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/* Copyright (c) 2006-2008 MetaCarta, Inc., published under the Clear BSD
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* license. See http://svn.openlayers.org/trunk/openlayers/license.txt for the
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* full text of the license. */
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* @requires OpenLayers/Layer.js
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* Class: OpenLayers.Layer.HTTPRequest
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* - <OpenLayers.Layer>
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OpenLayers.Layer.HTTPRequest = OpenLayers.Class(OpenLayers.Layer, {
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* Constant: URL_HASH_FACTOR
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* {Float} Used to hash URL param strings for multi-WMS server selection.
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* Set to the Golden Ratio per Knuth's recommendation.
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URL_HASH_FACTOR: (Math.sqrt(5) - 1) / 2,
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* {Array(String) or String} This is either an array of url strings or
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* a single url string.
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* {Object} Hashtable of key/value parameters
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* APIProperty: reproject
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* *Deprecated*. See http://trac.openlayers.org/wiki/SpatialMercator
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* for information on the replacement for this functionality.
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* {Boolean} Whether layer should reproject itself based on base layer
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* locations. This allows reprojection onto commercial layers.
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* Default is false: Most layers can't reproject, but layers
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* which can create non-square geographic pixels can, like WMS.
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* Constructor: OpenLayers.Layer.HTTPRequest
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* url - {Array(String) or String}
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* options - {Object} Hashtable of extra options to tag onto the layer
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initialize: function(name, url, params, options) {
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var newArguments = arguments;
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newArguments = [name, options];
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OpenLayers.Layer.prototype.initialize.apply(this, newArguments);
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this.params = OpenLayers.Util.extend( {}, params);
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OpenLayers.Layer.prototype.destroy.apply(this, arguments);
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* {<OpenLayers.Layer.HTTPRequest>} An exact clone of this
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* <OpenLayers.Layer.HTTPRequest>
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clone: function (obj) {
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obj = new OpenLayers.Layer.HTTPRequest(this.name,
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//get all additions from superclasses
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obj = OpenLayers.Layer.prototype.clone.apply(this, [obj]);
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// copy/set any non-init, non-simple values here
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setUrl: function(newUrl) {
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* APIMethod: mergeNewParams
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* newParams - {Object}
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* redrawn: {Boolean} whether the layer was actually redrawn.
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mergeNewParams:function(newParams) {
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this.params = OpenLayers.Util.extend(this.params, newParams);
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return this.redraw();
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* Redraws the layer. Returns true if the layer was redrawn, false if not.
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* force - {Boolean} Force redraw by adding random parameter.
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* {Boolean} The layer was redrawn.
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redraw: function(force) {
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return this.mergeNewParams({"_olSalt": Math.random()});
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return OpenLayers.Layer.prototype.redraw.apply(this, []);
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* selectUrl() implements the standard floating-point multiplicative
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* hash function described by Knuth, and hashes the contents of the
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* given param string into a float between 0 and 1. This float is then
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* scaled to the size of the provided urls array, and used to select
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* paramString - {String}
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* urls - {Array(String)}
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* {String} An entry from the urls array, deterministically selected based
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* on the paramString.
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selectUrl: function(paramString, urls) {
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for (var i=0, len=paramString.length; i<len; i++) {
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product *= paramString.charCodeAt(i) * this.URL_HASH_FACTOR;
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product -= Math.floor(product);
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return urls[Math.floor(product * urls.length)];
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* Method: getFullRequestString
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* Combine url with layer's params and these newParams.
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* does checking on the serverPath variable, allowing for cases when it
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* is supplied with trailing ? or &, as well as cases where not.
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* return in formatted string like this:
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* "server?key1=value1&key2=value2&key3=value3"
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* WARNING: The altUrl parameter is deprecated and will be removed in 3.0.
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* newParams - {Object}
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* altUrl - {String} Use this as the url instead of the layer's url
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getFullRequestString:function(newParams, altUrl) {
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// if not altUrl passed in, use layer's url
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var url = altUrl || this.url;
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// create a new params hashtable with all the layer params and the
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// new params together. then convert to string
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var allParams = OpenLayers.Util.extend({}, this.params);
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allParams = OpenLayers.Util.extend(allParams, newParams);
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var paramsString = OpenLayers.Util.getParameterString(allParams);
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// if url is not a string, it should be an array of strings,
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// in which case we will deterministically select one of them in
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// order to evenly distribute requests to different urls.
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if (url instanceof Array) {
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url = this.selectUrl(paramsString, url);
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// ignore parameters that are already in the url search string
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OpenLayers.Util.upperCaseObject(OpenLayers.Util.getParameters(url));
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for(var key in allParams) {
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if(key.toUpperCase() in urlParams) {
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delete allParams[key];
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paramsString = OpenLayers.Util.getParameterString(allParams);
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// requestString always starts with url
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var requestString = url;
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if (paramsString != "") {
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var lastServerChar = url.charAt(url.length - 1);
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if ((lastServerChar == "&") || (lastServerChar == "?")) {
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requestString += paramsString;
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if (url.indexOf('?') == -1) {
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//serverPath has no ? -- add one
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requestString += '?' + paramsString;
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//serverPath contains ?, so must already have
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// paramsString at the end
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requestString += '&' + paramsString;
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return requestString;
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CLASS_NAME: "OpenLayers.Layer.HTTPRequest"