/interpreter/tags/at2dist041108/src/edu/vub/at/objects/mirrors/NATIntrospectiveMirror.java
http://ambienttalk.googlecode.com/ · Java · 251 lines · 94 code · 24 blank · 133 comment · 8 complexity · 8b5f17870b3486e06317149be9820316 MD5 · raw file
- /**
- * AmbientTalk/2 Project
- * NATMirror.java created on Aug 13, 2006 at 10:09:29 AM
- * (c) Programming Technology Lab, 2006 - 2007
- * Authors: Tom Van Cutsem & Stijn Mostinckx
- *
- * Permission is hereby granted, free of charge, to any person
- * obtaining a copy of this software and associated documentation
- * files (the "Software"), to deal in the Software without
- * restriction, including without limitation the rights to use,
- * copy, modify, merge, publish, distribute, sublicense, and/or
- * sell copies of the Software, and to permit persons to whom the
- * Software is furnished to do so, subject to the following
- * conditions:
- *
- * The above copyright notice and this permission notice shall be
- * included in all copies or substantial portions of the Software.
- *
- * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
- * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
- * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
- * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
- * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
- * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
- * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
- * OTHER DEALINGS IN THE SOFTWARE.
- */
- package edu.vub.at.objects.mirrors;
- import edu.vub.at.actors.net.OBJNetwork;
- import edu.vub.at.eval.Evaluator;
- import edu.vub.at.exceptions.InterpreterException;
- import edu.vub.at.exceptions.XArityMismatch;
- import edu.vub.at.exceptions.XIllegalOperation;
- import edu.vub.at.exceptions.XSelectorNotFound;
- import edu.vub.at.exceptions.XTypeMismatch;
- import edu.vub.at.objects.ATBoolean;
- import edu.vub.at.objects.ATMethod;
- import edu.vub.at.objects.ATObject;
- import edu.vub.at.objects.ATTable;
- import edu.vub.at.objects.coercion.NativeTypeTags;
- import edu.vub.at.objects.grammar.ATSymbol;
- import edu.vub.at.objects.natives.NATBoolean;
- import edu.vub.at.objects.natives.NATByRef;
- import edu.vub.at.objects.natives.NATNil;
- import edu.vub.at.objects.natives.NATNumber;
- import edu.vub.at.objects.natives.NATTable;
- import edu.vub.at.objects.natives.NATText;
- /**
- * <p>NATIntrospectiveMirror is a default mirror to represent an ambienttalk object
- * which is capable of offering the java meta-interface of any language value at the
- * ambienttalk level. This allows introspection into the language value's internals
- * as well as invoking some meta-level operations on it. Technically, NATMirror is
- * simply a wrapper object around an ambienttalk object which deifies (ups) methods
- * invoked upon it.</p>
- *
- * <p>Note that whereas the mirror can offer e.g. an apply method when reifying a
- * closure, this does not affect its own meta-interface. A NATMirror is always an
- * object and can thus not be applied at the ambienttalk level.</p>
- *
- * Example:
- * <pre>
- * def clo := { | x | x * 2 };
- * def m := at.mirrors.Factory.createMirror(clo);
- *
- * clo( 5 ) <i> => 10 (legal) </i>
- * m.apply([5]) <i> => 10 (legal) </i>
- * m( 5 ) <i> => error (Application expected a closure, given a mirror) </i>
- * </pre>
- *
- * @author smostinc
- * @author tvcutsem
- */
- public class NATIntrospectiveMirror extends NATByRef {
- /** the object reflected on. This object is NOT a NATMirage */
- private final ATObject principal_;
-
- /**
- * Return a mirror on the given native or custom AmbientTalk object.
- *
- * @param objectRepresentation the object to reflect upon
- * @return either an introspective mirror (if the passed object is native), otherwise
- * a custom intercessive mirror.
- */
- public static final ATObject atValue(ATObject objectRepresentation) throws XTypeMismatch, XIllegalOperation {
- if (objectRepresentation.isMirage()) {
- ATObject mirror = objectRepresentation.asMirage().getMirror();
- if (mirror.equals(Evaluator.getNil())) {
- // this case is triggered if an introspective mirror is being created
- // for a new, empty, mirage object. Example:
- // object: {} mirroredBy: (reflect: (object:{}))
- // (here, reflect: (object:{}) returns an introspective mirror)
- //
- // Since mirages must be mirrored by intercessive mirrors, we simply return
- // a new instance of the defaultMirror (since introspective mirrors
- // encapsulate 'default' semantics anyway)
- return new NATMirrorRoot(objectRepresentation.asMirage());
- } else {
- return mirror;
- }
- } else {
- return new NATIntrospectiveMirror(objectRepresentation);
- }
- }
-
- /**
- * An introspective mirror is a wrapper which forwards a deified (upped) version of invoked
- * methods and field accesses to its principal. This principal is a Java object
- * representing an ambienttalk object. The deificiation process implies that
- * only the object's meta_level operations (implemented in Java) will be called
- * directly by the mirror.
