Add a formula function to reverse and array

Author: shroffk

core/formula/src/main/java/org/csstudio/apputil/formula/array/ArrayReversalFunction.java

@@ -0,0 +1,98 @@
+package org.csstudio.apputil.formula.array;
+
+import org.csstudio.apputil.formula.Formula;
+import org.epics.util.array.ListDouble;
+import org.epics.util.array.ListNumber;
+import org.epics.vtype.Alarm;
+import org.epics.vtype.Display;
+import org.epics.vtype.VNumberArray;
+import org.epics.vtype.VType;
+import org.phoebus.core.vtypes.VTypeHelper;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.logging.Level;
+
+/**
+ * A formula function for reversing the given array.
+ * <p>
+ * The function allows for reversing the order of elements in an array, such that the first element
+ * becomes the last, the second element becomes the second to last, and so on.
+ * </p>
+ *
+ * <b>Arguments:</b>
+ * <ul>
+ *     <li><b>array</b>: The input numeric array to reverse.</li>
+ * </ul>
+ *
+ * <b>Example:</b>
+ * <p>
+ * If given an array [1, 2, 3, 4, 5], the result will be [5, 4, 3, 2, 1].
+ * </p>
+ *
+ * @author Kunal Shroff
+ */
+public class ArrayReversalFunction extends BaseArrayFunction {
+
+    @Override
+    public String getName() {
+        return "arrayReverse";
+    }
+
+    @Override
+    public String getDescription() {
+        return "Reverses the given numeric array so that the first element becomes the last and vice versa.";
+    }
+
+    @Override
+    public List<String> getArguments() {
+        return List.of("array");
+    }
+
+    /**
+     * Reverses the elements of a numeric array.
+     *
+     * @param array The input numeric array (VNumberArray) to reverse.
+     * @return A {@link VNumberArray} containing the reversed elements.
+     */
+    protected VType getArrayData(final VNumberArray array) {
+        return VNumberArray.of(reverse(array.getData()), Alarm.none(), array.getTime(), Display.none());
+    }
+
+    private static ListDouble reverse(final ListNumber data) {
+        return new ListDouble() {
+            @Override
+            public double getDouble(int index) {
+                return data.getDouble(data.size() - 1 - index);
+            }
+
+            @Override
+            public int size() {
+                return data.size();
+            }
+        };
+    }
+
+    /**
+     * Computes the function's result by reversing the provided array.
+     *
+     * @param args The arguments to the function:
+     *             - args[0]: The input array to reverse.
+     * @return A {@link VType} containing the reversed array.
+     * @throws Exception If an invalid number of arguments or incorrect argument types are provided.
+     */
+    @Override
+    public VType compute(final VType... args) throws Exception {
+        if (args.length != 1) {
+            throw new Exception("Function " + getName() +
+                    " requires 1 argument but received " + Arrays.toString(args));
+        }
+        if (!VTypeHelper.isNumericArray(args[0])) {
+            Formula.logger.log(Level.WARNING, "Function " + getName() +
+                    " takes array but received " + Arrays.toString(args));
+            return DEFAULT_NAN_DOUBLE_ARRAY;
+        } else {
+            return getArrayData((VNumberArray) args[0]);
+        }
+    }
+}

core/formula/src/main/resources/META-INF/services/org.csstudio.apputil.formula.spi.FormulaFunction

@@ -59,6 +59,7 @@ org.csstudio.apputil.formula.array.ArrayScalarDivisionFunction
 org.csstudio.apputil.formula.array.ArrayInverseScalarDivisionFunction
 org.csstudio.apputil.formula.array.ArrayOfFunction
 org.csstudio.apputil.formula.array.ArrayRangeOfFunction
+org.csstudio.apputil.formula.array.ArrayReversalFunction
 org.csstudio.apputil.formula.array.ArraySampleWithLTTBFunction
 org.csstudio.apputil.formula.array.ArraySampleWithStrideFunction
 org.csstudio.apputil.formula.array.ArrayStatsFunction