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An auxiliary findbugs.sourceforge.net plugin for java bug detectors that fall outside the narrow scope of detectors to be packaged with the product itself.
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/*
 * fb-contrib - Auxiliary detectors for Java programs
 * Copyright (C) 2005-2019 Dave Brosius
 *
 * 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 com.mebigfatguy.fbcontrib.detect;

import java.util.List;

import org.apache.bcel.Constants;
import org.apache.bcel.classfile.JavaClass;
import org.apache.bcel.classfile.Method;

import com.mebigfatguy.fbcontrib.utils.BugType;
import com.mebigfatguy.fbcontrib.utils.SignatureBuilder;
import com.mebigfatguy.fbcontrib.utils.SignatureUtils;
import com.mebigfatguy.fbcontrib.utils.Values;

import edu.umd.cs.findbugs.BugInstance;
import edu.umd.cs.findbugs.BugReporter;
import edu.umd.cs.findbugs.Detector;
import edu.umd.cs.findbugs.ba.ClassContext;
import edu.umd.cs.findbugs.visitclass.PreorderVisitor;

/**
 * looks for definitions of methods that have an array as the last parameter.
 * Since this class is compiled with java 1.5 or better, it would be more
 * flexible for clients of this method to define this parameter as a vararg
 * parameter.
 */
public class UseVarArgs extends PreorderVisitor implements Detector {

	public static final String SIG_STRING_ARRAY_TO_VOID = new SignatureBuilder()
			.withParamTypes(SignatureBuilder.SIG_STRING_ARRAY).toString();

	private final BugReporter bugReporter;
	private JavaClass javaClass;

	public UseVarArgs(BugReporter bugReporter) {
		this.bugReporter = bugReporter;
	}

	/**
	 * overrides the visitor to make sure that the class was compiled by java 1.5 or
	 * later.
	 *
	 * @param classContext the context object of the currently parsed class
	 */
	@Override
	public void visitClassContext(ClassContext classContext) {
		try {
			javaClass = classContext.getJavaClass();
			if (javaClass.getMajor() >= Constants.MAJOR_1_5) {
				javaClass.accept(this);
			}
		} finally {
			javaClass = null;
		}
	}

	/**
	 * overrides the visitor to look for methods that has an array as a last
	 * parameter of an array type, where the base type is not like the previous
	 * parameter nor something like a char or byte array.
	 *
	 * @param obj the currently parse method
	 */
	@Override
	public void visitMethod(Method obj) {
		try {
			if (obj.isSynthetic()) {
				return;
			}

			if (Values.CONSTRUCTOR.equals(getMethodName()) && javaClass.getClassName().contains("$")) {
				return;
			}

			List types = SignatureUtils.getParameterSignatures(obj.getSignature());
			if ((types.isEmpty()) || (types.size() > 2)) {
				return;
			}

			if ((obj.getAccessFlags() & Constants.ACC_VARARGS) != 0) {
				return;
			}

			String lastParmSig = types.get(types.size() - 1);
			if (!lastParmSig.startsWith(Values.SIG_ARRAY_PREFIX)
					|| lastParmSig.startsWith(Values.SIG_ARRAY_OF_ARRAYS_PREFIX)) {
				return;
			}

			if (SignatureBuilder.SIG_BYTE_ARRAY.equals(lastParmSig)
					|| SignatureBuilder.SIG_CHAR_ARRAY.equals(lastParmSig)) {
				return;
			}

			if (hasSimilarParms(types)) {
				return;
			}

			if (obj.isStatic() && "main".equals(obj.getName()) && SIG_STRING_ARRAY_TO_VOID.equals(obj.getSignature())) {
				return;
			}

			if (!obj.isPrivate() && !obj.isStatic() && isInherited(obj)) {
				return;
			}

			super.visitMethod(obj);
			bugReporter.reportBug(new BugInstance(this, BugType.UVA_USE_VAR_ARGS.name(), LOW_PRIORITY).addClass(this)
					.addMethod(this));

		} catch (ClassNotFoundException cnfe) {
			bugReporter.reportMissingClass(cnfe);
		}
	}

	/**
	 * overrides the visitor, but not used
	 */
	@Override
	public void report() {
		// needed by Detector interface but not used
	}

	/**
	 * determines whether a bunch of types are similar and thus would be confusing
	 * to have one be a varargs.
	 *
	 * @param argTypes the parameter signatures to check
	 * @return whether the parameter are similar
	 */
	@edu.umd.cs.findbugs.annotations.SuppressFBWarnings(value = "LII_LIST_INDEXED_ITERATING", justification = "this doesn't iterate over every element, so we can't use a for-each loop")
	private static boolean hasSimilarParms(List argTypes) {

		for (int i = 0; i < (argTypes.size() - 1); i++) {
			if (argTypes.get(i).startsWith(Values.SIG_ARRAY_PREFIX)) {
				return true;
			}
		}

		String baseType = argTypes.get(argTypes.size() - 1);
		while (baseType.startsWith(Values.SIG_ARRAY_PREFIX)) {
			baseType = baseType.substring(1);
		}

		for (int i = 0; i < (argTypes.size() - 1); i++) {
			if (argTypes.get(i).equals(baseType)) {
				return true;
			}
		}

		return false;
	}

	/**
	 * looks to see if this method is derived from a super class. If it is we don't
	 * want to report on it, as that would entail changing a whole hierarchy
	 *
	 * @param m the current method
	 * @return if the method is inherited
	 *
	 * @throws ClassNotFoundException if the super class(s) aren't found
	 */
	private boolean isInherited(Method m) throws ClassNotFoundException {
		JavaClass[] infs = javaClass.getAllInterfaces();
		for (JavaClass inf : infs) {
			if (hasMethod(inf, m)) {
				return true;
			}
		}

		JavaClass[] sups = javaClass.getSuperClasses();
		for (JavaClass sup : sups) {
			if (hasMethod(sup, m)) {
				return true;
			}
		}

		return false;
	}

	/**
	 * looks to see if a class has a method with a specific name and signature
	 *
	 * @param c               the class to check
	 * @param candidateMethod the method to look for
	 *
	 * @return whether this class has the exact method
	 */
	private static boolean hasMethod(JavaClass c, Method candidateMethod) {
		String name = candidateMethod.getName();
		String sig = candidateMethod.getSignature();

		for (Method method : c.getMethods()) {
			if (!method.isStatic() && method.getName().equals(name) && method.getSignature().equals(sig)) {
				return true;
			}
		}

		return false;
	}
}