duplicati/Duplicati/Library/Main/Operation/Restore/VolumeDecompressor.cs

// Copyright (C) 2025, The Duplicati Team
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// 
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// 
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using System;
using System.Diagnostics;
using System.Threading.Tasks;
using CoCoL;
using Duplicati.Library.Utility;

namespace Duplicati.Library.Main.Operation.Restore
{

    /// <summary>
    /// Process that decompresses the volumes that the `VolumeDecryptor` process has decrypted.
    /// </summary>
    internal class VolumeDecompressor
    {
        /// <summary>
        /// The log tag for this class.
        /// </summary>
        private static readonly string LOGTAG = Logging.Log.LogTagFromType<VolumeDecompressor>();

        /// <summary>
        /// Runs the volume decompressor process.
        /// </summary>
        /// <param name="options">The restore options</param>
        public static Task Run(Channels channels, Options options)
        {
            return AutomationExtensions.RunTask(
            new
            {
                Input = channels.DecompressionRequest.AsRead(),
                Output = channels.DecompressedBlock.AsWrite()
            },
            async self =>
            {
                Stopwatch sw_read       = options.InternalProfiling ? new () : null;
                Stopwatch sw_write      = options.InternalProfiling ? new () : null;
                Stopwatch sw_decompress = options.InternalProfiling ? new () : null;
                Stopwatch sw_verify     = options.InternalProfiling ? new () : null;

                try {
                    using var block_hasher = HashFactory.CreateHasher(options.BlockHashAlgorithm);

                    while (true)
                    {
                        sw_read?.Start();
                        // Get the block request and volume from the `VolumeDecryptor` process.
                        var (block_request, volume_reader) = await self.Input.ReadAsync();
                        sw_read?.Stop();

                        sw_decompress?.Start();
                        var data = new byte[block_request.BlockSize];
                        lock (volume_reader) // The BlockVolumeReader is not thread-safe
                        {
                            volume_reader.ReadBlock(block_request.BlockHash, data);
                        }
                        sw_decompress?.Stop();

                        sw_verify?.Start();
                        var hash = Convert.ToBase64String(block_hasher.ComputeHash(data, 0, (int)block_request.BlockSize));
                        if (hash != block_request.BlockHash) {
                            Logging.Log.WriteErrorMessage(LOGTAG, "InvalidBlock", null, $"Invalid block detected for block {block_request.BlockID} in volume {block_request.VolumeID}, expected hash: {block_request.BlockHash}, actual hash: {hash}");
                        }
                        sw_verify?.Stop();

                        sw_write?.Start();
                        // Send the block to the `BlockManager` process.
                        await self.Output.WriteAsync((block_request, data));
                        sw_write?.Stop();
                    }
                }
                catch (RetiredException)
                {
                    Logging.Log.WriteVerboseMessage(LOGTAG, "RetiredProcess", null, "Volume decompressor retired");

                    if (options.InternalProfiling)
                    {
                        Logging.Log.WriteProfilingMessage(LOGTAG, "InternalTimings", $"Read: {sw_read.ElapsedMilliseconds}ms, Write: {sw_write.ElapsedMilliseconds}ms, Decompress: {sw_decompress.ElapsedMilliseconds}ms, Verify: {sw_verify.ElapsedMilliseconds}ms");
                    }
                }
                catch (Exception ex)
                {
                    Logging.Log.WriteErrorMessage(LOGTAG, "DecompressionError", ex, "Error during decompression");
                    throw;
                }
            });
        }
    }

}