Fix: c0.0.15a server join, improved Classic saving fix

src/main/java/uk/betacraft/legacyfix/LegacyFixAgent.java

@@ -42,11 +42,11 @@ public static void premain(String agentArgs, final Instrumentation inst) {
                 new BetaForgePatch(),
                 new ModloaderPatch(),
                 new BitDepthPatch(),
+                new ClassicPatch(),
                 new GameDirPatch(),
                 new DeAwtPatch(),
                 new MousePatch(),
-                new VSyncPatch(),
-                new C15aPatch()
+                new VSyncPatch()
         ));
 
         List<String> patchStates = new ArrayList<String>();

src/main/java/uk/betacraft/legacyfix/patch/impl/ClassicPatch.java

@@ -0,0 +1,141 @@
+package uk.betacraft.legacyfix.patch.impl;
+
+import java.lang.instrument.ClassDefinition;
+import java.lang.instrument.Instrumentation;
+
+import javassist.CtClass;
+import javassist.CtMethod;
+import javassist.bytecode.CodeAttribute;
+import javassist.bytecode.CodeIterator;
+import javassist.bytecode.ConstPool;
+import javassist.bytecode.Opcode;
+import uk.betacraft.legacyfix.LFLogger;
+import uk.betacraft.legacyfix.LegacyFixLauncher;
+import uk.betacraft.legacyfix.patch.Patch;
+import uk.betacraft.legacyfix.patch.PatchHelper;
+
+/**
+ * Fixes server joining for c0.0.15a and saving in early Classic
+ */
+public class ClassicPatch extends Patch {
+    public ClassicPatch() {
+        super("classicpatch", "Fixes server joining for c0.0.15a and saving in early Classic", true);
+    }
+
+    @Override
+    public void apply(Instrumentation inst) throws Exception {
+        CtClass minecraftAppletClass = PatchHelper.findMinecraftAppletClass(pool);
+        if (minecraftAppletClass.isFrozen())
+            minecraftAppletClass.defrost();
+
+        CtMethod initMethod = minecraftAppletClass.getDeclaredMethod("init");
+
+        ConstPool initConstPool = initMethod.getMethodInfo().getConstPool();
+
+        CodeAttribute codeAttribute = initMethod.getMethodInfo().getCodeAttribute();
+        CodeIterator codeIterator = codeAttribute.iterator();
+
+        while (codeIterator.hasNext()) {
+            int pos = codeIterator.next();
+
+            patch15aServerJoin(codeIterator, initConstPool, pos);
+            patchMinecraftUriPort(codeIterator, initConstPool, pos);
+        }
+
+        inst.redefineClasses(new ClassDefinition(Class.forName(minecraftAppletClass.getName()), minecraftAppletClass.toBytecode()));
+    }
+
+    public static void patch15aServerJoin(CodeIterator codeIterator, ConstPool constPool, int pos) {
+        String server = System.getProperty("server", null);
+        int port = Integer.parseInt(System.getProperty("port", "25565"));
+
+        if (codeIterator.byteAt(pos) != Opcode.ALOAD_0 ||
+                codeIterator.byteAt(pos + 1) != Opcode.GETFIELD ||
+                codeIterator.byteAt(pos + 4) != Opcode.LDC ||
+                codeIterator.byteAt(pos + 6) != Opcode.SIPUSH ||
+                codeIterator.byteAt(pos + 9) != Opcode.INVOKEVIRTUAL) {
+            return;
+        }
+
+        int ldcPos = codeIterator.byteAt(pos + 5);
+        if (constPool.getTag(ldcPos) != ConstPool.CONST_String)
+            return;
+
+        String defaultString = constPool.getStringInfo(ldcPos);
+        int defaultPort = codeIterator.s16bitAt(pos + 7);
+
+        if (!"79.136.77.240".equals(defaultString))
+            return;
+
+        if (defaultPort != 5565)
+            return;
+
+        String refType = constPool.getMethodrefType(codeIterator.u16bitAt(pos + 10));
+        if (!"(Ljava/lang/String;I)V".equals(refType))
+            return;
+
+        if (server != null) {
+            // Inject the intended server
+            int serverRef = constPool.addStringInfo(server);
+
+            codeIterator.writeByte(serverRef, pos + 5);
+            codeIterator.write16bit(port, pos + 7);
+        } else {
+            // Erase the call
+            for (int i = 0; i < 12; i++) {
+                codeIterator.writeByte(Opcode.NOP, pos + i);
