208 lines
7.5 KiB
JavaScript
208 lines
7.5 KiB
JavaScript
define("dojo/aspect", [], function(){
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// TODOC: after/before/around return object
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// TODOC: after/before/around param types.
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/*=====
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dojo.aspect = {
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// summary: provides aspect oriented programming functionality, allowing for
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// one to add before, around, or after advice on existing methods.
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//
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// example:
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// | define(["dojo/aspect"], function(aspect){
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// | var signal = aspect.after(targetObject, "methodName", function(someArgument){
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// | this will be called when targetObject.methodName() is called, after the original function is called
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// | });
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//
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// example:
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// The returned signal object can be used to cancel the advice.
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// | signal.remove(); // this will stop the advice from being executed anymore
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// | aspect.before(targetObject, "methodName", function(someArgument){
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// | // this will be called when targetObject.methodName() is called, before the original function is called
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// | });
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after: function(target, methodName, advice, receiveArguments){
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// summary: The "after" export of the aspect module is a function that can be used to attach
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// "after" advice to a method. This function will be executed after the original method
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// is executed. By default the function will be called with a single argument, the return
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// value of the original method, or the the return value of the last executed advice (if a previous one exists).
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// The fourth (optional) argument can be set to true to so the function receives the original
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// arguments (from when the original method was called) rather than the return value.
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// If there are multiple "after" advisors, they are executed in the order they were registered.
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// target: Object
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// This is the target object
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// methodName: String
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// This is the name of the method to attach to.
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// advice: Function
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// This is function to be called after the original method
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// receiveArguments: Boolean?
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// If this is set to true, the advice function receives the original arguments (from when the original mehtod
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// was called) rather than the return value of the original/previous method.
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// returns:
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// A signal object that can be used to cancel the advice. If remove() is called on this signal object, it will
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// stop the advice function from being executed.
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},
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before: function(target, methodName, advice){
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// summary: The "before" export of the aspect module is a function that can be used to attach
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// "before" advice to a method. This function will be executed before the original method
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// is executed. This function will be called with the arguments used to call the method.
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// This function may optionally return an array as the new arguments to use to call
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// the original method (or the previous, next-to-execute before advice, if one exists).
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// If the before method doesn't return anything (returns undefined) the original arguments
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// will be preserved.
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// If there are multiple "before" advisors, they are executed in the reverse order they were registered.
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//
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// target: Object
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// This is the target object
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// methodName: String
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// This is the name of the method to attach to.
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// advice: Function
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// This is function to be called before the original method
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},
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around: function(target, methodName, advice){
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// summary: The "around" export of the aspect module is a function that can be used to attach
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// "around" advice to a method. The advisor function is immediately executed when
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// the around() is called, is passed a single argument that is a function that can be
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// called to continue execution of the original method (or the next around advisor).
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// The advisor function should return a function, and this function will be called whenever
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// the method is called. It will be called with the arguments used to call the method.
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// Whatever this function returns will be returned as the result of the method call (unless after advise changes it).
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//
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// example:
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// If there are multiple "around" advisors, the most recent one is executed first,
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// which can then delegate to the next one and so on. For example:
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// | around(obj, "foo", function(originalFoo){
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// | return function(){
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// | var start = new Date().getTime();
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// | var results = originalFoo.apply(this, arguments); // call the original
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// | var end = new Date().getTime();
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// | console.log("foo execution took " + (end - start) + " ms");
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// | return results;
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// | };
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// | });
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//
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// target: Object
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// This is the target object
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// methodName: String
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// This is the name of the method to attach to.
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// advice: Function
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// This is function to be called around the original method
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}
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};
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=====*/
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"use strict";
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var nextId = 0;
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function advise(dispatcher, type, advice, receiveArguments){
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var previous = dispatcher[type];
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var around = type == "around";
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var signal;
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if(around){
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var advised = advice(function(){
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return previous.advice(this, arguments);
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});
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signal = {
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remove: function(){
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signal.cancelled = true;
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},
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advice: function(target, args){
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return signal.cancelled ?
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previous.advice(target, args) : // cancelled, skip to next one
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advised.apply(target, args); // called the advised function
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}
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};
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}else{
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// create the remove handler
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signal = {
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remove: function(){
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var previous = signal.previous;
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var next = signal.next;
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if(!next && !previous){
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delete dispatcher[type];
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}else{
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if(previous){
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previous.next = next;
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}else{
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dispatcher[type] = next;
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}
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if(next){
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next.previous = previous;
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}
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}
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},
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id: nextId++,
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advice: advice,
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receiveArguments: receiveArguments
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};
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}
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if(previous && !around){
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if(type == "after"){
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// add the listener to the end of the list
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var next = previous;
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while(next){
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previous = next;
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next = next.next;
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}
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previous.next = signal;
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signal.previous = previous;
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}else if(type == "before"){
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// add to beginning
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dispatcher[type] = signal;
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signal.next = previous;
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previous.previous = signal;
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}
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}else{
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// around or first one just replaces
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dispatcher[type] = signal;
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}
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return signal;
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}
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function aspect(type){
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return function(target, methodName, advice, receiveArguments){
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var existing = target[methodName], dispatcher;
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if(!existing || existing.target != target){
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// no dispatcher in place
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target[methodName] = dispatcher = function(){
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var executionId = nextId;
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// before advice
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var args = arguments;
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var before = dispatcher.before;
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while(before){
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args = before.advice.apply(this, args) || args;
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before = before.next;
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}
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// around advice
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if(dispatcher.around){
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var results = dispatcher.around.advice(this, args);
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}
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// after advice
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var after = dispatcher.after;
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while(after && after.id < executionId){
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results = after.receiveArguments ? after.advice.apply(this, args) || results :
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after.advice.call(this, results);
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after = after.next;
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}
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return results;
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};
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if(existing){
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dispatcher.around = {advice: function(target, args){
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return existing.apply(target, args);
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}};
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}
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dispatcher.target = target;
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}
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var results = advise((dispatcher || existing), type, advice, receiveArguments);
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advice = null;
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return results;
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};
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}
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return {
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before: aspect("before"),
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around: aspect("around"),
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after: aspect("after")
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};
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});
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