// ASM: a very small and fast Java bytecode manipulation framework
// Copyright (c) 2000-2011 INRIA, France Telecom
// All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// 1. Redistributions of source code must retain the above copyright
//    notice, this list of conditions and the following disclaimer.
// 2. Redistributions in binary form must reproduce the above copyright
//    notice, this list of conditions and the following disclaimer in the
//    documentation and/or other materials provided with the distribution.
// 3. Neither the name of the copyright holders nor the names of its
//    contributors may be used to endorse or promote products derived from
//    this software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
// AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
// IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
// ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
// LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
// CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
// SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
// INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
// CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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// THE POSSIBILITY OF SUCH DAMAGE.
package org.apache.tapestry5.internal.plastic.asm.commons;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import org.apache.tapestry5.internal.plastic.asm.ClassVisitor;
import org.apache.tapestry5.internal.plastic.asm.ConstantDynamic;
import org.apache.tapestry5.internal.plastic.asm.Handle;
import org.apache.tapestry5.internal.plastic.asm.Label;
import org.apache.tapestry5.internal.plastic.asm.MethodVisitor;
import org.apache.tapestry5.internal.plastic.asm.Opcodes;
import org.apache.tapestry5.internal.plastic.asm.Type;

/**
 * A {@link MethodVisitor} with convenient methods to generate code. For example, using this
 * adapter, the class below
 *
 * <pre>
 * public class Example {
 *   public static void main(String[] args) {
 *     System.out.println(&quot;Hello world!&quot;);
 *   }
 * }
 * </pre>
 *
 * <p>can be generated as follows:
 *
 * <pre>
 * ClassWriter cw = new ClassWriter(0);
 * cw.visit(V1_1, ACC_PUBLIC, &quot;Example&quot;, null, &quot;java/lang/Object&quot;, null);
 *
 * Method m = Method.getMethod(&quot;void &lt;init&gt; ()&quot;);
 * GeneratorAdapter mg = new GeneratorAdapter(ACC_PUBLIC, m, null, null, cw);
 * mg.loadThis();
 * mg.invokeConstructor(Type.getType(Object.class), m);
 * mg.returnValue();
 * mg.endMethod();
 *
 * m = Method.getMethod(&quot;void main (String[])&quot;);
 * mg = new GeneratorAdapter(ACC_PUBLIC + ACC_STATIC, m, null, null, cw);
 * mg.getStatic(Type.getType(System.class), &quot;out&quot;, Type.getType(PrintStream.class));
 * mg.push(&quot;Hello world!&quot;);
 * mg.invokeVirtual(Type.getType(PrintStream.class),
 *         Method.getMethod(&quot;void println (String)&quot;));
 * mg.returnValue();
 * mg.endMethod();
 *
 * cw.visitEnd();
 * </pre>
 *
 * @author Juozas Baliuka
 * @author Chris Nokleberg
 * @author Eric Bruneton
 * @author Prashant Deva
 */
public class GeneratorAdapter extends LocalVariablesSorter {

  private static final String CLASS_DESCRIPTOR = "Ljava/lang/Class;";

  private static final Type BYTE_TYPE = Type.getObjectType("java/lang/Byte");

  private static final Type BOOLEAN_TYPE = Type.getObjectType("java/lang/Boolean");

  private static final Type SHORT_TYPE = Type.getObjectType("java/lang/Short");

  private static final Type CHARACTER_TYPE = Type.getObjectType("java/lang/Character");

  private static final Type INTEGER_TYPE = Type.getObjectType("java/lang/Integer");

  private static final Type FLOAT_TYPE = Type.getObjectType("java/lang/Float");

  private static final Type LONG_TYPE = Type.getObjectType("java/lang/Long");

  private static final Type DOUBLE_TYPE = Type.getObjectType("java/lang/Double");

  private static final Type NUMBER_TYPE = Type.getObjectType("java/lang/Number");

  private static final Type OBJECT_TYPE = Type.getObjectType("java/lang/Object");

  private static final Method BOOLEAN_VALUE = Method.getMethod("boolean booleanValue()");

  private static final Method CHAR_VALUE = Method.getMethod("char charValue()");

  private static final Method INT_VALUE = Method.getMethod("int intValue()");

  private static final Method FLOAT_VALUE = Method.getMethod("float floatValue()");

  private static final Method LONG_VALUE = Method.getMethod("long longValue()");

  private static final Method DOUBLE_VALUE = Method.getMethod("double doubleValue()");

  /** Constant for the {@link #math} method. */
  public static final int ADD = Opcodes.IADD;

  /** Constant for the {@link #math} method. */
  public static final int SUB = Opcodes.ISUB;

  /** Constant for the {@link #math} method. */
  public static final int MUL = Opcodes.IMUL;

  /** Constant for the {@link #math} method. */
  public static final int DIV = Opcodes.IDIV;

  /** Constant for the {@link #math} method. */
  public static final int REM = Opcodes.IREM;

  /** Constant for the {@link #math} method. */
  public static final int NEG = Opcodes.INEG;

  /** Constant for the {@link #math} method. */
  public static final int SHL = Opcodes.ISHL;

  /** Constant for the {@link #math} method. */
  public static final int SHR = Opcodes.ISHR;

  /** Constant for the {@link #math} method. */
  public static final int USHR = Opcodes.IUSHR;

