/*
    * 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
    *
   *   https://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.ExceptionConst;
  import org.apache.bcel.classfile.ConstantPool;
  import org.apache.bcel.util.ByteSequence;
  
  /**
   * INVOKEINTERFACE - Invoke interface method
   *
   * <pre>
   * Stack: ..., objectref, [arg1, [arg2 ...]] -&gt; ...
   * </pre>
   *
   * @see <a href="https://docs.oracle.com/javase/specs/jvms/se8/html/jvms-6.html#jvms-6.5.invokeinterface"> The
   *      invokeinterface instruction in The Java Virtual Machine Specification</a>
   */
  public final class INVOKEINTERFACE extends InvokeInstruction {
  
      private int nargs; // Number of arguments on stack (number of stack slots), called "count" in vmspec2
  
      /**
       * Empty constructor needed for Instruction.readInstruction. Not to be used otherwise.
       */
      INVOKEINTERFACE() {
      }
  
      /**
       * Constructs an INVOKEINTERFACE instruction.
       *
       * @param index index into constant pool.
       * @param nargs number of arguments.
       */
      public INVOKEINTERFACE(final int index, final int nargs) {
          super(Const.INVOKEINTERFACE, index);
          super.setLength(5);
          if (nargs < 1 || nargs > Const.MAX_BYTE) {
              throw new ClassGenException("Number of arguments out of range (1 - " + Const.MAX_BYTE + "): " + nargs);
          }
          this.nargs = nargs;
      }
  
      /**
       * Call corresponding visitor method(s). The order is: Call visitor methods of implemented interfaces first, then call
       * methods according to the class hierarchy in descending order, that is, the most specific visitXXX() call comes last.
       *
       * @param v Visitor object.
       */
      @Override
      public void accept(final Visitor v) {
          v.visitExceptionThrower(this);
          v.visitTypedInstruction(this);
          v.visitStackConsumer(this);
          v.visitStackProducer(this);
          v.visitLoadClass(this);
          v.visitCPInstruction(this);
          v.visitFieldOrMethod(this);
          v.visitInvokeInstruction(this);
          v.visitINVOKEINTERFACE(this);
      }
  
      @Override
      public int consumeStack(final ConstantPoolGen cpg) { // nargs is given in byte-code
          return nargs; // nargs includes this reference
      }
  
      /**
       * Dumps instruction as byte code to stream out.
       *
       * @param out Output stream.
       */
      @Override
      public void dump(final DataOutputStream out) throws IOException {
          out.writeByte(super.getOpcode());
          out.writeShort(super.getIndex());
          out.writeByte(nargs);
          out.writeByte(0);
      }
 
     /**
      * The <strong>count</strong> argument according to the Java Language Specification, Second Edition.
      *
      * @return The count argument.
      */
     public int getCount() {
         return nargs;
     }
 
     @Override
     public Class<?>[] getExceptions() {
         return ExceptionConst.createExceptions(ExceptionConst.EXCS.EXCS_INTERFACE_METHOD_RESOLUTION, ExceptionConst.UNSATISFIED_LINK_ERROR,
             ExceptionConst.ABSTRACT_METHOD_ERROR, ExceptionConst.ILLEGAL_ACCESS_ERROR, ExceptionConst.INCOMPATIBLE_CLASS_CHANGE_ERROR);
     }
 
     /**
      * Reads needed data (that is, index) from file.
      */
     @Override
     protected void initFromFile(final ByteSequence bytes, final boolean wide) throws IOException {
         super.initFromFile(bytes, wide);
         super.setLength(5);
         nargs = bytes.readUnsignedByte();
         bytes.readByte(); // Skip 0 byte
     }
 
     /**
      * @return mnemonic for instruction with symbolic references resolved.
      */
     @Override
     public String toString(final ConstantPool cp) {
         return super.toString(cp) + " " + nargs;
     }
 }