core: fix switch statement processing (issue #9 case 2)

jadx-core/src/main/java/jadx/core/codegen/RegionGen.java

@@ -199,7 +199,7 @@ public class RegionGen extends InsnGen {
 		SwitchNode insn = (SwitchNode) sw.getHeader().getInstructions().get(0);
 		InsnArg arg = insn.getArg(0);
 		code.startLine("switch (");
-		addArg(code, arg);
+		addArg(code, arg, false);
 		code.add(") {");
 		code.incIndent();
 

jadx-core/src/main/java/jadx/core/dex/visitors/regions/RegionMaker.java

@@ -627,7 +627,7 @@ public class RegionMaker {
 
 		BitSet succ = BlockUtils.blocksToBitSet(mth, block.getSuccessors());
 		BitSet domsOn = BlockUtils.blocksToBitSet(mth, block.getDominatesOn());
-		domsOn.and(succ); // filter 'out' block
+		domsOn.xor(succ); // filter 'out' block
 
 		BlockNode defCase = getBlockByOffset(insn.getDefaultCaseOffset(), block.getSuccessors());
 		if (defCase != null) {
@@ -642,13 +642,11 @@ public class RegionMaker {
 		}
 		if (outCount > 1) {
 			// filter successors of other blocks
+			List<BlockNode> blocks = mth.getBasicBlocks();
 			for (int i = domsOn.nextSetBit(0); i >= 0; i = domsOn.nextSetBit(i + 1)) {
-				BlockNode b = mth.getBasicBlocks().get(i);
+				BlockNode b = blocks.get(i);
 				for (BlockNode s : b.getCleanSuccessors()) {
-					int id = s.getId();
-					if (domsOn.get(id)) {
-						domsOn.clear(id);
-					}
+					domsOn.clear(s.getId());
 				}
 			}
 			outCount = domsOn.cardinality();
@@ -658,19 +656,27 @@ public class RegionMaker {
 		if (outCount == 1) {
 			out = mth.getBasicBlocks().get(domsOn.nextSetBit(0));
 		} else if (outCount == 0) {
-			// default and out blocks are same
-			out = defCase;
+			// one or several case blocks are empty,
+			// run expensive algorithm for find 'out' block
+			for (BlockNode maybeOut : block.getSuccessors()) {
+				boolean allReached = true;
+				for (BlockNode s : block.getSuccessors()) {
+					if (!BlockUtils.isPathExists(s, maybeOut)) {
+						allReached = false;
+						break;
+					}
+				}
+				if (allReached) {
+					out = maybeOut;
+					break;
+				}
+			}
 		}
 
 		stack.push(sw);
 		if (out != null) {
 			stack.addExit(out);
 		}
-//		else {
-//			for (BlockNode e : BlockUtils.bitSetToBlocks(mth, domsOn)) {
-//				stack.addExit(e);
-//			}
-//		}
 
 		if (!stack.containsExit(defCase)) {
 			sw.setDefaultCase(makeRegion(defCase, stack));

jadx-core/src/main/java/jadx/core/utils/BlockUtils.java

@@ -203,10 +203,7 @@ public class BlockUtils {
 	}
 
 	public static boolean isPathExists(BlockNode start, BlockNode end) {
-		if (start == end) {
-			return true;
-		}
-		if (end.isDominator(start)) {
+		if (start == end || end.isDominator(start)) {
 			return true;
 		}
 		return traverseSuccessorsUntil(start, end, new BitSet());

jadx-core/src/test/java/jadx/tests/internal/switches/TestSwitch.java

@@ -1,4 +1,4 @@
-package jadx.tests.internal;
+package jadx.tests.internal.switches;
 
 import jadx.api.InternalJadxTest;
 import jadx.core.dex.nodes.ClassNode;
@@ -6,6 +6,7 @@ import jadx.core.dex.nodes.ClassNode;
 import org.junit.Test;
 
 import static org.hamcrest.CoreMatchers.containsString;
+import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertThat;
 
 public class TestSwitch extends InternalJadxTest {
@@ -45,5 +46,9 @@ public class TestSwitch extends InternalJadxTest {
 
 		assertThat(code, containsString("case '/':"));
 		assertThat(code, containsString(indent(5) + "break;"));
+		assertThat(code, containsString(indent(4) + "default:"));
+
+		assertEquals(1, count(code, "i++"));
+		assertEquals(4, count(code, "break;"));
 	}
 }

jadx-core/src/test/java/jadx/tests/internal/switches/TestSwitchLabels.java

@@ -1,4 +1,4 @@
-package jadx.tests.internal;
+package jadx.tests.internal.switches;
 
 import jadx.api.InternalJadxTest;
 import jadx.core.dex.nodes.ClassNode;

jadx-core/src/test/java/jadx/tests/internal/switches/TestSwitchNoDefault.java

@@ -0,0 +1,42 @@
+package jadx.tests.internal.switches;
+
+import jadx.api.InternalJadxTest;
+import jadx.core.dex.nodes.ClassNode;
+
+import org.junit.Test;
+
+import static org.junit.Assert.assertEquals;
+
+public class TestSwitchNoDefault extends InternalJadxTest {
+
+	public static class TestCls {
+		public void test(int a) {
+			String s = null;
+			switch (a) {
+				case 1:
+					s = "1";
+					break;
+				case 2:
+					s = "2";
+					break;
+				case 3:
+					s = "3";
+					break;
+				case 4:
+					s = "4";
+					break;
+			}
+			System.out.println(s);
+		}
+	}
+
+	@Test
+	public void test() {
+		ClassNode cls = getClassNode(TestCls.class);
+		String code = cls.getCode().toString();
+		System.out.println(code);
+
+		assertEquals(4, count(code, "break;"));
+		assertEquals(1, count(code, "System.out.println(s);"));
+	}
+}

jadx-core/src/test/java/jadx/tests/internal/switches/TestSwitchSimple.java

@@ -0,0 +1,52 @@
+package jadx.tests.internal.switches;
+
+import jadx.api.InternalJadxTest;
+import jadx.core.dex.nodes.ClassNode;
+
+import org.junit.Test;
+
+import static org.hamcrest.CoreMatchers.containsString;
+import static org.hamcrest.CoreMatchers.not;
+import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertThat;
+
+public class TestSwitchSimple extends InternalJadxTest {
+
+	public static class TestCls {
+		public void test(int a) {
+			String s = null;
+			switch (a % 4) {
+				case 1:
+					s = "1";
+					break;
+				case 2:
+					s = "2";
+					break;
+				case 3:
+					s = "3";
+					break;
+				case 4:
+					s = "4";
+					break;
+				default:
+					System.out.println("Not Reach");
+					break;
+			}
+			System.out.println(s);
+		}
+	}
+
+	@Test
+	public void test() {
+		ClassNode cls = getClassNode(TestCls.class);
+		String code = cls.getCode().toString();
+		System.out.println(code);
+
+		assertEquals(5, count(code, "break;"));
+		assertEquals(1, count(code, "System.out.println(s);"));
+		assertEquals(1, count(code, "System.out.println(\"Not Reach\");"));
+
+		assertThat(code, not(containsString("switch ((a % 4)) {")));
+		assertThat(code, containsString("switch (a % 4) {"));
+	}
+}