org.apache.tomcat.util.bcel.classfile.Code Maven / Gradle / Ivy
/*
* 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.tomcat.util.bcel.classfile;
import java.io.DataInputStream;
import java.io.IOException;
/**
* 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.
*
* @version $Id: Code.java 1398089 2012-10-14 14:26:18Z markt $
* @author M. Dahm
* @see Attribute
* @see LineNumberTable
* @see LocalVariableTable
*/
public final class Code extends Attribute {
private static final long serialVersionUID = 8936843273318969602L;
private int code_length; // Length of code in bytes
private byte[] code; // Actual byte code
private int exception_table_length;
private int attributes_count; // Attributes of code: LineNumber
private Attribute[] attributes; // or LocalVariable
/**
* @param name_index Index pointing to the name Code
* @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, (byte[]) null, (Attribute[]) null,
constant_pool);
file.readUnsignedShort(); // Unused max_stack
file.readUnsignedShort(); // Unused max_locals
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();
for (int i = 0; i < exception_table_length; i++) {
Utility.swallowCodeException(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 Code
* @param length Content length in bytes
* @param code Actual byte code
* @param attributes Attributes of code: LineNumber or LocalVariable
* @param constant_pool Array of constants
*/
public Code(int name_index, int length, byte[] code,
Attribute[] attributes, ConstantPool constant_pool) {
super(name_index, length, constant_pool);
setCode(code);
setAttributes(attributes); // Overwrites length!
}
/**
* @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
}
}