--- /dev/null
+/*
+ * Copyright 2004-2010 Brian S O'Neill
+ *
+ * Licensed 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.cojen.classfile;
+
+import java.io.Serializable;
+import java.io.Externalizable;
+import java.io.ObjectOutput;
+import java.io.ObjectInput;
+import java.io.IOException;
+import java.io.ObjectStreamException;
+import java.lang.ref.SoftReference;
+import java.lang.reflect.Array;
+import java.util.Collections;
+import java.util.Map;
+
+import org.cojen.util.SoftValuedHashMap;
+import org.cojen.util.WeakCanonicalSet;
+import org.cojen.util.WeakIdentityMap;
+
+/**
+ * This class is used to build field and return type descriptor strings as
+ * defined in <i>The Java Virtual Machine Specification</i>, section 4.3.2.
+ * TypeDesc instances are canonicalized and therefore "==" comparable.
+ *
+ * @author Brian S O'Neill
+ */
+@SuppressWarnings("rawtypes")
+public abstract class TypeDesc extends Descriptor implements Serializable {
+ /**
+ * Type code returned from getTypeCode, which can be used with the
+ * newarray instruction.
+ */
+ public final static int
+ OBJECT_CODE = 0,
+ VOID_CODE = 1,
+ BOOLEAN_CODE = 4,
+ CHAR_CODE = 5,
+ FLOAT_CODE = 6,
+ DOUBLE_CODE = 7,
+ BYTE_CODE = 8,
+ SHORT_CODE = 9,
+ INT_CODE = 10,
+ LONG_CODE = 11;
+
+ /** Primitive type void */
+ public final static TypeDesc VOID;
+ /** Primitive type boolean */
+ public final static TypeDesc BOOLEAN;
+ /** Primitive type char */
+ public final static TypeDesc CHAR;
+ /** Primitive type byte */
+ public final static TypeDesc BYTE;
+ /** Primitive type short */
+ public final static TypeDesc SHORT;
+ /** Primitive type int */
+ public final static TypeDesc INT;
+ /** Primitive type long */
+ public final static TypeDesc LONG;
+ /** Primitive type float */
+ public final static TypeDesc FLOAT;
+ /** Primitive type double */
+ public final static TypeDesc DOUBLE;
+
+ /** Object type java.lang.Object, provided for convenience */
+ public final static TypeDesc OBJECT;
+ /** Object type java.lang.String, provided for convenience */
+ public final static TypeDesc STRING;
+
+ // Pool of all shared instances. Ensures identity comparison works.
+ final static WeakCanonicalSet<Descriptor> cInstances;
+
+ // Cache that maps Classes to TypeDescs.
+ private final static Map<Class, TypeDesc> cClassesToInstances;
+
+ // Cache that maps String names to TypeDescs.
+ private final static Map<String, TypeDesc> cNamesToInstances;
+
+ // Cache that maps String descriptors to TypeDescs.
+ private final static Map<String, TypeDesc> cDescriptorsToInstances;
+
+ static {
+ cInstances = new WeakCanonicalSet<Descriptor>();
+
+ cClassesToInstances = Collections.synchronizedMap(new WeakIdentityMap<Class, TypeDesc>());
+ cNamesToInstances = Collections.synchronizedMap(new SoftValuedHashMap<String, TypeDesc>());
+ cDescriptorsToInstances = Collections.synchronizedMap
+ (new SoftValuedHashMap<String, TypeDesc>());
+
+ VOID = intern(new PrimitiveType("V", VOID_CODE));
+ BOOLEAN = intern(new PrimitiveType("Z", BOOLEAN_CODE));
+ CHAR = intern(new PrimitiveType("C", CHAR_CODE));
+ BYTE = intern(new PrimitiveType("B", BYTE_CODE));
+ SHORT = intern(new PrimitiveType("S", SHORT_CODE));
+ INT = intern(new PrimitiveType("I", INT_CODE));
+ LONG = intern(new PrimitiveType("J", LONG_CODE));
+ FLOAT = intern(new PrimitiveType("F", FLOAT_CODE));
+ DOUBLE = intern(new PrimitiveType("D", DOUBLE_CODE));
+
+ OBJECT = forClass("java.lang.Object");
+ STRING = forClass("java.lang.String");
+ }
+
+ static TypeDesc intern(TypeDesc type) {
+ return cInstances.put(type);
+ }
+
+ /**
+ * Acquire a TypeDesc from any class, including primitives and arrays.