- *
- * @param representation - the object to reflect upon, which is *not* a NATMirage
- */
- private NATIntrospectiveMirror(ATObject representation) {
- principal_ = representation;
- }
-
- public NATIntrospectiveMirror asNativeIntrospectiveMirror() {
- return this;
- }
- public boolean isNativeIntrospectiveMirror() {
- return true;
- }
- /**
- * This method is used to allow selecting the base field of an intercessive mirror using
- * the reflective selection of fields. This method is never invoked directly by the
- * implementation.
- * @return the base-level entity this mirror reflects on
- */
- public ATObject base_base() {
- return principal_;
- }
-
- public int hashCode() { return principal_.hashCode(); }
-
- public ATBoolean base__opeql__opeql_(ATObject other) throws InterpreterException {
- if (other.isNativeIntrospectiveMirror()) {
- return NATBoolean.atValue(principal_.equals(other.asNativeIntrospectiveMirror().principal_));
- } else {
- return NATBoolean._FALSE_;
- }
- }
-
- /* ------------------------------------------
- * -- Slot accessing and mutating protocol --
- * ------------------------------------------ */
-
- public ATMethod meta_grabMethod(ATSymbol methodName) throws InterpreterException {
- try {
- // try to find a meta_ method in the principal
- return Reflection.downMetaLevelMethod(principal_, methodName);
- } catch (XSelectorNotFound e) {
- e.catchOnlyIfSelectorEquals(methodName);
- // try to find a base_ method in the mirror
- return super.meta_grabMethod(methodName);
- }
- }
- /**
- * Listing the methods of a mirror requires us to list all of the meta_ methods
- * of the principal + all of the base_ methods of the mirror itself
- */
- public ATTable meta_listMethods() throws InterpreterException {
- ATMethod[] principalMetaMethods = Reflection.downMetaLevelMethods(principal_);
- ATMethod[] mirrorBaseMethods = Reflection.downBaseLevelMethods(this);
- return NATTable.atValue(NATTable.collate(principalMetaMethods, mirrorBaseMethods));
- }
-
- /* ------------------------------------
- * -- Extension and cloning protocol --
- * ------------------------------------ */
- /**
- * This method makes a new mirror object. However, since the link from a
- * mirror to its base object is immutable, this results in contacting the mirror
- * factory, to create a (new) mirror for the requested object.
- * @param initargs an ATObject[] containing as its first element the object that needs to be reflects upon
- * @return <b>another</b> (possibly new) mirror object
- */
- public ATObject meta_newInstance(ATTable initargs) throws InterpreterException {
- int len = initargs.base_length().asNativeNumber().javaValue;
- if (len != 1)
- throw new XArityMismatch("init method of mirror", 1, len);
- ATObject reflectee = initargs.base_at(NATNumber.ONE);
- return atValue(reflectee);
- }
-
- /* ---------------------------------
- * -- Abstract Grammar Protocol --
- * --------------------------------- */
-
- public NATText meta_print() throws InterpreterException {
- return NATText.atValue("<mirror on:"+principal_.meta_print().javaValue+">");
- }
-
- public ATTable meta_typeTags() throws InterpreterException {
- return NATTable.of(NativeTypeTags._MIRROR_);
- }
-
- /**
- * OBSOLETE: introspective mirrors are now pass-by-reference.
- * This has the following repercussions:
- * - when passing the mirror of an isolate, a remote ref to the mirror is passed instead.
- * The isolate is not copied.
- * - mirrors on far references can still be created, by passing the principal by ref
- * and by reflecting on the obtained far reference
- *
- * An introspective mirror is pass-by-copy.
- * When an introspective mirror is deserialized, it will become a mirror on
- * its deserialized principal. This means that, if the principal is passed
- * by copy, the mirror will be a local mirror on the copy. If the principal is passed
- * by reference, the mirror will be a local mirror on the far reference.
- */
- /*public ATObject meta_resolve() throws InterpreterException {
- if(principal_ instanceof NATMirage)
- return ((NATMirage)principal_).getMirror();
- else
- return this;
- }*/
- /**
- * For mirrors, first try to find a <tt>meta_</tt> method in the principal.
- * If this fails, try to find a <tt>base_</tt> method in the introspective mirror itself.
- */
- protected boolean hasLocalMethod(ATSymbol atSelector) throws InterpreterException {
- return Reflection.upRespondsTo(principal_, Reflection.upMetaLevelSelector(atSelector)) ||
- super.hasLocalMethod(atSelector);
- }
-
- /**
- * For mirrors, first try to find a <tt>meta_</tt> method in the principal.
- * If this fails, try to find a <tt>base_</tt> method in the introspective mirror itself.
- */
- protected ATMethod getLocalMethod(ATSymbol selector) throws InterpreterException {
- try {
- String methSelector = Reflection.upMetaLevelSelector(selector);
- return Reflection.upMethodSelection(principal_, methSelector, selector);
- } catch (XSelectorNotFound e) {
- e.catchOnlyIfSelectorEquals(selector);
- return super.getLocalMethod(selector);
- }
- }
- }