| using J2N.Threading.Atomic; |
| using System; |
| using System.Runtime.CompilerServices; |
| #if FEATURE_SERIALIZABLE_EXCEPTIONS |
| using System.Runtime.Serialization; |
| #endif |
| |
| namespace Lucene.Net.Util |
| { |
| /* |
| * Licensed to the Apache Software Foundation (ASF) under one or more |
| * contributor license agreements. See the NOTICE file distributed with |
| * this work for additional information regarding copyright ownership. |
| * The ASF licenses this file to You under the Apache License, Version 2.0 |
| * (the "License"); you may not use this file except in compliance with |
| * the License. You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| |
| /// <summary> |
| /// A convenient class which offers a semi-immutable object wrapper |
| /// implementation which allows one to set the value of an object exactly once, |
| /// and retrieve it many times. If <see cref="Set(T)"/> is called more than once, |
| /// <see cref="AlreadySetException"/> is thrown and the operation |
| /// will fail. |
| /// <para/> |
| /// @lucene.experimental |
| /// </summary> |
| public sealed class SetOnce<T> |
| #if FEATURE_CLONEABLE |
| : System.ICloneable |
| #endif |
| where T : class // LUCENENET specific - added class constraint so we don't accept value types (which cannot be volatile) |
| { |
| private volatile T obj = default; |
| private readonly AtomicBoolean set; |
| |
| /// <summary> |
| /// A default constructor which does not set the internal object, and allows |
| /// setting it by calling <see cref="Set(T)"/>. |
| /// </summary> |
| public SetOnce() |
| { |
| set = new AtomicBoolean(false); |
| } |
| |
| /// <summary> |
| /// Creates a new instance with the internal object set to the given object. |
| /// Note that any calls to <see cref="Set(T)"/> afterwards will result in |
| /// <see cref="AlreadySetException"/> |
| /// </summary> |
| /// <exception cref="AlreadySetException"> if called more than once </exception> |
| /// <seealso cref="Set(T)"/> |
| public SetOnce(T obj) |
| { |
| this.obj = obj; |
| set = new AtomicBoolean(true); |
| } |
| |
| /// <summary> |
| /// Sets the given object. If the object has already been set, an exception is thrown. </summary> |
| public void Set(T obj) |
| { |
| if (set.CompareAndSet(false, true)) |
| { |
| this.obj = obj; |
| } |
| else |
| { |
| throw new AlreadySetException(); |
| } |
| } |
| |
| /// <summary> |
| /// Returns the object set by <see cref="Set(T)"/>. </summary> |
| [MethodImpl(MethodImplOptions.AggressiveInlining)] |
| public T Get() |
| { |
| return obj; |
| } |
| |
| [MethodImpl(MethodImplOptions.AggressiveInlining)] |
| public object Clone() |
| { |
| return obj == null ? new SetOnce<T>() : new SetOnce<T>(obj); |
| } |
| } |
| |
| /// <summary> |
| /// Thrown when <see cref="SetOnce{T}.Set(T)"/> is called more than once. </summary> |
| // LUCENENET specific - de-nested the class from SetOnce<T> to allow the test |
| // framework to serialize it without the generic type. |
| // LUCENENET: It is no longer good practice to use binary serialization. |
| // See: https://github.com/dotnet/corefx/issues/23584#issuecomment-325724568 |
| #if FEATURE_SERIALIZABLE_EXCEPTIONS |
| [Serializable] |
| #endif |
| public sealed class AlreadySetException : InvalidOperationException |
| { |
| /// <summary> |
| /// Initializes a new instance of <see cref="AlreadySetException"/>. |
| /// </summary> |
| public AlreadySetException() |
| : base("The object cannot be set twice!") |
| { |
| } |
| |
| #if FEATURE_SERIALIZABLE_EXCEPTIONS |
| /// <summary> |
| /// Initializes a new instance of this class with serialized data. |
| /// </summary> |
| /// <param name="info">The <see cref="SerializationInfo"/> that holds the serialized object data about the exception being thrown.</param> |
| /// <param name="context">The <see cref="StreamingContext"/> that contains contextual information about the source or destination.</param> |
| private AlreadySetException(SerializationInfo info, StreamingContext context) |
| : base(info, context) |
| { |
| } |
| #endif |
| } |
| } |