+ */
+ public static TypeDesc forClass(final Class clazz) {
+ if (clazz == null) {
+ return null;
+ }
+
+ TypeDesc type = (TypeDesc)cClassesToInstances.get(clazz);
+
+ if (type == null || type.toClass() != clazz) {
+ if (clazz.isArray()) {
+ type = forClass(clazz.getComponentType()).toArrayType();
+ } else if (clazz.isPrimitive()) {
+ if (clazz == int.class) {
+ type = INT;
+ } else if (clazz == boolean.class) {
+ type = BOOLEAN;
+ } else if (clazz == char.class) {
+ type = CHAR;
+ } else if (clazz == byte.class) {
+ type = BYTE;
+ } else if (clazz == long.class) {
+ type = LONG;
+ } else if (clazz == float.class) {
+ type = FLOAT;
+ } else if (clazz == double.class) {
+ type = DOUBLE;
+ } else if (clazz == short.class) {
+ type = SHORT;
+ } else if (clazz == void.class) {
+ type = VOID;
+ }
+ } else {
+ String name = clazz.getName();
+ type = intern(new ObjectType(generateDescriptor(name), name));
+ }
+
+ if (type.toClass() != clazz) {
+ type = new ObjectType(type.getDescriptor(), clazz.getName());
+ ((ObjectType) type).setClass(clazz);
+ }
+
+ synchronized (cClassesToInstances) {
+ if (cClassesToInstances.containsKey(clazz)) {
+ type = (TypeDesc)cClassesToInstances.get(clazz);
+ } else {
+ cClassesToInstances.put(clazz, type);
+ }
+ }
+ }
+
+ return type;
+ }
+
+ /**
+ * Acquire a TypeDesc from any class name, including primitives and arrays.
+ * Primitive and array syntax matches Java declarations.
+ */
+ public static TypeDesc forClass(final String name) throws IllegalArgumentException {
+ if (name.length() < 1) {
+ throw invalidName(name);
+ }
+
+ // TODO: Support generics in name.
+
+ TypeDesc type = (TypeDesc)cNamesToInstances.get(name);
+ if (type != null) {
+ return type;
+ }
+
+ int index1 = name.lastIndexOf('[');
+ int index2 = name.lastIndexOf(']');
+ if (index2 >= 0) {
+ if (index2 + 1 != name.length() || index1 + 1 != index2) {
+ throw invalidName(name);
+ }
+ try {
+ type = forClass(name.substring(0, index1)).toArrayType();
+ } catch (IllegalArgumentException e) {
+ throw invalidName(name);
+ }
+ } else if (index1 >= 0) {
+ throw invalidName(name);
+ } else {
+ setType: {
+ switch (name.charAt(0)) {
+ case 'v':
+ if (name.equals("void")) {
+ type = VOID;
+ break setType;
+ }
+ break;
+ case 'b':
+ if (name.equals("boolean")) {
+ type = BOOLEAN;
+ break setType;
+ } else if (name.equals("byte")) {
+ type = BYTE;
+ break setType;
+ }
+ break;
+ case 'c':
+ if (name.equals("char")) {
+ type = CHAR;
+ break setType;
+ }
+ break;
+ case 's':
+ if (name.equals("short")) {
+ type = SHORT;
+ break setType;
+ }
+ break;
+ case 'i':
+ if (name.equals("int")) {
+ type = INT;
+ break setType;
+ }
+ break;
+ case 'l':
+ if (name.equals("long")) {
+ type = LONG;
+ break setType;
+ }
+ break;
+ case 'f':
+ if (name.equals("float")) {
+ type = FLOAT;
+ break setType;
+ }
+ break;
+ case 'd':
+ if (name.equals("double")) {
+ type = DOUBLE;
+ break setType;
+ }
+ break;
+ }
+
+ String desc = generateDescriptor(name);
+ if (name.indexOf('/') < 0) {
+ type = new ObjectType(desc, name);
+ } else {
+ type = new ObjectType(desc, name.replace('/', '.'));
+ }
+ type = intern(type);
+ }
+ }
+
+ cNamesToInstances.put(name, type);
+ return type;
+ }
+
+ private static IllegalArgumentException invalidName(String name) {
+ return new IllegalArgumentException("Invalid name: " + name);
+ }
+
+ /**
+ * Acquire a TypeDesc from a type descriptor. This syntax is described in
+ * section 4.3.2, Field Descriptors.
