classparser.java

A static analysis tool to find bugs in Java programs

/*
 * FindBugs - Find Bugs in Java programs
 * Copyright (C) 2006, University of Maryland
 * 
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 * 
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 * 
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 */

package edu.umd.cs.findbugs.classfile.engine;

import java.io.DataInputStream;
import java.io.IOException;
import java.util.TreeSet;

import edu.umd.cs.findbugs.classfile.ClassDescriptor;
import edu.umd.cs.findbugs.classfile.FieldDescriptor;
import edu.umd.cs.findbugs.classfile.IClassConstants;
import edu.umd.cs.findbugs.classfile.ICodeBaseEntry;
import edu.umd.cs.findbugs.classfile.InvalidClassFileFormatException;
import edu.umd.cs.findbugs.classfile.MethodDescriptor;
import edu.umd.cs.findbugs.classfile.analysis.ClassInfo;
import edu.umd.cs.findbugs.classfile.analysis.ClassNameAndSuperclassInfo;
import edu.umd.cs.findbugs.util.ClassName;

/**
 * Parse a class to extract symbolic information.
 * see <a href=http://java.sun.com/docs/books/vmspec/2nd-edition/html/ClassFile.doc.html">
   http://java.sun.com/docs/books/vmspec/2nd-edition/html/ClassFile.doc.html </a>
 * 
 * @author David Hovemeyer
 */
public class ClassParser {

	static class Constant {
		int tag;
		Object[] data;

		Constant(int tag, Object[] data) {
			this.tag = tag;
			this.data = data;
		}
	}

	private DataInputStream in;
	private ClassDescriptor expectedClassDescriptor;
	private ICodeBaseEntry codeBaseEntry;
	private Constant[] constantPool;

	/**
	 * Constructor.
	 * 
	 * @param in                       the DataInputStream to read class data from
	 * @param expectedClassDescriptor  ClassDescriptor expected: null if unknown
	 * @param codeBaseEntry            codebase entry class is loaded from
	 */
	public ClassParser(
			DataInputStream in,
			ClassDescriptor expectedClassDescriptor,
			ICodeBaseEntry codeBaseEntry) {
		this.in = in;
		this.expectedClassDescriptor = expectedClassDescriptor;
		this.codeBaseEntry = codeBaseEntry;
	}

	/**
	 * Parse the class data into a ClassNameAndSuperclassInfo object containing
	 * (some of) the class's symbolic information.
	 * 
	 * @param classInfo a ClassNameAndSuperclassInfo object to be filled in with (some of)
	 *                   the class's symbolic information
	 * @throws InvalidClassFileFormatException
	 */
	public void parse(ClassNameAndSuperclassInfo classInfo) throws InvalidClassFileFormatException {
		try {
			int magic = in.readInt();
			int major_version = in.readUnsignedShort();
			int minor_version = in.readUnsignedShort();
			int constant_pool_count = in.readUnsignedShort();

			constantPool = new Constant[constant_pool_count];
			for (int i = 1; i < constantPool.length; i++) {
				constantPool[i] = readConstant();
				if (constantPool[i].tag == IClassConstants.CONSTANT_Double ||
						constantPool[i].tag == IClassConstants.CONSTANT_Long) {
					// Double and Long constants take up two constant pool entries
					++i;
				}
			}

			int access_flags = in.readUnsignedShort();

			int this_class = in.readUnsignedShort();
			ClassDescriptor thisClassDescriptor =
				getClassDescriptor(this_class);

			int super_class = in.readUnsignedShort();
			ClassDescriptor superClassDescriptor =
				getClassDescriptor(super_class);

			int interfaces_count = in.readUnsignedShort();
			if (interfaces_count < 0) {
				throw new InvalidClassFileFormatException(expectedClassDescriptor, codeBaseEntry);
			}
			ClassDescriptor[] interfaceDescriptorList = new ClassDescriptor[interfaces_count];
			for (int i = 0; i < interfaceDescriptorList.length; i++) {
				interfaceDescriptorList[i] = getClassDescriptor(in.readUnsignedShort());
			}

			classInfo.setClassDescriptor(thisClassDescriptor);
			classInfo.setSuperclassDescriptor(superClassDescriptor);
			classInfo.setInterfaceDescriptorList(interfaceDescriptorList);
			classInfo.setCodeBaseEntry(codeBaseEntry);
			classInfo.setAccessFlags(access_flags);
		} catch (IOException e) {
			throw new InvalidClassFileFormatException(expectedClassDescriptor, codeBaseEntry, e);
		}
	}

