dirDeleteWindows

fn dirDeleteWindows(userdata: ?*anyopaque, dir: Dir, sub_path: []const u8, remove_dir: bool) (Dir.DeleteDirError || Dir.DeleteFileError)!void {
    const t: *Threaded = @ptrCast(@alignCast(userdata));
    _ = t;
    const w = windows;

    if (std.mem.eql(u8, sub_path, "..")) {
        // Can't remove the parent directory with an open handle.
        return error.FileBusy;
    }
    var sub_path_w = try sliceToPrefixedFileW(dir.handle, sub_path, .{});
    if (std.mem.eql(u8, sub_path, ".")) {
        // Windows does not recognize this, but it does work with empty string.
        sub_path_w.len = 0;
    }
    const attr: w.OBJECT.ATTRIBUTES = .{
        .RootDirectory = if (Dir.path.isAbsoluteWindowsWtf16(sub_path_w.span())) null else dir.handle,
        .ObjectName = @constCast(&sub_path_w.string()),
    };

    var io_status_block: w.IO_STATUS_BLOCK = undefined;
    var tmp_handle: w.HANDLE = undefined;
    {
        const syscall: Syscall = try .start();
        while (true) switch (w.ntdll.NtCreateFile(
            &tmp_handle,
            .{ .STANDARD = .{
                .RIGHTS = .{ .DELETE = true },
                .SYNCHRONIZE = true,
            } },
            &attr,
            &io_status_block,
            null,
            .{},
            .VALID_FLAGS,
            .OPEN,
            .{
                .DIRECTORY_FILE = remove_dir,
                .IO = .SYNCHRONOUS_NONALERT,
                .NON_DIRECTORY_FILE = !remove_dir,
                .OPEN_REPARSE_POINT = true, // would we ever want to delete the target instead?
            },
            null,
            0,
        )) {
            .SUCCESS => break syscall.finish(),
            .OBJECT_NAME_INVALID => |err| return syscall.ntstatusBug(err),
            .OBJECT_NAME_NOT_FOUND => return syscall.fail(error.FileNotFound),
            .OBJECT_PATH_NOT_FOUND => return syscall.fail(error.FileNotFound),
            .BAD_NETWORK_PATH => return syscall.fail(error.NetworkNotFound), // \\server was not found
            .BAD_NETWORK_NAME => return syscall.fail(error.NetworkNotFound), // \\server was found but \\server\share wasn't
            .INVALID_PARAMETER => |err| return syscall.ntstatusBug(err),
            .FILE_IS_A_DIRECTORY => return syscall.fail(error.IsDir),
            .NOT_A_DIRECTORY => return syscall.fail(error.NotDir),
            .SHARING_VIOLATION => return syscall.fail(error.FileBusy),
            .ACCESS_DENIED => return syscall.fail(error.AccessDenied),
            .DELETE_PENDING => return syscall.finish(),
            else => |rc| return syscall.unexpectedNtstatus(rc),
        };
    }
    defer w.CloseHandle(tmp_handle);

    // FileDispositionInformationEx has varying levels of support:
    // - FILE_DISPOSITION_INFORMATION_EX requires >= win10_rs1
    //   (INVALID_INFO_CLASS is returned if not supported)
    // - Requires the NTFS filesystem
    //   (on filesystems like FAT32, INVALID_PARAMETER is returned)
    // - FILE_DISPOSITION_POSIX_SEMANTICS requires >= win10_rs1
    // - FILE_DISPOSITION_IGNORE_READONLY_ATTRIBUTE requires >= win10_rs5
    //   (NOT_SUPPORTED is returned if a flag is unsupported)
    //
    // The strategy here is just to try using FileDispositionInformationEx and fall back to
    // FileDispositionInformation if the return value lets us know that some aspect of it is not supported.
    const rc = rc: {
        // Deletion with posix semantics if the filesystem supports it.
        var info: w.FILE.DISPOSITION.INFORMATION.EX = .{ .Flags = .{
            .DELETE = true,
            .POSIX_SEMANTICS = true,
            .IGNORE_READONLY_ATTRIBUTE = true,
        } };

        const syscall: Syscall = try .start();
        while (true) switch (w.ntdll.NtSetInformationFile(
            tmp_handle,
            &io_status_block,
            &info,
            @sizeOf(w.FILE.DISPOSITION.INFORMATION.EX),
            .DispositionEx,
        )) {
            .CANCELLED => {
                try syscall.checkCancel();
                continue;
            },
            // The filesystem does not support FileDispositionInformationEx
            .INVALID_PARAMETER,
            // The operating system does not support FileDispositionInformationEx
            .INVALID_INFO_CLASS,
            // The operating system does not support one of the flags
            .NOT_SUPPORTED,
            => break, // use fallback path below; `syscall` still active

            // For all other statuses, fall down to the switch below to handle them.
            else => |rc| {
                syscall.finish();
                break :rc rc;
            },
        };

        // Deletion with file pending semantics, which requires waiting or moving
        // files to get them removed (from here).
        var file_dispo: w.FILE.DISPOSITION.INFORMATION = .{ .DeleteFile = .TRUE };

        while (true) switch (w.ntdll.NtSetInformationFile(
            tmp_handle,
            &io_status_block,
            &file_dispo,
            @sizeOf(w.FILE.DISPOSITION.INFORMATION),
            .Disposition,
        )) {
            .CANCELLED => {
                try syscall.checkCancel();
                continue;
            },
            else => |rc| {
                syscall.finish();
                break :rc rc;
            },
        };
    };
    switch (rc) {
        .SUCCESS => {},
        .DIRECTORY_NOT_EMPTY => return error.DirNotEmpty,
        .INVALID_PARAMETER => |err| return w.statusBug(err),
        .CANNOT_DELETE => return error.AccessDenied,
        .MEDIA_WRITE_PROTECTED => return error.AccessDenied,
        .ACCESS_DENIED => return error.AccessDenied,
        else => return w.unexpectedStatus(rc),
    }
}