objectstreamclass.java

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    Object newInstance()
	throws InstantiationException, InvocationTargetException,
	       UnsupportedOperationException
    {
	if (cons != null) {
	    try {
		return cons.newInstance(new Object[0]);
	    } catch (IllegalAccessException ex) {
		// should not occur, as access checks have been suppressed
		InternalError ie = new InternalError();
		ie.initCause( ex ) ;
		throw ie ;
	    }
	} else {
	    throw new UnsupportedOperationException();
	}
    }
    
    /**
     * Returns public no-arg constructor of given class, or null if none found.
     * Access checks are disabled on the returned constructor (if any), since
     * the defining class may still be non-public.
     */
    private static Constructor getExternalizableConstructor(Class cl) {
	try {
	    Constructor cons = cl.getDeclaredConstructor(new Class[0]);
	    cons.setAccessible(true);
	    return ((cons.getModifiers() & Modifier.PUBLIC) != 0) ? 
		cons : null;
	} catch (NoSuchMethodException ex) {
	    return null;
	}
    }

    /**
     * Returns subclass-accessible no-arg constructor of first non-serializable
     * superclass, or null if none found.  Access checks are disabled on the
     * returned constructor (if any).
     */
    private static Constructor getSerializableConstructor(Class cl) {
	Class initCl = cl;
	while (Serializable.class.isAssignableFrom(initCl)) {
	    if ((initCl = initCl.getSuperclass()) == null) {
		return null;
	    }
	}
	try {
	    Constructor cons = initCl.getDeclaredConstructor(new Class[0]);
	    int mods = cons.getModifiers();
	    if ((mods & Modifier.PRIVATE) != 0 ||
		((mods & (Modifier.PUBLIC | Modifier.PROTECTED)) == 0 &&
		 !packageEquals(cl, initCl)))
	    {
		return null;
	    }
	    cons = bridge.newConstructorForSerialization(cl, cons);
	    cons.setAccessible(true);
	    return cons;
	} catch (NoSuchMethodException ex) {
	    return null;
	}
    }

    /*
     * Return the ObjectStreamClass of the local class this one is based on.
     */
    final ObjectStreamClass localClassDescriptor() {
	return localClassDesc;
    }

    /*
     * Get the Serializability of the class.
     */
    boolean isSerializable() {
	return serializable;
    }

    /*
     * Get the externalizability of the class.
     */
    boolean isExternalizable() {
	return externalizable;
    }

    boolean isNonSerializable() {
        return ! (externalizable || serializable);
    }

    /*
     * Calculate the size of the array needed to store primitive data and the
     * number of object references to read when reading from the input
     * stream.
     */
    private void computeFieldInfo() {
	primBytes = 0;
	objFields = 0;

	for (int i = 0; i < fields.length; i++ ) {
	    switch (fields[i].getTypeCode()) {
	    case 'B':
	    case 'Z':
	    	primBytes += 1;
	    	break;
	    case 'C':
	    case 'S':
	    	primBytes += 2;
	    	break;

	    case 'I':
	    case 'F':
	    	primBytes += 4;
	    	break;
	    case 'J':
	    case 'D' :
	    	primBytes += 8;
	    	break;

	    case 'L':
	    case '[':
	    	objFields += 1;
	    	break;
	    }
	}
    }

    private static void msg( String str )
    {
	System.out.println( str ) ;
    }

    /* JDK 1.5 has introduced some new modifier bits (such as SYNTHETIC)
     * that can affect the SVUID computation (see bug 4897937).  These bits
     * must be ignored, as otherwise interoperability with ORBs in earlier
     * JDK versions can be compromised.  I am adding these masks for this
     * purpose as discussed in the CCC for this bug (see http://ccc.sfbay/4897937).
     */

    public static final int CLASS_MASK = Modifier.PUBLIC | Modifier.FINAL |
	Modifier.INTERFACE | Modifier.ABSTRACT ;
    public static final int FIELD_MASK = Modifier.PUBLIC | Modifier.PRIVATE |
	Modifier.PROTECTED | Modifier.STATIC | Modifier.FINAL | 
	Modifier.TRANSIENT | Modifier.VOLATILE ;
    public static final int METHOD_MASK = Modifier.PUBLIC | Modifier.PRIVATE |
	Modifier.PROTECTED | Modifier.STATIC | Modifier.FINAL | 
	Modifier.SYNCHRONIZED | Modifier.NATIVE | Modifier.ABSTRACT |
	Modifier.STRICT ;
    
    /*
     * Compute a hash for the specified class.  Incrementally add
     * items to the hash accumulating in the digest stream.
     * Fold the hash into a long.  Use the SHA secure hash function.
     */
    private static long _computeSerialVersionUID(Class cl) {
	if (DEBUG_SVUID)
	    msg( "Computing SerialVersionUID for " + cl ) ; 
	ByteArrayOutputStream devnull = new ByteArrayOutputStream(512);

	long h = 0;
	try {
	    MessageDigest md = MessageDigest.getInstance("SHA");
	    DigestOutputStream mdo = new DigestOutputStream(devnull, md);
	    DataOutputStream data = new DataOutputStream(mdo);

	    if (DEBUG_SVUID)
		msg( "\twriteUTF( \"" + cl.getName() + "\" )" ) ;
	    data.writeUTF(cl.getName());

	    int classaccess = cl.getModifiers();
	    classaccess &= (Modifier.PUBLIC | Modifier.FINAL |
			    Modifier.INTERFACE | Modifier.ABSTRACT);

