Migrated source code from Simantics SVN

[simantics/platform.git] / bundles / org.simantics.utils.datastructures / src / org / simantics / utils / datastructures / persistent / ImmutableStack.java

diff --git a/bundles/org.simantics.utils.datastructures/src/org/simantics/utils/datastructures/persistent/ImmutableStack.java b/bundles/org.simantics.utils.datastructures/src/org/simantics/utils/datastructures/persistent/ImmutableStack.java
new file mode 100644 (file)
index 0000000..8256391
--- /dev/null
+++ b/bundles/org.simantics.utils.datastructures/src/org/simantics/utils/datastructures/persistent/ImmutableStack.java
@@ -0,0 +1,94 @@
+/*******************************************************************************\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.persistent;\r
+\r
+public abstract class ImmutableStack<T> {\r
+       \r
+       private ImmutableStack() {              \r
+       }\r
+       \r
+       private static class SingleStackNode<T> extends ImmutableStack<T> {\r
+               ImmutableStack<T> parent;\r
+               T value;\r
+               \r
+               public SingleStackNode(ImmutableStack<T> parent, T value) {             \r
+                       this.parent = parent;\r
+                       this.value = value;\r
+               }\r
+\r
+               @Override\r
+               public T get(int i) {\r
+                       return i==0 ? value : parent.get(i-1);\r
+               }       \r
+       }\r
+       \r
+       private static class MultiStackNode<T> extends ImmutableStack<T> {\r
+               ImmutableStack<T> parent;\r
+               T[] values;\r
+               \r
+               public MultiStackNode(ImmutableStack<T> parent, T[] values) {           \r
+                       this.parent = parent;\r
+                       this.values = values;\r
+               }\r
+\r
+               @Override\r
+               public T get(int i) {\r
+                       return i<values.length ? values[i] : parent.get(i-values.length);\r
+               }       \r
+       }\r
+       \r
+       private static class EmptyStack<T> extends ImmutableStack<T> {\r
+\r
+               @Override\r
+               public T get(int i) {\r
+                       throw new IllegalArgumentException("No such element in stack.");\r
+               }\r
+               \r
+       }\r
+       \r
+       @SuppressWarnings({ "rawtypes" })\r
+       static final EmptyStack EMPTY = new EmptyStack();\r
+       \r
+       public ImmutableStack<T> push(T value) {\r
+               return new SingleStackNode<T>(this, value);\r
+       }\r
+       \r
+       public ImmutableStack<T> push(T[] values) {\r
+               if(values.length > 1)\r
+                       return new MultiStackNode<T>(this, values);\r
+               else if(values.length == 1)\r
+                       return new SingleStackNode<T>(this, values[0]);\r
+               else\r
+                       return this;\r
+       }\r
+       \r
+       public abstract T get(int i); \r
+       \r
+       @SuppressWarnings("unchecked")\r
+       public static <T> ImmutableStack<T> empty() {\r
+               return (ImmutableStack<T>)EMPTY;\r
+       }\r
+       \r
+       public static <T> ImmutableStack<T> of(T value) {\r
+               return new SingleStackNode<T>(null, value);\r
+       }\r
+       \r
+       @SuppressWarnings("unchecked")\r
+       public static <T> ImmutableStack<T> of(T[] values) {\r
+               if(values.length > 1)\r
+                       return new MultiStackNode<T>((ImmutableStack<T>)empty(), values);\r
+               else if(values.length == 1)\r
+                       return new SingleStackNode<T>((ImmutableStack<T>)empty(), values[0]);\r
+               else\r
+                       return empty();\r
+       }\r
+}\r