/*
    * 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.classfile;
  
  import java.io.DataInputStream;
  import java.io.DataOutputStream;
  import java.io.IOException;
  import org.apache.bcel.Constants;
  
  /** 
   * This class represents a chunk of Java byte code contained in a
   * method. It is instantiated by the
   * <em>Attribute.readAttribute()</em> method. A <em>Code</em>
   * attribute contains informations about operand stack, local
   * variables, byte code and the exceptions handled within this
   * method.
   *
   * This attribute has attributes itself, namely <em>LineNumberTable</em> which
   * is used for debugging purposes and <em>LocalVariableTable</em> which 
   * contains information about the local variables.
   *
   * @version $Id: Code.java 1152077 2011-07-29 02:29:42Z dbrosius $
   * @author  <A HREF="mailto:m.dahm@gmx.de">M. Dahm</A>
   * @see     Attribute
   * @see     CodeException
   * @see     LineNumberTable
   * @see LocalVariableTable
   */
  public final class Code extends Attribute {
  
      private static final long serialVersionUID = -432884354459701506L;
      private int max_stack; // Maximum size of stack used by this method
      private int max_locals; // Number of local variables
      private int code_length; // Length of code in bytes
      private byte[] code; // Actual byte code
      private int exception_table_length;
      private CodeException[] exception_table; // Table of handled exceptions
      private int attributes_count; // Attributes of code: LineNumber
      private Attribute[] attributes; // or LocalVariable
  
  
      /**
       * Initialize from another object. Note that both objects use the same
       * references (shallow copy). Use copy() for a physical copy.
       */
      public Code(Code c) {
          this(c.getNameIndex(), c.getLength(), c.getMaxStack(), c.getMaxLocals(), c.getCode(), c
                  .getExceptionTable(), c.getAttributes(), c.getConstantPool());
      }
  
  
      /**
       * @param name_index Index pointing to the name <em>Code</em>
       * @param length Content length in bytes
       * @param file Input stream
       * @param constant_pool Array of constants
       */
      Code(int name_index, int length, DataInputStream file, ConstantPool constant_pool)
              throws IOException {
          // Initialize with some default values which will be overwritten later
          this(name_index, length, file.readUnsignedShort(), file.readUnsignedShort(), (byte[]) null,
                  (CodeException[]) null, (Attribute[]) null, constant_pool);
          code_length = file.readInt();
          code = new byte[code_length]; // Read byte code
          file.readFully(code);
          /* Read exception table that contains all regions where an exception
           * handler is active, i.e., a try { ... } catch() block.
           */
          exception_table_length = file.readUnsignedShort();
          exception_table = new CodeException[exception_table_length];
          for (int i = 0; i < exception_table_length; i++) {
              exception_table[i] = new CodeException(file);
          }
          /* Read all attributes, currently `LineNumberTable' and
           * `LocalVariableTable'
           */
          attributes_count = file.readUnsignedShort();
          attributes = new Attribute[attributes_count];
          for (int i = 0; i < attributes_count; i++) {
              attributes[i] = Attribute.readAttribute(file, constant_pool);
          }
          /* Adjust length, because of setAttributes in this(), s.b.  length
           * is incorrect, because it didn't take the internal attributes
           * into account yet! Very subtle bug, fixed in 3.1.1.
          */
         this.length = length;
     }
 
 
     /**
      * @param name_index Index pointing to the name <em>Code</em>
      * @param length Content length in bytes
      * @param max_stack Maximum size of stack
      * @param max_locals Number of local variables
      * @param code Actual byte code
      * @param exception_table Table of handled exceptions
      * @param attributes Attributes of code: LineNumber or LocalVariable
      * @param constant_pool Array of constants
      */
     public Code(int name_index, int length, int max_stack, int max_locals, byte[] code,
             CodeException[] exception_table, Attribute[] attributes, ConstantPool constant_pool) {
         super(Constants.ATTR_CODE, name_index, length, constant_pool);
         this.max_stack = max_stack;
         this.max_locals = max_locals;
         setCode(code);
         setExceptionTable(exception_table);
         setAttributes(attributes); // Overwrites length!
     }
 
 
     /**
      * Called by objects that are traversing the nodes of the tree implicitely
      * defined by the contents of a Java class. I.e., the hierarchy of methods,
      * fields, attributes, etc. spawns a tree of objects.
      *
      * @param v Visitor object
      */
     @Override
     public void accept( Visitor v ) {
         v.visitCode(this);
     }
 
 
     /**
      * Dump code attribute to file stream in binary format.
      *
      * @param file Output file stream
      * @throws IOException
      */
     @Override
     public final void dump( DataOutputStream file ) throws IOException {
         super.dump(file);
         file.writeShort(max_stack);
         file.writeShort(max_locals);
         file.writeInt(code_length);
         file.write(code, 0, code_length);
         file.writeShort(exception_table_length);
         for (int i = 0; i < exception_table_length; i++) {
             exception_table[i].dump(file);
         }
         file.writeShort(attributes_count);
         for (int i = 0; i < attributes_count; i++) {
             attributes[i].dump(file);
         }
     }
 
