Resolves #269 - creates a generic Viterbi decoder and a Digital Mobile Radio (DMR) 3/4 Rate Viterbi decoder implementation for decoding Trellis Coded Modulation (TCM) encoded DMR Data packets.

src/edac/trellis/Path.java

@@ -0,0 +1,131 @@
+/*******************************************************************************
+ * sdrtrunk
+ * Copyright (C) 2014-2017 Dennis Sheirer
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>
+ *
+ ******************************************************************************/
+package edac.trellis;
+
+import java.util.ArrayList;
+import java.util.List;
+
+public class Path
+{
+    private List<Node> mNodes = new ArrayList<>();
+    private int mError = 0;
+
+    /**
+     * Trellis Coded Modulation (TCM) path.  Represents a sequence of nodes that traverse various time instants and
+     * states across a trellis.
+     *
+     * Note: each node can be shared across multiple paths.  This class does not assume that any nodes are unique.
+     * @param startingNode to start the path.  This node normally contains an input value of zero, but is implementation
+     * specific.
+     */
+    public Path(Node startingNode)
+    {
+        add(startingNode);
+    }
+
+    /**
+     * Trellis Coded Modulation (TCM) path.  Represents a sequence of nodes that traverse various time instants and
+     * states across a trellis.
+     *
+     * Note: each node can be shared across multiple paths.  This class does not assume that any nodes are unique.
+     *
+     * @param original path to create a copy from.  Each of the nodes in the original will be added to this path and
+     * after construction both this path and the original will contain the exact same set of nodes.
+     */
+    private Path(Path original)
+    {
+        for(Node node: original.getNodes())
+        {
+            add(node);
+        }
+    }
+
+    /**
+     * Cumulative error across all nodes contained within this path.  Error value is updated as each new node is added
+     * to this path.
+     *
+     * @return cumulative error value
+     */
+    public int getError()
+    {
+        return mError;
+    }
+
+    /**
+     * Length or number of nodes contained within this path.  Note: this value includes the starting node and may
+     * also include a flushing node.  The values contained in the starting and flushing nodes are normally not used
+     * when decoding a path.
+     *
+     * @return number of nodes in this path
+     */
+    public int getLength()
+    {
+        return mNodes.size() - 1;
+    }
+
+    /**
+     * The set of nodes contained in this path.
+     * @return nodes
+     */
+    public List<Node> getNodes()
+    {
+        return mNodes;
+    }
+
+    /**
+     * Adds the node to this path and updates the cumulative error value for this path by adding the node's error
+     * value to the running error total.
+     *
+     * @param node to add to this path
+     */
+    public void add(Node node)
+    {
+        if(!mNodes.isEmpty())
+        {
+            mError += node.getError(getLastNode());
+        }
+
+        mNodes.add(node);
+    }
+
+    /**
+     * Last node in this path.
+     *
+     * @return last node
+     */
+    public Node getLastNode()
+    {
+        if(!mNodes.isEmpty())
+        {
+            return mNodes.get(mNodes.size() - 1);
+        }
+
+        return null;
+    }
+
+    /**
+     * Utility method to create an exact copy of this path.
+     *
+     * @return a new copy of this path.
+     */
+    public Path copyOf()
+    {
+        return new Path(this);
+    }
+}