// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
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package org.objectweb.asm.tree.analysis;

import java.util.List;
import org.objectweb.asm.Type;

An extended BasicVerifier that performs more precise verifications. This verifier computes exact class types, instead of using a single "object reference" type (as done in BasicVerifier). 
Author:
Eric Bruneton, Bing Ran/**
 * An extended {@link BasicVerifier} that performs more precise verifications. This verifier
 * computes exact class types, instead of using a single "object reference" type (as done in {@link
 * BasicVerifier}).
 *
 * @author Eric Bruneton
 * @author Bing Ran
 */
public class SimpleVerifier extends BasicVerifier {

  
The type of the class that is verified. /** The type of the class that is verified. */
  private final Type currentClass;

  
The type of the super class of the class that is verified. /** The type of the super class of the class that is verified. */
  private final Type currentSuperClass;

  
The types of the interfaces directly implemented by the class that is verified. /** The types of the interfaces directly implemented by the class that is verified. */
  private final List<Type> currentClassInterfaces;

  
Whether the class that is verified is an interface. /** Whether the class that is verified is an interface. */
  private final boolean isInterface;

  
The loader to use to load the referenced classes. /** The loader to use to load the referenced classes. */
  private ClassLoader loader = getClass().getClassLoader();

  
Constructs a new SimpleVerifier. Subclasses must not use this constructor. Instead, they must use the SimpleVerifier(int, Type, Type, List<Type>, boolean) version. /**
   * Constructs a new {@link SimpleVerifier}. <i>Subclasses must not use this constructor</i>.
   * Instead, they must use the {@link #SimpleVerifier(int, Type, Type, List, boolean)} version.
   */
  public SimpleVerifier() {
    this(null, null, false);
  }

  
Constructs a new SimpleVerifier to verify a specific class. This class will not be loaded into the JVM since it may be incorrect. Subclasses must not use this constructor. Instead, they must use the SimpleVerifier(int, Type, Type, List<Type>, boolean) version. 
Params:
currentClass – the type of the class to be verified.
currentSuperClass – the type of the super class of the class to be verified.
isInterface – whether the class to be verifier is an interface./**
   * Constructs a new {@link SimpleVerifier} to verify a specific class. This class will not be
   * loaded into the JVM since it may be incorrect. <i>Subclasses must not use this constructor</i>.
   * Instead, they must use the {@link #SimpleVerifier(int, Type, Type, List, boolean)} version.
   *
   * @param currentClass the type of the class to be verified.
   * @param currentSuperClass the type of the super class of the class to be verified.
   * @param isInterface whether the class to be verifier is an interface.
   */
  public SimpleVerifier(
      final Type currentClass, final Type currentSuperClass, final boolean isInterface) {
    this(currentClass, currentSuperClass, null, isInterface);
  }

  
Constructs a new SimpleVerifier to verify a specific class. This class will not be loaded into the JVM since it may be incorrect. Subclasses must not use this constructor. Instead, they must use the SimpleVerifier(int, Type, Type, List<Type>, boolean) version. 
Params:
currentClass – the type of the class to be verified.
currentSuperClass – the type of the super class of the class to be verified.
currentClassInterfaces – the types of the interfaces directly implemented by the class to
    be verified.
isInterface – whether the class to be verifier is an interface./**
   * Constructs a new {@link SimpleVerifier} to verify a specific class. This class will not be
   * loaded into the JVM since it may be incorrect. <i>Subclasses must not use this constructor</i>.
   * Instead, they must use the {@link #SimpleVerifier(int, Type, Type, List, boolean)} version.
   *
   * @param currentClass the type of the class to be verified.
   * @param currentSuperClass the type of the super class of the class to be verified.
   * @param currentClassInterfaces the types of the interfaces directly implemented by the class to
   *     be verified.
   * @param isInterface whether the class to be verifier is an interface.
   */
  public SimpleVerifier(
      final Type currentClass,
      final Type currentSuperClass,
      final List<Type> currentClassInterfaces,
      final boolean isInterface) {
    this(
        /* latest api = */ ASM8,
        currentClass,
        currentSuperClass,
        currentClassInterfaces,
        isInterface);
    if (getClass() != SimpleVerifier.class) {
      throw new IllegalStateException();
    }
  }