  /** Constant for the {@link #math} method. */
  public static final int AND = Opcodes.IAND;

  /** Constant for the {@link #math} method. */
  public static final int OR = Opcodes.IOR;

  /** Constant for the {@link #math} method. */
  public static final int XOR = Opcodes.IXOR;

  /** Constant for the {@link #ifCmp} method. */
  public static final int EQ = Opcodes.IFEQ;

  /** Constant for the {@link #ifCmp} method. */
  public static final int NE = Opcodes.IFNE;

  /** Constant for the {@link #ifCmp} method. */
  public static final int LT = Opcodes.IFLT;

  /** Constant for the {@link #ifCmp} method. */
  public static final int GE = Opcodes.IFGE;

  /** Constant for the {@link #ifCmp} method. */
  public static final int GT = Opcodes.IFGT;

  /** Constant for the {@link #ifCmp} method. */
  public static final int LE = Opcodes.IFLE;

  /** The access flags of the visited method. */
  private final int access;

  /** The name of the visited method. */
  private final String name;

  /** The return type of the visited method. */
  private final Type returnType;

  /** The argument types of the visited method. */
  private final Type[] argumentTypes;

  /** The types of the local variables of the visited method. */
  private final List<Type> localTypes = new ArrayList<>();

  /**
   * Constructs a new {@link GeneratorAdapter}. <i>Subclasses must not use this constructor</i>.
   * Instead, they must use the {@link #GeneratorAdapter(int, MethodVisitor, int, String, String)}
   * version.
   *
   * @param methodVisitor the method visitor to which this adapter delegates calls.
   * @param access the method's access flags (see {@link Opcodes}).
   * @param name the method's name.
   * @param descriptor the method's descriptor (see {@link Type}).
   * @throws IllegalStateException if a subclass calls this constructor.
   */
  public GeneratorAdapter(
      final MethodVisitor methodVisitor,
      final int access,
      final String name,
      final String descriptor) {
    this(/* latest api = */ Opcodes.ASM9, methodVisitor, access, name, descriptor);
    if (getClass() != GeneratorAdapter.class) {
      throw new IllegalStateException();
    }
  }

  /**
   * Constructs a new {@link GeneratorAdapter}.
   *
   * @param api the ASM API version implemented by this visitor. Must be one of the {@code
   *     ASM}<i>x</i> values in {@link Opcodes}.
   * @param methodVisitor the method visitor to which this adapter delegates calls.
   * @param access the method's access flags (see {@link Opcodes}).
   * @param name the method's name.
   * @param descriptor the method's descriptor (see {@link Type}).
   */
  protected GeneratorAdapter(
      final int api,
      final MethodVisitor methodVisitor,
      final int access,
      final String name,
      final String descriptor) {
    super(api, access, descriptor, methodVisitor);
    this.access = access;
    this.name = name;
    this.returnType = Type.getReturnType(descriptor);
    this.argumentTypes = Type.getArgumentTypes(descriptor);
  }

  /**
   * Constructs a new {@link GeneratorAdapter}. <i>Subclasses must not use this constructor</i>.
   * Instead, they must use the {@link #GeneratorAdapter(int, MethodVisitor, int, String, String)}
   * version.
   *
   * @param access access flags of the adapted method.
   * @param method the adapted method.
   * @param methodVisitor the method visitor to which this adapter delegates calls.
   */
  public GeneratorAdapter(
      final int access, final Method method, final MethodVisitor methodVisitor) {
    this(methodVisitor, access, method.getName(), method.getDescriptor());
  }

  /**
   * Constructs a new {@link GeneratorAdapter}. <i>Subclasses must not use this constructor</i>.
   * Instead, they must use the {@link #GeneratorAdapter(int, MethodVisitor, int, String, String)}
   * version.
   *
   * @param access access flags of the adapted method.
   * @param method the adapted method.
   * @param signature the signature of the adapted method (may be {@literal null}).
   * @param exceptions the exceptions thrown by the adapted method (may be {@literal null}).
   * @param classVisitor the class visitor to which this adapter delegates calls.
   */
  public GeneratorAdapter(
      final int access,
      final Method method,
      final String signature,
      final Type[] exceptions,
      final ClassVisitor classVisitor) {
    this(
        access,
        method,
        classVisitor.visitMethod(
            access,
            method.getName(),
            method.getDescriptor(),
            signature,
            exceptions == null ? null : getInternalNames(exceptions)));
  }

  /**
   * Returns the internal names of the given types.
   *
   * @param types a set of types.
   * @return the internal names of the given types (see {@link Type#getInternalName()}).
   */
  private static String[] getInternalNames(final Type[] types) {
    String[] names = new String[types.length];
    for (int i = 0; i < names.length; ++i) {
      names[i] = types[i].getInternalName();
    }
    return names;
  }

  public int getAccess() {
    return access;
  }

  public String getName() {
    return name;
  }

  public Type getReturnType() {
    return returnType;
  }

  public Type[] getArgumentTypes() {
    return argumentTypes.clone();
  }

  // -----------------------------------------------------------------------------------------------
  // Instructions to push constants on the stack
  // -----------------------------------------------------------------------------------------------

