From 55859158fbd0bf54473a0baeb486045a025c7c5d Mon Sep 17 00:00:00 2001 From: vnugent Date: Sun, 24 Mar 2024 21:01:06 -0400 Subject: Squashed commit of the following: commit 6c1667be23597513537f8190e2f55d65eb9b7c7a Author: vnugent Date: Fri Mar 22 12:01:53 2024 -0400 refactor: Overhauled native library loading and lazy init commit ebf688f2f974295beabf7b5def7e6f6f150551d0 Author: vnugent Date: Wed Mar 20 22:16:17 2024 -0400 refactor: Update compression header files and macros + Ci build commit 9c7b564911080ccd5cbbb9851a0757b05e1e9047 Author: vnugent Date: Tue Mar 19 21:54:49 2024 -0400 refactor: JWK overhaul & add length getter to FileUpload commit 6d8c3444e09561e5957491b3cc1ae858e0abdd14 Author: vnugent Date: Mon Mar 18 16:13:20 2024 -0400 feat: Add FNV1a software checksum and basic correction tests commit 00d182088cecefc08ca80b1faee9bed3f215f40b Author: vnugent Date: Fri Mar 15 01:05:27 2024 -0400 chore: #6 Use utils filewatcher instead of built-in commit d513c10d9895c6693519ef1d459c6a5a76929436 Author: vnugent Date: Sun Mar 10 21:58:14 2024 -0400 source tree project location updated --- lib/Utils/src/Resources/LazyInitializer.cs | 112 +++++++++++++++++++++++++++++ 1 file changed, 112 insertions(+) create mode 100644 lib/Utils/src/Resources/LazyInitializer.cs (limited to 'lib/Utils/src/Resources') diff --git a/lib/Utils/src/Resources/LazyInitializer.cs b/lib/Utils/src/Resources/LazyInitializer.cs new file mode 100644 index 0000000..5de43e0 --- /dev/null +++ b/lib/Utils/src/Resources/LazyInitializer.cs @@ -0,0 +1,112 @@ +/* +* Copyright (c) 2024 Vaughn Nugent +* +* Library: VNLib +* Package: VNLib.Utils +* File: LazyInitializer.cs +* +* LazyInitializer.cs is part of VNLib.Utils which is part of the larger +* VNLib collection of libraries and utilities. +* +* VNLib.Utils is free software: you can redistribute it and/or modify +* it under the terms of the GNU General Public License as published +* by the Free Software Foundation, either version 2 of the License, +* or (at your option) any later version. +* +* VNLib.Utils is distributed in the hope that it will be useful, +* but WITHOUT ANY WARRANTY; without even the implied warranty of +* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU +* General Public License for more details. +* +* You should have received a copy of the GNU General Public License +* along with VNLib.Utils. If not, see http://www.gnu.org/licenses/. +*/ + +using System; +using System.Threading; +using System.Diagnostics; + +namespace VNLib.Utils.Resources +{ + /// + /// A lazy initializer that creates a single instance of a type + /// and shares it across all threads. This class simply guarantees + /// that the instance is only created once and shared across all + /// threads as efficiently as possible for long running processes. + /// + /// + /// The callback function that initializes the instance + public sealed class LazyInitializer(Func initalizer) + { + private readonly object _lock = new(); + private readonly Func initalizer = initalizer ?? throw new ArgumentNullException(nameof(initalizer)); + + private T? _instance; + private bool _isLoaded; + + /// + /// A value indicating if the instance has ben loaded + /// + public bool IsLoaded => _isLoaded; + + /// + /// Gets or creates the instance only once and returns + /// the shared instance + /// + /// + /// NOTE: + /// Accessing this property may block the calling thread + /// if the instance has not yet been loaded. Only one thread + /// will create the instance, all other threads will wait + /// for the instance to be created. + /// + public T Instance + { + get + { + //See if instance is already loaded (this read is atomic in .NET) + if (_isLoaded) + { + return _instance!; + } + + /* + * Instance has not yet been loaded. Only one thread + * must load the object, all other threads must wait + * for the object to be loaded. + */ + + if (Monitor.TryEnter(_lock, 0)) + { + try + { + /* + * Lock was entered without waiting (lock was available), this will now be + * the thread that invokes the load function + */ + + _instance = initalizer(); + + //Finally set the load state + _isLoaded = true; + } + finally + { + Monitor.Exit(_lock); + } + } + else + { + //wait for lock to be released, when it is, the object should be loaded + Monitor.Enter(_lock); + Monitor.Exit(_lock); + + //object instance should now be available to non-creating threads + Debug.Assert(_isLoaded); + } + + return _instance!; + } + } + } +} \ No newline at end of file -- cgit