/*
    * 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.classfile;
  
  import java.io.DataInput;
  import java.io.DataOutputStream;
  import java.io.IOException;
  import java.util.Arrays;
  
  import org.apache.bcel.Const;
  import org.apache.bcel.util.Args;
  import org.apache.commons.lang3.ArrayUtils;
  
  /**
   * 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.
   *
   * <pre>
   * Code_attribute {
   *   u2 attribute_name_index;
   *   u4 attribute_length;
   *   u2 max_stack;
   *   u2 max_locals;
   *   u4 code_length;
   *   u1 code[code_length];
   *   u2 exception_table_length;
   *   {
   *     u2 start_pc;
   *     u2 end_pc;
   *     u2 handler_pc;
   *     u2 catch_type;
   *   } exception_table[exception_table_length];
   *   u2 attributes_count;
   *   attribute_info attributes[attributes_count];
   * }
   * </pre>
   *
   * @see Attribute
   * @see CodeException
   * @see LineNumberTable
   * @see LocalVariableTable
   */
  public final class Code extends Attribute {
  
      private int maxStack; // Maximum size of stack used by this method // TODO this could be made final (setter is not used)
      private int maxLocals; // Number of local variables // TODO this could be made final (setter is not used)
      private byte[] code; // Actual byte code
      private CodeException[] exceptionTable; // Table of handled exceptions
      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.
       *
       * @param code The source Code.
       */
      public Code(final Code code) {
          this(code.getNameIndex(), code.getLength(), code.getMaxStack(), code.getMaxLocals(), code.getCode(), code.getExceptionTable(), code.getAttributes(),
                  code.getConstantPool());
      }
  
      /**
       * Constructs a Code attribute object from a DataInput.
       *
       * @param nameIndex    Index pointing to the name <em>Code</em>.
       * @param length       Content length in bytes.
       * @param dataInput    Data input.
       * @param constantPool Array of constants.
       * @throws ClassFormatException if the code array read from {@code file} is greater than {@link Const#MAX_CODE_SIZE}.
       */
      Code(final int nameIndex, final int length, final DataInput dataInput, final ConstantPool constantPool) throws IOException {
          // Initialize with some default values which will be overwritten later
          this(nameIndex, length, dataInput.readUnsignedShort(), dataInput.readUnsignedShort(), (byte[]) null, (CodeException[]) null, (Attribute[]) null,
                  constantPool);
          final int codeLength = Args.requireU4(dataInput.readInt(), 0, Const.MAX_CODE_SIZE, "Code length attribute");
          code = new byte[codeLength]; // Read byte code
          dataInput.readFully(code);
          /*
          * Read exception table that contains all regions where an exception handler is active, that is, a try { ... } catch () block.
          */
         final int exceptionTableLength = dataInput.readUnsignedShort();
         exceptionTable = new CodeException[exceptionTableLength];
         for (int i = 0; i < exceptionTableLength; i++) {
             exceptionTable[i] = new CodeException(dataInput);
         }
         /*
          * Read all attributes, currently 'LineNumberTable' and 'LocalVariableTable'
          */
         final int attributesCount = dataInput.readUnsignedShort();
         attributes = new Attribute[attributesCount];
         for (int i = 0; i < attributesCount; i++) {
             attributes[i] = readAttribute(dataInput, constantPool);
         }
         /*
          * 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.
          */
         super.setLength(length);
     }
 
     /**
      * Constructs a Code attribute.
      *
      * @param nameIndex Index pointing to the name <em>Code</em>.
      * @param length Content length in bytes.
      * @param maxStack Maximum size of stack.
      * @param maxLocals Number of local variables.
      * @param code Actual byte code.
      * @param exceptionTable of handled exceptions.
      * @param attributes Attributes of code: LineNumber or LocalVariable.
      * @param constantPool Array of constants.
      * @throws ClassFormatException if the code array is greater than {@link Const#MAX_CODE_SIZE}.
      */
     public Code(final int nameIndex, final int length, final int maxStack, final int maxLocals, final byte[] code, final CodeException[] exceptionTable,
         final Attribute[] attributes, final ConstantPool constantPool) {
         super(Const.ATTR_CODE, nameIndex, length, constantPool);
         this.maxStack = Args.requireU2(maxStack, "maxStack");
         this.maxLocals = Args.requireU2(maxLocals, "maxLocals");
         this.code = ArrayUtils.nullToEmpty(code);
         Args.requireU4(this.code.length, 0, Const.MAX_CODE_SIZE, "Code length attribute");
         this.exceptionTable = ArrayUtils.nullToEmpty(exceptionTable, CodeException[].class);
         Args.requireU2(this.exceptionTable.length, "exceptionTable.length");
         this.attributes = attributes != null ? attributes : EMPTY_ARRAY;
         super.setLength(calculateLength()); // Adjust length
     }
 