  /**
   * Generates the instruction to push the given value on the stack.
   *
   * @param value the value to be pushed on the stack.
   */
  public void push(final boolean value) {
    push(value ? 1 : 0);
  }

  /**
   * Generates the instruction to push the given value on the stack.
   *
   * @param value the value to be pushed on the stack.
   */
  public void push(final int value) {
    if (value >= -1 && value <= 5) {
      mv.visitInsn(Opcodes.ICONST_0 + value);
    } else if (value >= Byte.MIN_VALUE && value <= Byte.MAX_VALUE) {
      mv.visitIntInsn(Opcodes.BIPUSH, value);
    } else if (value >= Short.MIN_VALUE && value <= Short.MAX_VALUE) {
      mv.visitIntInsn(Opcodes.SIPUSH, value);
    } else {
      mv.visitLdcInsn(value);
    }
  }

  /**
   * Generates the instruction to push the given value on the stack.
   *
   * @param value the value to be pushed on the stack.
   */
  public void push(final long value) {
    if (value == 0L || value == 1L) {
      mv.visitInsn(Opcodes.LCONST_0 + (int) value);
    } else {
      mv.visitLdcInsn(value);
    }
  }

  /**
   * Generates the instruction to push the given value on the stack.
   *
   * @param value the value to be pushed on the stack.
   */
  public void push(final float value) {
    int bits = Float.floatToIntBits(value);
    if (bits == 0L || bits == 0x3F800000 || bits == 0x40000000) { // 0..2
      mv.visitInsn(Opcodes.FCONST_0 + (int) value);
    } else {
      mv.visitLdcInsn(value);
    }
  }

  /**
   * Generates the instruction to push the given value on the stack.
   *
   * @param value the value to be pushed on the stack.
   */
  public void push(final double value) {
    long bits = Double.doubleToLongBits(value);
    if (bits == 0L || bits == 0x3FF0000000000000L) { // +0.0d and 1.0d
      mv.visitInsn(Opcodes.DCONST_0 + (int) value);
    } else {
      mv.visitLdcInsn(value);
    }
  }

  /**
   * Generates the instruction to push the given value on the stack.
   *
   * @param value the value to be pushed on the stack. May be {@literal null}.
   */
  public void push(final String value) {
    if (value == null) {
      mv.visitInsn(Opcodes.ACONST_NULL);
    } else {
      mv.visitLdcInsn(value);
    }
  }

  /**
   * Generates the instruction to push the given value on the stack.
   *
   * @param value the value to be pushed on the stack.
   */
  public void push(final Type value) {
    if (value == null) {
      mv.visitInsn(Opcodes.ACONST_NULL);
    } else {
      switch (value.getSort()) {
        case Type.BOOLEAN:
          mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/Boolean", "TYPE", CLASS_DESCRIPTOR);
          break;
        case Type.CHAR:
          mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/Character", "TYPE", CLASS_DESCRIPTOR);
          break;
        case Type.BYTE:
          mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/Byte", "TYPE", CLASS_DESCRIPTOR);
          break;
        case Type.SHORT:
          mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/Short", "TYPE", CLASS_DESCRIPTOR);
          break;
        case Type.INT:
          mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/Integer", "TYPE", CLASS_DESCRIPTOR);
          break;
        case Type.FLOAT:
          mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/Float", "TYPE", CLASS_DESCRIPTOR);
          break;
        case Type.LONG:
          mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/Long", "TYPE", CLASS_DESCRIPTOR);
          break;
        case Type.DOUBLE:
          mv.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/Double", "TYPE", CLASS_DESCRIPTOR);
          break;
        default:
          mv.visitLdcInsn(value);
          break;
      }
    }
  }

  /**
   * Generates the instruction to push a handle on the stack.
   *
   * @param handle the handle to be pushed on the stack.
   */
  public void push(final Handle handle) {
    if (handle == null) {
      mv.visitInsn(Opcodes.ACONST_NULL);
    } else {
      mv.visitLdcInsn(handle);
    }
  }

  /**
   * Generates the instruction to push a constant dynamic on the stack.
   *
   * @param constantDynamic the constant dynamic to be pushed on the stack.
   */
  public void push(final ConstantDynamic constantDynamic) {
    if (constantDynamic == null) {
      mv.visitInsn(Opcodes.ACONST_NULL);
    } else {
      mv.visitLdcInsn(constantDynamic);
    }
  }

  // -----------------------------------------------------------------------------------------------
  // Instructions to load and store method arguments
  // -----------------------------------------------------------------------------------------------

  /**
   * Returns the index of the given method argument in the frame's local variables array.
   *
   * @param arg the index of a method argument.
   * @return the index of the given method argument in the frame's local variables array.
   */
  private int getArgIndex(final int arg) {
    int index = (access & Opcodes.ACC_STATIC) == 0 ? 1 : 0;
    for (int i = 0; i < arg; i++) {
      index += argumentTypes[i].getSize();
    }
    return index;
  }

  /**
   * Generates the instruction to push a local variable on the stack.
   *
   * @param type the type of the local variable to be loaded.
   * @param index an index in the frame's local variables array.
   */
  private void loadInsn(final Type type, final int index) {
    mv.visitVarInsn(type.getOpcode(Opcodes.ILOAD), index);
  }

