/*
 * Copyright (c) 2017, Oracle and/or its affiliates. All rights reserved.
 */
/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.sun.org.apache.bcel.internal.generic;

import com.sun.org.apache.bcel.internal.Const;

Instances of this class may be used, e.g., to generate typed versions of
instructions. Its main purpose is to be used as the byte code generating
backend of a compiler. You can subclass it to add your own create methods.
 Note: The static createXXX methods return singleton instances from the InstructionConst class. 
See Also:
Const
InstructionConst
Version:
$Id: InstructionFactory.java 1749603 2016-06-21 20:50:19Z ggregory $
@LastModified
: Nov 2017/**
 * Instances of this class may be used, e.g., to generate typed versions of
 * instructions. Its main purpose is to be used as the byte code generating
 * backend of a compiler. You can subclass it to add your own create methods.
 * <p>
 * Note: The static createXXX methods return singleton instances from the
 * {@link InstructionConst} class.
 *
 * @version $Id: InstructionFactory.java 1749603 2016-06-21 20:50:19Z ggregory $
 * @see Const
 * @see InstructionConst
 * @LastModified: Nov 2017
 */
public class InstructionFactory {

    // N.N. These must agree with the order of Constants.T_CHAR through T_LONG
    private static final String[] short_names = {
        "C", "F", "D", "B", "S", "I", "L"
    };

    private ClassGen cg;
    private ConstantPoolGen cp;

    public InstructionFactory(final ClassGen cg, final ConstantPoolGen cp) {
        this.cg = cg;
        this.cp = cp;
    }

    
Initialize with ClassGen object
/**
     * Initialize with ClassGen object
     */
    public InstructionFactory(final ClassGen cg) {
        this(cg, cg.getConstantPool());
    }

    
Initialize just with ConstantPoolGen object
/**
     * Initialize just with ConstantPoolGen object
     */
    public InstructionFactory(final ConstantPoolGen cp) {
        this(null, cp);
    }

    
Create an invoke instruction. (Except for invokedynamic.)
Params:
class_name – name of the called class
name – name of the called method
ret_type – return type of method
arg_types – argument types of method
kind – how to invoke, i.e., INVOKEINTERFACE, INVOKESTATIC,
INVOKEVIRTUAL, or INVOKESPECIAL
See Also:
Const/**
     * Create an invoke instruction. (Except for invokedynamic.)
     *
     * @param class_name name of the called class
     * @param name name of the called method
     * @param ret_type return type of method
     * @param arg_types argument types of method
     * @param kind how to invoke, i.e., INVOKEINTERFACE, INVOKESTATIC,
     * INVOKEVIRTUAL, or INVOKESPECIAL
     * @see Const
     */
    public InvokeInstruction createInvoke(final String class_name, final String name, final Type ret_type,
            final Type[] arg_types, final short kind) {
        int index;
        int nargs = 0;
        final String signature = Type.getMethodSignature(ret_type, arg_types);
        for (final Type arg_type : arg_types) {
            nargs += arg_type.getSize();
        }
        if (kind == Const.INVOKEINTERFACE) {
            index = cp.addInterfaceMethodref(class_name, name, signature);
        } else {
            index = cp.addMethodref(class_name, name, signature);
        }
        switch (kind) {
            case Const.INVOKESPECIAL:
                return new INVOKESPECIAL(index);
            case Const.INVOKEVIRTUAL:
                return new INVOKEVIRTUAL(index);
            case Const.INVOKESTATIC:
                return new INVOKESTATIC(index);
            case Const.INVOKEINTERFACE:
                return new INVOKEINTERFACE(index, nargs + 1);
            case Const.INVOKEDYNAMIC:
                return new INVOKEDYNAMIC(index);
            default:
                throw new RuntimeException("Oops: Unknown invoke kind: " + kind);
        }
    }

