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 * Licensed to the Apache Software Foundation (ASF) under one or more
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 * 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,
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package com.sun.org.apache.bcel.internal.classfile;

import java.io.DataInput;
import java.io.DataOutputStream;
import java.io.IOException;

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


This class represents a chunk of Java byte code contained in a
method. It is instantiated by the
Attribute.readAttribute() method. A Code
attribute contains informations about operand stack, local
variables, byte code and the exceptions handled within this
method.
This attribute has attributes itself, namely LineNumberTable which
is used for debugging purposes and LocalVariableTable which
contains information about the local variables.

See Also:
Version:$Id: Code.java 1749603 2016-06-21 20:50:19Z ggregory $
/**
 * 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 1749603 2016-06-21 20:50:19Z ggregory $
 * @see     Attribute
 * @see     CodeException
 * @see     LineNumberTable
 * @see LocalVariableTable
 */
public final class Code extends Attribute {

    private int max_stack; // Maximum size of stack used by this method  // TODO this could be made final (setter is not used)
    private int max_locals; // Number of local variables  // TODO this could be made final (setter is not used)
    private byte[] code; // Actual byte code
    private CodeException[] exception_table; // 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.

/**
     * Initialize from another object. Note that both objects use the same
     * references (shallow copy). Use copy() for a physical copy.
     */
    public Code(final Code c) {
        this(c.getNameIndex(), c.getLength(), c.getMaxStack(), c.getMaxLocals(), c.getCode(), c
                .getExceptionTable(), c.getAttributes(), c.getConstantPool());
    }


    
Params:
  • name_index – Index pointing to the name Code
  • length – Content length in bytes
  • file – Input stream
  • constant_pool – Array of constants
/**
     * @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(final int name_index, final int length, final DataInput file, final 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);
        final int 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.
         */
        final int 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'
         */
        final int 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.
         */
        super.setLength(length);
    }


    
Params:
  • name_index – Index pointing to the name Code
  • length – Content length in bytes
  • max_stack – Maximum size of stack
  • max_locals – Number of local variables
  • code – Actual byte code
  • exception_table – Table of handled exceptions
  • attributes – Attributes of code: LineNumber or LocalVariable
  • constant_pool – Array of constants
/**
     * @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(final int name_index, final int length, final int max_stack, final int max_locals, final byte[] code,
            final CodeException[] exception_table, final Attribute[] attributes, final ConstantPool constant_pool) {
        super(Const.ATTR_CODE, name_index, length, constant_pool);
        this.max_stack = max_stack;
        this.max_locals = max_locals;
        this.code = code != null ? code : new byte[0];
        this.exception_table = exception_table != null ? exception_table : new CodeException[0];
        this.attributes = attributes != null ? attributes : new Attribute[0];
        super.setLength(calculateLength()); // Adjust 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.

Params:
  • v – Visitor object
/**
     * 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( final Visitor v ) {
        v.visitCode(this);
    }


    
Dump code attribute to file stream in binary format.

Params:
  • file – Output file stream
Throws:
/**
     * Dump code attribute to file stream in binary format.
     *
     * @param file Output file stream
     * @throws IOException
     */
    @Override
    public final void dump( final 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 (final CodeException exception : exception_table) {
            exception.dump(file);
        }
        file.writeShort(attributes.length);
        for (final Attribute attribute : attributes) {
            attribute.dump(file);
        }
    }


    
See Also:
Returns:Collection of code attributes.
/**
     * @return Collection of code attributes.
     * @see Attribute
     */
    public final Attribute[] getAttributes() {
        return attributes;
    }


    
Returns: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;
    }


    
Returns: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;
    }


    
Returns:Actual byte code of the method.
/**
     * @return Actual byte code of the method.
     */
    public final byte[] getCode() {
        return code;
    }


    
See Also:
Returns:Table of handled exceptions.
/**
     * @return Table of handled exceptions.
     * @see CodeException
     */
    public final CodeException[] getExceptionTable() {
        return exception_table;
    }


    
Returns:Number of local variables.
/**
     * @return Number of local variables.
     */
    public final int getMaxLocals() {
        return max_locals;
    }


    
Returns:Maximum size of stack used by this method.
/**
     * @return Maximum size of stack used by this method.
     */
    public final int getMaxStack() {
        return max_stack;
    }


    
Returns: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 /*max_stack*/+ 2 /*max_locals*/+ 4 /*code length*/
                + code.length /*byte-code*/
                + 2 /*exception-table length*/
                + 8 * (exception_table == null ? 0 : exception_table.length) /* exception table */
                + 2 /* attributes count */;
    }


    
Returns:the full size of this code attribute, minus its first 6 bytes,
including the size of all its contained attributes
/**
     * @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();
    }


    
Params:
  • attributes – the attributes to set for this Code
/**
     * @param attributes the attributes to set for this Code
     */
    public final void setAttributes( final Attribute[] attributes ) {
        this.attributes = attributes != null ? attributes : new Attribute[0];
        super.setLength(calculateLength()); // Adjust length
    }


    
Params:
  • code – byte code
/**
     * @param code byte code
     */
    public final void setCode( final byte[] code ) {
        this.code = code != null ? code : new byte[0];
        super.setLength(calculateLength()); // Adjust length
    }


    
Params:
  • exception_table – exception table
/**
     * @param exception_table exception table
     */
    public final void setExceptionTable( final CodeException[] exception_table ) {
        this.exception_table = exception_table != null ? exception_table : new CodeException[0];
        super.setLength(calculateLength()); // Adjust length
    }


    
Params:
  • max_locals – maximum number of local variables
/**
     * @param max_locals maximum number of local variables
     */
    public final void setMaxLocals( final int max_locals ) {
        this.max_locals = max_locals;
    }


    
Params:
  • max_stack – maximum stack size
/**
     * @param max_stack maximum stack size
     */
    public final void setMaxStack( final int max_stack ) {
        this.max_stack = max_stack;
    }


    
Returns:String representation of code chunk.
/**
     * @return String representation of code chunk.
     */
    public final String toString( final boolean verbose ) {
        final StringBuilder buf = new StringBuilder(100); // CHECKSTYLE IGNORE MagicNumber
        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, super.getConstantPool(), 0, -1, verbose));
        if (exception_table.length > 0) {
            buf.append("\nException handler(s) = \n").append("From\tTo\tHandler\tType\n");
            for (final CodeException exception : exception_table) {
                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);
            }
        }
        return buf.toString();
    }


    
Returns:String representation of code chunk.
/**
     * @return String representation of code chunk.
     */
    @Override
    public final String toString() {
        return toString(true);
    }


    
Params:
  • _constant_pool – the constant pool to duplicate
Returns:deep copy of this attribute
/**
     * @return deep copy of this attribute
     *
     * @param _constant_pool the constant pool to duplicate
     */
    @Override
    public Attribute copy( final ConstantPool _constant_pool ) {
        final Code c = (Code) clone();
        if (code != null) {
            c.code = new byte[code.length];
            System.arraycopy(code, 0, c.code, 0, code.length);
        }
        c.setConstantPool(_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.length];
        for (int i = 0; i < attributes.length; i++) {
            c.attributes[i] = attributes[i].copy(_constant_pool);
        }
        return c;
    }
}