Make LwM2mPath Comparable

leshan-core/src/main/java/org/eclipse/leshan/core/node/LwM2mPath.java

@@ -20,7 +20,7 @@
 /**
  * A path pointing to a LwM2M node (root, object, object instance, resource or resource instance).
  */
-public class LwM2mPath {
+public class LwM2mPath implements Comparable<LwM2mPath> {
 
     public static final byte ROOT_DEPTH = 1;
     public static final byte OBJECT_DEPTH = 2;
@@ -368,6 +368,35 @@ public boolean equals(Object obj) {
         return true;
     }
 
+    @Override
+    public int compareTo(LwM2mPath o) {
+        int res = compareInteger(this.objectId, o.objectId);
+        if (res != 0 || this.objectId == null)
+            return res;
+
+        res = compareInteger(this.objectInstanceId, o.objectInstanceId);
+        if (res != 0 || this.objectInstanceId == null)
+            return res;
+
+        res = compareInteger(this.resourceId, o.resourceId);
+        if (res != 0 || this.resourceId == null)
+            return res;
+
+        return compareInteger(this.resourceInstanceId, o.resourceInstanceId);
+    }
+
+    private int compareInteger(Integer i1, Integer i2) {
+        if (i1 == i2) {
+            return 0;
+        } else if (i1 == null) {
+            return -1;
+        } else if (i2 == null) {
+            return 1;
+        } else {
+            return i1.compareTo(i2);
+        }
+    }
+
     /**
      * Parse a string containing a full LWM2M path containing rootpath (rt="oma.lwm2m").
      * <p>

leshan-core/src/test/java/org/eclipse/leshan/core/node/LwM2mParhTest.java

@@ -0,0 +1,76 @@
+/*******************************************************************************
+ * Copyright (c) 2021 Sierra Wireless and others.
+ * 
+ * All rights reserved. This program and the accompanying materials
+ * are made available under the terms of the Eclipse Public License v2.0
+ * and Eclipse Distribution License v1.0 which accompany this distribution.
+ * 
+ * The Eclipse Public License is available at
+ *    http://www.eclipse.org/legal/epl-v20.html
+ * and the Eclipse Distribution License is available at
+ *    http://www.eclipse.org/org/documents/edl-v10.html.
+ * 
+ * Contributors:
+ *     Sierra Wireless - initial API and implementation
+ *******************************************************************************/
+package org.eclipse.leshan.core.node;
+
+import static org.junit.Assert.assertTrue;
+
+import org.junit.Test;
+
+public class LwM2mParhTest {
+
+    @Test
+    public void test_compare_path() {
+        assertEquals("/", "/");
+        assertEquals("/1", "/1");
+        assertEquals("/1/2", "/1/2");
+        assertEquals("/1/2/3", "/1/2/3");
+        assertEquals("/1/2/3/4", "/1/2/3/4");
+
+        assertFirstSmaller("/", "/1");
+        assertFirstSmaller("/", "/1/1");
+        assertFirstSmaller("/", "/1/1/1");
+        assertFirstSmaller("/", "/1/1/1/1");
+
+        assertFirstSmaller("/1", "/1/1");
+        assertFirstSmaller("/1", "/1/1/1");
+        assertFirstSmaller("/1", "/1/1/1/1");
+
+        assertFirstSmaller("/1/1", "/1/1/1");
+        assertFirstSmaller("/1/1", "/1/1/1/1");
+
+        assertFirstSmaller("/1/1/1", "/1/1/1/1");
+
+        assertFirstSmaller("/1", "/2");
+        assertFirstSmaller("/1/1", "/2");
+        assertFirstSmaller("/1/1/1", "/2");
+        assertFirstSmaller("/1/1/1/1", "/2");
+
+        assertFirstSmaller("/1", "/2/1");
+        assertFirstSmaller("/1/1", "/2/1");
+        assertFirstSmaller("/1/1/1", "/2/1");
+        assertFirstSmaller("/1/1/1/1", "/2/1");
+
+        assertFirstSmaller("/1", "/2/1/1");
+        assertFirstSmaller("/1/1", "/2/1/1");
+        assertFirstSmaller("/1/1/1", "/2/1/1");
+        assertFirstSmaller("/1/1/1/1", "/2/1/1");
+
+        assertFirstSmaller("/1", "/2/1/1/1");
+        assertFirstSmaller("/1/1", "/2/1/1/1");
+        assertFirstSmaller("/1/1/1", "/2/1/1/1");
+        assertFirstSmaller("/1/1/1/1", "/2/1/1/1");
+    }
+
+    private void assertEquals(String path1, String path2) {
+        assertTrue(new LwM2mPath(path1).compareTo(new LwM2mPath(path2)) == 0);
+    }
+
+    private void assertFirstSmaller(String path1, String path2) {
+        assertTrue(new LwM2mPath(path1).compareTo(new LwM2mPath(path2)) == -1);
+        assertTrue(new LwM2mPath(path2).compareTo(new LwM2mPath(path1)) == 1);
+
+    }
+}