     /**
      * Called by objects that are traversing the nodes of the tree implicitly defined by the contents of a Java class.
      * That is, the hierarchy of methods, fields, attributes, etc. spawns a tree of objects.
      *
      * @param v Visitor object.
      */
     @Override
     public void accept(final Visitor v) {
         v.visitCode(this);
     }
 
     /**
      * @return the full size of this code attribute, minus its first 6 bytes, including the size of all its contained attributes.
      */
     private int calculateLength() {
         int len = 0;
         if (attributes != null) {
             for (final Attribute attribute : attributes) {
                 len += attribute.getLength() + 6 /* attribute header size */;
             }
         }
         return len + getInternalLength();
     }
 
     /**
      * Creates a deep copy of this attribute.
      *
      * @param constantPool the constant pool to duplicate.
      * @return deep copy of this attribute.
      */
     @Override
     public Attribute copy(final ConstantPool constantPool) {
         final Code c = (Code) clone();
         if (code != null) {
             c.code = code.clone();
         }
         c.setConstantPool(constantPool);
         c.exceptionTable = new CodeException[exceptionTable.length];
         Arrays.setAll(c.exceptionTable, i -> exceptionTable[i].copy());
         c.attributes = new Attribute[attributes.length];
         Arrays.setAll(c.attributes, i -> attributes[i].copy(constantPool));
         return c;
     }
 
     /**
      * Dumps code attribute to file stream in binary format.
      *
      * @param file Output file stream.
      * @throws IOException if an I/O error occurs.
      */
     @Override
     public void dump(final DataOutputStream file) throws IOException {
         super.dump(file);
         file.writeShort(maxStack);
         file.writeShort(maxLocals);
         file.writeInt(code.length);
         file.write(code, 0, code.length);
         file.writeShort(exceptionTable.length);
         for (final CodeException exception : exceptionTable) {
             exception.dump(file);
         }
         file.writeShort(attributes.length);
         for (final Attribute attribute : attributes) {
             attribute.dump(file);
         }
     }
 
     /**
      * Gets the collection of code attributes.
      *
      * @return Collection of code attributes.
      * @see Attribute
      */
     public Attribute[] getAttributes() {
         return attributes;
     }
 
     /**
      * Gets the actual byte code of the method.
      *
      * @return Actual byte code of the method.
      */
     public byte[] getCode() {
         return code;
     }
 
     /**
      * Gets the table of handled exceptions.
      *
      * @return Table of handled exceptions.
      * @see CodeException
      */
     public CodeException[] getExceptionTable() {
         return exceptionTable;
     }
 
     /**
      * Gets the internal length of this code attribute (minus the first 6 bytes) and excluding all its attributes.
      *
      * @return the internal length of this code attribute (minus the first 6 bytes) and excluding all its attributes.
      */
     private int getInternalLength() {
         return 2 /* maxStack */ + 2 /* maxLocals */ + 4 /* code length */
             + code.length /* byte-code */
             + 2 /* exception-table length */
             + 8 * (exceptionTable == null ? 0 : exceptionTable.length) /* exception table */
             + 2 /* attributes count */;
     }
 
     /**
      * Gets the LineNumberTable of Code, if it has one.
      *
      * @return LineNumberTable of Code, if it has one.
      */
     public LineNumberTable getLineNumberTable() {
         for (final Attribute attribute : attributes) {
             if (attribute instanceof LineNumberTable) {
                 return (LineNumberTable) attribute;
             }
         }
         return null;
     }
 