+ */
+ public static TypeDesc forDescriptor(final String desc) throws IllegalArgumentException {
+ TypeDesc type = (TypeDesc)cDescriptorsToInstances.get(desc);
+ if (type != null) {
+ return type;
+ }
+
+ // TODO: Support generics in descriptor.
+
+ String rootDesc = desc;
+ int cursor = 0;
+ int dim = 0;
+ try {
+ char c;
+ while ((c = rootDesc.charAt(cursor++)) == '[') {
+ dim++;
+ }
+
+ switch (c) {
+ case 'V':
+ type = VOID;
+ break;
+ case 'Z':
+ type = BOOLEAN;
+ break;
+ case 'C':
+ type = CHAR;
+ break;
+ case 'B':
+ type = BYTE;
+ break;
+ case 'S':
+ type = SHORT;
+ break;
+ case 'I':
+ type = INT;
+ break;
+ case 'J':
+ type = LONG;
+ break;
+ case 'F':
+ type = FLOAT;
+ break;
+ case 'D':
+ type = DOUBLE;
+ break;
+ case 'L':
+ if (dim > 0) {
+ rootDesc = rootDesc.substring(dim);
+ cursor = 1;
+ }
+ StringBuffer name = new StringBuffer(rootDesc.length() - 2);
+ while ((c = rootDesc.charAt(cursor++)) != ';') {
+ if (c == '/') {
+ c = '.';
+ }
+ name.append(c);
+ }
+ type = intern(new ObjectType(rootDesc, name.toString()));
+ break;
+ default:
+ throw invalidDescriptor(desc);
+ }
+ } catch (NullPointerException e) {
+ throw invalidDescriptor(desc);
+ } catch (IndexOutOfBoundsException e) {
+ throw invalidDescriptor(desc);
+ }
+
+ if (cursor != rootDesc.length()) {
+ throw invalidDescriptor(desc);
+ }
+
+ while (--dim >= 0) {
+ type = type.toArrayType();
+ }
+
+ cDescriptorsToInstances.put(desc, type);
+ return type;
+ }
+
+ private static IllegalArgumentException invalidDescriptor(String desc) {
+ return new IllegalArgumentException("Invalid descriptor: " + desc);
+ }
+
+ private static String generateDescriptor(String classname) {
+ int length = classname.length();
+ char[] buf = new char[length + 2];
+ buf[0] = 'L';
+ classname.getChars(0, length, buf, 1);
+ int i;
+ for (i=1; i<=length; i++) {
+ char c = buf[i];
+ if (c == '.') {
+ buf[i] = '/';
+ }
+ }
+ buf[i] = ';';
+ return new String(buf);
+ }
+
+ transient final String mDescriptor;
+
+ TypeDesc(String desc) {
+ mDescriptor = desc;
+ }
+
+ /**
+ * Returns a type descriptor string, excluding generics.
+ */
+ public final String getDescriptor() {
+ return mDescriptor;
+ }
+
+ /**
+ * Returns a type descriptor string, including any generics.
+ */
+ //public abstract String getGenericDescriptor();
+
+ /**
+ * Returns the class name for this descriptor. If the type is primitive,
+ * then the Java primitive type name is returned. If the type is an array,
+ * only the root component type name is returned.
+ */
+ public abstract String getRootName();
+
+ /**
+ * Returns the class name for this descriptor. If the type is primitive,
+ * then the Java primitive type name is returned. If the type is an array,
+ * "[]" is append at the end of the name for each dimension.
+ */
+ public abstract String getFullName();
+
+ // TODO
+ //public abstract String getGenericRootName();
+
+ // TODO
+ //public abstract String getGenericFullName();
+
+ /**
+ * Returns a type code for operating on primitive types in switches. If
+ * not primitive, OBJECT_CODE is returned.