    /**
     * Create an invokedynamic instruction.
     *
     * @param bootstrap_index index into the bootstrap_methods array
     * @param name name of the called method
     * @param ret_type return type of method
     * @param arg_types argument types of method
     * @see Constants
     */
    /*
     * createInvokeDynamic only needed if instrumention code wants to generate
     * a new invokedynamic instruction.  I don't think we need.  (markro)
     *
     public InvokeInstruction createInvokeDynamic( int bootstrap_index, String name, Type ret_type,
     Type[] arg_types) {
     int index;
     int nargs = 0;
     String signature = Type.getMethodSignature(ret_type, arg_types);
     for (int i = 0; i < arg_types.length; i++) {
     nargs += arg_types[i].getSize();
     }
     // UNDONE - needs to be added to ConstantPoolGen
     //index = cp.addInvokeDynamic(bootstrap_index, name, signature);
     index = 0;
     return new INVOKEDYNAMIC(index);
     }
     */
    
Create a call to the most popular System.out.println() method.
Params:
s – the string to print/**
     * Create a call to the most popular System.out.println() method.
     *
     * @param s the string to print
     */
    public InstructionList createPrintln(final String s) {
        final InstructionList il = new InstructionList();
        final int out = cp.addFieldref("java.lang.System", "out", "Ljava/io/PrintStream;");
        final int println = cp.addMethodref("java.io.PrintStream", "println", "(Ljava/lang/String;)V");
        il.append(new GETSTATIC(out));
        il.append(new PUSH(cp, s));
        il.append(new INVOKEVIRTUAL(println));
        return il;
    }

    
Uses PUSH to push a constant value onto the stack.
Params:
value – must be of type Number, Boolean, Character or String/**
     * Uses PUSH to push a constant value onto the stack.
     *
     * @param value must be of type Number, Boolean, Character or String
     */
    public Instruction createConstant(final Object value) {
        PUSH push;
        if (value instanceof Number) {
            push = new PUSH(cp, (Number) value);
        } else if (value instanceof String) {
            push = new PUSH(cp, (String) value);
        } else if (value instanceof Boolean) {
            push = new PUSH(cp, (Boolean) value);
        } else if (value instanceof Character) {
            push = new PUSH(cp, (Character) value);
        } else {
            throw new ClassGenException("Illegal type: " + value.getClass());
        }
        return push.getInstruction();
    }

    private static class MethodObject {

        final Type[] arg_types;
        final Type result_type;
        final String class_name;
        final String name;

        MethodObject(final String c, final String n, final Type r, final Type[] a) {
            class_name = c;
            name = n;
            result_type = r;
            arg_types = a;
        }
    }

    private InvokeInstruction createInvoke(final MethodObject m, final short kind) {
        return createInvoke(m.class_name, m.name, m.result_type, m.arg_types, kind);
    }

    private static final MethodObject[] append_mos = {
        new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER, new Type[]{
            Type.STRING
        }),
        new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER, new Type[]{
            Type.OBJECT
        }),
        null,
        null, // indices 2, 3
        new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER, new Type[]{
            Type.BOOLEAN
        }),
        new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER, new Type[]{
            Type.CHAR
        }),
        new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER, new Type[]{
            Type.FLOAT
        }),
        new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER, new Type[]{
            Type.DOUBLE
        }),
        new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER, new Type[]{
            Type.INT
        }),
        new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER, // No append(byte)
        new Type[]{
            Type.INT
        }),
        new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER, // No append(short)
        new Type[]{
            Type.INT
        }),
        new MethodObject("java.lang.StringBuffer", "append", Type.STRINGBUFFER, new Type[]{
            Type.LONG
        })
    };

    private static boolean isString(final Type type) {
        return (type instanceof ObjectType)
                && ((ObjectType) type).getClassName().equals("java.lang.String");
    }

    public Instruction createAppend(final Type type) {
        final byte t = type.getType();
        if (isString(type)) {
            return createInvoke(append_mos[0], Const.INVOKEVIRTUAL);
        }
        switch (t) {
            case Const.T_BOOLEAN:
            case Const.T_CHAR:
            case Const.T_FLOAT:
            case Const.T_DOUBLE:
            case Const.T_BYTE:
            case Const.T_SHORT:
            case Const.T_INT:
            case Const.T_LONG:
                return createInvoke(append_mos[t], Const.INVOKEVIRTUAL);
            case Const.T_ARRAY:
            case Const.T_OBJECT:
                return createInvoke(append_mos[1], Const.INVOKEVIRTUAL);
            default:
                throw new RuntimeException("Oops: No append for this type? " + type);
        }
    }

