From 5f70f34b6173ca667d19d9de914aab96836cec6b Mon Sep 17 00:00:00 2001
From: Sam Harwell <sam@tunnelvisionlabs.com>
Date: Tue, 5 Aug 2014 17:46:36 -0500
Subject: [PATCH] Additional performance tweaks in edge map implementations

---
 .../antlr/v4/runtime/dfa/ArrayEdgeMap.java    |  2 +-
 .../v4/runtime/dfa/SingletonEdgeMap.java      |  2 +-
 .../antlr/v4/runtime/dfa/SparseEdgeMap.java   | 44 ++++++++-----------
 3 files changed, 21 insertions(+), 27 deletions(-)

diff --git a/runtime/Java/src/org/antlr/v4/runtime/dfa/ArrayEdgeMap.java b/runtime/Java/src/org/antlr/v4/runtime/dfa/ArrayEdgeMap.java
index d3029bb415..e0ce35408a 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/dfa/ArrayEdgeMap.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/dfa/ArrayEdgeMap.java
@@ -41,7 +41,7 @@
  *
  * @author Sam Harwell
  */
-public class ArrayEdgeMap<T> extends AbstractEdgeMap<T> {
+public final class ArrayEdgeMap<T> extends AbstractEdgeMap<T> {
 
 	private final AtomicReferenceArray<T> arrayData;
 	private final AtomicInteger size;
diff --git a/runtime/Java/src/org/antlr/v4/runtime/dfa/SingletonEdgeMap.java b/runtime/Java/src/org/antlr/v4/runtime/dfa/SingletonEdgeMap.java
index 0062b422da..73fefc87c0 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/dfa/SingletonEdgeMap.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/dfa/SingletonEdgeMap.java
@@ -37,7 +37,7 @@
  *
  * @author Sam Harwell
  */
-public class SingletonEdgeMap<T> extends AbstractEdgeMap<T> {
+public final class SingletonEdgeMap<T> extends AbstractEdgeMap<T> {
 
 	private final int key;
 	private final T value;
diff --git a/runtime/Java/src/org/antlr/v4/runtime/dfa/SparseEdgeMap.java b/runtime/Java/src/org/antlr/v4/runtime/dfa/SparseEdgeMap.java
index adad5e4a86..748f7fc51f 100644
--- a/runtime/Java/src/org/antlr/v4/runtime/dfa/SparseEdgeMap.java
+++ b/runtime/Java/src/org/antlr/v4/runtime/dfa/SparseEdgeMap.java
@@ -41,7 +41,7 @@
  *
  * @author Sam Harwell
  */
-public class SparseEdgeMap<T> extends AbstractEdgeMap<T> {
+public final class SparseEdgeMap<T> extends AbstractEdgeMap<T> {
 	private static final int DEFAULT_MAX_SIZE = 5;
 
 	private final int[] keys;
@@ -59,26 +59,26 @@ public SparseEdgeMap(int minIndex, int maxIndex, int maxSparseSize) {
 
 	private SparseEdgeMap(@NotNull SparseEdgeMap<T> map, int maxSparseSize) {
 		super(map.minIndex, map.maxIndex);
-		if (maxSparseSize < map.values.size()) {
-			throw new IllegalArgumentException();
-		}
-
 		synchronized (map) {
+			if (maxSparseSize < map.values.size()) {
+				throw new IllegalArgumentException();
+			}
+
 			keys = Arrays.copyOf(map.keys, maxSparseSize);
 			values = new ArrayList<T>(maxSparseSize);
 			values.addAll(map.values);
 		}
 	}
 
-	public int[] getKeys() {
+	public final int[] getKeys() {
 		return keys;
 	}
 
-	public List<T> getValues() {
+	public final List<T> getValues() {
 		return values;
 	}
 
-	public int getMaxSparseSize() {
+	public final int getMaxSparseSize() {
 		return keys.length;
 	}
 
@@ -99,14 +99,15 @@ public boolean containsKey(int key) {
 
 	@Override
 	public T get(int key) {
-		synchronized (this) {
-			int index = Arrays.binarySearch(keys, 0, size(), key);
-			if (index < 0) {
-				return null;
-			}
-
-			return values.get(index);
+		// Special property of this collection: values are only even added to
+		// the end, else a new object is returned from put(). Therefore no lock
+		// is required in this method.
+		int index = Arrays.binarySearch(keys, 0, size(), key);
+		if (index < 0) {
+			return null;
 		}
+
+		return values.get(index);
 	}
 
 	@Override
@@ -147,7 +148,7 @@ public AbstractEdgeMap<T> put(int key, T value) {
 			}
 			else {
 				SparseEdgeMap<T> resized = new SparseEdgeMap<T>(this, desiredSize);
-				System.arraycopy(resized.keys, insertIndex, resized.keys, insertIndex + 1, resized.keys.length - insertIndex - 1);
+				System.arraycopy(resized.keys, insertIndex, resized.keys, insertIndex + 1, size() - insertIndex);
 				resized.keys[insertIndex] = key;
 				resized.values.add(insertIndex, value);
 				return resized;
@@ -163,11 +164,6 @@ public SparseEdgeMap<T> remove(int key) {
 				return this;
 			}
 
-			if (index == values.size() - 1) {
-				values.remove(index);
-				return this;
-			}
-
 			SparseEdgeMap<T> result = new SparseEdgeMap<T>(this, getMaxSparseSize());
 			System.arraycopy(result.keys, index + 1, result.keys, index, size() - index - 1);
 			result.values.remove(index);
@@ -176,14 +172,12 @@ public SparseEdgeMap<T> remove(int key) {
 	}
 
 	@Override
-	public SparseEdgeMap<T> clear() {
+	public AbstractEdgeMap<T> clear() {
 		if (isEmpty()) {
 			return this;
 		}
 
-		SparseEdgeMap<T> result = new SparseEdgeMap<T>(this, getMaxSparseSize());
-		result.values.clear();
-		return result;
+		return new EmptyEdgeMap<T>(minIndex, maxIndex);
 	}
 
 	@Override