+ */
+ public abstract int getTypeCode();
+
+ /**
+ * Returns true if this is a primitive type.
+ */
+ public abstract boolean isPrimitive();
+
+ /**
+ * Returns true if this is a primitive long or double type.
+ */
+ public abstract boolean isDoubleWord();
+
+ /**
+ * Returns true if this is an array type.
+ */
+ public abstract boolean isArray();
+
+ /**
+ * Returns the number of dimensions this array type has. If not an array,
+ * zero is returned.
+ */
+ public abstract int getDimensions();
+
+ /**
+ * Returns the component type of this array type. If not an array, null is
+ * returned.
+ */
+ public abstract TypeDesc getComponentType();
+
+ /**
+ * Returns the root component type of this array type. If not an array,
+ * null is returned.
+ */
+ public abstract TypeDesc getRootComponentType();
+
+ /**
+ * Convertes this type to an array type. If already an array, another
+ * dimension is added.
+ */
+ public abstract TypeDesc toArrayType();
+
+ /**
+ * Returns the object peer of this primitive type. For int, the object peer
+ * is java.lang.Integer. If this type is an object type, it is simply
+ * returned.
+ */
+ public abstract TypeDesc toObjectType();
+
+ /**
+ * Returns the primitive peer of this object type, if one exists. For
+ * java.lang.Integer, the primitive peer is int. If this type is a
+ * primitive type, it is simply returned. Arrays have no primitive peer,
+ * and so null is returned instead.
+ */
+ public abstract TypeDesc toPrimitiveType();
+
+ /**
+ * Returns this type as a class. If the class isn't found, null is
+ * returned.
+ */
+ public abstract Class toClass();
+
+ /**
+ * Returns this type as a class. If the class isn't found, null is
+ * returned.
+ * @param loader optional ClassLoader to load class from
+ */
+ public abstract Class toClass(ClassLoader loader);
+
+ public String toString() {
+ // TODO: Return generic descriptor
+ return mDescriptor;
+ }
+
+ public int hashCode() {
+ return mDescriptor.hashCode();
+ }
+
+ public boolean equals(Object other) {
+ if (this == other) {
+ return true;
+ }
+ if (other instanceof TypeDesc) {
+ return ((TypeDesc)other).mDescriptor.equals(mDescriptor);
+ }
+ return false;
+ }
+
+ Object writeReplace() throws ObjectStreamException {
+ return new External(mDescriptor);
+ }
+
+ private static class PrimitiveType extends TypeDesc {
+ private transient final int mCode;
+ private transient TypeDesc mArrayType;
+ private transient TypeDesc mObjectType;
+
+ PrimitiveType(String desc, int code) {
+ super(desc);
+ mCode = code;
+ }
+
+ public String getRootName() {
+ switch (mCode) {
+ default:
+ case VOID_CODE:
+ return "void";
+ case BOOLEAN_CODE:
+ return "boolean";
+ case CHAR_CODE:
+ return "char";
+ case BYTE_CODE:
+ return "byte";
+ case SHORT_CODE:
+ return "short";
+ case INT_CODE:
+ return "int";
+ case LONG_CODE:
+ return "long";
+ case FLOAT_CODE:
+ return "float";
+ case DOUBLE_CODE:
+ return "double";
+ }
+ }
+
+ public String getFullName() {
+ return getRootName();
+ }
+
+ public int getTypeCode() {
+ return mCode;
+ }
+
+ public boolean isPrimitive() {
+ return true;
+ }
+
+ public boolean isDoubleWord() {
+ return mCode == DOUBLE_CODE || mCode == LONG_CODE;
+ }
+
+ public boolean isArray() {
+ return false;
+ }
+
+ public int getDimensions() {
+ return 0;
+ }
+
+ public TypeDesc getComponentType() {
+ return null;
+ }
+
+ public TypeDesc getRootComponentType() {
+ return null;
