Explorer-Workbench/src/Explorer.Windows/WindowsUsnJournal.cs

using System.ComponentModel;
using System.Runtime.InteropServices;
using Explorer.Domain.Abstractions;
using Microsoft.Extensions.Logging;

namespace Explorer.Windows;

public sealed class WindowsUsnJournal : IUsnJournal
{
    private readonly ILogger<WindowsUsnJournal> _logger;

    public WindowsUsnJournal(ILogger<WindowsUsnJournal> logger) => _logger = logger;

    public bool TryQuery(string rootPath, out UsnJournalState state, out string? error)
    {
        state = new UsnJournalState();
        error = null;
        var volume = OpenVolume(rootPath, out error);
        if (volume == nint.Zero)
        {
            return false;
        }

        try
        {
            var size = Marshal.SizeOf<NativeMethods.UsnJournalDataV2>();
            var buffer = Marshal.AllocHGlobal(size);
            try
            {
                if (!NativeMethods.DeviceIoControl(volume, NativeMethods.IoctlQueryUsnJournal, 0, 0, buffer, (uint)size, out _, 0))
                {
                    error = new Win32Exception(Marshal.GetLastWin32Error()).Message;
                    return false;
                }

                var data = Marshal.PtrToStructure<NativeMethods.UsnJournalDataV2>(buffer);
                state = new UsnJournalState
                {
                    JournalId = unchecked((long)data.UsnJournalId),
                    NextUsn = data.NextUsn
                };
                return true;
            }
            finally
            {
                Marshal.FreeHGlobal(buffer);
            }
        }
        catch (Exception ex)
        {
            error = ex.Message;
            _logger.LogDebug(ex, "USN query failed for {Path}", rootPath);
            return false;
        }
        finally
        {
            NativeMethods.CloseHandle(volume);
        }
    }

    public IReadOnlyList<UsnRecord> Read(string rootPath, UsnJournalState from, int maxRecords, out UsnJournalState next, out UsnReadStatus status)
    {
        next = from;
        status = UsnReadStatus.Unavailable;
        var records = new List<UsnRecord>();
        if (!TryQuery(rootPath, out var current, out var error))
        {
            status = error?.Contains("denied", StringComparison.OrdinalIgnoreCase) == true
                ? UsnReadStatus.AccessDenied
                : UsnReadStatus.Unavailable;
            return records;
        }

        if (from.JournalId != 0 && from.JournalId != current.JournalId)
        {
            status = UsnReadStatus.JournalReset;
            next = current;
            return records;
        }

        var volume = OpenVolume(rootPath, out _);
        if (volume == nint.Zero)
        {
            status = UsnReadStatus.AccessDenied;
            return records;
        }

        try
        {
            var read = new NativeMethods.ReadUsnJournalDataV1
            {
                StartUsn = from.NextUsn == 0 ? current.NextUsn : from.NextUsn,
                ReasonMask = 0xFFFFFFFF,
                ReturnOnlyOnClose = 0,
                Timeout = 0,
                BytesToWaitFor = 0,
                UsnJournalId = unchecked((ulong)current.JournalId),
                MinMajorVersion = 2,
                MaxMajorVersion = 3
            };

            var inSize = Marshal.SizeOf(read);
            var inPtr = Marshal.AllocHGlobal(inSize);
            var outSize = 64 * 1024;
            var outPtr = Marshal.AllocHGlobal(outSize);
            try
            {
                Marshal.StructureToPtr(read, inPtr, false);
                if (!NativeMethods.DeviceIoControl(volume, NativeMethods.IoctlReadUsnJournal, inPtr, (uint)inSize, outPtr, (uint)outSize, out var returned, 0))
                {
                    var code = Marshal.GetLastWin32Error();
                    status = code is 5 or 1314 ? UsnReadStatus.AccessDenied : UsnReadStatus.Error;
                    if (code is 1179 or 1180)
                    {
                        status = UsnReadStatus.JournalReset;
                    }

                    return records;
                }

                if (returned < 8)
                {
                    status = UsnReadStatus.Ok;
                    next = current;
                    return records;
                }

                var nextUsn = Marshal.ReadInt64(outPtr);
                var offset = 8;
                while (offset + 60 < returned && records.Count < maxRecords)
                {
                    var recordLength = Marshal.ReadInt32(outPtr, offset);
                    if (recordLength <= 0)
                    {
                        break;
                    }

                    var major = Marshal.ReadInt16(outPtr, offset + 4);
                    var frn = Marshal.ReadInt64(outPtr, offset + 8);
                    var parentFrn = Marshal.ReadInt64(outPtr, offset + 16);
                    var usn = Marshal.ReadInt64(outPtr, offset + 24);
                    var reason = Marshal.ReadInt32(outPtr, offset + 40);
                    var attrs = Marshal.ReadInt32(outPtr, offset + 52);
                    var nameLength = Marshal.ReadInt16(outPtr, offset + 56);
                    var nameOffset = Marshal.ReadInt16(outPtr, offset + 58);
                    var name = Marshal.PtrToStringUni(outPtr + offset + nameOffset, nameLength / 2) ?? "";
                    records.Add(new UsnRecord
                    {
                        FileReferenceNumber = frn,
                        ParentFileReferenceNumber = parentFrn,
                        Usn = usn,
                        FileName = name,
                        Reason = reason,
                        FileAttributes = attrs
                    });
                    offset += recordLength;
                    _ = major;
                }

                next = new UsnJournalState { JournalId = current.JournalId, NextUsn = nextUsn };
                status = UsnReadStatus.Ok;
                return records;
            }
            finally
            {
                Marshal.FreeHGlobal(inPtr);
                Marshal.FreeHGlobal(outPtr);
            }
        }
        catch (Exception ex)
        {
            _logger.LogDebug(ex, "USN read failed for {Path}", rootPath);
            status = UsnReadStatus.Error;
            return records;
        }
        finally
        {
            NativeMethods.CloseHandle(volume);
        }
    }

    private static nint OpenVolume(string rootPath, out string? error)
    {
        error = null;
        var letter = Path.GetPathRoot(rootPath)?.TrimEnd('\\');
        if (string.IsNullOrEmpty(letter))
        {
            error = "Invalid volume";
            return nint.Zero;
        }

        var volumePath = @"\\.\" + letter;
        var handle = NativeMethods.CreateFile(
            volumePath,
            NativeMethods.GenericRead,
            NativeMethods.FileShareRead | NativeMethods.FileShareWrite,
            0,
            NativeMethods.OpenExisting,
            0,
            0);
        if (handle == nint.Zero || handle == new nint(-1))
        {
            error = new Win32Exception(Marshal.GetLastWin32Error()).Message;
            return nint.Zero;
        }

        return handle;
    }
}