isTty

fn isTty(file: File) Io.Cancelable!bool {
    if (is_windows) {
        var get_console_mode = windows.CONSOLE.USER_IO.GET_MODE;
        switch ((try deviceIoControl(&.{
            .file = .{
                .handle = windows.peb().ProcessParameters.ConsoleHandle,
                .flags = .{ .nonblocking = false },
            },
            .code = windows.IOCTL.CONDRV.ISSUE_USER_IO,
            .in = @ptrCast(&get_console_mode.request(file, 0, .{}, 0, .{})),
        })).u.Status) {
            .SUCCESS => return true,
            .CANCELLED => unreachable,
            .INVALID_HANDLE => return isCygwinPty(file),
            else => return false,
        }
    }

    if (builtin.link_libc) {
        const syscall: Syscall = try .start();
        while (true) {
            const rc = posix.system.isatty(file.handle);
            switch (posix.errno(rc - 1)) {
                .SUCCESS => {
                    syscall.finish();
                    return true;
                },
                .INTR => {
                    try syscall.checkCancel();
                    continue;
                },
                else => {
                    syscall.finish();
                    return false;
                },
            }
        }
    }

    if (native_os == .wasi) {
        var statbuf: std.os.wasi.fdstat_t = undefined;
        const err = std.os.wasi.fd_fdstat_get(file.handle, &statbuf);
        if (err != .SUCCESS)
            return false;

        // A tty is a character device that we can't seek or tell on.
        if (statbuf.fs_filetype != .CHARACTER_DEVICE)
            return false;
        if (statbuf.fs_rights_base.FD_SEEK or statbuf.fs_rights_base.FD_TELL)
            return false;

        return true;
    }

    if (native_os == .linux) {
        const linux = std.os.linux;
        const syscall: Syscall = try .start();
        while (true) {
            var wsz: posix.winsize = undefined;
            const fd: usize = @bitCast(@as(isize, file.handle));
            const rc = linux.syscall3(.ioctl, fd, linux.T.IOCGWINSZ, @intFromPtr(&wsz));
            switch (linux.errno(rc)) {
                .SUCCESS => {
                    syscall.finish();
                    return true;
                },
                .INTR => {
                    try syscall.checkCancel();
                    continue;
                },
                else => {
                    syscall.finish();
                    return false;
                },
            }
        }
    }

    @compileError("unimplemented");
}