Merge pull request #8 from NBTSolutions/kelvin/update-cache-size

Implement setting cache size after initialization

Leaflet.VectorTiles.js

@@ -547,6 +547,17 @@ L.VectorTiles = L.GridLayer.extend({
     return this;
   },
 
+  /**
+   * Set the maximum size of the cache
+   *
+   * @param {number} size
+   * returns {L.VectorTiles} this
+   */
+  setTileCacheSize(size) {
+    this._tileCache.setSize(size);
+    return this;
+  },
+
   /**
    * Convert a GeoJSON feature into a Leaflet feature
    * Point -> L.Circle

example/index.html

@@ -18,6 +18,12 @@
   <div>
     search: <input id="search" type="text"/>
   </div>
+  <div>
+    <div>
+      set cache size: <input id="cache-size-input" type="range" min="0" max="150" value="50"/>
+    </div>
+    <div>cache size: <span id="cache-size">50</span></div>
+  </div>
   <div id="map"></div>
   <script src="index.js"></script>
 </body>

example/index.js

@@ -63,4 +63,10 @@ function main(geojson) {
       .filter(c => c.indexOf(q) > -1)
       .forEach(id => vtLayer.setFeatureStyle(id, { color: 'black' }));
   };
+
+  document.getElementById('cache-size-input').onchange = e => {
+    const cacheSize = +e.target.value;
+    document.getElementById('cache-size').innerHTML = cacheSize;
+    vtLayer.setTileCacheSize(cacheSize);
+  };
 }

tile_cache.js

@@ -11,9 +11,9 @@
  */
 class Node {
   constructor(data) {
-    self.data = data;
-    self.prev = null;
-    self.next = null;
+    this.data = data;
+    this.prev = null;
+    this.next = null;
   }
 }
 
@@ -44,7 +44,10 @@ export default class TileCache {
   }
 
   /**
+   * Retrieve an item from the cache
+   *
    * @param {string} tileKey
+   * @returns {Tile|null}
    */
   get(tileKey) {
     if (!(tileKey in this._cache)) {
@@ -78,6 +81,7 @@ export default class TileCache {
   put(tileKey, tile) {
     if (this._debug) {
       console.log('tile cache:', 'caching', tileKey);
+      console.log(this._stringifyList());
     }
 
     if (tileKey in this._cache) {
@@ -93,7 +97,7 @@ export default class TileCache {
     }
 
     // place at heaad of order linked list
-    let node = new Node({ tile, tileKey });
+    let node = new Node({ tileKey });
     if (this._head) {
       this._head.prev = node;
     }
@@ -114,9 +118,78 @@ export default class TileCache {
       const tailtileKey = tailNode.data.tileKey;
       if (this._debug) {
         console.log('tile cache:', 'evicting', tileKey);
+        console.log(this._stringifyList());
       }
       delete this._cache[tailtileKey];
     }
   }
+
+  /**
+   * @param {number} size
+   */
+  setSize(size) {
+    if (size < 0) {
+      throw "Size cannot be a negative number";
+    }
+
+    if (this._debug) {
+      console.log('tile cache:', 'changing cache size from', this._size, 'to', size);
+    }
+
+    if (size >= this._size) {
+      // we are increasing the size, no need to remove items from the cache
+      this._size = size;
+      return;
+    }
+
+    this._size = size;
+
+    if (this._head == null) {
+      // this cache is empty
+      return;
+    }
+
+    let node = this._head;
+    let garbage = node;
+    if (size > 0) {
+      let c = 1;
+      while (c < size && node.next != null) {
+        node = node.next;
+        c++;
+      }
+      garbage = node.next;
+      node.next = null;
+    }
+
+    // collect the garbage
+    while (garbage != null) {
+      let { tileKey } = garbage.data;
+      if (this._debug) {
+        console.log('tile cache:', 'removing tile', tileKey, 'due to cache resize');
+        console.log(this._stringifyList());
+      }
+      delete this._cache[tileKey]; // delete from cache
+      garbage = garbage.next;
+    }
+
+    // when this function exits, there should be no more references to the garbage
+    // nodes in the linked list, so they will be garbage collected as usual
+  }
+
+  /**
+   * Returns a string reprenting the current order of tiles in the cache
+   *
+   * @returns {string}
+   * @private
+   */
+  _stringifyList() {
+    let node = this._head;
+    let out = '';
+    while (node !== null) {
+      out += `(coords = ${node.data.tileKey}, feature count = ${Object.keys(this._cache[node.data.tileKey].tile._features).length}) -> `;
+      node = node.next;
+    }
+    return out;
+  }
 }