+            }
+        }
+    }
+
+    /**
+     * Patch for negative port number during saving
+     */
+    public static void patchMinecraftUriPort(CodeIterator codeIterator, ConstPool constPool, int pos) {
+        if (codeIterator.byteAt(pos) != Opcode.INVOKESPECIAL ||
+                codeIterator.byteAt(pos + 3) != Opcode.ALOAD_0 ||
+                codeIterator.byteAt(pos + 4) != Opcode.INVOKEVIRTUAL ||
+                codeIterator.byteAt(pos + 7) != Opcode.INVOKEVIRTUAL ||
+                codeIterator.byteAt(pos + 10) != Opcode.INVOKEVIRTUAL ||
+                codeIterator.byteAt(pos + 13) != Opcode.LDC ||
+                codeIterator.byteAt(pos + 15) != Opcode.INVOKEVIRTUAL ||
+                codeIterator.byteAt(pos + 18) != Opcode.ALOAD_0 ||
+                codeIterator.byteAt(pos + 19) != Opcode.INVOKEVIRTUAL ||
+                codeIterator.byteAt(pos + 22) != Opcode.INVOKEVIRTUAL ||
+                codeIterator.byteAt(pos + 25) != Opcode.INVOKEVIRTUAL) {
+            return;
+        }
+
+        int ldcPos = codeIterator.byteAt(pos + 14);
+        if (constPool.getTag(ldcPos) != ConstPool.CONST_String)
+            return;
+
+        String separatorString = constPool.getStringInfo(ldcPos);
+        if (!":".equals(separatorString))
+            return;
+
+        String appendStringType = "(Ljava/lang/String;)Ljava/lang/StringBuilder;";
+        String appendIntType = "(I)Ljava/lang/StringBuilder;";
+
+        if (!appendStringType.equals(constPool.getMethodrefType(codeIterator.u16bitAt(pos + 11))) ||
+                !appendStringType.equals(constPool.getMethodrefType(codeIterator.u16bitAt(pos + 16))) ||
+                !appendIntType.equals(constPool.getMethodrefType(codeIterator.u16bitAt(pos + 26))))
+            return;
+
+        String getDocumentBaseType = "()Ljava/net/URL;";
+        if (!getDocumentBaseType.equals(constPool.getMethodrefType(codeIterator.u16bitAt(pos + 5))) ||
+                !"getDocumentBase".equals(constPool.getMethodrefName(codeIterator.u16bitAt(pos + 5))) ||
+                !"()Ljava/lang/String;".equals(constPool.getMethodrefType(codeIterator.u16bitAt(pos + 8))) ||
+                !"getHost".equals(constPool.getMethodrefName(codeIterator.u16bitAt(pos + 8))) ||
+                !getDocumentBaseType.equals(constPool.getMethodrefType(codeIterator.u16bitAt(pos + 20))) ||
+                !"getDocumentBase".equals(constPool.getMethodrefName(codeIterator.u16bitAt(pos + 20))) ||
+                !"()I".equals(constPool.getMethodrefType(codeIterator.u16bitAt(pos + 23))) ||
+                !"getPort".equals(constPool.getMethodrefName(codeIterator.u16bitAt(pos + 23))))
+            return;
+
+        // Erase the port
+        for (int i = 0; i < 15; i++) {
+            codeIterator.writeByte(Opcode.NOP, pos + 13 + i);
+        }
+    }
+}

src/main/java/uk/betacraft/legacyfix/patch/impl/DeAwtPatch.java

@@ -37,6 +37,9 @@ public void apply(final Instrumentation inst) throws Exception {
             throw new PatchException("No applet class could be found");
         }
 
+        if (minecraftAppletClass.isFrozen())
+            minecraftAppletClass.defrost();
+
         CtField minecraftField = PatchHelper.findMinecraftField(pool);
         CtClass minecraftClass = PatchHelper.findMinecraftClass(pool);
         if (minecraftField == null || minecraftClass == null) {
@@ -117,11 +120,9 @@ public void edit(MethodCall mc) throws CannotCompileException {
 
         CtMethod getDocumentBaseMethod = javaAppletClass.getDeclaredMethod("getDocumentBase");
 
-        // TODO: Investigate another way to patch early classic saving
-        final int documentPort = minecraftClass.getPackageName().startsWith("com") ? 80 : -1;
         // @formatter:off
         getDocumentBaseMethod.insertBefore(
-            "return new java.net.URL(\"http\", \"www.minecraft.net\", " + documentPort + ", \"\");"
+            "return new java.net.URL(\"http://www.minecraft.net/\");"
         );
         // @formatter:on