/*
* Copyright (c) 2023 Vaughn Nugent
*
* Library: VNLib
* Package: VNLib.Plugins.Extensions.Loading
* File: AssemblyLoader.cs
*
* AssemblyLoader.cs is part of VNLib.Plugins.Extensions.Loading which is part of the larger
* VNLib collection of libraries and utilities.
*
* VNLib.Plugins.Extensions.Loading is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* VNLib.Plugins.Extensions.Loading 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 Affero General Public License for more details.
*
* You should have received a copy of the GNU Affero General Public License
* along with this program. If not, see https://www.gnu.org/licenses/.
*/
using System;
using System.IO;
using System.Threading;
using System.Reflection;
using System.Runtime.Loader;
using VNLib.Utils.IO;
using VNLib.Utils.Resources;
namespace VNLib.Plugins.Extensions.Loading
{
///
///
/// Represents a disposable assembly loader wrapper for
/// exporting a single type from a loaded assembly
///
///
/// If the loaded type implements the
/// dispose method is called when the loader is disposed
///
///
/// The exported type to manage
public sealed class AssemblyLoader : ManagedLibrary, IDisposable
{
private readonly CancellationTokenRegistration _reg;
private readonly Lazy _instance;
private bool disposedValue;
///
/// The instance of the loaded type
///
public T Resource => _instance.Value;
private AssemblyLoader(string assemblyPath, AssemblyLoadContext parentContext, CancellationToken unloadToken)
:base(assemblyPath, parentContext)
{
//Init lazy type loader
_instance = new(LoadTypeFromAssembly, LazyThreadSafetyMode.PublicationOnly);
//Register dispose
_reg = unloadToken.Register(Dispose);
}
///
/// Creates a method delegate for the given method name from
/// the instance wrapped by the current loader
///
///
/// The name of the method to recover
/// The delegate method wrapper if found, null otherwise
///
///
public TDelegate? TryGetMethod(string methodName) where TDelegate : Delegate
{
//get the type info of the actual resource
return Resource.GetType()
.GetMethod(methodName, BindingFlags.Public | BindingFlags.Instance)
?.CreateDelegate(Resource);
}
private void Dispose(bool disposing)
{
if (!disposedValue)
{
//Call base unload during dispose (or finalize)
OnUnload();
//Always cleanup registration
_reg.Dispose();
if (disposing)
{
//If the instance is disposable, call its dispose method on unload
if (_instance.IsValueCreated && _instance.Value is IDisposable disposable)
{
disposable.Dispose();
}
}
disposedValue = true;
}
}
///
/// Cleans up any unused internals
///
~AssemblyLoader()
{
// Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
Dispose(disposing: false);
}
///
/// Disposes the assembly loader and cleans up resources. If the
/// inherits the intrance is disposed.
///
public void Dispose()
{
// Do not change this code. Put cleanup code in 'Dispose(bool disposing)' method
Dispose(disposing: true);
GC.SuppressFinalize(this);
}
///
/// Creates a new loader for the desired assembly. The assembly and its dependencies
/// will be loaded into the specified context. If no context is specified the current assemblie's load
/// context is captured.
///
/// The name of the assmbly within the current plugin directory
/// The plugin unload token
/// The assembly load context to load the assmbly into
///
internal static AssemblyLoader Load(string assemblyName, AssemblyLoadContext loadContext, CancellationToken unloadToken)
{
_ = loadContext ?? throw new ArgumentNullException(nameof(loadContext));
//Make sure the file exists
if (!FileOperations.FileExists(assemblyName))
{
throw new FileNotFoundException($"The desired assembly {assemblyName} could not be found at the file path");
}
//Create the loader from its absolute file path
FileInfo fi = new(assemblyName);
return new(fi.FullName, loadContext, unloadToken);
}
}
}