step.java

java1.6众多例子参考

		il.append(new INVOKEINTERFACE(iter, 3));
		return;
	    }

	    SyntaxTreeNode parent = getParent();
	    // Special case for '.'
	    if (isAbbreviatedDot()) {
		if (_type == Type.Node) {
		    // Put context node on stack if using Type.Node
		    il.append(methodGen.loadContextNode());
		}
		else {
		    if (parent instanceof ParentLocationPath){
			// Wrap the context node in a singleton iterator if not.
			int init = cpg.addMethodref(SINGLETON_ITERATOR,
						    "<init>",
						    "("+NODE_SIG+")V");
			il.append(new NEW(cpg.addClass(SINGLETON_ITERATOR)));
			il.append(DUP);
			il.append(methodGen.loadContextNode());
			il.append(new INVOKESPECIAL(init));
		    } else {
			// DOM.getAxisIterator(int axis);
			int git = cpg.addInterfaceMethodref(DOM_INTF,
						"getAxisIterator",
						"(I)"+NODE_ITERATOR_SIG);
			il.append(methodGen.loadDOM());
			il.append(new PUSH(cpg, _axis));
			il.append(new INVOKEINTERFACE(git, 2));
		    }
		}
		return;
	    }

	    // Special case for /foo/*/bar
	    if ((parent instanceof ParentLocationPath) &&
		(parent.getParent() instanceof ParentLocationPath)) {
		if ((_nodeType == NodeTest.ELEMENT) && (!_hadPredicates)) {
		    _nodeType = NodeTest.ANODE;
		}
	    }

	    // "ELEMENT" or "*" or "@*" or ".." or "@attr" with a parent.
	    switch (_nodeType) {
	    case NodeTest.ATTRIBUTE:
		_axis = Axis.ATTRIBUTE;
	    case NodeTest.ANODE:
		// DOM.getAxisIterator(int axis);
		int git = cpg.addInterfaceMethodref(DOM_INTF,
						    "getAxisIterator",
						    "(I)"+NODE_ITERATOR_SIG);
		il.append(methodGen.loadDOM());
		il.append(new PUSH(cpg, _axis));
		il.append(new INVOKEINTERFACE(git, 2));
		break;
	    default:
		if (star > 1) {
		    final String namespace;
		    if (_axis == Axis.ATTRIBUTE)
			namespace = name.substring(0,star-2);
		    else
			namespace = name.substring(0,star-1);

		    final int nsType = xsltc.registerNamespace(namespace);
		    final int ns = cpg.addInterfaceMethodref(DOM_INTF,
						    "getNamespaceAxisIterator",
						    "(II)"+NODE_ITERATOR_SIG);
		    il.append(methodGen.loadDOM());
		    il.append(new PUSH(cpg, _axis));
		    il.append(new PUSH(cpg, nsType));
		    il.append(new INVOKEINTERFACE(ns, 3));
		    break;
		}
	    case NodeTest.ELEMENT:
		// DOM.getTypedAxisIterator(int axis, int type);
		final int ty = cpg.addInterfaceMethodref(DOM_INTF,
						"getTypedAxisIterator",
						"(II)"+NODE_ITERATOR_SIG);
		// Get the typed iterator we're after
		il.append(methodGen.loadDOM());
		il.append(new PUSH(cpg, _axis));
		il.append(new PUSH(cpg, _nodeType));
		il.append(new INVOKEINTERFACE(ty, 3));

		break;
	    }
	}
    }


    /**
     * Translate a sequence of predicates. Each predicate is translated
     * by constructing an instance of <code>CurrentNodeListIterator</code>
     * which is initialized from another iterator (recursive call),
     * a filter and a closure (call to translate on the predicate) and "this". 
     */
    public void translatePredicates(ClassGenerator classGen,
				    MethodGenerator methodGen) {
	final ConstantPoolGen cpg = classGen.getConstantPool();
	final InstructionList il = methodGen.getInstructionList();

	int idx = 0;

	if (_predicates.size() == 0) {
	    translate(classGen, methodGen);
	}
	else {
	    final Predicate predicate = (Predicate)_predicates.lastElement();
	    _predicates.remove(predicate);

	    // Special case for predicates that can use the NodeValueIterator
	    // instead of an auxiliary class. Certain path/predicates pairs
	    // are translated into a base path, on top of which we place a
	    // node value iterator that tests for the desired value:
	    //   foo[@attr = 'str']  ->  foo/@attr + test(value='str')
	    //   foo[bar = 'str']    ->  foo/bar + test(value='str')
	    //   foo/bar[. = 'str']  ->  foo/bar + test(value='str')
	    if (predicate.isNodeValueTest()) {
		Step step = predicate.getStep();

		il.append(methodGen.loadDOM());
		// If the predicate's Step is simply '.' we translate this Step
		// and place the node test on top of the resulting iterator
		if (step.isAbbreviatedDot()) {
		    translate(classGen, methodGen);
		    il.append(new ICONST(DOM.RETURN_CURRENT));
		}
		// Otherwise we create a parent location path with this Step and
		// the predicates Step, and place the node test on top of that
		else {
		    ParentLocationPath path = new ParentLocationPath(this, step);
                    _parent = step._parent = path;      // Force re-parenting
                    