  /**
   * Generates the instruction to store the top stack value in a local variable.
   *
   * @param type the type of the local variable to be stored.
   * @param index an index in the frame's local variables array.
   */
  private void storeInsn(final Type type, final int index) {
    mv.visitVarInsn(type.getOpcode(Opcodes.ISTORE), index);
  }

  /** Generates the instruction to load 'this' on the stack. */
  public void loadThis() {
    if ((access & Opcodes.ACC_STATIC) != 0) {
      throw new IllegalStateException("no 'this' pointer within static method");
    }
    mv.visitVarInsn(Opcodes.ALOAD, 0);
  }

  /**
   * Generates the instruction to load the given method argument on the stack.
   *
   * @param arg the index of a method argument.
   */
  public void loadArg(final int arg) {
    loadInsn(argumentTypes[arg], getArgIndex(arg));
  }

  /**
   * Generates the instructions to load the given method arguments on the stack.
   *
   * @param arg the index of the first method argument to be loaded.
   * @param count the number of method arguments to be loaded.
   */
  public void loadArgs(final int arg, final int count) {
    int index = getArgIndex(arg);
    for (int i = 0; i < count; ++i) {
      Type argumentType = argumentTypes[arg + i];
      loadInsn(argumentType, index);
      index += argumentType.getSize();
    }
  }

  /** Generates the instructions to load all the method arguments on the stack. */
  public void loadArgs() {
    loadArgs(0, argumentTypes.length);
  }

  /**
   * Generates the instructions to load all the method arguments on the stack, as a single object
   * array.
   */
  public void loadArgArray() {
    push(argumentTypes.length);
    newArray(OBJECT_TYPE);
    for (int i = 0; i < argumentTypes.length; i++) {
      dup();
      push(i);
      loadArg(i);
      box(argumentTypes[i]);
      arrayStore(OBJECT_TYPE);
    }
  }

  /**
   * Generates the instruction to store the top stack value in the given method argument.
   *
   * @param arg the index of a method argument.
   */
  public void storeArg(final int arg) {
    storeInsn(argumentTypes[arg], getArgIndex(arg));
  }

  // -----------------------------------------------------------------------------------------------
  // Instructions to load and store local variables
  // -----------------------------------------------------------------------------------------------

  /**
   * Returns the type of the given local variable.
   *
   * @param local a local variable identifier, as returned by {@link
   *     LocalVariablesSorter#newLocal(Type)}.
   * @return the type of the given local variable.
   */
  public Type getLocalType(final int local) {
    return localTypes.get(local - firstLocal);
  }

  @Override
  protected void setLocalType(final int local, final Type type) {
    int index = local - firstLocal;
    while (localTypes.size() < index + 1) {
      localTypes.add(null);
    }
    localTypes.set(index, type);
  }

  /**
   * Generates the instruction to load the given local variable on the stack.
   *
   * @param local a local variable identifier, as returned by {@link
   *     LocalVariablesSorter#newLocal(Type)}.
   */
  public void loadLocal(final int local) {
    loadInsn(getLocalType(local), local);
  }

  /**
   * Generates the instruction to load the given local variable on the stack.
   *
   * @param local a local variable identifier, as returned by {@link
   *     LocalVariablesSorter#newLocal(Type)}.
   * @param type the type of this local variable.
   */
  public void loadLocal(final int local, final Type type) {
    setLocalType(local, type);
    loadInsn(type, local);
  }

  /**
   * Generates the instruction to store the top stack value in the given local variable.
   *
   * @param local a local variable identifier, as returned by {@link
   *     LocalVariablesSorter#newLocal(Type)}.
   */
  public void storeLocal(final int local) {
    storeInsn(getLocalType(local), local);
  }

  /**
   * Generates the instruction to store the top stack value in the given local variable.
   *
   * @param local a local variable identifier, as returned by {@link
   *     LocalVariablesSorter#newLocal(Type)}.
   * @param type the type of this local variable.
   */
  public void storeLocal(final int local, final Type type) {
    setLocalType(local, type);
    storeInsn(type, local);
  }

  /**
   * Generates the instruction to load an element from an array.
   *
   * @param type the type of the array element to be loaded.
   */
  public void arrayLoad(final Type type) {
    mv.visitInsn(type.getOpcode(Opcodes.IALOAD));
  }

  /**
   * Generates the instruction to store an element in an array.
   *
   * @param type the type of the array element to be stored.
   */
  public void arrayStore(final Type type) {
    mv.visitInsn(type.getOpcode(Opcodes.IASTORE));
  }

  // -----------------------------------------------------------------------------------------------
  // Instructions to manage the stack
  // -----------------------------------------------------------------------------------------------

  /** Generates a POP instruction. */
  public void pop() {
    mv.visitInsn(Opcodes.POP);
  }

  /** Generates a POP2 instruction. */
  public void pop2() {
    mv.visitInsn(Opcodes.POP2);
  }

  /** Generates a DUP instruction. */
  public void dup() {
    mv.visitInsn(Opcodes.DUP);
  }

  /** Generates a DUP2 instruction. */
  public void dup2() {
    mv.visitInsn(Opcodes.DUP2);
  }

  /** Generates a DUP_X1 instruction. */
  public void dupX1() {
    mv.visitInsn(Opcodes.DUP_X1);
  }

