dirAccessWasi

fn dirAccessWasi(
    userdata: ?*anyopaque,
    dir: Dir,
    sub_path: []const u8,
    options: Dir.AccessOptions,
) Dir.AccessError!void {
    if (builtin.link_libc) return dirAccessPosix(userdata, dir, sub_path, options);
    const t: *Threaded = @ptrCast(@alignCast(userdata));
    _ = t;
    const wasi = std.os.wasi;
    const flags: wasi.lookupflags_t = .{
        .SYMLINK_FOLLOW = options.follow_symlinks,
    };
    var stat: wasi.filestat_t = undefined;

    const syscall: Syscall = try .start();
    while (true) {
        switch (wasi.path_filestat_get(dir.handle, flags, sub_path.ptr, sub_path.len, &stat)) {
            .SUCCESS => {
                syscall.finish();
                break;
            },
            .INTR => {
                try syscall.checkCancel();
                continue;
            },
            else => |e| {
                syscall.finish();
                switch (e) {
                    .INVAL => |err| return errnoBug(err),
                    .BADF => |err| return errnoBug(err), // File descriptor used after closed.
                    .NOMEM => return error.SystemResources,
                    .ACCES => return error.AccessDenied,
                    .FAULT => |err| return errnoBug(err),
                    .NAMETOOLONG => return error.NameTooLong,
                    .NOENT => return error.FileNotFound,
                    .NOTDIR => return error.FileNotFound,
                    .NOTCAPABLE => return error.AccessDenied,
                    .ILSEQ => return error.BadPathName,
                    else => |err| return posix.unexpectedErrno(err),
                }
            },
        }
    }

    if (!options.read and !options.write and !options.execute)
        return;

    var directory: wasi.fdstat_t = undefined;
    if (wasi.fd_fdstat_get(dir.handle, &directory) != .SUCCESS)
        return error.AccessDenied;

    var rights: wasi.rights_t = .{};
    if (options.read) {
        if (stat.filetype == .DIRECTORY) {
            rights.FD_READDIR = true;
        } else {
            rights.FD_READ = true;
        }
    }
    if (options.write)
        rights.FD_WRITE = true;

    // No validation for execution.

    // https://github.com/ziglang/zig/issues/18882
    const rights_int: u64 = @bitCast(rights);
    const inheriting_int: u64 = @bitCast(directory.fs_rights_inheriting);
    if ((rights_int & inheriting_int) != rights_int)
        return error.AccessDenied;
}