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Add --base-path option to preserve original archive paths on repack #3

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Copilot Apr 14, 2026
f1eb3c9
Add --base-path option to DFS create command to fix Area 51 asset loa…
Copilot Apr 14, 2026
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28 changes: 26 additions & 2 deletions README.md
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Original file line number Diff line number Diff line change
Expand Up @@ -33,9 +33,33 @@ dotnet build
```bash
Usage: dfs <command> [options]
Commands:
create <inputDir> <outputFileName> [--crc] Creates a DFS file from the specified directory with optional CRC.
create <inputDir> <outputFileName> [--crc] [--base-path <path>] Creates a DFS file from the specified directory with optional CRC and base path.
extract <inputFile> <extractPath> Extracts files from the specified DFS file to the specified path.
verify <inputFile> Verifies the integrity of the specified DFS file.
list <inputFile> Lists the contents of the specified DFS file.
help Displays this help text.
```
```

### Remastering Area 51 assets

The original Area 51 DFS archives store an absolute Windows path (e.g. `C:\GAMEDATA\A51\RELEASE\PC\`) for every file. The game uses this path to locate assets inside the archive, so the packed archive must use the same path.

To repack a modified archive while preserving the original path:

1. Find the base path stored in the original archive:
```bash
dfs list <original.dfs>
```
The path shown before each filename is the base path (e.g. `C:\GAMEDATA\A51\RELEASE\PC\`).

2. Extract the original archive:
```bash
dfs extract <original.dfs> <outputDir>
```

3. Replace or modify the files in `<outputDir>`.

4. Repack with the original base path:
```bash
dfs create <outputDir> <repacked.dfs> --base-path "C:\GAMEDATA\A51\RELEASE\PC\"
```
26 changes: 22 additions & 4 deletions dfs/Program.cs
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Expand Up @@ -31,7 +31,7 @@ static void PrintHelp()
{
Console.WriteLine("Usage: dfs <command> [options]");
Console.WriteLine("Commands:");
Console.WriteLine(" create <inputDir> <outputFileName> [--crc] Creates a DFS file from the specified directory with optional CRC.");
Console.WriteLine(" create <inputDir> <outputFileName> [--crc] [--base-path <path>] Creates a DFS file from the specified directory with optional CRC and base path.");
Console.WriteLine(" extract <inputFile> <extractPath> Extracts files from the specified DFS file to the specified path.");
Console.WriteLine(" verify <inputFile> Verifies the integrity of the specified DFS file.");
Console.WriteLine(" list <inputFile> Lists the contents of the specified DFS file.");
Expand Down Expand Up @@ -60,8 +60,26 @@ static bool CreateCommand(string[] args)
return false;
}

bool enableCrc = args.Length > 3 && args[3] == "--crc";
Console.WriteLine($"Creating DFS file {outputFileName} from {inputDir} with {(enableCrc ? "CRC" : "no CRC")}...");
bool enableCrc = false;
string? basePath = null;
for (int i = 3; i < args.Length; i++)
{
if (args[i] == "--crc")
{
enableCrc = true;
}
else if (args[i] == "--base-path")
{
if (i + 1 >= args.Length)
{
Console.Error.WriteLine("--base-path requires a value");
return false;
}
basePath = args[++i];
}
}

Console.WriteLine($"Creating DFS file {outputFileName} from {inputDir} with {(enableCrc ? "CRC" : "no CRC")}{(basePath != null ? $" and base path '{basePath}'" : "")}...");
if (File.Exists(outputFileName))
{
File.Delete(outputFileName);
Expand All @@ -82,7 +100,7 @@ static bool CreateCommand(string[] args)
.ThenBy(f => f.FileName)
.ThenBy(f => f.Extension)
.Select(f => f.FullPath);
using var writer = new DfsWriter(outputFileName, sourceFiles, sectorAligned, enableCrc: enableCrc);
using var writer = new DfsWriter(outputFileName, sourceFiles, sectorAligned, enableCrc: enableCrc, basePath: basePath);
writer.Write();
return true;
}
Expand Down
70 changes: 47 additions & 23 deletions dfslib/DfsWriter.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@ public sealed class DfsWriter : IDisposable
private readonly IEnumerable<string> _filePaths;
private readonly HashSet<string> _sectorAlignedExtensions;
private CheckSummer _checkSummer;
private readonly string? _basePath;

private readonly StringTable _stringTable;

