BUG-6972: Add OptionaBoolean utility

[yangtools.git] / common / util / src / main / java / org / opendaylight / yangtools / util / OptionalBoolean.java

diff --git a/common/util/src/main/java/org/opendaylight/yangtools/util/OptionalBoolean.java b/common/util/src/main/java/org/opendaylight/yangtools/util/OptionalBoolean.java
new file mode 100644 (file)
index 0000000..824dbe6
--- /dev/null
+++ b/common/util/src/main/java/org/opendaylight/yangtools/util/OptionalBoolean.java
@@ -0,0 +1,156 @@
+/*
+ * 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);
+    }
+}