  
Constructs a new SimpleVerifier to verify a specific class. This class will not be loaded into the JVM since it may be incorrect. 
Params:
api – the ASM API version supported by this verifier. Must be one of Opcodes.ASM4, Opcodes.ASM5, Opcodes.ASM6, Opcodes.ASM7 or Opcodes.ASM8.
currentClass – the type of the class to be verified.
currentSuperClass – the type of the super class of the class to be verified.
currentClassInterfaces – the types of the interfaces directly implemented by the class to
    be verified.
isInterface – whether the class to be verifier is an interface./**
   * Constructs a new {@link SimpleVerifier} to verify a specific class. This class will not be
   * loaded into the JVM since it may be incorrect.
   *
   * @param api the ASM API version supported by this verifier. Must be one of {@link
   *     org.objectweb.asm.Opcodes#ASM4}, {@link org.objectweb.asm.Opcodes#ASM5}, {@link
   *     org.objectweb.asm.Opcodes#ASM6}, {@link org.objectweb.asm.Opcodes#ASM7} or {@link
   *     org.objectweb.asm.Opcodes#ASM8}.
   * @param currentClass the type of the class to be verified.
   * @param currentSuperClass the type of the super class of the class to be verified.
   * @param currentClassInterfaces the types of the interfaces directly implemented by the class to
   *     be verified.
   * @param isInterface whether the class to be verifier is an interface.
   */
  protected SimpleVerifier(
      final int api,
      final Type currentClass,
      final Type currentSuperClass,
      final List<Type> currentClassInterfaces,
      final boolean isInterface) {
    super(api);
    this.currentClass = currentClass;
    this.currentSuperClass = currentSuperClass;
    this.currentClassInterfaces = currentClassInterfaces;
    this.isInterface = isInterface;
  }

  
Sets the ClassLoader to be used in Object.getClass. 
Params:
loader – the ClassLoader to use./**
   * Sets the <code>ClassLoader</code> to be used in {@link #getClass}.
   *
   * @param loader the <code>ClassLoader</code> to use.
   */
  public void setClassLoader(final ClassLoader loader) {
    this.loader = loader;
  }

  @Override
  public BasicValue newValue(final Type type) {
    if (type == null) {
      return BasicValue.UNINITIALIZED_VALUE;
    }

    boolean isArray = type.getSort() == Type.ARRAY;
    if (isArray) {
      switch (type.getElementType().getSort()) {
        case Type.BOOLEAN:
        case Type.CHAR:
        case Type.BYTE:
        case Type.SHORT:
          return new BasicValue(type);
        default:
          break;
      }
    }

    BasicValue value = super.newValue(type);
    if (BasicValue.REFERENCE_VALUE.equals(value)) {
      if (isArray) {
        value = newValue(type.getElementType());
        StringBuilder descriptor = new StringBuilder();
        for (int i = 0; i < type.getDimensions(); ++i) {
          descriptor.append('[');
        }
        descriptor.append(value.getType().getDescriptor());
        value = new BasicValue(Type.getType(descriptor.toString()));
      } else {
        value = new BasicValue(type);
      }
    }
    return value;
  }

  @Override
  protected boolean isArrayValue(final BasicValue value) {
    Type type = value.getType();
    return type != null && (type.getSort() == Type.ARRAY || type.equals(NULL_TYPE));
  }

  @Override
  protected BasicValue getElementValue(final BasicValue objectArrayValue) throws AnalyzerException {
    Type arrayType = objectArrayValue.getType();
    if (arrayType != null) {
      if (arrayType.getSort() == Type.ARRAY) {
        return newValue(Type.getType(arrayType.getDescriptor().substring(1)));
      } else if (arrayType.equals(NULL_TYPE)) {
        return objectArrayValue;
      }
    }
    throw new AssertionError();
  }

  @Override
  protected boolean isSubTypeOf(final BasicValue value, final BasicValue expected) {
    Type expectedType = expected.getType();
    Type type = value.getType();
    switch (expectedType.getSort()) {
      case Type.INT:
      case Type.FLOAT:
      case Type.LONG:
      case Type.DOUBLE:
        return type.equals(expectedType);
      case Type.ARRAY:
      case Type.OBJECT:
        if (type.equals(NULL_TYPE)) {
          return true;
        } else if (type.getSort() == Type.OBJECT || type.getSort() == Type.ARRAY) {
          if (isAssignableFrom(expectedType, type)) {
            return true;
          } else if (getClass(expectedType).isInterface()) {
            // The merge of class or interface types can only yield class types (because it is not
            // possible in general to find an unambiguous common super interface, due to multiple
            // inheritance). Because of this limitation, we need to relax the subtyping check here
            // if 'value' is an interface.
            return Object.class.isAssignableFrom(getClass(type));
          } else {
            return false;
          }
        } else {
          return false;
        }
      default:
        throw new AssertionError();
    }
  }

  @Override
  public BasicValue merge(final BasicValue value1, final BasicValue value2) {
    if (!value1.equals(value2)) {
      Type type1 = value1.getType();
      Type type2 = value2.getType();
      if (type1 != null
          && (type1.getSort() == Type.OBJECT || type1.getSort() == Type.ARRAY)
          && type2 != null
          && (type2.getSort() == Type.OBJECT || type2.getSort() == Type.ARRAY)) {
        if (type1.equals(NULL_TYPE)) {
          return value2;
        }
        if (type2.equals(NULL_TYPE)) {
          return value1;
        }
        if (isAssignableFrom(type1, type2)) {
          return value1;
        }
        if (isAssignableFrom(type2, type1)) {
          return value2;
        }
        int numDimensions = 0;
        if (type1.getSort() == Type.ARRAY
            && type2.getSort() == Type.ARRAY
            && type1.getDimensions() == type2.getDimensions()
            && type1.getElementType().getSort() == Type.OBJECT
            && type2.getElementType().getSort() == Type.OBJECT) {
          numDimensions = type1.getDimensions();
          type1 = type1.getElementType();
          type2 = type2.getElementType();
        }
        while (true) {
          if (type1 == null || isInterface(type1)) {
            return newArrayValue(Type.getObjectType("java/lang/Object"), numDimensions);
          }
          type1 = getSuperClass(type1);
          if (isAssignableFrom(type1, type2)) {
            return newArrayValue(type1, numDimensions);
          }
        }
      }
      return BasicValue.UNINITIALIZED_VALUE;
    }
    return value1;
  }

