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[exFAT] Implement directory operations.

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Natalia Portillo
2026-02-03 12:02:08 +00:00
parent d8e58f69e3
commit d9e85a2bc0
4 changed files with 391 additions and 128 deletions
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309
Aaru.Filesystems/exFAT/Dir.cs
View File

@@ -28,7 +28,10 @@
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using Aaru.CommonTypes.Enums;
using Aaru.CommonTypes.Interfaces;
using Marshal = Aaru.Helpers.Marshal;
namespace Aaru.Filesystems;
@@ -37,14 +40,149 @@ namespace Aaru.Filesystems;
/// <inheritdoc />
public sealed partial class exFAT
{
/// <summary>Parses a directory and populates the cache.</summary>
/// <inheritdoc />
public ErrorNumber OpenDir(string path, out IDirNode node)
{
node = null;
if(!_mounted) return ErrorNumber.AccessDenied;
ErrorNumber errno = GetDirectoryEntries(path, out Dictionary<string, CompleteDirectoryEntry> entries);
if(errno != ErrorNumber.NoError) return errno;
node = new ExFatDirNode
{
Path = path,
Position = 0,
Entries = entries.Values.ToArray()
};
return ErrorNumber.NoError;
}
/// <inheritdoc />
public ErrorNumber CloseDir(IDirNode node)
{
if(node is not ExFatDirNode myNode) return ErrorNumber.InvalidArgument;
myNode.Position = -1;
myNode.Entries = null;
return ErrorNumber.NoError;
}
/// <inheritdoc />
public ErrorNumber ReadDir(IDirNode node, out string filename)
{
filename = null;
if(!_mounted) return ErrorNumber.AccessDenied;
if(node is not ExFatDirNode myNode) return ErrorNumber.InvalidArgument;
if(myNode.Position < 0) return ErrorNumber.InvalidArgument;
if(myNode.Position >= myNode.Entries.Length) return ErrorNumber.NoError;
filename = myNode.Entries[myNode.Position].FileName;
myNode.Position++;
return ErrorNumber.NoError;
}
/// <summary>Gets directory entries for a given path, using cache when available.</summary>
/// <param name="path">Path to the directory.</param>
/// <param name="entries">Directory entries if found.</param>
/// <returns>Error number.</returns>
ErrorNumber GetDirectoryEntries(string path, out Dictionary<string, CompleteDirectoryEntry> entries)
{
entries = null;
// Root directory
if(string.IsNullOrWhiteSpace(path) || path == "/")
{
entries = _rootDirectoryCache;
return ErrorNumber.NoError;
}
string cutPath = path.StartsWith("/", StringComparison.Ordinal) ? path[1..] : path;
// Check cache first
if(_directoryCache.TryGetValue(cutPath, out entries)) return ErrorNumber.NoError;
string[] pieces = cutPath.Split('/', StringSplitOptions.RemoveEmptyEntries);
Dictionary<string, CompleteDirectoryEntry> currentDirectory = _rootDirectoryCache;
var currentPath = "";
for(var i = 0; i < pieces.Length; i++)
{
// Find the entry in current directory (case-insensitive per exFAT spec)
CompleteDirectoryEntry entry = null;
foreach(KeyValuePair<string, CompleteDirectoryEntry> kvp in currentDirectory)
{
if(kvp.Key.Equals(pieces[i], StringComparison.OrdinalIgnoreCase))
{
entry = kvp.Value;
break;
}
}
if(entry == null) return ErrorNumber.NoSuchFile;
if(!entry.IsDirectory) return ErrorNumber.NotDirectory;
currentPath = i == 0 ? pieces[0] : $"{currentPath}/{pieces[i]}";
// Check cache for this path
if(_directoryCache.TryGetValue(currentPath, out currentDirectory)) continue;
// Read directory contents
ErrorNumber errno = ReadDirectoryContents(entry, out currentDirectory);
if(errno != ErrorNumber.NoError) return errno;
// Cache this directory
_directoryCache[currentPath] = currentDirectory;
}
entries = currentDirectory;
return ErrorNumber.NoError;
}
/// <summary>Reads and parses directory contents from a directory entry.</summary>
/// <param name="dirEntry">The directory entry to read.</param>
/// <param name="entries">Parsed directory entries.</param>
/// <returns>Error number.</returns>
ErrorNumber ReadDirectoryContents(CompleteDirectoryEntry dirEntry,
out Dictionary<string, CompleteDirectoryEntry> entries)
{
entries = new Dictionary<string, CompleteDirectoryEntry>();
if(dirEntry.FirstCluster < 2) return ErrorNumber.NoError; // Empty directory
