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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.faking;

import java.lang.instrument.*;
import java.lang.reflect.*;
import javax.annotation.*;

import mockit.*;
import mockit.external.asm.*;
import mockit.external.asm.ClassReader.*;
import mockit.internal.*;
import mockit.internal.startup.*;
import mockit.internal.state.*;

public final class FakeClassSetup
{
   @Nonnull final Class realClass;
   @Nullable private ClassReader rcReader;
   @Nonnull private final FakeMethods fakeMethods;
   @Nonnull final MockUp fake;
   private final boolean forStartupFake;

   public FakeClassSetup(
      @Nonnull Class realClass, @Nonnull Class classToFake, @Nullable Type fakedType, @Nonnull MockUp fake)
   {
      this(realClass, classToFake, fakedType, fake, null);
   }

   FakeClassSetup(
      @Nonnull Class realClass, @Nullable Type fakedType, @Nonnull MockUp fake, @Nullable byte[] realClassCode)
   {
      this(realClass, realClass, fakedType, fake, realClassCode);
   }

   private FakeClassSetup(
      @Nonnull Class realClass, @Nonnull Class classToFake, @Nullable Type fakedType, @Nonnull MockUp fake,
      @Nullable byte[] realClassCode)
   {
      this.realClass = classToFake;
      fakeMethods = new FakeMethods(realClass, fakedType);
      this.fake = fake;
      forStartupFake = Startup.initializing;
      rcReader = realClassCode == null ? null : new ClassReader(realClassCode);

      Class fakeClass = fake.getClass();
      new FakeMethodCollector(fakeMethods).collectFakeMethods(fakeClass);

      fakeMethods.registerFakeStates(fake, forStartupFake);

      FakeClasses fakeClasses = TestRun.getFakeClasses();

      if (forStartupFake) {
         fakeClasses.addFake(fakeMethods.getFakeClassInternalName(), fake);
      }
      else {
         fakeClasses.addFake(fake);
      }
   }

   void redefineMethodsInGeneratedClass()
   {
      byte[] modifiedClassFile = modifyRealClass(realClass);

      if (modifiedClassFile != null) {
         applyClassModifications(realClass, modifiedClassFile);
      }
   }

   public void redefineMethods()
   {
      @Nullable Class classToModify = realClass;

      while (classToModify != null && fakeMethods.hasUnusedFakes()) {
         byte[] modifiedClassFile = modifyRealClass(classToModify);

         if (modifiedClassFile != null) {
            applyClassModifications(classToModify, modifiedClassFile);
         }

         Class superClass = classToModify.getSuperclass();
         classToModify = superClass == Object.class || superClass == Proxy.class ? null : superClass;
         rcReader = null;
      }
   }

   @Nullable
   private byte[] modifyRealClass(@Nonnull Class classToModify)
   {
      if (rcReader == null) {
         rcReader = ClassFile.createReaderFromLastRedefinitionIfAny(classToModify);
      }

      FakedClassModifier modifier = new FakedClassModifier(rcReader, classToModify, fake, fakeMethods);
      rcReader.accept(modifier, Flags.SKIP_INNER_CLASSES);

      return modifier.wasModified() ? modifier.toByteArray() : null;
   }

   @Nonnull
   BaseClassModifier createClassModifier(@Nonnull ClassReader cr)
   {
      return new FakedClassModifier(cr, realClass, fake, fakeMethods);
   }

   void applyClassModifications(@Nonnull Class classToModify, @Nonnull byte[] modifiedClassFile)
   {
      ClassDefinition classDef = new ClassDefinition(classToModify, modifiedClassFile);
      Startup.redefineMethods(classDef);

      if (forStartupFake) {
         CachedClassfiles.addClassfile(classToModify, modifiedClassFile);
      }
      else {
         String fakeClassDesc = fakeMethods.getFakeClassInternalName();
         TestRun.mockFixture().addRedefinedClass(fakeClassDesc, classDef);
      }
   }
}