/*
    * 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 org.apache.bcel.generic;
  
  import java.io.DataOutputStream;
  import java.io.IOException;
  
  import org.apache.bcel.Const;
  import org.apache.bcel.util.ByteSequence;
  
  /**
   * Abstract super class for instructions dealing with local variables.
   */
  public abstract class LocalVariableInstruction extends Instruction implements TypedInstruction, IndexedInstruction {
  
      /**
       * @deprecated (since 6.0) will be made private; do not access directly, use getter/setter
       */
      @Deprecated
      protected int n = -1; // index of referenced variable
  
      private short cTag = -1; // compact version, such as ILOAD_0
      private short canonTag = -1; // canonical tag such as ILOAD
  
      /**
       * Empty constructor needed for Instruction.readInstruction. Also used by IINC()!
       */
      LocalVariableInstruction() {
      }
  
      /**
       * Empty constructor needed for Instruction.readInstruction. Not to be used otherwise. tag and length are defined in
       * readInstruction and initFromFile, respectively.
       */
      LocalVariableInstruction(final short canonTag, final short cTag) {
          this.canonTag = canonTag;
          this.cTag = cTag;
      }
  
      /**
       * @param opcode Instruction opcode
       * @param cTag Instruction number for compact version, ALOAD_0, e.g.
       * @param n local variable index (unsigned short)
       */
      protected LocalVariableInstruction(final short opcode, final short cTag, final int n) {
          super(opcode, (short) 2);
          this.cTag = cTag;
          canonTag = opcode;
          setIndex(n);
      }
  
      /**
       * Dump instruction as byte code to stream out.
       *
       * @param out Output stream
       */
      @Override
      public void dump(final DataOutputStream out) throws IOException {
          if (wide()) {
              out.writeByte(Const.WIDE);
          }
          out.writeByte(super.getOpcode());
          if (super.getLength() > 1) { // Otherwise ILOAD_n, instruction, e.g.
              if (wide()) {
                  out.writeShort(n);
              } else {
                  out.writeByte(n);
              }
          }
      }
  
      /**
       * @return canonical tag for instruction, e.g., ALOAD for ALOAD_0
       */
      public short getCanonicalTag() {
          return canonTag;
      }
  
      /**
       * @return local variable index (n) referred by this instruction.
       */
      @Override
      public final int getIndex() {
          return n;
      }
 
     /**
      * Returns the type associated with the instruction - in case of ALOAD or ASTORE Type.OBJECT is returned. This is just a
      * bit incorrect, because ALOAD and ASTORE may work on every ReferenceType (including Type.NULL) and ASTORE may even
      * work on a ReturnaddressType .
      *
      * @return type associated with the instruction
      */
     @Override
     public Type getType(final ConstantPoolGen cp) {
         switch (canonTag) {
         case Const.ILOAD:
         case Const.ISTORE:
             return Type.INT;
         case Const.LLOAD:
         case Const.LSTORE:
             return Type.LONG;
         case Const.DLOAD:
         case Const.DSTORE:
             return Type.DOUBLE;
         case Const.FLOAD:
         case Const.FSTORE:
             return Type.FLOAT;
         case Const.ALOAD:
         case Const.ASTORE:
             return Type.OBJECT;
         default:
             throw new ClassGenException("Unknown case in switch" + canonTag);
         }
     }
 
     /**
      * Read needed data (e.g. index) from file.
      *
      * <pre>
      * (ILOAD &lt;= tag &lt;= ALOAD_3) || (ISTORE &lt;= tag &lt;= ASTORE_3)
      * </pre>
      */
     @Override
     protected void initFromFile(final ByteSequence bytes, final boolean wide) throws IOException {
         if (wide) {
             n = bytes.readUnsignedShort();
             super.setLength(4);
         } else {
             final short opcode = super.getOpcode();
             if (opcode >= Const.ILOAD && opcode <= Const.ALOAD || opcode >= Const.ISTORE && opcode <= Const.ASTORE) {
                 n = bytes.readUnsignedByte();
                 super.setLength(2);
             } else {
                 if (opcode <= Const.ALOAD_3) { // compact load instruction such as ILOAD_2
                     n = (opcode - Const.ILOAD_0) % 4;
                 } else { // Assert ISTORE_0 <= tag <= ASTORE_3
                     n = (opcode - Const.ISTORE_0) % 4;
                 }
                 super.setLength(1);
             }
         }
     }
 
     /**
      * Sets the local variable index. also updates opcode and length TODO Why?
      *
      * @see #setIndexOnly(int)
      */
     @Override
     public void setIndex(final int n) { // TODO could be package-protected?
         if (n < 0 || n > Const.MAX_SHORT) {
             throw new ClassGenException("Illegal value: " + n);
         }
         this.n = n;
         // Cannot be < 0 as this is checked above
         if (n <= 3) { // Use more compact instruction xLOAD_n
             super.setOpcode((short) (cTag + n));
             super.setLength(1);
         } else {
             super.setOpcode(canonTag);
             if (wide()) {
                 super.setLength(4);
             } else {
                 super.setLength(2);
             }
         }
     }
 
     /**
      * Sets the index of the referenced variable (n) only
      *
      * @since 6.0
      * @see #setIndex(int)
      */
     final void setIndexOnly(final int n) {
         this.n = n;
     }
 
     /**
      * Long output format:
      *
      * &lt;name of opcode&gt; "["&lt;opcode number&gt;"]" "("&lt;length of instruction&gt;")" "&lt;"&lt; local variable
      * index&gt;"&gt;"
      *
      * @param verbose long/short format switch
      * @return mnemonic for instruction
      */
     @Override
     public String toString(final boolean verbose) {
         final short opcode = super.getOpcode();
         if (opcode >= Const.ILOAD_0 && opcode <= Const.ALOAD_3 || opcode >= Const.ISTORE_0 && opcode <= Const.ASTORE_3) {
             return super.toString(verbose);
         }
         return super.toString(verbose) + " " + n;
     }
 
     private boolean wide() {
         return n > Const.MAX_BYTE;
     }
 }