    
Create a field instruction.
Params:
class_name – name of the accessed class
name – name of the referenced field
type – type of field
kind – how to access, i.e., GETFIELD, PUTFIELD, GETSTATIC, PUTSTATIC
See Also:
Const/**
     * Create a field instruction.
     *
     * @param class_name name of the accessed class
     * @param name name of the referenced field
     * @param type type of field
     * @param kind how to access, i.e., GETFIELD, PUTFIELD, GETSTATIC, PUTSTATIC
     * @see Const
     */
    public FieldInstruction createFieldAccess(final String class_name, final String name, final Type type, final short kind) {
        int index;
        final String signature = type.getSignature();
        index = cp.addFieldref(class_name, name, signature);
        switch (kind) {
            case Const.GETFIELD:
                return new GETFIELD(index);
            case Const.PUTFIELD:
                return new PUTFIELD(index);
            case Const.GETSTATIC:
                return new GETSTATIC(index);
            case Const.PUTSTATIC:
                return new PUTSTATIC(index);
            default:
                throw new RuntimeException("Oops: Unknown getfield kind:" + kind);
        }
    }

    
Create reference to `this'
/**
     * Create reference to `this'
     */
    public static Instruction createThis() {
        return new ALOAD(0);
    }

    
Create typed return
/**
     * Create typed return
     */
    public static ReturnInstruction createReturn(final Type type) {
        switch (type.getType()) {
            case Const.T_ARRAY:
            case Const.T_OBJECT:
                return InstructionConst.ARETURN;
            case Const.T_INT:
            case Const.T_SHORT:
            case Const.T_BOOLEAN:
            case Const.T_CHAR:
            case Const.T_BYTE:
                return InstructionConst.IRETURN;
            case Const.T_FLOAT:
                return InstructionConst.FRETURN;
            case Const.T_DOUBLE:
                return InstructionConst.DRETURN;
            case Const.T_LONG:
                return InstructionConst.LRETURN;
            case Const.T_VOID:
                return InstructionConst.RETURN;
            default:
                throw new RuntimeException("Invalid type: " + type);
        }
    }

    private static ArithmeticInstruction createBinaryIntOp(final char first, final String op) {
        switch (first) {
            case '-':
                return InstructionConst.ISUB;
            case '+':
                return InstructionConst.IADD;
            case '%':
                return InstructionConst.IREM;
            case '*':
                return InstructionConst.IMUL;
            case '/':
                return InstructionConst.IDIV;
            case '&':
                return InstructionConst.IAND;
            case '|':
                return InstructionConst.IOR;
            case '^':
                return InstructionConst.IXOR;
            case '<':
                return InstructionConst.ISHL;
            case '>':
                return op.equals(">>>") ? InstructionConst.IUSHR : InstructionConst.ISHR;
            default:
                throw new RuntimeException("Invalid operand " + op);
        }
    }

    private static ArithmeticInstruction createBinaryLongOp(final char first, final String op) {
        switch (first) {
            case '-':
                return InstructionConst.LSUB;
            case '+':
                return InstructionConst.LADD;
            case '%':
                return InstructionConst.LREM;
            case '*':
                return InstructionConst.LMUL;
            case '/':
                return InstructionConst.LDIV;
            case '&':
                return InstructionConst.LAND;
            case '|':
                return InstructionConst.LOR;
            case '^':
                return InstructionConst.LXOR;
            case '<':
                return InstructionConst.LSHL;
            case '>':
                return op.equals(">>>") ? InstructionConst.LUSHR : InstructionConst.LSHR;
            default:
                throw new RuntimeException("Invalid operand " + op);
        }
    }

    private static ArithmeticInstruction createBinaryFloatOp(final char op) {
        switch (op) {
            case '-':
                return InstructionConst.FSUB;
            case '+':
                return InstructionConst.FADD;
            case '*':
                return InstructionConst.FMUL;
            case '/':
                return InstructionConst.FDIV;
            case '%':
                return InstructionConst.FREM;
            default:
                throw new RuntimeException("Invalid operand " + op);
        }
    }

    private static ArithmeticInstruction createBinaryDoubleOp(final char op) {
        switch (op) {
            case '-':
                return InstructionConst.DSUB;
            case '+':
                return InstructionConst.DADD;
            case '*':
                return InstructionConst.DMUL;
            case '/':
                return InstructionConst.DDIV;
            case '%':
                return InstructionConst.DREM;
            default:
                throw new RuntimeException("Invalid operand " + op);
        }
    }