  /** Generates a DUP_X2 instruction. */
  public void dupX2() {
    mv.visitInsn(Opcodes.DUP_X2);
  }

  /** Generates a DUP2_X1 instruction. */
  public void dup2X1() {
    mv.visitInsn(Opcodes.DUP2_X1);
  }

  /** Generates a DUP2_X2 instruction. */
  public void dup2X2() {
    mv.visitInsn(Opcodes.DUP2_X2);
  }

  /** Generates a SWAP instruction. */
  public void swap() {
    mv.visitInsn(Opcodes.SWAP);
  }

  /**
   * Generates the instructions to swap the top two stack values.
   *
   * @param prev type of the top - 1 stack value.
   * @param type type of the top stack value.
   */
  public void swap(final Type prev, final Type type) {
    if (type.getSize() == 1) {
      if (prev.getSize() == 1) {
        swap(); // Same as dupX1 pop.
      } else {
        dupX2();
        pop();
      }
    } else {
      if (prev.getSize() == 1) {
        dup2X1();
        pop2();
      } else {
        dup2X2();
        pop2();
      }
    }
  }

  // -----------------------------------------------------------------------------------------------
  // Instructions to do mathematical and logical operations
  // -----------------------------------------------------------------------------------------------

  /**
   * Generates the instruction to do the specified mathematical or logical operation.
   *
   * @param op a mathematical or logical operation. Must be one of ADD, SUB, MUL, DIV, REM, NEG,
   *     SHL, SHR, USHR, AND, OR, XOR.
   * @param type the type of the operand(s) for this operation.
   */
  public void math(final int op, final Type type) {
    mv.visitInsn(type.getOpcode(op));
  }

  /** Generates the instructions to compute the bitwise negation of the top stack value. */
  public void not() {
    mv.visitInsn(Opcodes.ICONST_1);
    mv.visitInsn(Opcodes.IXOR);
  }

  /**
   * Generates the instruction to increment the given local variable.
   *
   * @param local the local variable to be incremented.
   * @param amount the amount by which the local variable must be incremented.
   */
  public void iinc(final int local, final int amount) {
    mv.visitIincInsn(local, amount);
  }

  /**
   * Generates the instructions to cast a numerical value from one type to another.
   *
   * @param from the type of the top stack value
   * @param to the type into which this value must be cast.
   */
  public void cast(final Type from, final Type to) {
    if (from != to) {
      if (from.getSort() < Type.BOOLEAN
          || from.getSort() > Type.DOUBLE
          || to.getSort() < Type.BOOLEAN
          || to.getSort() > Type.DOUBLE) {
        throw new IllegalArgumentException("Cannot cast from " + from + " to " + to);
      }
      InstructionAdapter.cast(mv, from, to);
    }
  }

  // -----------------------------------------------------------------------------------------------
  // Instructions to do boxing and unboxing operations
  // -----------------------------------------------------------------------------------------------

  private static Type getBoxedType(final Type type) {
    switch (type.getSort()) {
      case Type.BYTE:
        return BYTE_TYPE;
      case Type.BOOLEAN:
        return BOOLEAN_TYPE;
      case Type.SHORT:
        return SHORT_TYPE;
      case Type.CHAR:
        return CHARACTER_TYPE;
      case Type.INT:
        return INTEGER_TYPE;
      case Type.FLOAT:
        return FLOAT_TYPE;
      case Type.LONG:
        return LONG_TYPE;
      case Type.DOUBLE:
        return DOUBLE_TYPE;
      default:
        return type;
    }
  }

  /**
   * Generates the instructions to box the top stack value. This value is replaced by its boxed
   * equivalent on top of the stack.
   *
   * @param type the type of the top stack value.
   */
  public void box(final Type type) {
    if (type.getSort() == Type.OBJECT || type.getSort() == Type.ARRAY) {
      return;
    }
    if (type == Type.VOID_TYPE) {
      push((String) null);
    } else {
      Type boxedType = getBoxedType(type);
      newInstance(boxedType);
      if (type.getSize() == 2) {
        // Pp -> Ppo -> oPpo -> ooPpo -> ooPp -> o
        dupX2();
        dupX2();
        pop();
      } else {
        // p -> po -> opo -> oop -> o
        dupX1();
        swap();
      }
      invokeConstructor(boxedType, new Method("<init>", Type.VOID_TYPE, new Type[] {type}));
    }
  }

  /**
   * Generates the instructions to box the top stack value using Java 5's valueOf() method. This
   * value is replaced by its boxed equivalent on top of the stack.
   *
   * @param type the type of the top stack value.
   */
  public void valueOf(final Type type) {
    if (type.getSort() == Type.OBJECT || type.getSort() == Type.ARRAY) {
      return;
    }
    if (type == Type.VOID_TYPE) {
      push((String) null);
    } else {
      Type boxedType = getBoxedType(type);
      invokeStatic(boxedType, new Method("valueOf", boxedType, new Type[] {type}));
    }
  }