     /**
      * Gets the LocalVariableTable of Code, if it has one.
      *
      * @return LocalVariableTable of Code, if it has one.
      */
     public LocalVariableTable getLocalVariableTable() {
         for (final Attribute attribute : attributes) {
             if (attribute instanceof LocalVariableTable) {
                 return (LocalVariableTable) attribute;
             }
         }
         return null;
     }
 
     /**
      * Gets the local variable type table attribute {@link LocalVariableTypeTable}.
      *
      * @return LocalVariableTypeTable of Code, if it has one, null otherwise.
      * @since 6.10.0
      */
     public LocalVariableTypeTable getLocalVariableTypeTable() {
         for (final Attribute attribute : attributes) {
             if (attribute instanceof LocalVariableTypeTable) {
                 return (LocalVariableTypeTable) attribute;
             }
         }
         return null;
     }
 
     /**
      * Gets the number of local variables.
      *
      * @return Number of local variables.
      */
     public int getMaxLocals() {
         return maxLocals;
     }
 
     /**
      * Gets the maximum size of stack used by this method.
      *
      * @return Maximum size of stack used by this method.
      */
     public int getMaxStack() {
         return maxStack;
     }
 
     /**
      * Finds the attribute of {@link StackMap} instance.
      *
      * @return StackMap of Code, if it has one, else null.
      * @since 6.8.0
      */
     public StackMap getStackMap() {
         for (final Attribute attribute : attributes) {
             if (attribute instanceof StackMap) {
                 return (StackMap) attribute;
             }
         }
         return null;
     }
 
     /**
      * Sets the attributes for this Code.
      *
      * @param attributes the attributes to set for this Code.
      */
     public void setAttributes(final Attribute[] attributes) {
         this.attributes = attributes != null ? attributes : EMPTY_ARRAY;
         super.setLength(calculateLength()); // Adjust length
     }
 
     /**
      * Sets the byte code.
      *
      * @param code byte code.
      * @throws ClassFormatException if the code array is greater than {@link Const#MAX_CODE_SIZE}.
      */
     public void setCode(final byte[] code) {
         this.code = ArrayUtils.nullToEmpty(code);
         Args.requireU4(this.code.length, 0, Const.MAX_CODE_SIZE, "Code length attribute");
         super.setLength(calculateLength()); // Adjust length
     }
 
     /**
      * Sets the exception table.
      *
      * @param exceptionTable exception table.
      */
     public void setExceptionTable(final CodeException[] exceptionTable) {
         this.exceptionTable = exceptionTable != null ? exceptionTable : CodeException.EMPTY_ARRAY;
         super.setLength(calculateLength()); // Adjust length
     }
 
     /**
      * Sets the maximum number of local variables.
      *
      * @param maxLocals maximum number of local variables.
      */
     public void setMaxLocals(final int maxLocals) {
         this.maxLocals = maxLocals;
     }
 
     /**
      * Sets the maximum stack size.
      *
      * @param maxStack maximum stack size.
      */
     public void setMaxStack(final int maxStack) {
         this.maxStack = maxStack;
     }
 
     /**
      * @return String representation of code chunk.
      */
     @Override
     public String toString() {
         return toString(true);
     }
 
     /**
      * Converts this object to a String.
      *
      * @param verbose Provides verbose output when true.
      * @return String representation of code chunk.
      */
     public String toString(final boolean verbose) {
         final StringBuilder buf = new StringBuilder(100); // CHECKSTYLE IGNORE MagicNumber
         buf.append("Code(maxStack = ").append(maxStack).append(", maxLocals = ").append(maxLocals).append(", code_length = ").append(code.length).append(")\n")
             .append(Utility.codeToString(code, super.getConstantPool(), 0, -1, verbose));
         if (exceptionTable.length > 0) {
             buf.append("\nException handler(s) = \n").append("From\tTo\tHandler\tType\n");
             for (final CodeException exception : exceptionTable) {
                 buf.append(exception.toString(super.getConstantPool(), verbose)).append("\n");
             }
         }
         if (attributes.length > 0) {
             buf.append("\nAttribute(s) = ");
             for (final Attribute attribute : attributes) {
                 buf.append("\n").append(attribute.getName()).append(":");
                 buf.append("\n").append(attribute);
             }
         }
         return buf.toString();
     }
 }