byte[] directoryData = ReadClusterChain(dirEntry.FirstCluster, dirEntry.IsContiguous, dirEntry.DataLength);
if(directoryData == null) return ErrorNumber.InvalidArgument;
ParseDirectoryContents(directoryData, entries);
return ErrorNumber.NoError;
}
/// <summary>Parses directory data into entries without modifying volume metadata.</summary>
/// <param name="directoryData">Raw directory data.</param>
/// <param name="cache">Cache to populate with parsed entries.</param>
void ParseDirectory(byte[] directoryData, Dictionary<string, CompleteDirectoryEntry> cache)
void ParseDirectoryContents(byte[] directoryData, Dictionary<string, CompleteDirectoryEntry> cache)
{
const int ENTRY_SIZE = 32;
const int entrySize = 32;
for(var i = 0; i < directoryData.Length; i += ENTRY_SIZE)
for(var i = 0; i < directoryData.Length; i += entrySize)
{
byte entryType = directoryData[i];
@@ -54,48 +192,27 @@ public sealed partial class exFAT
// Unused entry (deleted or available)
if(entryType < 0x80) continue;
// Volume Label (0x83)
if(entryType == (byte)EntryType.VolumeLabel)
{
VolumeLabelDirectoryEntry volumeLabelEntry =
Marshal.ByteArrayToStructureLittleEndian<VolumeLabelDirectoryEntry>(directoryData, i, ENTRY_SIZE);
if(volumeLabelEntry.CharacterCount > 0 && volumeLabelEntry.CharacterCount <= 11)
{
Metadata.VolumeName =
Encoding.Unicode.GetString(volumeLabelEntry.VolumeLabel,
0,
volumeLabelEntry.CharacterCount * 2);
}
// Skip non-file entries (Allocation Bitmap, Up-case Table, Volume Label, Volume GUID, TexFAT Padding)
if(entryType is (byte)EntryType.AllocationBitmap
or (byte)EntryType.UpcaseTable
or (byte)EntryType.VolumeLabel
or (byte)EntryType.VolumeGuid
or (byte)EntryType.TexFatPadding)
continue;
}
// Allocation Bitmap (0x81) - skip
if(entryType == (byte)EntryType.AllocationBitmap) continue;
// Up-case Table (0x82) - skip
if(entryType == (byte)EntryType.UpcaseTable) continue;
// Volume GUID (0xA0) - skip
if(entryType == (byte)EntryType.VolumeGuid) continue;
// TexFAT Padding (0xA1) - skip
if(entryType == (byte)EntryType.TexFatPadding) continue;
// File entry (0x85)
if(entryType == (byte)EntryType.File)
{
if(entryType != (byte)EntryType.File) continue;
FileDirectoryEntry fileEntry =
Marshal.ByteArrayToStructureLittleEndian<FileDirectoryEntry>(directoryData, i, ENTRY_SIZE);
Marshal.ByteArrayToStructureLittleEndian<FileDirectoryEntry>(directoryData, i, entrySize);
if(fileEntry.SecondaryCount < 2) continue; // Need at least Stream Extension and one File Name entry
// Check we have enough data for all secondary entries
if(i + (fileEntry.SecondaryCount + 1) * ENTRY_SIZE > directoryData.Length) continue;
if(i + (fileEntry.SecondaryCount + 1) * entrySize > directoryData.Length) continue;
// Read Stream Extension entry (must be immediately after File entry)
int streamOffset = i + ENTRY_SIZE;
int streamOffset = i + entrySize;
byte streamEntryType = directoryData[streamOffset];
if(streamEntryType != (byte)EntryType.StreamExtension) continue;
@@ -103,7 +220,7 @@ public sealed partial class exFAT
StreamExtensionDirectoryEntry streamEntry =
Marshal.ByteArrayToStructureLittleEndian<StreamExtensionDirectoryEntry>(directoryData,
streamOffset,
ENTRY_SIZE);
entrySize);
// Read File Name entries
var fileNameBuilder = new StringBuilder();
@@ -112,7 +229,7 @@ public sealed partial class exFAT
for(var j = 2; j <= fileEntry.SecondaryCount && fileNameEntriesRead < fileNameEntriesNeeded; j++)
{
int nameOffset = i + j * ENTRY_SIZE;
int nameOffset = i + j * entrySize;
byte nameEntryType = directoryData[nameOffset];
if(nameEntryType != (byte)EntryType.FileName) continue;
@@ -120,7 +237,7 @@ public sealed partial class exFAT
FileNameDirectoryEntry nameEntry =
Marshal.ByteArrayToStructureLittleEndian<FileNameDirectoryEntry>(directoryData,
nameOffset,
ENTRY_SIZE);
entrySize);
// Each File Name entry contains up to 15 Unicode characters (30 bytes)
int charsToRead = Math.Min(15, streamEntry.NameLength - fileNameEntriesRead * 15);
@@ -136,7 +253,7 @@ public sealed partial class exFAT
if(string.IsNullOrEmpty(fileName)) continue;