+ }
+
+ public TypeDesc toArrayType() {
+ if (mArrayType == null) {
+ char[] buf = new char[2];
+ buf[0] = '[';
+ buf[1] = mDescriptor.charAt(0);
+ mArrayType = intern(new ArrayType(new String(buf), this));
+ }
+ return mArrayType;
+ }
+
+ public TypeDesc toObjectType() {
+ if (mObjectType == null) {
+ switch (mCode) {
+ default:
+ case VOID_CODE:
+ mObjectType = forClass("java.lang.Void");
+ break;
+ case BOOLEAN_CODE:
+ mObjectType = forClass("java.lang.Boolean");
+ break;
+ case CHAR_CODE:
+ mObjectType = forClass("java.lang.Character");
+ break;
+ case BYTE_CODE:
+ mObjectType = forClass("java.lang.Byte");
+ break;
+ case SHORT_CODE:
+ mObjectType = forClass("java.lang.Short");
+ break;
+ case INT_CODE:
+ mObjectType = forClass("java.lang.Integer");
+ break;
+ case LONG_CODE:
+ mObjectType = forClass("java.lang.Long");
+ break;
+ case FLOAT_CODE:
+ mObjectType = forClass("java.lang.Float");
+ break;
+ case DOUBLE_CODE:
+ mObjectType = forClass("java.lang.Double");
+ break;
+ }
+ }
+ return mObjectType;
+ }
+
+ public TypeDesc toPrimitiveType() {
+ return this;
+ }
+
+ public Class toClass() {
+ switch (mCode) {
+ default:
+ case VOID_CODE:
+ return void.class;
+ case BOOLEAN_CODE:
+ return boolean.class;
+ case CHAR_CODE:
+ return char.class;
+ case BYTE_CODE:
+ return byte.class;
+ case SHORT_CODE:
+ return short.class;
+ case INT_CODE:
+ return int.class;
+ case LONG_CODE:
+ return long.class;
+ case FLOAT_CODE:
+ return float.class;
+ case DOUBLE_CODE:
+ return double.class;
+ }
+ }
+
+ public Class toClass(ClassLoader loader) {
+ return toClass();
+ }
+ }
+
+ private static class ObjectType extends TypeDesc {
+ private transient final String mName;
+ private transient TypeDesc mArrayType;
+ private transient TypeDesc mPrimitiveType;
+
+ // Since cClassesToInstances may reference this instance, softly
+ // reference back to class to allow it to be garbage collected.
+ private transient SoftReference<Class> mClassRef;
+
+ ObjectType(String desc, String name) {
+ super(desc);
+ mName = name;
+ }
+
+ public String getRootName() {
+ return mName;
+ }
+
+ public String getFullName() {
+ return mName;
+ }
+
+ public int getTypeCode() {
+ return OBJECT_CODE;
+ }
+
+ public boolean isPrimitive() {
+ return false;
+ }
+
+ public boolean isDoubleWord() {
+ return false;
+ }
+
+ public boolean isArray() {
+ return false;
+ }
+
+ public int getDimensions() {
+ return 0;
+ }
+
+ public TypeDesc getComponentType() {
+ return null;
+ }
+
+ public TypeDesc getRootComponentType() {
+ return null;
+ }
+
+ public TypeDesc toArrayType() {
+ if (mArrayType == null) {
+ int length = mDescriptor.length();
+ char[] buf = new char[length + 1];
+ buf[0] = '[';
+ mDescriptor.getChars(0, length, buf, 1);
+ mArrayType = intern(new ArrayType(new String(buf), this));
+ }
+ return mArrayType;
+ }
+
+ public TypeDesc toObjectType() {
+ return this;
+ }
+
+ public TypeDesc toPrimitiveType() {
+ if (mPrimitiveType == null) {
+ String name = mName;
+ if (name.startsWith("java.lang.") && name.length() > 10) {
+ switch (name.charAt(10)) {
+ case 'V':
+ if (name.equals("java.lang.Void")) {
+ mPrimitiveType = VOID;
+ }
+ break;
+ case 'B':
+ if (name.equals("java.lang.Boolean")) {
+ mPrimitiveType = BOOLEAN;
+ } else if (name.equals("java.lang.Byte")) {
+ mPrimitiveType = BYTE;
+ }
+ break;
+ case 'C':
+ if (name.equals("java.lang.Character")) {
+ mPrimitiveType = CHAR;
+ }
+ break;
