you should be able to get going with eclipse pretty quickly. You might need to pick a particular JDK version to run with (try OpenJDK "1.7.0_51")
 
 Particularly anyone who wants to get more of the bytecode instructions implemented, or who wants to help with java standard library compatiblity, or work on performance/scalability.
 

svm-partition-trace/src/main/java/com/lexicalscope/svm/partition/trace/Trace.java

@@ -1,7 +1,6 @@
 package com.lexicalscope.svm.partition.trace;
 
 import static com.lexicalscope.svm.partition.trace.Trace.CallReturn.CALL;
-import static java.util.Arrays.copyOf;
 
 import java.util.Arrays;
 import java.util.HashMap;
@@ -44,38 +43,16 @@ private Trace(
    }
 
    public Trace extend(final SMethodDescriptor methodCalled, final CallReturn callReturn, final Object ... args) {
-      final Object[] normalisedArgs = copyOf(args, args.length);
-      int newNextAlias = nextAlias;
-      Map<Object, Alias> newMap = map;
-
-      if(callReturn.equals(CallReturn.CALL)) {
-         for (final int i : methodCalled.objectArgIndexes()) {
-            Alias alias;
-            if(null == (alias = newMap.get(args[i + 1]))) {
-               // TODO[tim] do COW here
-               if(map == newMap) {
-                  newMap = new HashMap<>(map);
-               }
-               alias = new Alias(newNextAlias++);
-               newMap.put(args[i + 1], alias);
-            }
-            normalisedArgs[i + 1] = alias;
-         }
+      final TraceExtender traceExtender = new TraceExtender(args, map, nextAlias);
+
+      if(callReturn.equals(CALL)) {
+         traceExtender.aliasesForCallArguments(methodCalled.objectArgIndexes());
       }
-      if(callReturn.equals(CallReturn.CALL) || methodCalled.returnIsObject()) {
-         Alias alias;
-         if(null == (alias = newMap.get(args[0]))) {
-            // TODO[tim] do COW here
-            if(map == newMap) {
-               newMap = new HashMap<>(map);
-            }
-            alias = new Alias(newNextAlias++);
-            newMap.put(args[0], alias);
-         }
-         normalisedArgs[0] = alias;
+      if(callReturn.equals(CALL) || methodCalled.returnIsObject()) {
+         traceExtender.aliasesForZerothArguments();
       }
 
-      return new Trace(this, newMap, newNextAlias, methodCalled, callReturn, normalisedArgs);
+      return new Trace(this, traceExtender.newMap(), traceExtender.newNextAlias(), methodCalled, callReturn, traceExtender.normalisedArgs());
    }
 
    public List<Trace> asList() {

svm-partition-trace/src/main/java/com/lexicalscope/svm/partition/trace/TraceExtender.java

@@ -0,0 +1,60 @@
+package com.lexicalscope.svm.partition.trace;
+
+import static java.util.Arrays.copyOf;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class TraceExtender {
+   private final Object[] normalisedArgs;
+   private int newNextAlias;
+   private Map<Object, Alias> newMap;
+   private final Map<Object, Alias> map;
+
+   public TraceExtender(final Object[] args, final Map<Object, Alias> map, final int nextAlias) {
+      this.normalisedArgs = copyOf(args, args.length);
+      this.newNextAlias = nextAlias;
+      this.map = map;
+      this.newMap = map;
+   }
+
+   public void aliasesForZerothArguments() {
+      normalisedArgs[0] = aliasForArg(normalisedArgs[0]);
+   }
+
+   public void aliasesForCallArguments(final int[] objectArgIndexes) {
+      for (final int i : objectArgIndexes) {
+         normalisedArgs[i + 1] = aliasForArg(normalisedArgs[i + 1]);
+      }
+   }
+
+   private Alias aliasForArg(final Object arg) {
+      Alias alias;
+      if(null == (alias = newMap.get(arg))) {
+         alias = newAlias(arg);
+      }
+      return alias;
+   }
+
+   private Alias newAlias(final Object arg) {
+      // TODO[tim] do proper COW here
+      if(map == newMap) {
+         newMap = new HashMap<>(map);
+      }
+      final Alias alias = new Alias(newNextAlias++);
+      newMap.put(arg, alias);
+      return alias;
+   }
+
+   public Map<Object, Alias> newMap() {
+      return newMap;
+   }
+
+   public int newNextAlias() {
+      return newNextAlias;
+   }
+
+   public Object[] normalisedArgs() {
+      return normalisedArgs;
+   }
+}