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colonymech / docs / www / colonyscout / internal / includes / uploadify / com / adobe / serialization / json / JSONEncoder.as @ f59acf11

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/*
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  Copyright (c) 2008, Adobe Systems Incorporated
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  All rights reserved.
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  Redistribution and use in source and binary forms, with or without 
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  modification, are permitted provided that the following conditions are
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  met:
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  * Redistributions of source code must retain the above copyright notice, 
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    this list of conditions and the following disclaimer.
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  * Redistributions in binary form must reproduce the above copyright
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    notice, this list of conditions and the following disclaimer in the 
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    documentation and/or other materials provided with the distribution.
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  * Neither the name of Adobe Systems Incorporated nor the names of its 
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    contributors may be used to endorse or promote products derived from 
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    this software without specific prior written permission.
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  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
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  IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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  THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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  PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR 
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  CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
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  EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
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  PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
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  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
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  LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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  NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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  SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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package com.adobe.serialization.json 
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{
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	import flash.utils.describeType;
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	public class JSONEncoder {
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		/** The string that is going to represent the object we're encoding */
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		private var jsonString:String;
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		/**
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		 * Creates a new JSONEncoder.
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		 *
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		 * @param o The object to encode as a JSON string
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		 * @langversion ActionScript 3.0
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		 * @playerversion Flash 9.0
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		 * @tiptext
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		 */
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		public function JSONEncoder( value:* ) {
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			jsonString = convertToString( value );
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		}
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		/**
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		 * Gets the JSON string from the encoder.
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		 *
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		 * @return The JSON string representation of the object
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		 * 		that was passed to the constructor
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		 * @langversion ActionScript 3.0
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		 * @playerversion Flash 9.0
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		 * @tiptext
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		 */
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		public function getString():String {
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			return jsonString;
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		}
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		/**
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		 * Converts a value to it's JSON string equivalent.
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		 *
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		 * @param value The value to convert.  Could be any 
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		 *		type (object, number, array, etc)
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		 */
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		private function convertToString( value:* ):String {
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			// determine what value is and convert it based on it's type
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			if ( value is String ) {
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				// escape the string so it's formatted correctly
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				return escapeString( value as String );
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			} else if ( value is Number ) {
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				// only encode numbers that finate
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				return isFinite( value as Number) ? value.toString() : "null";
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			} else if ( value is Boolean ) {
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				// convert boolean to string easily
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				return value ? "true" : "false";
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			} else if ( value is Array ) {
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				// call the helper method to convert an array
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				return arrayToString( value as Array );
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			} else if ( value is Object && value != null ) {
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				// call the helper method to convert an object
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				return objectToString( value );
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			}
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            return "null";
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		}
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		/**
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		 * Escapes a string accoding to the JSON specification.
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		 *
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		 * @param str The string to be escaped
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		 * @return The string with escaped special characters
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		 * 		according to the JSON specification
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		 */
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		private function escapeString( str:String ):String {
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			// create a string to store the string's jsonstring value
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			var s:String = "";
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			// current character in the string we're processing
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			var ch:String;
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			// store the length in a local variable to reduce lookups
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			var len:Number = str.length;
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			// loop over all of the characters in the string
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			for ( var i:int = 0; i < len; i++ ) {
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				// examine the character to determine if we have to escape it
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				ch = str.charAt( i );
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				switch ( ch ) {
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					case '"':	// quotation mark
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						s += "\\\"";
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						break;
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					//case '/':	// solidus
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					//	s += "\\/";
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					//	break;
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					case '\\':	// reverse solidus
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						s += "\\\\";
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						break;
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					case '\b':	// bell
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						s += "\\b";
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						break;
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					case '\f':	// form feed
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						s += "\\f";
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						break;
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					case '\n':	// newline
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						s += "\\n";
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						break;
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					case '\r':	// carriage return
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						s += "\\r";
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						break;
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					case '\t':	// horizontal tab
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						s += "\\t";
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						break;
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					default:	// everything else
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						// check for a control character and escape as unicode
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						if ( ch < ' ' ) {
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							// get the hex digit(s) of the character (either 1 or 2 digits)
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							var hexCode:String = ch.charCodeAt( 0 ).toString( 16 );
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							// ensure that there are 4 digits by adjusting
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							// the # of zeros accordingly.