		    try {
			path.typeCheck(getParser().getSymbolTable());
		    }
		    catch (TypeCheckError e) { }
		    path.translate(classGen, methodGen);
		    il.append(new ICONST(DOM.RETURN_PARENT));
		}
		predicate.translate(classGen, methodGen);
		idx = cpg.addInterfaceMethodref(DOM_INTF,
						GET_NODE_VALUE_ITERATOR,
						GET_NODE_VALUE_ITERATOR_SIG);
		il.append(new INVOKEINTERFACE(idx, 5));
	    }            
	    // Handle '//*[n]' expression
	    else if (predicate.isNthDescendant()) {
		il.append(methodGen.loadDOM());
		// il.append(new ICONST(NodeTest.ELEMENT));
		il.append(new ICONST(predicate.getPosType()));
		predicate.translate(classGen, methodGen);
		il.append(new ICONST(0));
		idx = cpg.addInterfaceMethodref(DOM_INTF,
						"getNthDescendant",
						"(IIZ)"+NODE_ITERATOR_SIG);
		il.append(new INVOKEINTERFACE(idx, 4));
	    }
	    // Handle 'elem[n]' expression
	    else if (predicate.isNthPositionFilter()) {
		idx = cpg.addMethodref(NTH_ITERATOR_CLASS,
				       "<init>",
				       "("+NODE_ITERATOR_SIG+"I)V");

                // Backwards branches are prohibited if an uninitialized object
                // is on the stack by section 4.9.4 of the JVM Specification,
                // 2nd Ed.  We don't know whether this code might contain
                // backwards branches, so we mustn't create the new object until
                // after we've created the suspect arguments to its constructor.
                // Instead we calculate the values of the arguments to the
                // constructor first, store them in temporary variables, create
                // the object and reload the arguments from the temporaries to
                // avoid the problem.
		translatePredicates(classGen, methodGen); // recursive call
                LocalVariableGen iteratorTemp
                        = methodGen.addLocalVariable("step_tmp1",
                                         Util.getJCRefType(NODE_ITERATOR_SIG),
                                         il.getEnd(), null);
                il.append(new ASTORE(iteratorTemp.getIndex()));

		predicate.translate(classGen, methodGen);
                LocalVariableGen predicateValueTemp
                        = methodGen.addLocalVariable("step_tmp2",
                                         Util.getJCRefType("I"),
                                         il.getEnd(), null);
                il.append(new ISTORE(predicateValueTemp.getIndex()));

		il.append(new NEW(cpg.addClass(NTH_ITERATOR_CLASS)));
		il.append(DUP);
                il.append(new ALOAD(iteratorTemp.getIndex()));
                il.append(new ILOAD(predicateValueTemp.getIndex()));
		il.append(new INVOKESPECIAL(idx));
	    }
	    else {
		idx = cpg.addMethodref(CURRENT_NODE_LIST_ITERATOR,
				       "<init>",
				       "("
				       + NODE_ITERATOR_SIG
				       + CURRENT_NODE_LIST_FILTER_SIG
				       + NODE_SIG
				       + TRANSLET_SIG
				       + ")V");

                // Backwards branches are prohibited if an uninitialized object
                // is on the stack by section 4.9.4 of the JVM Specification,
                // 2nd Ed.  We don't know whether this code might contain
                // backwards branches, so we mustn't create the new object until
                // after we've created the suspect arguments to its constructor.
                // Instead we calculate the values of the arguments to the
                // constructor first, store them in temporary variables, create
                // the object and reload the arguments from the temporaries to
                // avoid the problem.
		translatePredicates(classGen, methodGen); // recursive call
                LocalVariableGen iteratorTemp
                        = methodGen.addLocalVariable("step_tmp1",
                                         Util.getJCRefType(NODE_ITERATOR_SIG),
                                         il.getEnd(), null);
                il.append(new ASTORE(iteratorTemp.getIndex()));

		predicate.translateFilter(classGen, methodGen);
                LocalVariableGen filterTemp
                        = methodGen.addLocalVariable("step_tmp2",
                              Util.getJCRefType(CURRENT_NODE_LIST_FILTER_SIG),
                              il.getEnd(), null);
                il.append(new ASTORE(filterTemp.getIndex()));

		// create new CurrentNodeListIterator
		il.append(new NEW(cpg.addClass(CURRENT_NODE_LIST_ITERATOR)));
		il.append(DUP);

                il.append(new ALOAD(iteratorTemp.getIndex()));
                il.append(new ALOAD(filterTemp.getIndex()));
		
		il.append(methodGen.loadCurrentNode());
		il.append(classGen.loadTranslet());
		if (classGen.isExternal()) {
		    final String className = classGen.getClassName();
		    il.append(new CHECKCAST(cpg.addClass(className)));
		}
		il.append(new INVOKESPECIAL(idx));
	    }
	}
    }

    /**
     * Returns a string representation of this step.
     */
    public String toString() {
	final StringBuffer buffer = new StringBuffer("step(\"");
        buffer.append(Axis.getNames(_axis)).append("\", ").append(_nodeType);
	if (_predicates != null) {
	    final int n = _predicates.size();
	    for (int i = 0; i < n; i++) {
		final Predicate pred = (Predicate)_predicates.elementAt(i);
		buffer.append(", ").append(pred.toString());
	    }
	}
	return buffer.append(')').toString();
    }
}