genericsignatureparser.java

A static analysis tool to find bugs in Java programs

/*
 * Bytecode Analysis Framework
 * Copyright (C) 2004, 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.ba.generic;

import java.util.Iterator;
import java.util.NoSuchElementException;

import org.apache.bcel.classfile.Attribute;
import org.apache.bcel.classfile.FieldOrMethod;
import org.apache.bcel.classfile.Method;
import org.apache.bcel.classfile.Signature;
import org.apache.bcel.generic.ConstantPoolGen;
import org.apache.bcel.generic.InvokeInstruction;
import org.apache.bcel.generic.ObjectType;
import org.apache.bcel.generic.Type;

import edu.umd.cs.findbugs.annotations.CheckForNull;

/**
 * A simple class to parse method signatures that include 
 * generic information. <p>
 * 
 * Modified from edu.umd.cs.findbugs.ba.SignatureParser
 *
 * @author Nat Ayewah
 */
public class GenericSignatureParser {
	private class ParameterSignatureIterator implements Iterator<String> {
		private int index = 1;

		public boolean hasNext() {
			return index < signature.length()
					&& signature.charAt(index) != ')';
		}

		public String next() {
			if (!hasNext()) throw new NoSuchElementException();
			StringBuffer result = new StringBuffer();
			boolean done;
			do {
				done = true;
				int ch = signature.charAt(index);
				switch (ch) {
				case 'B':
				case 'C':
				case 'D':
				case 'F':
				case 'I':
				case 'J':
				case 'S':
				case 'Z':
				case '*':  // wildcard
					result.append(signature.charAt(index));
					++index;
					break;

				case 'L':
				case 'T':
					String tmp = "";
					int startsemi = index;
					int semi = -1;
					// find the substring that ends with a semicolon and
					// contains the same number of '<' and '>' braces
					do {
						semi = signature.indexOf(';', startsemi + 1);
						if (semi < 0)
							throw new IllegalArgumentException("Invalid method signature: " + signature);
						tmp = signature.substring(index, semi + 1);
						startsemi = semi;
					} while(tmp.split("<").length != tmp.split(">").length);
					result.append(tmp);
					index = semi + 1;
					break;

				case '[':
				case '+':
				case '-':
					result.append(signature.charAt(index));
					++index;
					done = false;
					break;

				case 'V':
				default:
					throw new IllegalStateException("Invalid method signature: " + signature);
				}
			} while (!done);

			return result.toString();
		}

		public void remove() {
			throw new UnsupportedOperationException();
		}
	}

	private final String signature;

	/**
	 * Parses a generic method signature of the form:
	 * <code>(argument_signature)return_type_signature</code>
	 *
	 * @param signature the method signature to be parsed
	 */
	public GenericSignatureParser(String signature) {
		// XXX not currently handling Type parameters for class, interface or method definitions
		if (signature.indexOf('(') < 0 || signature.indexOf(':') >= 0)
			throw new IllegalArgumentException("Bad method signature: " + signature);
		if (!signature.startsWith("(")) 
			this.signature = signature.substring( signature.indexOf("(") );
		else 
			this.signature = signature;
	}

	/**
	 * Get an Iterator over signatures of the method parameters.
	 *
	 * @return Iterator which returns the parameter type signatures in order
	 */
	public Iterator<String> parameterSignatureIterator() {
		return new ParameterSignatureIterator();
	}

	/**
	 * Get the method return type signature.
	 * 
	 * @return the method return type signature
	 */
	public String getReturnTypeSignature() {
		int endOfParams = signature.lastIndexOf(')');
		if (endOfParams < 0)
			throw new IllegalArgumentException("Bad method signature: " + signature);
		return signature.substring(endOfParams + 1);
	}

	/**
	 * Get the number of parameters in the signature.
	 * 
	 * @return the number of parameters
	 */
	public int getNumParameters() {
		int count = 0;
		for (Iterator<String> i = parameterSignatureIterator(); i.hasNext();) {
			i.next();
			++count;
		}
		return count;
	}

	/**
	 * Get the number of parameters passed to method invocation.
	 * 
	 * @param inv
	 * @param cpg
	 * @return int number of parameters
	 */
	public static int getNumParametersForInvocation(InvokeInstruction inv, ConstantPoolGen cpg) {
		GenericSignatureParser sigParser = new GenericSignatureParser(inv.getSignature(cpg));
		return sigParser.getNumParameters();
	}

	/**
	 * @param method
	 * @return an iterator over the parameters of the generic 
	 *  		signature of method. Returns null if the
	 *  		generic signature cannot be parsed
	 */
	public static @CheckForNull Iterator<String> getGenericSignatureIterator(Method target) {
		try {
			GenericSignatureParser parser = null;
			String genericSignature = null;			
			for (Attribute a : target.getAttributes()) {
				if (a instanceof Signature) {

					Signature sig = (Signature) a;
					if ( genericSignature != null) {
						if (!genericSignature.equals(sig.getSignature()) ) {
							if (false) {
								System.out.println("Inconsistent signatures: " );
								System.out.println(genericSignature);
								System.out.println(sig.getSignature());
								}
							return null; // we've seen two inconsistent signatures
						}
						continue;
					}

					genericSignature = sig.getSignature();
					if (compareSignatures(target.getSignature(), genericSignature))
						parser = new GenericSignatureParser( genericSignature );
				}
			}
			Iterator<String> iter = parser == null ? null :
				parser.parameterSignatureIterator();			
			return iter;
		} catch (RuntimeException e) {} // degrade gracefully
		return null;
	}

	/**
	 * Compare a plain method signature to the a generic method Signature and
	 * return true if they match
	 */
	public static boolean compareSignatures(
			String plainSignature, String genericSignature) {
		GenericSignatureParser plainParser =
			new GenericSignatureParser( plainSignature );
		GenericSignatureParser genericParser =
			new GenericSignatureParser( genericSignature );

		if (plainParser.getNumParameters() != genericParser.getNumParameters())
			return false;

		return true;
	}


	public static void main(String[] args) {
		if (args.length != 1) {
			System.err.println("Usage: " + GenericSignatureParser.class.getName() + " '<method signature>'");
			System.exit(1);
		}
		GenericSignatureParser parser = new GenericSignatureParser(args[0]);
		for (Iterator<String> i = parser.parameterSignatureIterator(); i.hasNext();){
			String s = i.next();
			System.out.println(s);
			Type t = GenericUtilities.getType(s);
			System.out.println("-~- " + t);
			if (t instanceof ObjectType)
				System.out.println("-~- " + ( (ObjectType) t).toString());
			System.out.println("-~- " + t.getClass());
		}
		System.out.println(parser.getNumParameters() + " parameter(s)");


	}
}