	/**
	 * Parse the class data into a ClassInfo object containing
	 * (some of) the class's symbolic information.
	 * 
	 * @param classInfo a ClassInfo object to be filled in with (some of)
	 *                   the class's symbolic information
	 * @throws InvalidClassFileFormatException
	 */
	public void parse(ClassInfo classInfo) throws InvalidClassFileFormatException {
		parse((ClassNameAndSuperclassInfo) classInfo);

		try {
			int fields_count = in.readUnsignedShort();
			if (fields_count < 0 ) {
				throw new InvalidClassFileFormatException(expectedClassDescriptor, codeBaseEntry);
			}
			FieldDescriptor[] fieldDescriptorList = new FieldDescriptor[fields_count];
			for (int i = 0; i < fields_count; i++) {
				fieldDescriptorList[i] = readField(classInfo.getClassDescriptor());
			}

			int methods_count = in.readUnsignedShort();
			if (methods_count < 0) {
				throw new InvalidClassFileFormatException(expectedClassDescriptor, codeBaseEntry);
			}
			MethodDescriptor[] methodDescriptorList = new MethodDescriptor[methods_count];
			for (int i = 0; i < methods_count; i++) {
				methodDescriptorList[i] = readMethod(classInfo.getClassDescriptor());
			}

			// Extract all references to other classes,
			// both CONSTANT_Class entries and also referenced method
			// signatures.
			ClassDescriptor[] referencedClassDescriptorList = extractReferencedClasses();

			classInfo.setFieldDescriptorList(fieldDescriptorList);
			classInfo.setMethodDescriptorList(methodDescriptorList);
			classInfo.setReferencedClassDescriptorList(referencedClassDescriptorList);
		} catch (IOException e) {
			throw new InvalidClassFileFormatException(expectedClassDescriptor, codeBaseEntry, e);
		}

	}

	/**
	 * Extract references to other classes.
	 * 
	 * @return array of ClassDescriptors of referenced classes
	 * @throws InvalidClassFileFormatException
	 */
	private ClassDescriptor[] extractReferencedClasses() throws InvalidClassFileFormatException {
		TreeSet<ClassDescriptor> referencedClassSet = new TreeSet<ClassDescriptor>();
		for (Constant constant : constantPool) {
			if (constant == null) {
				continue;
			}
			if (constant.tag == IClassConstants.CONSTANT_Class) {
				String className = getUtf8String((Integer)constant.data[0]);
				if (className.indexOf('[') >= 0) {
					extractReferencedClassesFromSignature(referencedClassSet, className);
				} else if (ClassName.isValidClassName(className)) {
					referencedClassSet.add(new ClassDescriptor(className));
				}
			} else if (constant.tag == IClassConstants.CONSTANT_Methodref
					|| constant.tag == IClassConstants.CONSTANT_Fieldref
					|| constant.tag == IClassConstants.CONSTANT_InterfaceMethodref) {
				// Get the target class name
				String className = getClassName((Integer) constant.data[0]);
				extractReferencedClassesFromSignature(referencedClassSet, className);

				// Parse signature to extract class names
				String signature = getSignatureFromNameAndType((Integer)constant.data[1]);
				extractReferencedClassesFromSignature(referencedClassSet, signature);
			}
		}
		ClassDescriptor[] referencedClassDescriptorList = 
			referencedClassSet.toArray(new ClassDescriptor[referencedClassSet.size()]);
		return referencedClassDescriptorList;
	}

	/**
	 * @param referencedClassSet
	 * @param signature
	 */
	private void extractReferencedClassesFromSignature(TreeSet<ClassDescriptor> referencedClassSet, String signature) {
		while (signature.length() > 0) {
			int start = signature.indexOf('L');
			if (start < 0) {
				break;
			}
			signature = signature.substring(start);
			int end = signature.indexOf(';');
			if (end < 0) {
				break;
			}
			String className = signature.substring(1, end);
			if (ClassName.isValidClassName(className)) {
				referencedClassSet.add(new ClassDescriptor(className));
			}
			signature = signature.substring(end + 1);
		}
	}

	// 8: UTF-8 string
	// I: int
	// F: float
	// L: long
	// D: double
	// i: 2-byte constant pool index
	private static final String[] CONSTANT_FORMAT_MAP = {
		null,
		"8", // 1: CONSTANT_Utf8