// Skip . and .. entries
if(fileName == "." || fileName == "..") continue;
if(fileName is "." or "..") continue;
// Create complete entry
var completeEntry = new CompleteDirectoryEntry
@@ -154,8 +271,116 @@ public sealed partial class exFAT
cache[fileName] = completeEntry;
// Skip the secondary entries we've processed
i += fileEntry.SecondaryCount * ENTRY_SIZE;
}
i += fileEntry.SecondaryCount * entrySize;
}
}
/// <summary>Parses a directory and populates the cache, also extracting volume label.</summary>
/// <param name="directoryData">Raw directory data.</param>
/// <param name="cache">Cache to populate with parsed entries.</param>
void ParseDirectory(byte[] directoryData, Dictionary<string, CompleteDirectoryEntry> cache)
{
const int entrySize = 32;
for(var i = 0; i < directoryData.Length; i += entrySize)
{
byte entryType = directoryData[i];
// End of directory
if(entryType == 0x00) break;
// Unused entry (deleted or available)
if(entryType < 0x80) continue;
// Volume Label (0x83) - only in root directory
if(entryType == (byte)EntryType.VolumeLabel)
{
VolumeLabelDirectoryEntry volumeLabelEntry =
Marshal.ByteArrayToStructureLittleEndian<VolumeLabelDirectoryEntry>(directoryData, i, entrySize);
if(volumeLabelEntry.CharacterCount > 0 && volumeLabelEntry.CharacterCount <= 11)
{
Metadata.VolumeName =
Encoding.Unicode.GetString(volumeLabelEntry.VolumeLabel,
0,
volumeLabelEntry.CharacterCount * 2);
}
continue;
}
// Skip other non-file entries
if(entryType is (byte)EntryType.AllocationBitmap
or (byte)EntryType.UpcaseTable
or (byte)EntryType.VolumeGuid
or (byte)EntryType.TexFatPadding)
continue;
// File entry (0x85)
if(entryType != (byte)EntryType.File) continue;
FileDirectoryEntry fileEntry =
Marshal.ByteArrayToStructureLittleEndian<FileDirectoryEntry>(directoryData, i, entrySize);
if(fileEntry.SecondaryCount < 2) continue;
if(i + (fileEntry.SecondaryCount + 1) * entrySize > directoryData.Length) continue;
int streamOffset = i + entrySize;
byte streamEntryType = directoryData[streamOffset];
if(streamEntryType != (byte)EntryType.StreamExtension) continue;
StreamExtensionDirectoryEntry streamEntry =
Marshal.ByteArrayToStructureLittleEndian<StreamExtensionDirectoryEntry>(directoryData,
streamOffset,
entrySize);
var fileNameBuilder = new StringBuilder();
int fileNameEntriesNeeded = (streamEntry.NameLength + 14) / 15;
var fileNameEntriesRead = 0;
for(var j = 2; j <= fileEntry.SecondaryCount && fileNameEntriesRead < fileNameEntriesNeeded; j++)
{
int nameOffset = i + j * entrySize;
byte nameEntryType = directoryData[nameOffset];
if(nameEntryType != (byte)EntryType.FileName) continue;
FileNameDirectoryEntry nameEntry =
Marshal.ByteArrayToStructureLittleEndian<FileNameDirectoryEntry>(directoryData,
nameOffset,
entrySize);
int charsToRead = Math.Min(15, streamEntry.NameLength - fileNameEntriesRead * 15);
if(charsToRead > 0)
fileNameBuilder.Append(Encoding.Unicode.GetString(nameEntry.FileName, 0, charsToRead * 2));
fileNameEntriesRead++;
}
var fileName = fileNameBuilder.ToString();
if(string.IsNullOrEmpty(fileName)) continue;
if(fileName is "." or "..") continue;
var completeEntry = new CompleteDirectoryEntry
{
FileEntry = fileEntry,
StreamEntry = streamEntry,
FileName = fileName,
FirstCluster = streamEntry.FirstCluster,
DataLength = streamEntry.DataLength,
ValidDataLength = streamEntry.ValidDataLength,
IsContiguous = (streamEntry.GeneralSecondaryFlags & (byte)GeneralSecondaryFlags.NoFatChain) != 0,
IsDirectory = fileEntry.FileAttributes.HasFlag(FileAttributes.Directory)
};
cache[fileName] = completeEntry;
i += fileEntry.SecondaryCount * entrySize;
}
}
}

84
Aaru.Filesystems/exFAT/Internal.cs Normal file
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@@ -0,0 +1,84 @@
// /***************************************************************************
// Aaru Data Preservation Suite
// ----------------------------------------------------------------------------
//
// Filename : Internal.cs
// Author(s) : Natalia Portillo <claunia@claunia.com>
//
// Component : Microsoft exFAT filesystem plugin.