    
Create binary operation for simple basic types, such as int and float.
Params:
op – operation, such as "+", "*", "<<", etc./**
     * Create binary operation for simple basic types, such as int and float.
     *
     * @param op operation, such as "+", "*", "&lt;&lt;", etc.
     */
    public static ArithmeticInstruction createBinaryOperation(final String op, final Type type) {
        final char first = op.charAt(0);
        switch (type.getType()) {
            case Const.T_BYTE:
            case Const.T_SHORT:
            case Const.T_INT:
            case Const.T_CHAR:
                return createBinaryIntOp(first, op);
            case Const.T_LONG:
                return createBinaryLongOp(first, op);
            case Const.T_FLOAT:
                return createBinaryFloatOp(first);
            case Const.T_DOUBLE:
                return createBinaryDoubleOp(first);
            default:
                throw new RuntimeException("Invalid type " + type);
        }
    }

    
Params:
size – size of operand, either 1 (int, e.g.) or 2 (double)/**
     * @param size size of operand, either 1 (int, e.g.) or 2 (double)
     */
    public static StackInstruction createPop(final int size) {
        return (size == 2) ? InstructionConst.POP2 : InstructionConst.POP;
    }

    
Params:
size – size of operand, either 1 (int, e.g.) or 2 (double)/**
     * @param size size of operand, either 1 (int, e.g.) or 2 (double)
     */
    public static StackInstruction createDup(final int size) {
        return (size == 2) ? InstructionConst.DUP2 : InstructionConst.DUP;
    }

    
Params:
size – size of operand, either 1 (int, e.g.) or 2 (double)/**
     * @param size size of operand, either 1 (int, e.g.) or 2 (double)
     */
    public static StackInstruction createDup_2(final int size) {
        return (size == 2) ? InstructionConst.DUP2_X2 : InstructionConst.DUP_X2;
    }

    
Params:
size – size of operand, either 1 (int, e.g.) or 2 (double)/**
     * @param size size of operand, either 1 (int, e.g.) or 2 (double)
     */
    public static StackInstruction createDup_1(final int size) {
        return (size == 2) ? InstructionConst.DUP2_X1 : InstructionConst.DUP_X1;
    }

    
Params:
index – index of local variable/**
     * @param index index of local variable
     */
    public static LocalVariableInstruction createStore(final Type type, final int index) {
        switch (type.getType()) {
            case Const.T_BOOLEAN:
            case Const.T_CHAR:
            case Const.T_BYTE:
            case Const.T_SHORT:
            case Const.T_INT:
                return new ISTORE(index);
            case Const.T_FLOAT:
                return new FSTORE(index);
            case Const.T_DOUBLE:
                return new DSTORE(index);
            case Const.T_LONG:
                return new LSTORE(index);
            case Const.T_ARRAY:
            case Const.T_OBJECT:
                return new ASTORE(index);
            default:
                throw new RuntimeException("Invalid type " + type);
        }
    }

    
Params:
index – index of local variable/**
     * @param index index of local variable
     */
    public static LocalVariableInstruction createLoad(final Type type, final int index) {
        switch (type.getType()) {
            case Const.T_BOOLEAN:
            case Const.T_CHAR:
            case Const.T_BYTE:
            case Const.T_SHORT:
            case Const.T_INT:
                return new ILOAD(index);
            case Const.T_FLOAT:
                return new FLOAD(index);
            case Const.T_DOUBLE:
                return new DLOAD(index);
            case Const.T_LONG:
                return new LLOAD(index);
            case Const.T_ARRAY:
            case Const.T_OBJECT:
                return new ALOAD(index);
            default:
                throw new RuntimeException("Invalid type " + type);
        }
    }