	    /* Workaround for javac bug that only set ABSTRACT for
	     * interfaces if the interface had some methods.
	     * The ABSTRACT bit reflects that the number of methods > 0.
	     * This is required so correct hashes can be computed
	     * for existing class files.
	     * Previously this hack was previously present in the VM.
	     */
            Method[] method = cl.getDeclaredMethods();
	    if ((classaccess & Modifier.INTERFACE) != 0) {
		classaccess &= (~Modifier.ABSTRACT);
		if (method.length > 0) {
		    classaccess |= Modifier.ABSTRACT;
		}
	    }

	    // Mask out any post-1.4 attributes
	    classaccess &= CLASS_MASK ;

	    if (DEBUG_SVUID)
		msg( "\twriteInt( " + classaccess + " ) " ) ;
	    data.writeInt(classaccess);

	    /*
	     * Get the list of interfaces supported,
	     * Accumulate their names their names in Lexical order
	     * and add them to the hash
	     */
            if (!cl.isArray()) {
                /* In 1.2fcs, getInterfaces() was modified to return
                 * {java.lang.Cloneable, java.io.Serializable} when
                 * called on array classes.  These values would upset
                 * the computation of the hash, so we explicitly omit
                 * them from its computation.
                 */

	        Class interfaces[] = cl.getInterfaces();
	        Arrays.sort(interfaces, compareClassByName);

	        for (int i = 0; i < interfaces.length; i++) {
		    if (DEBUG_SVUID)
			msg( "\twriteUTF( \"" + interfaces[i].getName() + "\" ) " ) ;
		    data.writeUTF(interfaces[i].getName());
	        }
	    }

	    /* Sort the field names to get a deterministic order */
            Field[] field = cl.getDeclaredFields();
	    Arrays.sort(field, compareMemberByName);

	    for (int i = 0; i < field.length; i++) {
		Field f = field[i];

		/* Include in the hash all fields except those that are
		 * private transient and private static.
		 */
		int m = f.getModifiers();
		if (Modifier.isPrivate(m) &&
		    (Modifier.isTransient(m) || Modifier.isStatic(m)))
		    continue;

		if (DEBUG_SVUID)
		    msg( "\twriteUTF( \"" + f.getName() + "\" ) " ) ;
		data.writeUTF(f.getName());

		// Mask out any post-1.4 bits
		m &= FIELD_MASK ;

		if (DEBUG_SVUID)
		    msg( "\twriteInt( " + m + " ) " ) ;
		data.writeInt(m);

		if (DEBUG_SVUID)
		    msg( "\twriteUTF( \"" + getSignature(f.getType()) + "\" ) " ) ;
		data.writeUTF(getSignature(f.getType()));
	    }

	    if (hasStaticInitializer(cl)) {
		if (DEBUG_SVUID)
		    msg( "\twriteUTF( \"<clinit>\" ) " ) ;
		data.writeUTF("<clinit>");

		if (DEBUG_SVUID)
		    msg( "\twriteInt( " + Modifier.STATIC + " )" ) ;
		data.writeInt(Modifier.STATIC); // TBD: what modifiers does it have

		if (DEBUG_SVUID)
		    msg( "\twriteUTF( \"()V\" )" ) ;
		data.writeUTF("()V");
	    }

	    /*
	     * Get the list of constructors including name and signature
	     * Sort lexically, add all except the private constructors
	     * to the hash with their access flags
	     */

	    MethodSignature[] constructors =
		MethodSignature.removePrivateAndSort(cl.getDeclaredConstructors());
	    for (int i = 0; i < constructors.length; i++) {
		MethodSignature c = constructors[i];
		String mname = "<init>";
		String desc = c.signature;
		desc = desc.replace('/', '.');
		if (DEBUG_SVUID)
		    msg( "\twriteUTF( \"" + mname + "\" )" ) ;
		data.writeUTF(mname);

		// mask out post-1.4 modifiers
		int modifier = c.member.getModifiers() & METHOD_MASK ;

		if (DEBUG_SVUID)
		    msg( "\twriteInt( " + modifier + " ) " ) ;
		data.writeInt( modifier ) ;

		if (DEBUG_SVUID)
		    msg( "\twriteUTF( \"" + desc+ "\" )" ) ;
		data.writeUTF(desc);
	    }

	    /* Include in the hash all methods except those that are
	     * private transient and private static.
	     */
	    MethodSignature[] methods =
		MethodSignature.removePrivateAndSort(method);
	    for (int i = 0; i < methods.length; i++ ) {
		MethodSignature m = methods[i];
		String desc = m.signature;
		desc = desc.replace('/', '.');

		if (DEBUG_SVUID)
		    msg( "\twriteUTF( \"" + m.member.getName()+ "\" )" ) ;
		data.writeUTF(m.member.getName());

