duplicati/Duplicati/Library/DynamicLoader/CompressionLoader.cs

// Copyright (C) 2025, The Duplicati Team
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using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Duplicati.Library.Compression;
using Duplicati.Library.Interface;

namespace Duplicati.Library.DynamicLoader
{
    /// <summary>
    /// Loads all compression modules dynamically and exposes a list of those
    /// </summary>
    public class CompressionLoader
    {
        /// <summary>
        /// Implementation overrides specific to compression
        /// </summary>
        private class CompressionLoaderSub : DynamicLoader<ICompression>
        {
            /// <summary>
            /// Returns the filename extension, which is also the key
            /// </summary>
            /// <param name="item">The item to load the key for</param>
            /// <returns>The file extension used by the module</returns>
            protected override string GetInterfaceKey(ICompression item)
            {
                return item.FilenameExtension;
            }

            /// <summary>
            /// Returns the subfolders searched for compression modules
            /// </summary>
            protected override string[] Subfolders => ["compression"];

            /// <summary>
            /// The built-in modules
            /// </summary>
            protected override IEnumerable<ICompression> BuiltInModules => CompressionModules.BuiltInCompressionModules;

            /// <summary>
            /// Instanciates a specific compression module, given the file extension and options
            /// </summary>
            /// <param name="fileExtension">The file extension to create the instance for</param>
            /// <param name="stream">The stream of the file used to compress/decompress contents</param>
            /// <param name="mode">The mode for compression/decompression</param>
            /// <param name="options">The options to pass to the instance constructor</param>
            /// <returns>The instanciated encryption module or null if the file extension is not supported</returns>
            public ICompression GetModule(string fileExtension, Stream stream, ArchiveMode mode, Dictionary<string, string> options)
            {
                if (string.IsNullOrEmpty(fileExtension))
                    throw new ArgumentNullException(nameof(fileExtension));

                LoadInterfaces();

                lock (m_lock)
                {
                    if (m_interfaces.ContainsKey(fileExtension))
                        return (ICompression)Activator.CreateInstance(m_interfaces[fileExtension].GetType(), stream, mode, options);
                    else
                        return null;
                }
            }

            /// <summary>
            /// Gets the supported commands for a certain key
            /// </summary>
            /// <param name="key">The key to find commands for</param>
            /// <returns>The supported commands or null if the key was not found</returns>
            public IReadOnlyList<ICommandLineArgument> GetSupportedCommands(string key)
            {
                if (string.IsNullOrEmpty(key))
                    throw new ArgumentNullException(nameof(key));

                LoadInterfaces();

                lock (m_lock)
                {
                    ICompression b;
                    if (m_interfaces.TryGetValue(key, out b) && b != null)
                        return GetSupportedCommandsCached(b).ToList();
                    else
                        return null;
                }
            }
        }

        /// <summary>
        /// The static instance used to access compression module information
        /// </summary>
        private static readonly CompressionLoaderSub _compressionLoader = new CompressionLoaderSub();

        #region Public static API

        /// <summary>
        /// Gets a list of loaded compression modules, the instances can be used to extract interface information, not used to interact with the module.
        /// </summary>
        public static ICompression[] Modules { get { return _compressionLoader.Interfaces; } }

        /// <summary>
        /// Gets a list of keys supported
        /// </summary>
        public static string[] Keys { get { return _compressionLoader.Keys; } }

        /// <summary>
        /// Gets the supported commands for a given compression module
        /// </summary>
        /// <param name="key">The compression module to find the commands for</param>
        /// <returns>The supported commands or null if the key is not supported</returns>
        public static IReadOnlyList<ICommandLineArgument> GetSupportedCommands(string key)
        {
            return _compressionLoader.GetSupportedCommands(key);
        }

        /// <summary>
        /// Instanciates a specific compression module, given the file extension and options
        /// </summary>
        /// <param name="fileextension">The file extension to create the instance for</param>
        /// <param name="stream">The stream of the file used to compress/decompress contents</param>
        /// <param name="mode">The mode for compression/decompression</param>
        /// <param name="options">The options to pass to the instance constructor</param>
        /// <returns>The instanciated compression module or null if the file extension is not supported</returns>
        public static ICompression GetModule(string fileextension, Stream stream, ArchiveMode mode, Dictionary<string, string> options)
        {
            return _compressionLoader.GetModule(fileextension, stream, mode, options);
        }
        #endregion

        /// <summary>
        /// Removes all compression modules except the specified ones
        /// </summary>
        /// <param name="allowedModules">The module keys to keep, comma-separated</param>
        public static void OnlyAllowModules(string allowedModules)
            => _compressionLoader.RemoveAllModulesExcept(allowedModules);
    }
}