  /**
   * Generates the instructions to unbox the top stack value. This value is replaced by its unboxed
   * equivalent on top of the stack.
   *
   * @param type the type of the top stack value.
   */
  public void unbox(final Type type) {
    Type boxedType = NUMBER_TYPE;
    Method unboxMethod;
    switch (type.getSort()) {
      case Type.VOID:
        return;
      case Type.CHAR:
        boxedType = CHARACTER_TYPE;
        unboxMethod = CHAR_VALUE;
        break;
      case Type.BOOLEAN:
        boxedType = BOOLEAN_TYPE;
        unboxMethod = BOOLEAN_VALUE;
        break;
      case Type.DOUBLE:
        unboxMethod = DOUBLE_VALUE;
        break;
      case Type.FLOAT:
        unboxMethod = FLOAT_VALUE;
        break;
      case Type.LONG:
        unboxMethod = LONG_VALUE;
        break;
      case Type.INT:
      case Type.SHORT:
      case Type.BYTE:
        unboxMethod = INT_VALUE;
        break;
      default:
        unboxMethod = null;
        break;
    }
    if (unboxMethod == null) {
      checkCast(type);
    } else {
      checkCast(boxedType);
      invokeVirtual(boxedType, unboxMethod);
    }
  }

  // -----------------------------------------------------------------------------------------------
  // Instructions to jump to other instructions
  // -----------------------------------------------------------------------------------------------

  /**
   * Constructs a new {@link Label}.
   *
   * @return a new {@link Label}.
   */
  public Label newLabel() {
    return new Label();
  }

  /**
   * Marks the current code position with the given label.
   *
   * @param label a label.
   */
  public void mark(final Label label) {
    mv.visitLabel(label);
  }

  /**
   * Marks the current code position with a new label.
   *
   * @return the label that was created to mark the current code position.
   */
  public Label mark() {
    Label label = new Label();
    mv.visitLabel(label);
    return label;
  }

  /**
   * Generates the instructions to jump to a label based on the comparison of the top two stack
   * values.
   *
   * @param type the type of the top two stack values.
   * @param mode how these values must be compared. One of EQ, NE, LT, GE, GT, LE.
   * @param label where to jump if the comparison result is {@literal true}.
   */
  public void ifCmp(final Type type, final int mode, final Label label) {
    switch (type.getSort()) {
      case Type.LONG:
        mv.visitInsn(Opcodes.LCMP);
        break;
      case Type.DOUBLE:
        mv.visitInsn(mode == GE || mode == GT ? Opcodes.DCMPL : Opcodes.DCMPG);
        break;
      case Type.FLOAT:
        mv.visitInsn(mode == GE || mode == GT ? Opcodes.FCMPL : Opcodes.FCMPG);
        break;
      case Type.ARRAY:
      case Type.OBJECT:
        if (mode == EQ) {
          mv.visitJumpInsn(Opcodes.IF_ACMPEQ, label);
          return;
        } else if (mode == NE) {
          mv.visitJumpInsn(Opcodes.IF_ACMPNE, label);
          return;
        } else {
          throw new IllegalArgumentException("Bad comparison for type " + type);
        }
      default:
        int intOp = -1;
        switch (mode) {
          case EQ:
            intOp = Opcodes.IF_ICMPEQ;
            break;
          case NE:
            intOp = Opcodes.IF_ICMPNE;
            break;
          case GE:
            intOp = Opcodes.IF_ICMPGE;
            break;
          case LT:
            intOp = Opcodes.IF_ICMPLT;
            break;
          case LE:
            intOp = Opcodes.IF_ICMPLE;
            break;
          case GT:
            intOp = Opcodes.IF_ICMPGT;
            break;
          default:
            throw new IllegalArgumentException("Bad comparison mode " + mode);
        }
        mv.visitJumpInsn(intOp, label);
        return;
    }
    mv.visitJumpInsn(mode, label);
  }

  /**
   * Generates the instructions to jump to a label based on the comparison of the top two integer
   * stack values.
   *
   * @param mode how these values must be compared. One of EQ, NE, LT, GE, GT, LE.
   * @param label where to jump if the comparison result is {@literal true}.
   */
  public void ifICmp(final int mode, final Label label) {
    ifCmp(Type.INT_TYPE, mode, label);
  }

  /**
   * Generates the instructions to jump to a label based on the comparison of the top integer stack
   * value with zero.
   *
   * @param mode how these values must be compared. One of EQ, NE, LT, GE, GT, LE.
   * @param label where to jump if the comparison result is {@literal true}.
   */
  public void ifZCmp(final int mode, final Label label) {
    mv.visitJumpInsn(mode, label);
  }

  /**
   * Generates the instruction to jump to the given label if the top stack value is null.
   *
   * @param label where to jump if the condition is {@literal true}.
   */
  public void ifNull(final Label label) {
    mv.visitJumpInsn(Opcodes.IFNULL, label);
  }

  /**
   * Generates the instruction to jump to the given label if the top stack value is not null.
   *
   * @param label where to jump if the condition is {@literal true}.
   */
  public void ifNonNull(final Label label) {
    mv.visitJumpInsn(Opcodes.IFNONNULL, label);
  }

  /**
   * Generates the instruction to jump to the given label.
   *
   * @param label where to jump if the condition is {@literal true}.
   */
  public void goTo(final Label label) {
    mv.visitJumpInsn(Opcodes.GOTO, label);
  }

  /**
   * Generates a RET instruction.
   *
   * @param local a local variable identifier, as returned by {@link
   *     LocalVariablesSorter#newLocal(Type)}.
   */
  public void ret(final int local) {
    mv.visitVarInsn(Opcodes.RET, local);
  }