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							var zeroPad:String = hexCode.length == 2 ? "00" : "000";
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							// create the unicode escape sequence with 4 hex digits
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							s += "\\u" + zeroPad + hexCode;
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						} else {
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							// no need to do any special encoding, just pass-through
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							s += ch;
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						}
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				}	// end switch
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			}	// end for loop
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			return "\"" + s + "\"";
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		}
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		/**
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		 * Converts an array to it's JSON string equivalent
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		 *
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		 * @param a The array to convert
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		 * @return The JSON string representation of <code>a</code>
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		 */
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		private function arrayToString( a:Array ):String {
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			// create a string to store the array's jsonstring value
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			var s:String = "";
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			// loop over the elements in the array and add their converted
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			// values to the string
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			for ( var i:int = 0; i < a.length; i++ ) {
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				// when the length is 0 we're adding the first element so
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				// no comma is necessary
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				if ( s.length > 0 ) {
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					// we've already added an element, so add the comma separator
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					s += ","
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				}
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				// convert the value to a string
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				s += convertToString( a[i] );	
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			}
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			// KNOWN ISSUE:  In ActionScript, Arrays can also be associative
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			// objects and you can put anything in them, ie:
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			//		myArray["foo"] = "bar";
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			//
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			// These properties aren't picked up in the for loop above because
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			// the properties don't correspond to indexes.  However, we're
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			// sort of out luck because the JSON specification doesn't allow
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			// these types of array properties.
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			//
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			// So, if the array was also used as an associative object, there
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			// may be some values in the array that don't get properly encoded.
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			//
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			// A possible solution is to instead encode the Array as an Object
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			// but then it won't get decoded correctly (and won't be an
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			// Array instance)
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			// close the array and return it's string value
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			return "[" + s + "]";
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		}
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		/**
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		 * Converts an object to it's JSON string equivalent
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		 *
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		 * @param o The object to convert
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		 * @return The JSON string representation of <code>o</code>
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		 */
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		private function objectToString( o:Object ):String
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		{
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			// create a string to store the object's jsonstring value
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			var s:String = "";
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			// determine if o is a class instance or a plain object
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			var classInfo:XML = describeType( o );
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			if ( classInfo.@name.toString() == "Object" )
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			{
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				// the value of o[key] in the loop below - store this 
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				// as a variable so we don't have to keep looking up o[key]
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				// when testing for valid values to convert
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				var value:Object;
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				// loop over the keys in the object and add their converted
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				// values to the string
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				for ( var key:String in o )
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				{
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					// assign value to a variable for quick lookup
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					value = o[key];
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					// don't add function's to the JSON string
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					if ( value is Function )
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					{
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						// skip this key and try another
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						continue;
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					}
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					// when the length is 0 we're adding the first item so
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					// no comma is necessary
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					if ( s.length > 0 ) {
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						// we've already added an item, so add the comma separator
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						s += ","
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					}
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					s += escapeString( key ) + ":" + convertToString( value );
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				}
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			}
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			else // o is a class instance
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			{
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				// Loop over all of the variables and accessors in the class and 
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				// serialize them along with their values.
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				for each ( var v:XML in classInfo..*.( name() == "variable" || name() == "accessor" ) )
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				{
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					// When the length is 0 we're adding the first item so
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					// no comma is necessary
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					if ( s.length > 0 ) {
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						// We've already added an item, so add the comma separator
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						s += ","
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					}
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					s += escapeString( v.@name.toString() ) + ":" 
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							+ convertToString( o[ v.@name ] );
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				}
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			}
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			return "{" + s + "}";
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		}
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	}
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}