feat($cacheFactory): add general purpose $cacheFactory service

1 files changed, 152 insertions, 0 deletions

diff --git a/src/service/cacheFactory.js b/src/service/cacheFactory.js
new file mode 100644
index 00000000..ccc69313
--- /dev/null
+++ b/src/service/cacheFactory.js
@@ -0,0 +1,152 @@
+/**
+ * @ngdoc object
+ * @name angular.module.ng.$cacheFactory
+ *
+ * @description
+ * Factory that constructs cache objects.
+ *
+ *
+ * @param {string} cacheId Name or id of the newly created cache.
+ * @param {object=} options Options object that specifies the cache behavior. Properties:
+ *
+ *   - `{number=}` `capacity` — turns the cache into LRU cache.
+ *
+ * @returns {object} Newly created cache object with the following set of methods:
+ *
+ * - `{string}` `id()` — Returns id or name of the cache.
+ * - `{number}` `size()` — Returns number of items currently in the cache
+ * - `{void}` `put({string} key, {*} value)` — Puts a new key-value pair into the cache
+ * - `{(*}} `get({string} key) — Returns cached value for `key` or undefined for cache miss.
+ * - `{void}` `remove{string} key) — Removes a key-value pair from the cache.
+ * - `{void}` `removeAll() — Removes all cached values.
+ *
+ */
+function $CacheFactoryProvider() {
+
+  this.$get = function() {
+    var caches = {};
+
+    function cacheFactory(cacheId, options) {
+      if (cacheId in caches) {
+        throw Error('cacheId ' + cacheId + ' taken');
+      }
+
+      var size = 0,
+          stats = extend({}, options, {id: cacheId}),
+          data = {},
+          capacity = (options && options.capacity) || Number.MAX_VALUE,
+          lruHash = {},
+          freshEnd = null,
+          staleEnd = null;
+
+      return caches[cacheId] = {
+
+        put: function(key, value) {
+          var lruEntry = lruHash[key] || (lruHash[key] = {key: key});
+
+          refresh(lruEntry);
+
+          if (isUndefined(value)) return;
+          if (!(key in data)) size++;
+          data[key] = value;
+
+          if (size > capacity) {
+            this.remove(staleEnd.key);
+          }
+        },
+
+
+        get: function(key) {
+          var lruEntry = lruHash[key];
+
+          if (!lruEntry) return;
+
+          refresh(lruEntry);
+
+          return data[key];
+        },
+
+
+        remove: function(key) {
+          var lruEntry = lruHash[key];
+
+          if (lruEntry == freshEnd) freshEnd = lruEntry.p;
+          if (lruEntry == staleEnd) staleEnd = lruEntry.n;
+          link(lruEntry.n,lruEntry.p);
+
+          delete lruHash[key];
+          delete data[key];
+          size--;
+        },
+
+
+        removeAll: function() {
+          data = {};
+          size = 0;
+          lruHash = {};
+          freshEnd = staleEnd = null;
+        },
+
+
+        destroy: function() {
+          data = null;
+          stats = null;
+          lruHash = null;
+          delete caches[cacheId];
+        },
+
+
+        info: function() {
+          return extend({}, stats, {size: size});
+        }
+      };
+
+
+      /**
+       * makes the `entry` the freshEnd of the LRU linked list
+       */
+      function refresh(entry) {
+        if (entry != freshEnd) {
+          if (!staleEnd) {
+            staleEnd = entry;
+          } else if (staleEnd == entry) {
+            staleEnd = entry.n;
+          }
+
+          link(entry.n, entry.p);
+          link(entry, freshEnd);
+          freshEnd = entry;
+          freshEnd.n = null;
+        }
+      }
+
+
+      /**
+       * bidirectionally links two entries of the LRU linked list
+       */
+      function link(nextEntry, prevEntry) {
+        if (nextEntry != prevEntry) {
+          if (nextEntry) nextEntry.p = prevEntry; //p stands for previous, 'prev' didn't minify
+          if (prevEntry) prevEntry.n = nextEntry; //n stands for next, 'next' didn't minify
+        }
+      }
+    }
+
+
+    cacheFactory.info = function() {
+      var info = {};
+      forEach(caches, function(cache, cacheId) {
+        info[cacheId] = cache.info();
+      });
+      return info;
+    };
+
+
+    cacheFactory.get = function(cacheId) {
+      return caches[cacheId];
+    };
+
+
+    return cacheFactory;
+  };
+}