1 files changed, 106 insertions, 0 deletions
diff --git a/src/main/java/org/apache/commons/math3/ode/EquationsMapper.java b/src/main/java/org/apache/commons/math3/ode/EquationsMapper.java
new file mode 100644
index 0000000..c123cec
--- /dev/null
+++ b/src/main/java/org/apache/commons/math3/ode/EquationsMapper.java
@@ -0,0 +1,106 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.commons.math3.ode;
+
+import org.apache.commons.math3.exception.DimensionMismatchException;
+
+import java.io.Serializable;
+
+/**
+ * Class mapping the part of a complete state or derivative that pertains to a specific differential
+ * equation.
+ *
+ * <p>Instances of this class are guaranteed to be immutable.
+ *
+ * @see SecondaryEquations
+ * @since 3.0
+ */
+public class EquationsMapper implements Serializable {
+
+    /** Serializable UID. */
+    private static final long serialVersionUID = 20110925L;
+
+    /** Index of the first equation element in complete state arrays. */
+    private final int firstIndex;
+
+    /** Dimension of the secondary state parameters. */
+    private final int dimension;
+
+    /**
+     * simple constructor.
+     *
+     * @param firstIndex index of the first equation element in complete state arrays
+     * @param dimension dimension of the secondary state parameters
+     */
+    public EquationsMapper(final int firstIndex, final int dimension) {
+        this.firstIndex = firstIndex;
+        this.dimension = dimension;
+    }
+
+    /**
+     * Get the index of the first equation element in complete state arrays.
+     *
+     * @return index of the first equation element in complete state arrays
+     */
+    public int getFirstIndex() {
+        return firstIndex;
+    }
+
+    /**
+     * Get the dimension of the secondary state parameters.
+     *
+     * @return dimension of the secondary state parameters
+     */
+    public int getDimension() {
+        return dimension;
+    }
+
+    /**
+     * Extract equation data from a complete state or derivative array.
+     *
+     * @param complete complete state or derivative array from which equation data should be
+     *     retrieved
+     * @param equationData placeholder where to put equation data
+     * @throws DimensionMismatchException if the dimension of the equation data does not match the
+     *     mapper dimension
+     */
+    public void extractEquationData(double[] complete, double[] equationData)
+            throws DimensionMismatchException {
+        if (equationData.length != dimension) {
+            throw new DimensionMismatchException(equationData.length, dimension);
+        }
+        System.arraycopy(complete, firstIndex, equationData, 0, dimension);
+    }
+
+    /**
+     * Insert equation data into a complete state or derivative array.
+     *
+     * @param equationData equation data to be inserted into the complete array
+     * @param complete placeholder where to put equation data (only the part corresponding to the
+     *     equation will be overwritten)
+     * @throws DimensionMismatchException if the dimension of the equation data does not match the
+     *     mapper dimension
+     */
+    public void insertEquationData(double[] equationData, double[] complete)
+            throws DimensionMismatchException {
+        if (equationData.length != dimension) {
+            throw new DimensionMismatchException(equationData.length, dimension);
+        }
+        System.arraycopy(equationData, 0, complete, firstIndex, dimension);
+    }
+}