    
Params:
type – type of elements of array, i.e., array.getElementType()/**
     * @param type type of elements of array, i.e., array.getElementType()
     */
    public static ArrayInstruction createArrayLoad(final Type type) {
        switch (type.getType()) {
            case Const.T_BOOLEAN:
            case Const.T_BYTE:
                return InstructionConst.BALOAD;
            case Const.T_CHAR:
                return InstructionConst.CALOAD;
            case Const.T_SHORT:
                return InstructionConst.SALOAD;
            case Const.T_INT:
                return InstructionConst.IALOAD;
            case Const.T_FLOAT:
                return InstructionConst.FALOAD;
            case Const.T_DOUBLE:
                return InstructionConst.DALOAD;
            case Const.T_LONG:
                return InstructionConst.LALOAD;
            case Const.T_ARRAY:
            case Const.T_OBJECT:
                return InstructionConst.AALOAD;
            default:
                throw new RuntimeException("Invalid type " + type);
        }
    }

    
Params:
type – type of elements of array, i.e., array.getElementType()/**
     * @param type type of elements of array, i.e., array.getElementType()
     */
    public static ArrayInstruction createArrayStore(final Type type) {
        switch (type.getType()) {
            case Const.T_BOOLEAN:
            case Const.T_BYTE:
                return InstructionConst.BASTORE;
            case Const.T_CHAR:
                return InstructionConst.CASTORE;
            case Const.T_SHORT:
                return InstructionConst.SASTORE;
            case Const.T_INT:
                return InstructionConst.IASTORE;
            case Const.T_FLOAT:
                return InstructionConst.FASTORE;
            case Const.T_DOUBLE:
                return InstructionConst.DASTORE;
            case Const.T_LONG:
                return InstructionConst.LASTORE;
            case Const.T_ARRAY:
            case Const.T_OBJECT:
                return InstructionConst.AASTORE;
            default:
                throw new RuntimeException("Invalid type " + type);
        }
    }

    
Create conversion operation for two stack operands, this may be an I2C,
instruction, e.g., if the operands are basic types and CHECKCAST if they
are reference types.
/**
     * Create conversion operation for two stack operands, this may be an I2C,
     * instruction, e.g., if the operands are basic types and CHECKCAST if they
     * are reference types.
     */
    public Instruction createCast(final Type src_type, final Type dest_type) {
        if ((src_type instanceof BasicType) && (dest_type instanceof BasicType)) {
            final byte dest = dest_type.getType();
            byte src = src_type.getType();
            if (dest == Const.T_LONG
                    && (src == Const.T_CHAR || src == Const.T_BYTE || src == Const.T_SHORT)) {
                src = Const.T_INT;
            }
            final String name = "com.sun.org.apache.bcel.internal.generic." + short_names[src - Const.T_CHAR] + "2"
                    + short_names[dest - Const.T_CHAR];
            Instruction i = null;
            try {
                i = (Instruction) java.lang.Class.forName(name).getDeclaredConstructor().newInstance();
            } catch (final Exception e) {
                throw new RuntimeException("Could not find instruction: " + name, e);
            }
            return i;
        } else if ((src_type instanceof ReferenceType) && (dest_type instanceof ReferenceType)) {
            if (dest_type instanceof ArrayType) {
                return new CHECKCAST(cp.addArrayClass((ArrayType) dest_type));
            }
            return new CHECKCAST(cp.addClass(((ObjectType) dest_type).getClassName()));
        } else {
            throw new RuntimeException("Can not cast " + src_type + " to " + dest_type);
        }
    }

    public GETFIELD createGetField(final String class_name, final String name, final Type t) {
        return new GETFIELD(cp.addFieldref(class_name, name, t.getSignature()));
    }

    public GETSTATIC createGetStatic(final String class_name, final String name, final Type t) {
        return new GETSTATIC(cp.addFieldref(class_name, name, t.getSignature()));
    }

    public PUTFIELD createPutField(final String class_name, final String name, final Type t) {
        return new PUTFIELD(cp.addFieldref(class_name, name, t.getSignature()));
    }

    public PUTSTATIC createPutStatic(final String class_name, final String name, final Type t) {
        return new PUTSTATIC(cp.addFieldref(class_name, name, t.getSignature()));
    }

    public CHECKCAST createCheckCast(final ReferenceType t) {
        if (t instanceof ArrayType) {
            return new CHECKCAST(cp.addArrayClass((ArrayType) t));
        }
        return new CHECKCAST(cp.addClass((ObjectType) t));
    }

    public INSTANCEOF createInstanceOf(final ReferenceType t) {
        if (t instanceof ArrayType) {
            return new INSTANCEOF(cp.addArrayClass((ArrayType) t));
        }
        return new INSTANCEOF(cp.addClass((ObjectType) t));
    }

    public NEW createNew(final ObjectType t) {
        return new NEW(cp.addClass(t));
    }

    public NEW createNew(final String s) {
        return createNew(ObjectType.getInstance(s));
    }

