1 files changed, 105 insertions, 0 deletions

diff --git a/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/matchers/util/SingletonMemoryView.java b/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/matchers/util/SingletonMemoryView.java
new file mode 100644
index 00000000..b303f9ad
--- /dev/null
+++ b/subprojects/viatra-runtime/src/main/java/tools/refinery/viatra/runtime/matchers/util/SingletonMemoryView.java
@@ -0,0 +1,105 @@
+/*******************************************************************************
+ * Copyright (c) 2010-2018, Gabor Bergmann, IncQuery Labs Ltd.
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v. 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-v20.html.
+ * 
+ * SPDX-License-Identifier: EPL-2.0
+ *******************************************************************************/
+package tools.refinery.viatra.runtime.matchers.util;
+
+import java.util.Collections;
+import java.util.Iterator;
+import java.util.NoSuchElementException;
+import java.util.Set;
+
+/**
+ * An immutable memory view that consists of a single non-null element with multiplicity 1.
+ * @author Gabor Bergmann
+ * @since 2.0
+ */
+public final class SingletonMemoryView<Value> implements IMemoryView<Value> {
+
+    private Value wrapped;
+    private static final int ONE_HASH = Integer.valueOf(1).hashCode();
+
+    public SingletonMemoryView(Value value) {
+        this.wrapped = value;
+    }
+
+    @Override
+    public Iterator<Value> iterator() {
+        return new Iterator<Value>() {
+            boolean hasNext = true;
+            
+            @Override
+            public boolean hasNext() {
+                return hasNext;
+            }
+
+            @Override
+            public Value next() {
+                if (hasNext) {
+                    hasNext = false;
+                    return wrapped;
+                } else throw new NoSuchElementException();
+            }
+        };
+    }
+
+    @Override
+    public int getCount(Value value) {
+        return wrapped.equals(value) ? 1 : 0;
+    }
+
+    @Override
+    public int getCountUnsafe(Object value) {
+        return wrapped.equals(value) ? 1 : 0;
+    }
+
+    @Override
+    public boolean containsNonZero(Value value) {
+        return wrapped.equals(value);
+    }
+
+    @Override
+    public boolean containsNonZeroUnsafe(Object value) {
+        return wrapped.equals(value);
+    }
+
+    @Override
+    public int size() {
+        return 1;
+    }
+
+    @Override
+    public boolean isEmpty() {
+        return false;
+    }
+
+    @Override
+    public Set<Value> distinctValues() {
+        return Collections.singleton(wrapped);
+    }
+    
+    @Override
+    public boolean equals(Object obj) {
+        if (obj instanceof IMemoryView<?>) {
+            IMemoryView<?> other = (IMemoryView<?>) obj;
+            if (1 != other.size()) return false;
+            if (1 != other.getCountUnsafe(wrapped)) return false;
+            return true;
+        }
+        return false;
+    }
+    
+    @Override
+    public int hashCode() {
+        return wrapped.hashCode() ^ ONE_HASH;
+    }
+
+    @Override
+    public String toString() {
+        return "{" + wrapped + "}";
+    }
+}