  private BasicValue newArrayValue(final Type type, final int dimensions) {
    if (dimensions == 0) {
      return newValue(type);
    } else {
      StringBuilder descriptor = new StringBuilder();
      for (int i = 0; i < dimensions; ++i) {
        descriptor.append('[');
      }
      descriptor.append(type.getDescriptor());
      return newValue(Type.getType(descriptor.toString()));
    }
  }

  
Returns whether the given type corresponds to the type of an interface. The default
implementation of this method loads the class and uses the reflection API to return its result
(unless the given type corresponds to the class being verified).
Params:
type – a type.
Returns:
whether 'type' corresponds to an interface./**
   * Returns whether the given type corresponds to the type of an interface. The default
   * implementation of this method loads the class and uses the reflection API to return its result
   * (unless the given type corresponds to the class being verified).
   *
   * @param type a type.
   * @return whether 'type' corresponds to an interface.
   */
  protected boolean isInterface(final Type type) {
    if (currentClass != null && currentClass.equals(type)) {
      return isInterface;
    }
    return getClass(type).isInterface();
  }

  
Returns the type corresponding to the super class of the given type. The default implementation
of this method loads the class and uses the reflection API to return its result (unless the
given type corresponds to the class being verified).
Params:
type – a type.
Returns:
the type corresponding to the super class of 'type'./**
   * Returns the type corresponding to the super class of the given type. The default implementation
   * of this method loads the class and uses the reflection API to return its result (unless the
   * given type corresponds to the class being verified).
   *
   * @param type a type.
   * @return the type corresponding to the super class of 'type'.
   */
  protected Type getSuperClass(final Type type) {
    if (currentClass != null && currentClass.equals(type)) {
      return currentSuperClass;
    }
    Class<?> superClass = getClass(type).getSuperclass();
    return superClass == null ? null : Type.getType(superClass);
  }

  
Returns whether the class corresponding to the first argument is either the same as, or is a
superclass or superinterface of the class corresponding to the second argument. The default
implementation of this method loads the classes and uses the reflection API to return its
result (unless the result can be computed from the class being verified, and the types of its
super classes and implemented interfaces).
Params:
type1 – a type.
type2 – another type.
Returns:
whether the class corresponding to 'type1' is either the same as, or is a superclass or
    superinterface of the class corresponding to 'type2'./**
   * Returns whether the class corresponding to the first argument is either the same as, or is a
   * superclass or superinterface of the class corresponding to the second argument. The default
   * implementation of this method loads the classes and uses the reflection API to return its
   * result (unless the result can be computed from the class being verified, and the types of its
   * super classes and implemented interfaces).
   *
   * @param type1 a type.
   * @param type2 another type.
   * @return whether the class corresponding to 'type1' is either the same as, or is a superclass or
   *     superinterface of the class corresponding to 'type2'.
   */
  protected boolean isAssignableFrom(final Type type1, final Type type2) {
    if (type1.equals(type2)) {
      return true;
    }
    if (currentClass != null && currentClass.equals(type1)) {
      if (getSuperClass(type2) == null) {
        return false;
      } else {
        if (isInterface) {
          return type2.getSort() == Type.OBJECT || type2.getSort() == Type.ARRAY;
        }
        return isAssignableFrom(type1, getSuperClass(type2));
      }
    }
    if (currentClass != null && currentClass.equals(type2)) {
      if (isAssignableFrom(type1, currentSuperClass)) {
        return true;
      }
      if (currentClassInterfaces != null) {
        for (Type currentClassInterface : currentClassInterfaces) {
          if (isAssignableFrom(type1, currentClassInterface)) {
            return true;
          }
        }
      }
      return false;
    }
    return getClass(type1).isAssignableFrom(getClass(type2));
  }

  
Loads the class corresponding to the given type. The class is loaded with the class loader specified with setClassLoader, or with the class loader of this class if no class loader was specified. 
Params:
type – a type.
Returns:
the class corresponding to 'type'./**
   * Loads the class corresponding to the given type. The class is loaded with the class loader
   * specified with {@link #setClassLoader}, or with the class loader of this class if no class
   * loader was specified.
   *
   * @param type a type.
   * @return the class corresponding to 'type'.
   */
  protected Class<?> getClass(final Type type) {
    try {
      if (type.getSort() == Type.ARRAY) {
        return Class.forName(type.getDescriptor().replace('/', '.'), false, loader);
      }
      return Class.forName(type.getClassName(), false, loader);
    } catch (ClassNotFoundException e) {
      throw new TypeNotPresentException(e.toString(), e);
    }
  }
}