+ case 'S':
+ if (name.equals("java.lang.Short")) {
+ mPrimitiveType = SHORT;
+ }
+ break;
+ case 'I':
+ if (name.equals("java.lang.Integer")) {
+ mPrimitiveType = INT;
+ }
+ break;
+ case 'L':
+ if (name.equals("java.lang.Long")) {
+ mPrimitiveType = LONG;
+ }
+ break;
+ case 'F':
+ if (name.equals("java.lang.Float")) {
+ mPrimitiveType = FLOAT;
+ }
+ break;
+ case 'D':
+ if (name.equals("java.lang.Double")) {
+ mPrimitiveType = DOUBLE;
+ }
+ break;
+ }
+ }
+ }
+
+ return mPrimitiveType;
+ }
+
+ public final synchronized Class toClass() {
+ Class clazz;
+ if (mClassRef != null) {
+ clazz = mClassRef.get();
+ if (clazz != null) {
+ return clazz;
+ }
+ }
+ clazz = toClass(null);
+ mClassRef = new SoftReference<Class>(clazz);
+ return clazz;
+ }
+
+ public Class toClass(ClassLoader loader) {
+ TypeDesc type = toPrimitiveType();
+ if (type != null) {
+ switch (type.getTypeCode()) {
+ default:
+ case VOID_CODE:
+ return Void.class;
+ case BOOLEAN_CODE:
+ return Boolean.class;
+ case CHAR_CODE:
+ return Character.class;
+ case FLOAT_CODE:
+ return Float.class;
+ case DOUBLE_CODE:
+ return Double.class;
+ case BYTE_CODE:
+ return Byte.class;
+ case SHORT_CODE:
+ return Short.class;
+ case INT_CODE:
+ return Integer.class;
+ case LONG_CODE:
+ return Long.class;
+ }
+ }
+
+ try {
+ if (loader == null) {
+ return Class.forName(mName);
+ } else {
+ return loader.loadClass(mName);
+ }
+ } catch (ClassNotFoundException e) {
+ return null;
+ }
+ }
+
+ void setClass(Class clazz) {
+ mClassRef = new SoftReference<Class>(clazz);
+ }
+ }
+
+ private static class ArrayType extends ObjectType {
+ private transient final TypeDesc mComponent;
+ private transient final String mFullName;
+
+ ArrayType(String desc, TypeDesc component) {
+ super(desc, component.getRootName());
+ mComponent = component;
+ mFullName = component.getFullName().concat("[]");
+ }
+
+ public String getFullName() {
+ return mFullName;
+ }
+
+ public boolean isArray() {
+ return true;
+ }
+
+ public int getDimensions() {
+ return mComponent.getDimensions() + 1;
+ }
+
+ public TypeDesc getComponentType() {
+ return mComponent;
+ }
+
+ public TypeDesc getRootComponentType() {
+ TypeDesc type = mComponent;
+ while (type.isArray()) {
+ type = type.getComponentType();
+ }
+ return type;
+ }
+
+ public TypeDesc toPrimitiveType() {
+ return null;
+ }
+
+ public Class toClass(ClassLoader loader) {
+ if (loader == null) {
+ return arrayClass(getRootComponentType().toClass());
+ } else {
+ return arrayClass(getRootComponentType().toClass(loader));
+ }
+ }
+
+ private Class arrayClass(Class clazz) {
+ if (clazz == null) {
+ return null;
+ }
+ int dim = getDimensions();
+ try {
+ if (dim == 1) {
+ return Array.newInstance(clazz, 0).getClass();
+ } else {
+ return Array.newInstance(clazz, new int[dim]).getClass();
+ }
+ } catch (IllegalArgumentException e) {
+ return null;
+ }
+ }
+ }
+
+ private static class External implements Externalizable {
+ private String mDescriptor;
+
+ public External() {
+ }
+
+ public External(String desc) {
+ mDescriptor = desc;
+ }
+
+ public void writeExternal(ObjectOutput out) throws IOException {
+ out.writeUTF(mDescriptor);
+ }
+
+ public void readExternal(ObjectInput in) throws IOException {
+ mDescriptor = in.readUTF();
+ }
+
+ public Object readResolve() throws ObjectStreamException {
+ return forDescriptor(mDescriptor);
+ }
+ }
+}
Code Review / simantics / platform.git / blobdiff