4ccfbdfa45
the original reason for longer term storage were the frequent error==TIMEOUT from map tiles. since these are now retried, as the stock site does, the remaining use for the cache is more short term, while panning around an area
86 lines
2.6 KiB
JavaScript
86 lines
2.6 KiB
JavaScript
// MAP DATA CACHE ///////////////////////////////////
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// cache for map data tiles.
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window.DataCache = function() {
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this.REQUEST_CACHE_FRESH_AGE = 60; // if younger than this, use data in the cache rather than fetching from the server
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this.REQUEST_CACHE_MAX_AGE = 180; // maximum cache age. entries are deleted from the cache after this time
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if (L.Browser.mobile) {
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// on mobile devices, smaller cache size
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this.REQUEST_CACHE_MAX_SIZE = 300; // if more than this many entries, expire early
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} else {
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// but on desktop, allow more
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this.REQUEST_CACHE_MAX_SIZE = 1000; // if more than this many entries, expire early
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}
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this._cache = {};
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this._interval = undefined;
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}
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window.DataCache.prototype.store = function(qk,data,date) {
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// fixme? common behaviour for objects is that properties are kept in the order they're added
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// this is handy, as it allows easy retrieval of the oldest entries for expiring
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// however, this is not guaranteed by the standards, but all our supported browsers work this way
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delete this._cache[qk];
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if (date === undefined) date = new Date();
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this._cache[qk] = { time: date.getTime(), data: data };
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}
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window.DataCache.prototype.get = function(qk) {
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if (qk in this._cache) return this._cache[qk].data;
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else return undefined;
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}
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window.DataCache.prototype.getTime = function(qk) {
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if (qk in this._cache) return this._cache[qk].time;
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else return 0;
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}
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window.DataCache.prototype.isFresh = function(qk) {
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if (qk in this._cache) {
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var d = new Date();
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var t = d.getTime() - this.REQUEST_CACHE_FRESH_AGE*1000;
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if (this._cache[qk].time >= t) return true;
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else return false;
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}
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return undefined;
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}
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window.DataCache.prototype.startExpireInterval = function(period) {
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if (this._interval === undefined) {
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var savedContext = this;
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this._interval = setInterval (function() { savedContext.runExpire(); }, period*1000);
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}
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}
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window.DataCache.prototype.stopExpireInterval = function() {
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if (this._interval !== undefined) {
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stopInterval (this._interval);
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this._interval = undefined;
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}
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}
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window.DataCache.prototype.runExpire = function() {
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var d = new Date();
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var t = d.getTime()-this.REQUEST_CACHE_MAX_AGE*1000;
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var cacheSize = Object.keys(this._cache).length;
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for(var qk in this._cache) {
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// fixme? our MAX_SIZE test here assumes we're processing the oldest first. this relies
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// on looping over object properties in the order they were added. this is true in most browsers,
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// but is not a requirement of the standards
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if (cacheSize > this.REQUEST_CACHE_MAX_SIZE || this._cache[qk].time < t) {
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delete this._cache[qk];
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cacheSize--;
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}
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}
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}
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