 
     /**
      * @return Collection of code attributes.
      * @see Attribute
      */
     public final Attribute[] getAttributes() {
         return attributes;
     }
 
 
     /**
      * @return LineNumberTable of Code, if it has one
      */
     public LineNumberTable getLineNumberTable() {
         for (int i = 0; i < attributes_count; i++) {
             if (attributes[i] instanceof LineNumberTable) {
                 return (LineNumberTable) attributes[i];
             }
         }
         return null;
     }
 
 
     /**
      * @return LocalVariableTable of Code, if it has one
      */
     public LocalVariableTable getLocalVariableTable() {
         for (int i = 0; i < attributes_count; i++) {
             if (attributes[i] instanceof LocalVariableTable) {
                 return (LocalVariableTable) attributes[i];
             }
         }
         return null;
     }
 
 
     /**
      * @return Actual byte code of the method.
      */
     public final byte[] getCode() {
         return code;
     }
 
 
     /**
      * @return Table of handled exceptions.
      * @see CodeException
      */
     public final CodeException[] getExceptionTable() {
         return exception_table;
     }
 
 
     /**
      * @return Number of local variables.
      */
     public final int getMaxLocals() {
         return max_locals;
     }
 
 
     /**
      * @return Maximum size of stack used by this method.
      */
     public final int getMaxStack() {
         return max_stack;
     }
 
 
     /**
      * @return the internal length of this code attribute (minus the first 6 bytes) 
      * and excluding all its attributes
      */
     private final int getInternalLength() {
         return 2 /*max_stack*/+ 2 /*max_locals*/+ 4 /*code length*/
                 + code_length /*byte-code*/
                 + 2 /*exception-table length*/
                 + 8 * exception_table_length /* exception table */
                 + 2 /* attributes count */;
     }
 
 
     /**
      * @return the full size of this code attribute, minus its first 6 bytes,
      * including the size of all its contained attributes
      */
     private final int calculateLength() {
         int len = 0;
         for (int i = 0; i < attributes_count; i++) {
             len += attributes[i].length + 6 /*attribute header size*/;
         }
         return len + getInternalLength();
     }
 
 
     /**
      * @param attributes the attributes to set for this Code
      */
     public final void setAttributes( Attribute[] attributes ) {
         this.attributes = attributes;
         attributes_count = (attributes == null) ? 0 : attributes.length;
         length = calculateLength(); // Adjust length
     }
 
 
     /**
      * @param code byte code
      */
     public final void setCode( byte[] code ) {
         this.code = code;
         code_length = (code == null) ? 0 : code.length;
         length = calculateLength(); // Adjust length
     }
 
 
     /**
      * @param exception_table exception table
      */
     public final void setExceptionTable( CodeException[] exception_table ) {
         this.exception_table = exception_table;
         exception_table_length = (exception_table == null) ? 0 : exception_table.length;
         length = calculateLength(); // Adjust length
     }
 
 
     /**
      * @param max_locals maximum number of local variables
      */
     public final void setMaxLocals( int max_locals ) {
         this.max_locals = max_locals;
     }
 
 
     /**
      * @param max_stack maximum stack size
      */
     public final void setMaxStack( int max_stack ) {
         this.max_stack = max_stack;
     }
 
 
     /**
      * @return String representation of code chunk.
      */
     public final String toString( boolean verbose ) {
         StringBuilder buf = new StringBuilder(100);
         buf.append("Code(max_stack = ").append(max_stack).append(", max_locals = ").append(
                 max_locals).append(", code_length = ").append(code_length).append(")\n").append(
                 Utility.codeToString(code, constant_pool, 0, -1, verbose));
         if (exception_table_length > 0) {
             buf.append("\nException handler(s) = \n").append("From\tTo\tHandler\tType\n");
             for (int i = 0; i < exception_table_length; i++) {
                 buf.append(exception_table[i].toString(constant_pool, verbose)).append("\n");
             }
         }
         if (attributes_count > 0) {
             buf.append("\nAttribute(s) = \n");
             for (int i = 0; i < attributes_count; i++) {
                 buf.append(attributes[i].toString()).append("\n");
             }
         }
         return buf.toString();
     }
 
 
     /**
      * @return String representation of code chunk.
      */
     @Override
     public final String toString() {
         return toString(true);
     }
 
 
     /**
      * @return deep copy of this attribute
      * 
      * @param _constant_pool the constant pool to duplicate
      */
     @Override
     public Attribute copy( ConstantPool _constant_pool ) {
         Code c = (Code) clone();
         if (code != null) {
             c.code = new byte[code.length];
             System.arraycopy(code, 0, c.code, 0, code.length);
         }
         c.constant_pool = _constant_pool;
         c.exception_table = new CodeException[exception_table_length];
         for (int i = 0; i < exception_table_length; i++) {
             c.exception_table[i] = exception_table[i].copy();
         }
         c.attributes = new Attribute[attributes_count];
         for (int i = 0; i < attributes_count; i++) {
             c.attributes[i] = attributes[i].copy(_constant_pool);
         }
         return c;
     }
 }