private static (FullPath path, FullPath innerPath, Stream lockFile) CreateUniqueDirectory(FullPath folderPath)
{
/*
* Structure
* - temp/<folder>/lock => allows to detect concurrency
* - temp/<folder>/<returned_value>/
*/
var count = 1;
while (true)
{
Stream?lockFileStream = null;
try
{
var tempPath = folderPath.Value + "_";
while (Directory.Exists(folderPath))
{
folderPath = FullPath.FromPath(tempPath + count.ToString(CultureInfo.InvariantCulture));
if (count == int.MaxValue)
{
throw new InvalidOperationException("Cannot create a temporary directory");
}
count++;
}
Directory.CreateDirectory(folderPath);
var lockFilePath = folderPath / LockFileName;
lockFileStream = new FileStream(lockFilePath, FileMode.CreateNew, FileAccess.ReadWrite, FileShare.None);
var innerFolderPath = folderPath / DirectoryName;
if (Directory.Exists(innerFolderPath))
{
lockFileStream.Dispose();
continue;
}
Directory.CreateDirectory(innerFolderPath);
// Assert folder is empty
if (Directory.EnumerateFileSystemEntries(innerFolderPath).Any())
{
lockFileStream.Dispose();
continue;
}
return(folderPath, innerFolderPath, lockFileStream);
}
catch (IOException)
{
// The folder may already in use
}
catch
{
lockFileStream?.Dispose();
throw;
}
lockFileStream?.Dispose();
}
}
private TemporaryDirectory(FullPath path, FullPath innerPath, Stream lockFile)
{
_path = path;
FullPath = innerPath;
_lockFile = lockFile;
}