Mon 21 Jul 22:43:21 CEST 2025

js/dos/cache.js

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+/**
+ **      ==================================
+ **      OOOO   OOOO OOOO  O      O   OOOO
+ **      O   O  O    O     O     O O  O   O
+ **      O   O  O    O     O     O O  O   O
+ **      OOOO   OOOO OOOO  O     OOO  OOOO
+ **      O   O     O    O  O    O   O O   O
+ **      O   O     O    O  O    O   O O   O
+ **      OOOO   OOOO OOOO  OOOO O   O OOOO
+ **      ==================================
+ **      BSSLAB, Dr. Stefan Bosse http://www.bsslab.de
+ **
+ **      COPYRIGHT: THIS SOFTWARE, EXECUTABLE AND SOURCE CODE IS OWNED
+ **                 BY THE AUTHOR.
+ **                 THIS SOURCE CODE MAY NOT BE COPIED, EXTRACTED,
+ **                 MODIFIED, OR OTHERWISE USED IN A CONTEXT
+ **                 OUTSIDE OF THE SOFTWARE SYSTEM.
+ **
+ **    $AUTHORS:     Stefan Bosse
+ **    $INITIAL:     (C) 2006-2016 BSSLAB
+ **    $CREATED:     7/8/15 by sbosse.
+ **    $VERSION:     1.2.2
+ **
+ **    $INFO:
+ **
+ **  DOS: Cache module. 
+ **
+ ** Provides a fixed table cache. 
+ ** Searching is done from the newest entry down to the oldest.
+ ** It's possible to invalidate (remove) a cache entry.
+ ** Garbage collection and cache updating is optionally provided.
+ ** Basically a caching hash table with a bound size.
+ *
+ **
+ **    $ENDOFINFO
+ */
+
+
+/**
+ *
+ * @param size
+ * @constructor
+ * @typedef {{cache_size,cache_head,cache_hit,cache_miss,cache_table:* []}} cache~obj
+ * @see cache~obj
+ * @see cache~meth
+ */
+var cache = function (size) {
+    this.cache_size=size;
+    this.cache_head=0;
+    this.cache_table={};
+};
+
+/**
+ * @typedef {{add:cache.add,lookup:cache.lookup,invalidate:cache.invalidate}} cache~meth
+ */
+
+/**
+ *
+ * @param size
+ * @returns {cache}
+ */
+function Cache(size) {
+    var obj = new cache(size);
+    Object.preventExtensions(obj);
+    return obj;
+}
+
+/** Add a new cache entry
+ *
+ * @param key
+ * @param data
+ * @param [tmo]
+ * @param [stat]
+ */
+cache.prototype.add = function (key,data) {
+  
+  if (this.cache_head==this.cache_size) {
+      /*
+      ** Invalidate oldest cache entry
+      */
+      for (i in this.cache_table) {
+        delete this.cache_table[i];
+        break;
+      }
+  } else this.cache_head++;
+  this.cache_table[key]=data;    // We use the JS array hash table feature here!
+};
+
+/** Invalidate (remove) a cache entry
+ *
+ * @param key
+ */
+cache.prototype.invalidate = function (key) {
+  if (this.cache_table[key]) {
+    delete this.cache_table[key];
+    this.cache_head--;
+  }
+};
+
+
+/** Find a cache entry
+ *
+ * @param key
+ * @returns {*}
+ */
+cache.prototype.lookup = function (key) {
+  var data=this.cache_table[key];
+  if (data) return data;
+};
+
+cache.prototype.map = function (key,data) {
+  var map={};
+  map[key]=data;
+  return map;  
+}
+
+/** Refresh and garabage collection handler
+ *
+ * @param key
+ * @returns {*}
+ */
+cache.prototype.refresh = function (f) {
+  var p,data;
+  for(p in this.cache_table) {
+    data=this.cache_table[p];
+    if (!f(p,data)) this.invalidate(p);
+  }
+};
+
+/** Update a cache entry
+ *
+ * @param key
+ * @returns {*}
+ */
+cache.prototype.update = function (key,data) {
+  var entry=this.cache_table[key];
+  if (entry) for (var p in data) {
+    entry[i]=data[i];
+  } else this.add(key,data);
+};
+
+module.exports = {
+    Cache: Cache
+};