    
Create new array of given size and type.
Returns:
an instruction that creates the corresponding array at runtime,
i.e. is an AllocationInstruction/**
     * Create new array of given size and type.
     *
     * @return an instruction that creates the corresponding array at runtime,
     * i.e. is an AllocationInstruction
     */
    public Instruction createNewArray(final Type t, final short dim) {
        if (dim == 1) {
            if (t instanceof ObjectType) {
                return new ANEWARRAY(cp.addClass((ObjectType) t));
            } else if (t instanceof ArrayType) {
                return new ANEWARRAY(cp.addArrayClass((ArrayType) t));
            } else {
                return new NEWARRAY(t.getType());
            }
        }
        ArrayType at;
        if (t instanceof ArrayType) {
            at = (ArrayType) t;
        } else {
            at = new ArrayType(t, dim);
        }
        return new MULTIANEWARRAY(cp.addArrayClass(at), dim);
    }

    
Create "null" value for reference types, 0 for basic types like int
/**
     * Create "null" value for reference types, 0 for basic types like int
     */
    public static Instruction createNull(final Type type) {
        switch (type.getType()) {
            case Const.T_ARRAY:
            case Const.T_OBJECT:
                return InstructionConst.ACONST_NULL;
            case Const.T_INT:
            case Const.T_SHORT:
            case Const.T_BOOLEAN:
            case Const.T_CHAR:
            case Const.T_BYTE:
                return InstructionConst.ICONST_0;
            case Const.T_FLOAT:
                return InstructionConst.FCONST_0;
            case Const.T_DOUBLE:
                return InstructionConst.DCONST_0;
            case Const.T_LONG:
                return InstructionConst.LCONST_0;
            case Const.T_VOID:
                return InstructionConst.NOP;
            default:
                throw new RuntimeException("Invalid type: " + type);
        }
    }

    
Create branch instruction by given opcode, except LOOKUPSWITCH and
TABLESWITCH. For those you should use the SWITCH compound instruction.
/**
     * Create branch instruction by given opcode, except LOOKUPSWITCH and
     * TABLESWITCH. For those you should use the SWITCH compound instruction.
     */
    public static BranchInstruction createBranchInstruction(final short opcode, final InstructionHandle target) {
        switch (opcode) {
            case Const.IFEQ:
                return new IFEQ(target);
            case Const.IFNE:
                return new IFNE(target);
            case Const.IFLT:
                return new IFLT(target);
            case Const.IFGE:
                return new IFGE(target);
            case Const.IFGT:
                return new IFGT(target);
            case Const.IFLE:
                return new IFLE(target);
            case Const.IF_ICMPEQ:
                return new IF_ICMPEQ(target);
            case Const.IF_ICMPNE:
                return new IF_ICMPNE(target);
            case Const.IF_ICMPLT:
                return new IF_ICMPLT(target);
            case Const.IF_ICMPGE:
                return new IF_ICMPGE(target);
            case Const.IF_ICMPGT:
                return new IF_ICMPGT(target);
            case Const.IF_ICMPLE:
                return new IF_ICMPLE(target);
            case Const.IF_ACMPEQ:
                return new IF_ACMPEQ(target);
            case Const.IF_ACMPNE:
                return new IF_ACMPNE(target);
            case Const.GOTO:
                return new GOTO(target);
            case Const.JSR:
                return new JSR(target);
            case Const.IFNULL:
                return new IFNULL(target);
            case Const.IFNONNULL:
                return new IFNONNULL(target);
            case Const.GOTO_W:
                return new GOTO_W(target);
            case Const.JSR_W:
                return new JSR_W(target);
            default:
                throw new RuntimeException("Invalid opcode: " + opcode);
        }
    }

    public void setClassGen(final ClassGen c) {
        cg = c;
    }

    public ClassGen getClassGen() {
        return cg;
    }

    public void setConstantPool(final ConstantPoolGen c) {
        cp = c;
    }

    public ConstantPoolGen getConstantPool() {
        return cp;
    }
}