fix: unload attributes map if empty (#2433)

Author: skylot

.gitignore

@@ -32,6 +32,7 @@ jadx-output/
 *.jadx
 
 *.class
+*.jar
 *.dump
 *.log
 *.cfg

jadx-core/src/main/java/jadx/core/dex/attributes/AttrNode.java

@@ -12,7 +12,7 @@
 
 public abstract class AttrNode implements IAttributeNode {
 
-	private static final AttributeStorage EMPTY_ATTR_STORAGE = new EmptyAttrStorage();
+	private static final AttributeStorage EMPTY_ATTR_STORAGE = EmptyAttrStorage.INSTANCE;
 
 	private AttributeStorage storage = EMPTY_ATTR_STORAGE;
 
@@ -35,6 +35,9 @@ public void addAttr(IJadxAttribute attr) {
 
 	@Override
 	public void addAttrs(List<IJadxAttribute> list) {
+		if (list.isEmpty()) {
+			return;
+		}
 		initStorage().add(list);
 	}
 

jadx-core/src/main/java/jadx/core/dex/attributes/AttributeStorage.java

@@ -18,30 +18,34 @@
 import jadx.core.utils.exceptions.JadxRuntimeException;
 
 /**
- * Storage for different attribute types:
- * 1. flags - boolean attribute (set or not)
- * 2. attribute - class instance associated with attribute type.
+ * Storage for different attribute types:<br>
+ * 1. Flags - boolean attribute (set or not)<br>
+ * 2. Attributes - class instance ({@link IJadxAttribute}) associated with an attribute type
+ * ({@link IJadxAttrType})<br>
  */
 public class AttributeStorage {
 
+	public static AttributeStorage fromList(List<IJadxAttribute> list) {
+		AttributeStorage storage = new AttributeStorage();
+		storage.add(list);
+		return storage;
+	}
+
 	static {
 		int flagsCount = AFlag.values().length;
 		if (flagsCount >= 64) {
 			throw new JadxRuntimeException("Try to reduce flags count to 64 for use one long in EnumSet, now " + flagsCount);
 		}
 	}
 
+	private static final Map<IJadxAttrType<?>, IJadxAttribute> EMPTY_ATTRIBUTES = Collections.emptyMap();
+
 	private final Set<AFlag> flags;
 	private Map<IJadxAttrType<?>, IJadxAttribute> attributes;
 
 	public AttributeStorage() {
 		flags = EnumSet.noneOf(AFlag.class);
-		attributes = Collections.emptyMap();
-	}
-
-	public AttributeStorage(List<IJadxAttribute> attributesList) {
-		this();
-		add(attributesList);
+		attributes = EMPTY_ATTRIBUTES;
 	}
 
 	public void add(AFlag flag) {
@@ -125,21 +129,22 @@ public void remove(IJadxAttribute attr) {
 	}
 
 	private void writeAttributes(Consumer<Map<IJadxAttrType<?>, IJadxAttribute>> mapConsumer) {
-		if (attributes.isEmpty()) {
-			attributes = new IdentityHashMap<>(5);
-		}
 		synchronized (this) {
+			if (attributes == EMPTY_ATTRIBUTES) {
+				attributes = new IdentityHashMap<>(2); // only 1 or 2 attributes added in most cases
+			}
 			mapConsumer.accept(attributes);
+			if (attributes.isEmpty()) {
+				attributes = EMPTY_ATTRIBUTES;
+			}
 		}
 	}
 
 	public void unloadAttributes() {
 		if (attributes.isEmpty()) {
 			return;
 		}
-		synchronized (this) {
-			attributes.entrySet().removeIf(entry -> !entry.getValue().keepLoaded());
-		}
+		writeAttributes(map -> map.entrySet().removeIf(entry -> !entry.getValue().keepLoaded()));
 	}
 
 	public List<String> getAttributeStrings() {

jadx-core/src/main/java/jadx/core/dex/attributes/EmptyAttrStorage.java

@@ -9,6 +9,12 @@
 
 public final class EmptyAttrStorage extends AttributeStorage {
 
+	public static final AttributeStorage INSTANCE = new EmptyAttrStorage();
+
+	private EmptyAttrStorage() {
+		// singleton
+	}
+
 	@Override
 	public boolean contains(AFlag flag) {
 		return false;

jadx-gui/src/main/java/jadx/gui/device/debugger/smali/Smali.java

@@ -185,16 +185,14 @@ private void writeClass(SmaliWriter smali, ClassNode cls) {
 			smali.startLine(String.format("###### Class %s is created by jadx", cls.getFullName()));
 			return;
 		}
-		AttributeStorage attributes = new AttributeStorage();
-		attributes.add(clsData.getAttributes());
-
+		AttributeStorage clsAttributes = AttributeStorage.fromList(clsData.getAttributes());
 		smali.startLine("Class: " + clsData.getType())
 				.startLine("AccessFlags: " + AccessFlags.format(clsData.getAccessFlags(), AccessFlagsScope.CLASS))
 				.startLine("SuperType: " + clsData.getSuperType())
 				.startLine("Interfaces: " + clsData.getInterfacesTypes())
-				.startLine("SourceFile: " + attributes.get(JadxAttrType.SOURCE_FILE));
+				.startLine("SourceFile: " + clsAttributes.get(JadxAttrType.SOURCE_FILE));
 
-		AnnotationsAttr annotationsAttr = attributes.get(JadxAttrType.ANNOTATION_LIST);
+		AnnotationsAttr annotationsAttr = clsAttributes.get(JadxAttrType.ANNOTATION_LIST);
 		if (annotationsAttr != null) {
 			Collection<IAnnotation> annos = annotationsAttr.getList();
 			if (!annos.isEmpty()) {
@@ -451,7 +449,8 @@ private void writeMethodDef(SmaliWriter smali, IMethodData mth, LineInfo lineInf
 		smali.add(')');
 		smali.add(methodRef.getReturnType());
 
-		AnnotationsAttr annotationsAttr = new AttributeStorage(mth.getAttributes()).get(JadxAttrType.ANNOTATION_LIST);
+		AttributeStorage mthAttributes = AttributeStorage.fromList(mth.getAttributes());
+		AnnotationsAttr annotationsAttr = mthAttributes.get(JadxAttrType.ANNOTATION_LIST);
 		if (annotationsAttr != null && !annotationsAttr.isEmpty()) {
 			smali.incIndent();
 			writeAnnotations(smali, annotationsAttr.getList());
@@ -1074,7 +1073,7 @@ private static RawField make(IFieldData f) {
 			field.accessFlag = AccessFlags.format(f.getAccessFlags(), FIELD);
 			field.name = f.getName();
 			field.type = f.getType();
-			field.attributes = new AttributeStorage(f.getAttributes());
+			field.attributes = AttributeStorage.fromList(f.getAttributes());
 			return field;
 		}
 	}

jadx-plugins/jadx-input-api/src/main/java/jadx/api/plugins/input/data/attributes/IJadxAttribute.java

@@ -1,11 +1,14 @@
 package jadx.api.plugins.input.data.attributes;
 
+/**
+ * Jadx attribute: custom data container, can be added to most jadx nodes.
+ */
 public interface IJadxAttribute {
 
 	IJadxAttrType<? extends IJadxAttribute> getAttrType();
 
 	/**
-	 * Mark type to skip unloading on node unload
+	 * Mark type to skip unloading on node unload event
 	 */
 	default boolean keepLoaded() {
 		return false;