//
// --[ License ] --------------------------------------------------------------
//
// This library is free software; you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as
// published by the Free Software Foundation; either version 2.1 of the
// License, or (at your option) any later version.
//
// This library 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
// Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public
// License along with this library; if not, see <http://www.gnu.org/licenses/>.
//
// ----------------------------------------------------------------------------
// Copyright © 2011-2026 Natalia Portillo
// ****************************************************************************/
using Aaru.CommonTypes.Interfaces;
namespace Aaru.Filesystems;
// Information from https://github.com/MicrosoftDocs/win32/blob/docs/desktop-src/FileIO/exfat-specification.md
/// <inheritdoc />
public sealed partial class exFAT
{
#region Nested type: CompleteDirectoryEntry
/// <summary>Represents a complete directory entry set with file entry, stream extension, and file name.</summary>
sealed class CompleteDirectoryEntry
{
/// <summary>Data length in bytes.</summary>
public ulong DataLength;
/// <summary>The File directory entry.</summary>
public FileDirectoryEntry FileEntry;
/// <summary>The complete file name assembled from File Name directory entries.</summary>
public string FileName;
/// <summary>First cluster of the file data.</summary>
public uint FirstCluster;
/// <summary>Whether the allocation is contiguous (NoFatChain).</summary>
public bool IsContiguous;
/// <summary>Whether this entry is a directory.</summary>
public bool IsDirectory;
/// <summary>The Stream Extension directory entry.</summary>
public StreamExtensionDirectoryEntry StreamEntry;
/// <summary>Valid data length in bytes.</summary>
public ulong ValidDataLength;
/// <inheritdoc />
public override string ToString() => FileName ?? string.Empty;
}
#endregion
#region Nested type: ExFatDirNode
sealed class ExFatDirNode : IDirNode
{
internal CompleteDirectoryEntry[] Entries;
internal int Position;
/// <inheritdoc />
public string Path { get; init; }
}
#endregion
}

12
Aaru.Filesystems/exFAT/Unimplemented.cs
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@@ -45,9 +45,6 @@ public sealed partial class exFAT
throw new NotImplementedException();
/// <inheritdoc />
public ErrorNumber StatFs(out FileSystemInfo stat) => throw new NotImplementedException();
/// <inheritdoc />
public ErrorNumber Stat(string path, out FileEntryInfo stat) => throw new NotImplementedException();
@@ -61,13 +58,4 @@ public sealed partial class exFAT
/// <inheritdoc />
public ErrorNumber ReadFile(IFileNode node, long length, byte[] buffer, out long read) =>
throw new NotImplementedException();
/// <inheritdoc />
public ErrorNumber OpenDir(string path, out IDirNode node) => throw new NotImplementedException();
/// <inheritdoc />
public ErrorNumber CloseDir(IDirNode node) => throw new NotImplementedException();
/// <inheritdoc />
public ErrorNumber ReadDir(IDirNode node, out string filename) => throw new NotImplementedException();
}

34
Aaru.Filesystems/exFAT/exFAT.cs
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@@ -96,39 +96,5 @@ public sealed partial class exFAT : IReadOnlyFilesystem
}
};
#endregion
#region Nested type: CompleteDirectoryEntry
/// <summary>Represents a complete directory entry set with file entry, stream extension, and file name.</summary>
sealed class CompleteDirectoryEntry
{
/// <summary>Data length in bytes.</summary>
public ulong DataLength;
/// <summary>The File directory entry.</summary>
public FileDirectoryEntry FileEntry;
/// <summary>The complete file name assembled from File Name directory entries.</summary>
public string FileName;
/// <summary>First cluster of the file data.</summary>
public uint FirstCluster;
/// <summary>Whether the allocation is contiguous (NoFatChain).</summary>
public bool IsContiguous;
/// <summary>Whether this entry is a directory.</summary>
public bool IsDirectory;
/// <summary>The Stream Extension directory entry.</summary>
public StreamExtensionDirectoryEntry StreamEntry;
/// <summary>Valid data length in bytes.</summary>
public ulong ValidDataLength;
/// <inheritdoc />
public override string ToString() => FileName ?? string.Empty;
}
#endregion
}