Add ol.TileCache

src/ol/tilecache.js

@@ -0,0 +1,58 @@
+goog.provide('ol.TileCache');
+
+goog.require('goog.dispose');
+goog.require('goog.structs.LinkedMap');
+goog.require('ol.Tile');
+goog.require('ol.TileRange');
+
+
+/**
+ * @define {number} Default high water mark.
+ */
+ol.DEFAULT_TILE_CACHE_HIGH_WATER_MARK = 512;
+
+
+
+/**
+ * @constructor
+ * @extends {goog.structs.LinkedMap}
+ * @param {number=} opt_highWaterMark High water mark.
+ */
+ol.TileCache = function(opt_highWaterMark) {
+
+  goog.base(this, undefined, true);
+
+  /**
+   * @private
+   * @type {number}
+   */
+  this.highWaterMark_ = goog.isDef(opt_highWaterMark) ?
+      opt_highWaterMark : ol.DEFAULT_TILE_CACHE_HIGH_WATER_MARK;
+
+};
+goog.inherits(ol.TileCache, goog.structs.LinkedMap);
+
+
+/**
+ * @return {boolean} Can expire cache.
+ */
+ol.TileCache.prototype.canExpireCache = function() {
+  return this.getCount() > this.highWaterMark_;
+};
+
+
+/**
+ * @param {Object.<string, ol.TileRange>} usedTiles Used tiles.
+ */
+ol.TileCache.prototype.expireCache = function(usedTiles) {
+  var tile, zKey;
+  while (this.canExpireCache()) {
+    tile = /** @type {ol.Tile} */ (this.peekLast());
+    zKey = tile.tileCoord.z.toString();
+    if (zKey in usedTiles && usedTiles[zKey].contains(tile.tileCoord)) {
+      break;
+    } else {
+      this.pop();
+    }
+  }
+};