UID: allow to encode arbitrary string (+decode) (#864)

Signed-off-by: Markus Rathgeb <maggu2810@gmail.com>

bundles/org.openhab.core/src/main/java/org/eclipse/smarthome/core/util/UIDUtils.java

@@ -0,0 +1,96 @@
+/**
+ * Copyright (c) 2010-2019 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.eclipse.smarthome.core.util;
+
+import java.nio.charset.StandardCharsets;
+
+import org.eclipse.jdt.annotation.NonNullByDefault;
+
+/**
+ * Utilities for UIDs.
+ *
+ * @author Markus Rathgeb - Initial contribution
+ */
+@NonNullByDefault
+public class UIDUtils {
+
+    /**
+     * Encodes a given string to an UID using only allowed characters.
+     *
+     * <p>
+     * The generated UID can be given to the {@link #decode(String)} function and it will result into the given value.
+     *
+     * @param value the string that should be encoded to a valid UID
+     * @return a string that if a valid UID (with respect to the allowed characters)
+     */
+    public static String encode(final String value) {
+        if (value.isEmpty()) {
+            return value;
+        }
+
+        final byte[] in = value.getBytes(StandardCharsets.UTF_8);
+        final byte[] out = new byte[in.length * 3];
+
+        int opos = 0;
+        for (int ipos = 0; ipos < in.length; ++ipos, ++opos) {
+            final byte cur = in[ipos];
+            if (cur >= '0' && cur <= '9' || cur >= 'A' && cur <= 'Z' || cur >= 'a' && cur <= 'z') {
+                out[opos] = cur;
+            } else {
+                out[opos++] = '_';
+                final byte[] hex = HexUtils.byteToHex(cur);
+                out[opos++] = hex[0];
+                out[opos] = hex[1];
+            }
+        }
+
+        return new String(out, 0, opos, StandardCharsets.UTF_8);
+    }
+
+    /**
+     * Decodes an UID that has been generated by the {@link #encode(String)} function.
+     *
+     * <p>
+     * This function should only be used for UIDs generated by the {@link #encode(String)} function. For every other UID
+     * the result is rather useless or could result into an {@link IllegalArgumentException}.
+     *
+     * @param value the UID to decode
+     * @return the decoded UID string
+     * @throws IllegalArgumentException if the given UID is not a valid encoded input
+     */
+    public static String decode(final String value) {
+        if (value.isEmpty()) {
+            return value;
+        }
+
+        final byte[] in = value.getBytes(StandardCharsets.UTF_8);
+        final byte[] out = new byte[in.length];
+
+        int opos = 0;
+        for (int ipos = 0; ipos < in.length; ++ipos, ++opos) {
+            final byte cur = in[ipos];
+            if (cur >= '0' && cur <= '9' || cur >= 'A' && cur <= 'Z' || cur >= 'a' && cur <= 'z') {
+                out[opos] = cur;
+            } else if (cur == '_') {
+                final byte curHigh = in[++ipos];
+                final byte curLow = in[++ipos];
+                out[opos] = HexUtils.hexToByte(curHigh, curLow);
+            } else {
+                throw new IllegalArgumentException("Invalid input");
+            }
+        }
+
+        return new String(out, 0, opos, StandardCharsets.UTF_8);
+    }
+
+}

bundles/org.openhab.core/src/test/java/org/eclipse/smarthome/core/common/UIDUtilsTest.java

@@ -0,0 +1,45 @@
+/**
+ * Copyright (c) 2010-2019 Contributors to the openHAB project
+ *
+ * See the NOTICE file(s) distributed with this work for additional
+ * information.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License 2.0 which is available at
+ * http://www.eclipse.org/legal/epl-2.0
+ *
+ * SPDX-License-Identifier: EPL-2.0
+ */
+package org.eclipse.smarthome.core.common;
+
+import java.util.function.Consumer;
+
+import org.eclipse.smarthome.core.util.UIDUtils;
+import org.hamcrest.core.IsEqual;
+import org.junit.Assert;
+import org.junit.Test;
+
+/**
+ * Tests for {@link AbstractUID}.
+ *
+ * @author Markus Rathgeb - Initial contribution
+ */
+public class UIDUtilsTest {
+
+    @Test
+    public void encodeDecode() {
+        Consumer<String> test = in -> {
+            final String encoded = UIDUtils.encode(in);
+            final String decoded = UIDUtils.decode(encoded);
+            System.out.printf("in: %s%n encoded: %s%n decoded: %s%n equals: %b%n", in, encoded, decoded,
+                    in.equals(decoded));
+            Assert.assertThat(decoded, IsEqual.equalTo(in));
+        };
+        test.accept("test");
+        test.accept("TEST");
+        test.accept("test123TEST");
+        test.accept("test_test-test%test");
+        test.accept("äöø€");
+    }
+
+}