Migrated source code from Simantics SVN

[simantics/platform.git] / bundles / org.simantics.utils.datastructures / src / org / simantics / utils / datastructures / cache / CachedProvider.java

diff --git a/bundles/org.simantics.utils.datastructures/src/org/simantics/utils/datastructures/cache/CachedProvider.java b/bundles/org.simantics.utils.datastructures/src/org/simantics/utils/datastructures/cache/CachedProvider.java
new file mode 100644 (file)
index 0000000..9ccb068
--- /dev/null
+++ b/bundles/org.simantics.utils.datastructures/src/org/simantics/utils/datastructures/cache/CachedProvider.java
@@ -0,0 +1,57 @@
+/*******************************************************************************\r
+ * Copyright (c) 2007, 2010 Association for Decentralized Information Management\r
+ * in Industry THTH ry.\r
+ * All rights reserved. This program and the accompanying materials\r
+ * are made available under the terms of the Eclipse Public License v1.0\r
+ * which accompanies this distribution, and is available at\r
+ * http://www.eclipse.org/legal/epl-v10.html\r
+ *\r
+ * Contributors:\r
+ *     VTT Technical Research Centre of Finland - initial API and implementation\r
+ *******************************************************************************/\r
+package org.simantics.utils.datastructures.cache;\r
+\r
+\r
+/**\r
+ * Caches the value provided by the back-end provider.\r
+ * <p>\r
+ * Cached version is equal to original in hashCode/equals wise.\r
+ * \r
+ * @author Toni Kalajainen\r
+ */\r
+public class CachedProvider<V> implements IProvider<V> {\r
+\r
+    public static final <V> IProvider<V> cache(IProvider<V> provider)\r
+    {\r
+        if (provider instanceof CachedProvider<?>)\r
+            return provider;\r
+        return new CachedProvider<V>(provider);\r
+    }\r
+\r
+    IProvider<V> backendProvider;\r
+    V value;\r
+\r
+    CachedProvider(IProvider<V> orig)\r
+    {\r
+        this.backendProvider = orig;\r
+    }\r
+\r
+    @Override\r
+    public synchronized V get() throws ProvisionException {\r
+        if (value==null) {\r
+            value = backendProvider.get();\r
+        }\r
+        return value;\r
+    }\r
+\r
+    @Override\r
+    public int hashCode() {\r
+        return backendProvider.hashCode();\r
+    }\r
+\r
+    @Override\r
+    public boolean equals(Object obj) {\r
+        return backendProvider.equals(obj);\r
+    }\r
+\r
+}\r