Merge pull request #32 from EpicPlayerA10/fix/wide-instruction-size

Fix computed size of WideInstruction

core/src/main/java/software/coley/cafedude/classfile/instruction/WideInstruction.java

@@ -26,16 +26,22 @@ public Instruction getBacking() {
 
 	@Override
 	public int computeSize() {
-		switch (backing.getOpcode()) {
-			case Opcodes.IINC:
-				return 6;
-			case Opcodes.LLOAD:
-			case Opcodes.DLOAD:
-			case Opcodes.LSTORE:
-			case Opcodes.DSTORE:
-				return 4;
-			default:
-				return 3;
+		if (backing.getOpcode() == Opcodes.IINC) {
+			// IINC is unique in that it becomes 6 bytes:
+			//   https://docs.oracle.com/javase/specs/jvms/se21/html/jvms-6.html#jvms-6.5.wide
+			//
+			// opcode
+			// iinc
+			// indexbyte1
+			// indexbyte2
+			// constbyte1
+			// constbyte2
+			return 6;
 		}
+		// opcode
+		// input opcode
+		// indexbyte1
+		// indexbyte2
+		return 4;
 	}
 }

core/src/test/java/software/coley/cafedude/RegressionTests.java

@@ -1,8 +1,10 @@
 package software.coley.cafedude;
 
+import software.coley.cafedude.classfile.ClassFile;
 import software.coley.cafedude.io.ClassFileReader;
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.MethodSource;
+import software.coley.cafedude.io.ClassFileWriter;
 
 import java.io.File;
 import java.io.IOException;
@@ -23,7 +25,8 @@ public void testNoErrors(File sample) {
 		try {
 			byte[] code = Files.readAllBytes(sample.toPath());
 			assertDoesNotThrow(() -> {
-				new ClassFileReader().read(code);
+				ClassFile classFile = new ClassFileReader().read(code);
+				new ClassFileWriter().write(classFile);
 			}, "Library crashes when reading: " + sample.getName());
 		} catch (IOException error) {
 			fail("Failed to read class, IO error", error);

core/src/test/java/software/coley/cafedude/SizeTest.java

@@ -38,26 +38,18 @@ void testIincInstruction() {
 
 		@Test
 		void testWideInstruction() {
-			int[] four_byte_ops = {
-					LLOAD, DLOAD, LSTORE, DSTORE
-			};
-			int[] three_byte_ops = {
-					RET, ILOAD, FLOAD, ALOAD, ISTORE, FSTORE, ASTORE
-			};
-
 			// IINC is 6 bytes
 			WideInstruction instruction = new WideInstruction(new IincInstruction(0, 0));
 			assertEquals(6, instruction.computeSize());
 
+			int[] four_byte_ops = {
+				LLOAD, DLOAD, LSTORE, DSTORE, RET, ILOAD, FLOAD, ALOAD, ISTORE, FSTORE, ASTORE
+			};
+
 			// Wide type variable insns are 4
 			for (int op : four_byte_ops) {
-				instruction = new WideInstruction(new IntOperandInstruction(op, 0));
-				assertEquals(4, instruction.computeSize());
-			}
-			// Normal variable insns are 3
-			for (int op : three_byte_ops) {
-				instruction = new WideInstruction(new IntOperandInstruction(op, 0));
-				assertEquals(3, instruction.computeSize());
+				WideInstruction instruction1 = new WideInstruction(new IntOperandInstruction(op, 0));
+				assertEquals(4, instruction1.computeSize());
 			}
 		}