Expand Down Expand Up @@ -42,11 +43,13 @@ public sealed class DfsWriter : IDisposable
/// <param name="splitSize">The split size to use for the DFS archive.</param>
/// <param name="chunkSize">The chunk size to use for the DFS archive.</param>
/// <param name="enableCrc">Whether to enable CRC checksums for the DFS archive.</param>
public DfsWriter(string outputPath, IEnumerable<string> filePaths, IEnumerable<string> sectorAlignedExtensions, uint sectorSize = DfsConstants.DefaultSectorSize, uint splitSize = DfsConstants.DefaultSplitSize, uint chunkSize = DfsConstants.DefaultChunkSize, bool enableCrc = false)
/// <param name="basePath">Optional base path to store for all files in the archive (e.g. "C:\GAMEDATA\A51\RELEASE\PC\"). When provided, overrides the path derived from the actual file location.</param>
public DfsWriter(string outputPath, IEnumerable<string> filePaths, IEnumerable<string> sectorAlignedExtensions, uint sectorSize = DfsConstants.DefaultSectorSize, uint splitSize = DfsConstants.DefaultSplitSize, uint chunkSize = DfsConstants.DefaultChunkSize, bool enableCrc = false, string? basePath = null)
{
_outputPath = outputPath;
_filePaths = filePaths;
_sectorAlignedExtensions = new HashSet<string>(sectorAlignedExtensions, StringComparer.OrdinalIgnoreCase);
_basePath = basePath != null ? NormalizeBasePath(basePath) : null;
_sectorSize = sectorSize;
_splitSize = splitSize;
_enableCrc = enableCrc;
Expand Down Expand Up @@ -100,34 +103,42 @@ public void Write()
// Assert that currentFile.Path is not empty
Debug.Assert(!string.IsNullOrEmpty(currentFile.Path));

// Set drive to always "C:\"
string root = Path.GetPathRoot(currentFile.Path);



// Get the directory without the root
string directory = Path.GetDirectoryName(currentFile.Path) ?? string.Empty;

if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
string pathForEntry;
if (_basePath != null)
{
// Remove the drive root (e.g., "C:\") from the directory
if (!string.IsNullOrEmpty(root) && directory.StartsWith(root, StringComparison.OrdinalIgnoreCase))
{
directory = directory[root.Length..];
}
// Use the user-specified base path for all files
pathForEntry = _basePath;
}
else
{
// On Unix-based systems, remove the leading forward slash
if (directory.StartsWith(Path.DirectorySeparatorChar.ToString()))
// Set drive to always "C:\"
string root = Path.GetPathRoot(currentFile.Path);

// Get the directory without the root
string directory = Path.GetDirectoryName(currentFile.Path) ?? string.Empty;

if (RuntimeInformation.IsOSPlatform(OSPlatform.Windows))
{
directory = directory[1..];
// Remove the drive root (e.g., "C:\") from the directory
if (!string.IsNullOrEmpty(root) && directory.StartsWith(root, StringComparison.OrdinalIgnoreCase))
{
directory = directory[root.Length..];
}
}
else
{
// On Unix-based systems, remove the leading forward slash
if (directory.StartsWith(Path.DirectorySeparatorChar.ToString()))
{
directory = directory[1..];
}
}
}

// Normalize directory separators from '/' to '\\'
directory = directory.Replace('/', '\\');
root = root.Replace('/', '\\');
// Normalize directory separators from '/' to '\\'
directory = directory.Replace('/', '\\');
root = root.Replace('/', '\\');
pathForEntry = root + directory;
}

string fileName = Path.GetFileNameWithoutExtension(currentFile.Path);
string extension = Path.GetExtension(currentFile.Path);
Expand All @@ -139,7 +150,7 @@ public void Write()
(string substring1, string substring2) = FindCommonSubstring(previousFileName, fileName, nextFileName);

// Add path substrings to dictionary
uint pathIndex = GetStringOffset(root + directory);
uint pathIndex = GetStringOffset(pathForEntry);
uint fileNamePart1Index = GetStringOffset(substring1);
uint fileNamePart2Index = GetStringOffset(substring2);
uint extensionIndex = GetStringOffset(extension);
Expand Down Expand Up @@ -440,4 +451,17 @@ private static (string, string) FindCommonSubstring(string str0, string str1, st
return (str1[..commonLen].ToUpperInvariant(), str1[commonLen..].ToUpperInvariant());
}

/// <summary>
/// Normalizes a base path by replacing forward slashes with backslashes and ensuring it ends with a backslash.
/// </summary>
private static string NormalizeBasePath(string basePath)
{
basePath = basePath.Replace('/', '\\');
if (!basePath.EndsWith('\\'))
{
basePath += '\\';
}
return basePath;
}

}