		// mask out post-1.4 modifiers
		int modifier = m.member.getModifiers() & METHOD_MASK ;

		if (DEBUG_SVUID)
		    msg( "\twriteInt( " + modifier + " ) " ) ;
		data.writeInt( modifier ) ;

		if (DEBUG_SVUID)
		    msg( "\twriteUTF( \"" + desc + "\" )" ) ;
		data.writeUTF(desc);
	    }

	    /* Compute the hash value for this class.
	     * Use only the first 64 bits of the hash.
	     */
	    data.flush();
	    byte hasharray[] = md.digest();
	    for (int i = 0; i < Math.min(8, hasharray.length); i++) {
		h += (long)(hasharray[i] & 255) << (i * 8);
	    }
	} catch (IOException ignore) {
	    /* can't happen, but be deterministic anyway. */
	    h = -1;
	} catch (NoSuchAlgorithmException complain) {
	    SecurityException se = new SecurityException() ;
	    se.initCause( complain ) ;
	    throw se ;
	}

	return h;
    }

    private static long computeStructuralUID(com.sun.corba.se.impl.io.ObjectStreamClass osc, Class cl) {
	ByteArrayOutputStream devnull = new ByteArrayOutputStream(512);
		
	long h = 0;
	try {

	    if ((!java.io.Serializable.class.isAssignableFrom(cl)) ||
		(cl.isInterface())){
		return 0;
	    }
			
	    if (java.io.Externalizable.class.isAssignableFrom(cl)) {
		return 1;
	    }

	    MessageDigest md = MessageDigest.getInstance("SHA");
	    DigestOutputStream mdo = new DigestOutputStream(devnull, md);
	    DataOutputStream data = new DataOutputStream(mdo);

	    // Get SUID of parent
	    Class parent = cl.getSuperclass();
	    if ((parent != null))  
	    // SerialBug 1; acc. to spec the one for 
	    // java.lang.object
	    // should be computed and put
	    //     && (parent != java.lang.Object.class)) 
	    {
				//data.writeLong(computeSerialVersionUID(null,parent));
		data.writeLong(computeStructuralUID(lookup(parent), parent));
	    }

	    if (osc.hasWriteObject())
		data.writeInt(2);
	    else
		data.writeInt(1);

            // CORBA formal 00-11-03 10.6.2:  For each field of the
            // class that is mapped to IDL, sorted lexicographically
            // by Java field name, in increasing order...
            ObjectStreamField[] field = osc.getFields();
            if (field.length > 1) {
                Arrays.sort(field, compareObjStrFieldsByName);
            }

            // ...Java field name in UTF encoding, field
            // descriptor, as defined by the JVM spec...
            for (int i = 0; i < field.length; i++) {
                data.writeUTF(field[i].getName());
                data.writeUTF(field[i].getSignature());
            }
			
	    /* Compute the hash value for this class.
	     * Use only the first 64 bits of the hash.
	     */
	    data.flush();
	    byte hasharray[] = md.digest();
	    // int minimum = Math.min(8, hasharray.length);
	    // SerialBug 3: SHA computation is wrong; for loop reversed
	    //for (int i = minimum; i > 0; i--) 
	    for (int i = 0; i < Math.min(8, hasharray.length); i++) {
		h += (long)(hasharray[i] & 255) << (i * 8);
	    }
	} catch (IOException ignore) {
	    /* can't happen, but be deterministic anyway. */
	    h = -1;
	} catch (NoSuchAlgorithmException complain) {
	    SecurityException se = new SecurityException();
	    se.initCause( complain ) ;
	    throw se ;
	}
	return h;
    }

    /**
     * Compute the JVM signature for the class.
     */
    static String getSignature(Class clazz) {
	String type = null;
	if (clazz.isArray()) {
	    Class cl = clazz;
	    int dimensions = 0;
	    while (cl.isArray()) {
		dimensions++;
		cl = cl.getComponentType();
	    }
	    StringBuffer sb = new StringBuffer();
	    for (int i = 0; i < dimensions; i++) {
		sb.append("[");
	    }
	    sb.append(getSignature(cl));
	    type = sb.toString();
	} else if (clazz.isPrimitive()) {
	    if (clazz == Integer.TYPE) {
		type = "I";
	    } else if (clazz == Byte.TYPE) {
		type = "B";
	    } else if (clazz == Long.TYPE) {
		type = "J";
	    } else if (clazz == Float.TYPE) {
		type = "F";
	    } else if (clazz == Double.TYPE) {
		type = "D";
	    } else if (clazz == Short.TYPE) {
		type = "S";
	    } else if (clazz == Character.TYPE) {
		type = "C";
	    } else if (clazz == Boolean.TYPE) {
		type = "Z";
	    } else if (clazz == Void.TYPE) {
		type = "V";
	    }
	} else {
	    type = "L" + clazz.getName().replace('.', '/') + ";";
	}
	return type;
    }

    /*
     * Compute the JVM method descriptor for the method.
     */