Add ModbusDevice as preparation for server implementations.

AMWD.Protocols.Modbus.Common/Extensions/ReaderWriterLockSlimExtensions.cs

@@ -0,0 +1,92 @@
+namespace System.Threading
+{
+	// ================================================================================================================================================== //
+	// Source: https://git.am-wd.de/am-wd/common/-/blob/d4b390ad911ce302cc371bb2121fa9c31db1674a/AMWD.Common/Extensions/ReaderWriterLockSlimExtensions.cs //
+	// ================================================================================================================================================== //
+	[System.Diagnostics.CodeAnalysis.ExcludeFromCodeCoverage]
+	internal static class ReaderWriterLockSlimExtensions
+	{
+		/// <summary>
+		/// Acquires a read lock on a lock object that can be released with an
+		/// <see cref="IDisposable"/> instance.
+		/// </summary>
+		/// <param name="rwLock">The lock object.</param>
+		/// <param name="timeoutMilliseconds">The number of milliseconds to wait, or -1
+		///   (<see cref="Timeout.Infinite"/>) to wait indefinitely.</param>
+		/// <returns>An <see cref="IDisposable"/> instance to release the lock.</returns>
+		public static IDisposable GetReadLock(this ReaderWriterLockSlim rwLock, int timeoutMilliseconds = -1)
+		{
+			if (!rwLock.TryEnterReadLock(timeoutMilliseconds))
+				throw new TimeoutException("The read lock could not be acquired.");
+
+			return new DisposableReadWriteLock(rwLock, LockMode.Read);
+		}
+
+		/// <summary>
+		/// Acquires a upgradeable read lock on a lock object that can be released with an
+		/// <see cref="IDisposable"/> instance. The lock can be upgraded to a write lock temporarily
+		/// with <see cref="GetWriteLock"/> or until the lock is released with
+		/// <see cref="ReaderWriterLockSlim.EnterWriteLock"/> alone.
+		/// </summary>
+		/// <param name="rwLock">The lock object.</param>
+		/// <param name="timeoutMilliseconds">The number of milliseconds to wait, or -1
+		///   (<see cref="Timeout.Infinite"/>) to wait indefinitely.</param>
+		/// <returns>An <see cref="IDisposable"/> instance to release the lock. If the lock was
+		///   upgraded to a write lock, that will be released as well.</returns>
+		public static IDisposable GetUpgradeableReadLock(this ReaderWriterLockSlim rwLock, int timeoutMilliseconds = -1)
+		{
+			if (!rwLock.TryEnterUpgradeableReadLock(timeoutMilliseconds))
+				throw new TimeoutException("The upgradeable read lock could not be acquired.");
+
+			return new DisposableReadWriteLock(rwLock, LockMode.Upgradable);
+		}
+
+		/// <summary>
+		/// Acquires a write lock on a lock object that can be released with an
+		/// <see cref="IDisposable"/> instance.
+		/// </summary>
+		/// <param name="rwLock">The lock object.</param>
+		/// <param name="timeoutMilliseconds">The number of milliseconds to wait, or -1
+		///   (<see cref="Timeout.Infinite"/>) to wait indefinitely.</param>
+		/// <returns>An <see cref="IDisposable"/> instance to release the lock.</returns>
+		public static IDisposable GetWriteLock(this ReaderWriterLockSlim rwLock, int timeoutMilliseconds = -1)
+		{
+			if (!rwLock.TryEnterWriteLock(timeoutMilliseconds))
+				throw new TimeoutException("The write lock could not be acquired.");
+
+			return new DisposableReadWriteLock(rwLock, LockMode.Write);
+		}
+
+		private struct DisposableReadWriteLock(ReaderWriterLockSlim rwLock, LockMode lockMode)
+			: IDisposable
+		{
+			private readonly ReaderWriterLockSlim _rwLock = rwLock;
+			private LockMode _lockMode = lockMode;
+
+			public void Dispose()
+			{
+				if (_lockMode == LockMode.Read)
+					_rwLock.ExitReadLock();
+
+				if (_lockMode == LockMode.Upgradable && _rwLock.IsWriteLockHeld)   // Upgraded with EnterWriteLock alone
+					_rwLock.ExitWriteLock();
+
+				if (_lockMode == LockMode.Upgradable)
+					_rwLock.ExitUpgradeableReadLock();
+
+				if (_lockMode == LockMode.Write)
+					_rwLock.ExitWriteLock();
+
+				_lockMode = LockMode.None;
+			}
+		}
+
+		private enum LockMode
+		{
+			None = 0,
+			Read = 1,
+			Upgradable = 2,
+			Write = 3,
+		}
+	}
+}