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/*
* 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.BufferedInputStream;
import java.io.DataInputStream;
import java.io.IOException;
import java.io.InputStream;
import org.apache.tomcat.util.bcel.Constants;
/**
* Wrapper class that parses a given Java .class file. The method parse returns a
* JavaClass object on success. When an I/O error or an
* inconsistency occurs an appropiate exception is propagated back to
* the caller.
*
* The structure and the names comply, except for a few conveniences,
* exactly with the
* JVM specification 1.0. See this paper for
* further details about the structure of a bytecode file.
*
* @author M. Dahm
*/
public final class ClassParser {
private static final int MAGIC = 0xCAFEBABE;
private DataInputStream file;
private String file_name;
private int class_name_index, superclass_name_index;
private int access_flags; // Access rights of parsed class
private int[] interfaces; // Names of implemented interfaces
private ConstantPool constant_pool; // collection of constants
private FieldOrMethod[] fields; // class fields, i.e., its variables
private FieldOrMethod[] methods; // methods defined in the class
private Attribute[] attributes; // attributes defined in the class
private static final int BUFSIZE = 8192;
/**
* Parse class from the given stream.
*
* @param file Input stream
* @param file_name File name
*/
public ClassParser(InputStream file, String file_name) {
this.file_name = file_name;
if (file instanceof DataInputStream) {
this.file = (DataInputStream) file;
} else {
this.file = new DataInputStream(new BufferedInputStream(file, BUFSIZE));
}
}
/**
* Parse the given Java class file and return an object that represents
* the contained data, i.e., constants, methods, fields and commands.
* A ClassFormatException is raised, if the file is not a valid
* .class file. (This does not include verification of the byte code as it
* is performed by the java interpreter).
*
* @return Class object representing the parsed class file
* @throws IOException
* @throws ClassFormatException
*/
public JavaClass parse() throws IOException, ClassFormatException {
/****************** Read headers ********************************/
// Check magic tag of class file
readID();
// Get compiler version
readVersion();
/****************** Read constant pool and related **************/
// Read constant pool entries
readConstantPool();
// Get class information
readClassInfo();
// Get interface information, i.e., implemented interfaces
readInterfaces();
/****************** Read class fields and methods ***************/
// Read class fields, i.e., the variables of the class
readFields();
// Read class methods, i.e., the functions in the class
readMethods();
// Read class attributes
readAttributes();
// Check for unknown variables
//Unknown[] u = Unknown.getUnknownAttributes();
//for(int i=0; i < u.length; i++)
// System.err.println("WARNING: " + u[i]);
// Everything should have been read now
// if(file.available() > 0) {
// int bytes = file.available();
// byte[] buf = new byte[bytes];
// file.read(buf);
// if(!(is_zip && (buf.length == 1))) {
// System.err.println("WARNING: Trailing garbage at end of " + file_name);
// System.err.println(bytes + " extra bytes: " + Utility.toHexString(buf));
// }
// }
// Return the information we have gathered in a new object
return new JavaClass(class_name_index, superclass_name_index,
access_flags, constant_pool, interfaces, attributes);
}
/**
* Read information about the attributes of the class.
* @throws IOException
* @throws ClassFormatException
*/
private void readAttributes() throws IOException, ClassFormatException {
int attributes_count;
attributes_count = file.readUnsignedShort();
attributes = new Attribute[attributes_count];
for (int i = 0; i < attributes_count; i++) {
attributes[i] = Attribute.readAttribute(file, constant_pool);
}
}
/**
* Read information about the class and its super class.
* @throws IOException
* @throws ClassFormatException
*/
private void readClassInfo() throws IOException, ClassFormatException {
access_flags = file.readUnsignedShort();
/* Interfaces are implicitely abstract, the flag should be set
* according to the JVM specification.
*/
if ((access_flags & Constants.ACC_INTERFACE) != 0) {
access_flags |= Constants.ACC_ABSTRACT;
}
if (((access_flags & Constants.ACC_ABSTRACT) != 0)
&& ((access_flags & Constants.ACC_FINAL) != 0)) {
throw new ClassFormatException("Class " + file_name + " can't be both final and abstract");
}
class_name_index = file.readUnsignedShort();
superclass_name_index = file.readUnsignedShort();
}
/**
* Read constant pool entries.
* @throws IOException
* @throws ClassFormatException
*/
private void readConstantPool() throws IOException, ClassFormatException {
constant_pool = new ConstantPool(file);
}
/**
* Read information about the fields of the class, i.e., its variables.
* @throws IOException
* @throws ClassFormatException
*/
private void readFields() throws IOException, ClassFormatException {
int fields_count;
fields_count = file.readUnsignedShort();
fields = new FieldOrMethod[fields_count];
for (int i = 0; i < fields_count; i++) {
fields[i] = new FieldOrMethod(file, constant_pool);
}
}
/******************** Private utility methods **********************/
/**
* Check whether the header of the file is ok.
* Of course, this has to be the first action on successive file reads.
* @throws IOException
* @throws ClassFormatException
*/
private void readID() throws IOException, ClassFormatException {
if (file.readInt() != MAGIC) {
throw new ClassFormatException(file_name + " is not a Java .class file");
}
}
/**
* Read information about the interfaces implemented by this class.
* @throws IOException
* @throws ClassFormatException
*/
private void readInterfaces() throws IOException, ClassFormatException {
int interfaces_count;
interfaces_count = file.readUnsignedShort();
interfaces = new int[interfaces_count];
for (int i = 0; i < interfaces_count; i++) {
interfaces[i] = file.readUnsignedShort();
}
}
/**
* Read information about the methods of the class.
* @throws IOException
* @throws ClassFormatException
*/
private void readMethods() throws IOException, ClassFormatException {
int methods_count;
methods_count = file.readUnsignedShort();
methods = new FieldOrMethod[methods_count];
for (int i = 0; i < methods_count; i++) {
methods[i] = new FieldOrMethod(file, constant_pool);
}
}
/**
* Read major and minor version of compiler which created the file.
* @throws IOException
* @throws ClassFormatException
*/
private void readVersion() throws IOException, ClassFormatException {
file.readUnsignedShort(); // Unused minor
file.readUnsignedShort(); // Unused major
}
}
