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JMockit is a Java toolkit for automated developer testing. It contains APIs for the creation of the objects to be tested, for mocking dependencies, and for faking external APIs; JUnit (4 & 5) and TestNG test runners are supported. It also contains an advanced code coverage tool.

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/*
 * Copyright (c) 2006 Rogério Liesenfeld
 * This file is subject to the terms of the MIT license (see LICENSE.txt).
 */
package mockit.internal.expectations.transformation;

import java.lang.instrument.*;
import java.security.*;
import java.util.*;
import javax.annotation.*;
import static java.lang.reflect.Modifier.*;

import mockit.external.asm.*;
import mockit.internal.*;
import mockit.internal.startup.*;
import mockit.internal.util.*;

public final class ExpectationsTransformer implements ClassFileTransformer
{
   @Nonnull private final List baseSubclasses;

   public ExpectationsTransformer(@Nonnull Instrumentation instrumentation)
   {
      baseSubclasses = new ArrayList();
      baseSubclasses.add("mockit/Expectations");
      baseSubclasses.add("mockit/Verifications");
      baseSubclasses.add("mockit/FullVerifications");
      baseSubclasses.add("mockit/VerificationsInOrder");
      baseSubclasses.add("mockit/FullVerificationsInOrder");

      Class[] alreadyLoaded = instrumentation.getAllLoadedClasses();
      findAndModifyOtherBaseSubclasses(alreadyLoaded);
      modifyFinalSubclasses(alreadyLoaded);
   }

   private void findAndModifyOtherBaseSubclasses(@Nonnull Class[] alreadyLoaded)
   {
      for (Class aClass : alreadyLoaded) {
         if (
            aClass.getClassLoader() != null && !isFinalClass(aClass) &&
            isExpectationsOrVerificationsSubclassFromUserCode(aClass)
         ) {
            modifyInvocationsSubclass(aClass, false);
         }
      }
   }

   private static boolean isFinalClass(@Nonnull Class aClass)
   {
      return isFinal(aClass.getModifiers()) || ClassNaming.isAnonymousClass(aClass);
   }

   private static boolean isExpectationsOrVerificationsSubclassFromUserCode(@Nonnull Class aClass)
   {
      if (isExpectationsOrVerificationsAPIClass(aClass)) {
         return false;
      }

      Class superclass = aClass.getSuperclass();

      while (superclass != null && superclass != Object.class && superclass.getClassLoader() != null) {
         if (isExpectationsOrVerificationsAPIClass(superclass)) {
            return true;
         }

         superclass = superclass.getSuperclass();
      }

      return false;
   }

   private static boolean isExpectationsOrVerificationsAPIClass(@Nonnull Class aClass)
   {
      return
         ("mockit.Expectations mockit.Verifications mockit.FullVerifications mockit.VerificationsInOrder " +
          "mockit.FullVerificationsInOrder").contains(aClass.getName());
   }

   private void modifyFinalSubclasses(@Nonnull Class[] alreadyLoaded)
   {
      for (Class aClass : alreadyLoaded) {
         if (
            aClass.getClassLoader() != null && isFinalClass(aClass) &&
            isExpectationsOrVerificationsSubclassFromUserCode(aClass)
         ) {
            modifyInvocationsSubclass(aClass, true);
         }
      }
   }

   private void modifyInvocationsSubclass(@Nonnull Class aClass, boolean isFinalClass)
   {
      ClassReader cr = ClassFile.createClassFileReader(aClass);
      byte[] modifiedClassfile = modifyInvocationsSubclass(cr, aClass.getClassLoader(), isFinalClass);

      if (modifiedClassfile != null) {
         Startup.redefineMethods(aClass, modifiedClassfile);
      }
   }

   @Nullable
   private byte[] modifyInvocationsSubclass(@Nonnull ClassReader cr, ClassLoader loader, boolean finalClass)
   {
      ClassVisitor modifier = new EndOfBlockModifier(cr, loader, baseSubclasses, finalClass);

      try {
         cr.accept(modifier);
         return modifier.toByteArray();
      }
      catch (VisitInterruptedException ignore) {}
      catch (Throwable e) { e.printStackTrace(); }

      return null;
   }

   @Nullable @Override
   public byte[] transform(
      @Nullable ClassLoader loader, @Nonnull String className, @Nullable Class classBeingRedefined,
      @Nullable ProtectionDomain protectionDomain, @Nonnull byte[] classfileBuffer)
   {
      if (classBeingRedefined == null && protectionDomain != null) {
         ClassReader cr = new ClassReader(classfileBuffer);
         String superClassName = cr.getSuperName();

         if (
            !baseSubclasses.contains(superClassName) &&
            !superClassName.endsWith("Expectations") && !superClassName.endsWith("Verifications")
         ) {
            return null;
         }

         boolean finalClass = ClassNaming.isAnonymousClass(className);
         return modifyInvocationsSubclass(cr, loader, finalClass);
      }

      return null;
   }
}