  /**
   * Generates the instructions for a switch statement.
   *
   * @param keys the switch case keys.
   * @param generator a generator to generate the code for the switch cases.
   */
  public void tableSwitch(final int[] keys, final TableSwitchGenerator generator) {
    float density;
    if (keys.length == 0) {
      density = 0;
    } else {
      density = (float) keys.length / (keys[keys.length - 1] - keys[0] + 1);
    }
    tableSwitch(keys, generator, density >= 0.5f);
  }

  /**
   * Generates the instructions for a switch statement.
   *
   * @param keys the switch case keys.
   * @param generator a generator to generate the code for the switch cases.
   * @param useTable {@literal true} to use a TABLESWITCH instruction, or {@literal false} to use a
   *     LOOKUPSWITCH instruction.
   */
  public void tableSwitch(
      final int[] keys, final TableSwitchGenerator generator, final boolean useTable) {
    for (int i = 1; i < keys.length; ++i) {
      if (keys[i] < keys[i - 1]) {
        throw new IllegalArgumentException("keys must be sorted in ascending order");
      }
    }
    Label defaultLabel = newLabel();
    Label endLabel = newLabel();
    if (keys.length > 0) {
      int numKeys = keys.length;
      if (useTable) {
        int min = keys[0];
        int max = keys[numKeys - 1];
        int range = max - min + 1;
        Label[] labels = new Label[range];
        Arrays.fill(labels, defaultLabel);
        for (int i = 0; i < numKeys; ++i) {
          labels[keys[i] - min] = newLabel();
        }
        mv.visitTableSwitchInsn(min, max, defaultLabel, labels);
        for (int i = 0; i < range; ++i) {
          Label label = labels[i];
          if (label != defaultLabel) {
            mark(label);
            generator.generateCase(i + min, endLabel);
          }
        }
      } else {
        Label[] labels = new Label[numKeys];
        for (int i = 0; i < numKeys; ++i) {
          labels[i] = newLabel();
        }
        mv.visitLookupSwitchInsn(defaultLabel, keys, labels);
        for (int i = 0; i < numKeys; ++i) {
          mark(labels[i]);
          generator.generateCase(keys[i], endLabel);
        }
      }
    }
    mark(defaultLabel);
    generator.generateDefault();
    mark(endLabel);
  }

  /** Generates the instruction to return the top stack value to the caller. */
  public void returnValue() {
    mv.visitInsn(returnType.getOpcode(Opcodes.IRETURN));
  }

  // -----------------------------------------------------------------------------------------------
  // Instructions to load and store fields
  // -----------------------------------------------------------------------------------------------

  /**
   * Generates a get field or set field instruction.
   *
   * @param opcode the instruction's opcode.
   * @param ownerType the class in which the field is defined.
   * @param name the name of the field.
   * @param fieldType the type of the field.
   */
  private void fieldInsn(
      final int opcode, final Type ownerType, final String name, final Type fieldType) {
    mv.visitFieldInsn(opcode, ownerType.getInternalName(), name, fieldType.getDescriptor());
  }

  /**
   * Generates the instruction to push the value of a static field on the stack.
   *
   * @param owner the class in which the field is defined.
   * @param name the name of the field.
   * @param type the type of the field.
   */
  public void getStatic(final Type owner, final String name, final Type type) {
    fieldInsn(Opcodes.GETSTATIC, owner, name, type);
  }

  /**
   * Generates the instruction to store the top stack value in a static field.
   *
   * @param owner the class in which the field is defined.
   * @param name the name of the field.
   * @param type the type of the field.
   */
  public void putStatic(final Type owner, final String name, final Type type) {
    fieldInsn(Opcodes.PUTSTATIC, owner, name, type);
  }

  /**
   * Generates the instruction to push the value of a non static field on the stack.
   *
   * @param owner the class in which the field is defined.
   * @param name the name of the field.
   * @param type the type of the field.
   */
  public void getField(final Type owner, final String name, final Type type) {
    fieldInsn(Opcodes.GETFIELD, owner, name, type);
  }

  /**
   * Generates the instruction to store the top stack value in a non static field.
   *
   * @param owner the class in which the field is defined.
   * @param name the name of the field.
   * @param type the type of the field.
   */
  public void putField(final Type owner, final String name, final Type type) {
    fieldInsn(Opcodes.PUTFIELD, owner, name, type);
  }

  // -----------------------------------------------------------------------------------------------
  // Instructions to invoke methods
  // -----------------------------------------------------------------------------------------------

  /**
   * Generates an invoke method instruction.
   *
   * @param opcode the instruction's opcode.
   * @param type the class in which the method is defined.
   * @param method the method to be invoked.
   * @param isInterface whether the 'type' class is an interface or not.
   */
  private void invokeInsn(
      final int opcode, final Type type, final Method method, final boolean isInterface) {
    String owner = type.getSort() == Type.ARRAY ? type.getDescriptor() : type.getInternalName();
    mv.visitMethodInsn(opcode, owner, method.getName(), method.getDescriptor(), isInterface);
  }

  /**
   * Generates the instruction to invoke a normal method.
   *
   * @param owner the class in which the method is defined.
   * @param method the method to be invoked.
   */
  public void invokeVirtual(final Type owner, final Method method) {
    invokeInsn(Opcodes.INVOKEVIRTUAL, owner, method, false);
  }

