+/*
+ * Copyright (c) 2017 Pantheon Technologies, s.r.o. and others. All rights reserved.
+ *
+ * This program and the accompanying materials are made available under the
+ * terms of the Eclipse Public License v1.0 which accompanies this distribution,
+ * and is available at http://www.eclipse.org/legal/epl-v10.html
+ */
+package org.opendaylight.yangtools.util;
+
+import com.google.common.annotations.Beta;
+import java.util.Optional;
+import javax.annotation.Nullable;
+
+/**
+ * Utility class for storing an optional boolean in a single byte value. This cuts down the memory requirement quite
+ * at very small computational cost.
+ *
+ * <p>
+ * Note: fields do not have to be explicitly initialized, as default initialization value for 'byte', 0, is used to
+ * represent 'absent' condition.
+ *
+ * @author Robert Varga
+ */
+@Beta
+public final class OptionalBoolean {
+ private static final byte ABSENT = 0;
+ private static final byte FALSE = 1;
+ private static final byte TRUE = 2;
+
+ private OptionalBoolean() {
+ throw new UnsupportedOperationException();
+ }
+
+ /**
+ * Check if a field value has been set, just like {@link Optional#isPresent()}.
+ *
+ * @param value field value
+ * @return True if the value is set.
+ * @throws IllegalArgumentException if value is invalid
+ */
+ public static boolean isPresent(final byte value) {
+ switch (value) {
+ case ABSENT:
+ return false;
+ case FALSE:
+ case TRUE:
+ return true;
+ default:
+ throw invalidValue(value);
+ }
+ }
+
+ /**
+ * Decode boolean from a field value, just like {@link Optional#get()}.
+ *
+ * @param value Field value
+ * @return Decoded boolean.
+ * @throws IllegalArgumentException if value is invalid
+ * @throws IllegalStateException if value has not been set
+ */
+ public static boolean get(final byte value) {
+ switch (value) {
+ case ABSENT:
+ throw new IllegalStateException("Field has not been initialized");
+ case FALSE:
+ return false;
+ case TRUE:
+ return true;
+ default:
+ throw invalidValue(value);
+ }
+ }
+
+ /**
+ * Encode a boolean to a field value, just like {@link Optional#of(Object)}.
+ *
+ * @param bool Boolean value.
+ * @return Field value.
+ */
+ public static byte of(final boolean bool) {
+ return bool ? TRUE : FALSE;
+ }
+
+ /**
+ * Convert a nullable {@link Boolean} into a field value, just like {@link Optional#ofNullable(Object)}.
+ *
+ * @param bool Boolean value.
+ * @return Field value.
+ */
+ public static byte ofNullable(final @Nullable Boolean bool) {
+ return bool == null ? ABSENT : of(bool.booleanValue());
+ }
+
+ /**
+ * Convert a field value to a nullable {@link Boolean}. Similar to {@code Optional.orElse(null)}.
+ *
+ * @param value Fied value.
+ * @return Nullable Boolean.
+ */
+ public static @Nullable Boolean toNullable(final byte value) {
+ switch (value) {
+ case ABSENT:
+ return null;
+ case FALSE:
+ return Boolean.FALSE;
+ case TRUE:
+ return Boolean.TRUE;
+ default:
+ throw invalidValue(value);
+ }
+ }
+
+ /**
+ * Convert a field value into an {@link Optional} {@link Boolean}.
+ *
+ * @param value Field value.
+ * @return Optional {@link Boolean}.
+ * @throws IllegalArgumentException if value is invalid.
+ */
+ public static Optional<Boolean> toOptional(final byte value) {
+ switch (value) {
+ case ABSENT:
+ return Optional.empty();
+ case FALSE:
+ return Optional.of(Boolean.FALSE);
+ case TRUE:
+ return Optional.of(Boolean.TRUE);
+ default:
+ throw invalidValue(value);
+ }
+ }
+
+ /**
+ * Convert a field value into a String representation.
+ *
+ * @param value Field value.
+ * @return Boolean-compatible string, or "absent".
+ * @throws IllegalArgumentException if value is invalid.
+ */
+ public static String toString(final byte value) {
+ switch (value) {
+ case ABSENT:
+ return "absent";
+ case FALSE:
+ return Boolean.toString(false);
+ case TRUE:
+ return Boolean.toString(true);
+ default:
+ throw invalidValue(value);
+ }
+ }
+
+ private static IllegalArgumentException invalidValue(final byte value) {
+ throw new IllegalArgumentException("Invalid field value " + value);
+ }
+}