Fixed class version comparisons

Author: RaphiMC

impl-classtransform/src/main/java/net/raphimc/javadowngrader/impl/classtransform/JavaDowngraderTransformer.java

@@ -24,7 +24,6 @@
 import net.raphimc.javadowngrader.RuntimeDepCollector;
 import org.objectweb.asm.tree.ClassNode;
 
-import java.nio.ByteBuffer;
 import java.util.function.Predicate;
 
 public class JavaDowngraderTransformer implements IBytecodeTransformer {
@@ -76,15 +75,16 @@ public JavaDowngraderTransformer(final TransformerManager transformerManager, fi
 
     @Override
     public byte[] transform(String className, byte[] bytecode, boolean calculateStackMapFrames) {
-        if (ByteBuffer.wrap(bytecode, 4, 4).getInt() <= this.targetVersion) {
+        final int majorVersion = (bytecode[6] & 0xFF) << 8 | (bytecode[7] & 0xFF);
+        if (majorVersion <= this.targetVersion) {
             return null;
         }
         if (!this.classFilter.test(className)) {
             return null;
         }
 
         final ClassNode classNode = ASMUtils.fromBytes(bytecode);
-        JavaDowngrader.downgrade(classNode, this.targetVersion, depCollector);
+        JavaDowngrader.downgrade(classNode, this.targetVersion, this.depCollector);
 
         if (calculateStackMapFrames) {
             return ASMUtils.toBytes(classNode, this.transformerManager.getClassTree(), this.transformerManager.getClassProvider());

src/main/java/net/raphimc/javadowngrader/JavaDowngrader.java

@@ -79,7 +79,7 @@ public static void downgrade(final ClassNode classNode, final int targetVersion)
      */
     public static void downgrade(final ClassNode classNode, final int targetVersion, final RuntimeDepCollector depCollector) {
         for (DowngradingTransformer transformer : TRANSFORMER) {
-            if (transformer.getTargetVersion() >= targetVersion && classNode.version > transformer.getTargetVersion()) {
+            if (transformer.getTargetVersion() >= targetVersion && (classNode.version & 0xFF) > transformer.getTargetVersion()) {
                 transformer.transform(classNode, depCollector);
             }
         }

src/main/java/net/raphimc/javadowngrader/transformer/DowngradingTransformer.java

@@ -84,10 +84,10 @@ public void transform(final ClassNode classNode) {
     }
 
     public void transform(final ClassNode classNode, final RuntimeDepCollector depCollector) {
-        if (classNode.version > this.sourceVersion) {
+        if ((classNode.version & 0xFF) > this.sourceVersion) {
             throw new IllegalArgumentException("Input class version is higher than supported");
         }
-        if (classNode.version <= this.targetVersion) {
+        if ((classNode.version & 0xFF) <= this.targetVersion) {
             return;
         }