  /**
   * Generates the instruction to invoke a constructor.
   *
   * @param type the class in which the constructor is defined.
   * @param method the constructor to be invoked.
   */
  public void invokeConstructor(final Type type, final Method method) {
    invokeInsn(Opcodes.INVOKESPECIAL, type, method, false);
  }

  /**
   * Generates the instruction to invoke a static method.
   *
   * @param owner the class in which the method is defined.
   * @param method the method to be invoked.
   */
  public void invokeStatic(final Type owner, final Method method) {
    invokeInsn(Opcodes.INVOKESTATIC, owner, method, false);
  }

  /**
   * Generates the instruction to invoke an interface method.
   *
   * @param owner the class in which the method is defined.
   * @param method the method to be invoked.
   */
  public void invokeInterface(final Type owner, final Method method) {
    invokeInsn(Opcodes.INVOKEINTERFACE, owner, method, true);
  }

  /**
   * Generates an invokedynamic instruction.
   *
   * @param name the method's name.
   * @param descriptor the method's descriptor (see {@link Type}).
   * @param bootstrapMethodHandle the bootstrap method.
   * @param bootstrapMethodArguments the bootstrap method constant arguments. Each argument must be
   *     an {@link Integer}, {@link Float}, {@link Long}, {@link Double}, {@link String}, {@link
   *     Type} or {@link Handle} value. This method is allowed to modify the content of the array so
   *     a caller should expect that this array may change.
   */
  public void invokeDynamic(
      final String name,
      final String descriptor,
      final Handle bootstrapMethodHandle,
      final Object... bootstrapMethodArguments) {
    mv.visitInvokeDynamicInsn(name, descriptor, bootstrapMethodHandle, bootstrapMethodArguments);
  }

  // -----------------------------------------------------------------------------------------------
  // Instructions to create objects and arrays
  // -----------------------------------------------------------------------------------------------

  /**
   * Generates a type dependent instruction.
   *
   * @param opcode the instruction's opcode.
   * @param type the instruction's operand.
   */
  private void typeInsn(final int opcode, final Type type) {
    mv.visitTypeInsn(opcode, type.getInternalName());
  }

  /**
   * Generates the instruction to create a new object.
   *
   * @param type the class of the object to be created.
   */
  public void newInstance(final Type type) {
    typeInsn(Opcodes.NEW, type);
  }

  /**
   * Generates the instruction to create a new array.
   *
   * @param type the type of the array elements.
   */
  public void newArray(final Type type) {
    InstructionAdapter.newarray(mv, type);
  }

  // -----------------------------------------------------------------------------------------------
  // Miscellaneous instructions
  // -----------------------------------------------------------------------------------------------

  /** Generates the instruction to compute the length of an array. */
  public void arrayLength() {
    mv.visitInsn(Opcodes.ARRAYLENGTH);
  }

  /** Generates the instruction to throw an exception. */
  public void throwException() {
    mv.visitInsn(Opcodes.ATHROW);
  }

  /**
   * Generates the instructions to create and throw an exception. The exception class must have a
   * constructor with a single String argument.
   *
   * @param type the class of the exception to be thrown.
   * @param message the detailed message of the exception.
   */
  public void throwException(final Type type, final String message) {
    newInstance(type);
    dup();
    push(message);
    invokeConstructor(type, Method.getMethod("void <init> (String)"));
    throwException();
  }

  /**
   * Generates the instruction to check that the top stack value is of the given type.
   *
   * @param type a class or interface type.
   */
  public void checkCast(final Type type) {
    if (!type.equals(OBJECT_TYPE)) {
      typeInsn(Opcodes.CHECKCAST, type);
    }
  }

  /**
   * Generates the instruction to test if the top stack value is of the given type.
   *
   * @param type a class or interface type.
   */
  public void instanceOf(final Type type) {
    typeInsn(Opcodes.INSTANCEOF, type);
  }

  /** Generates the instruction to get the monitor of the top stack value. */
  public void monitorEnter() {
    mv.visitInsn(Opcodes.MONITORENTER);
  }

  /** Generates the instruction to release the monitor of the top stack value. */
  public void monitorExit() {
    mv.visitInsn(Opcodes.MONITOREXIT);
  }

  // -----------------------------------------------------------------------------------------------
  // Non instructions
  // -----------------------------------------------------------------------------------------------

  /** Marks the end of the visited method. */
  public void endMethod() {
    if ((access & Opcodes.ACC_ABSTRACT) == 0) {
      mv.visitMaxs(0, 0);
    }
    mv.visitEnd();
  }

  /**
   * Marks the start of an exception handler.
   *
   * @param start beginning of the exception handler's scope (inclusive).
   * @param end end of the exception handler's scope (exclusive).
   * @param exception internal name of the type of exceptions handled by the handler (see {@link
   *     Type#getInternalName()}).
   */
  public void catchException(final Label start, final Label end, final Type exception) {
    Label catchLabel = new Label();
    if (exception == null) {
      mv.visitTryCatchBlock(start, end, catchLabel, null);
    } else {
      mv.visitTryCatchBlock(start, end, catchLabel, exception.getInternalName());
    }
    mark(catchLabel);
  }
}
