1package pty
2
3import (
4	"errors"
5	"os"
6	"syscall"
7	"unsafe"
8)
9
10func open() (pty, tty *os.File, err error) {
11	pFD, err := syscall.Open("/dev/ptmx", syscall.O_RDWR|syscall.O_CLOEXEC, 0)
12	if err != nil {
13		return nil, nil, err
14	}
15	p := os.NewFile(uintptr(pFD), "/dev/ptmx")
16	// In case of error after this point, make sure we close the ptmx fd.
17	defer func() {
18		if err != nil {
19			_ = p.Close() // Best effort.
20		}
21	}()
22
23	sname, err := ptsname(p)
24	if err != nil {
25		return nil, nil, err
26	}
27
28	if err := grantpt(p); err != nil {
29		return nil, nil, err
30	}
31
32	if err := unlockpt(p); err != nil {
33		return nil, nil, err
34	}
35
36	t, err := os.OpenFile(sname, os.O_RDWR, 0)
37	if err != nil {
38		return nil, nil, err
39	}
40	return p, t, nil
41}
42
43func ptsname(f *os.File) (string, error) {
44	n := make([]byte, _IOC_PARM_LEN(syscall.TIOCPTYGNAME))
45
46	err := ioctl(f.Fd(), syscall.TIOCPTYGNAME, uintptr(unsafe.Pointer(&n[0])))
47	if err != nil {
48		return "", err
49	}
50
51	for i, c := range n {
52		if c == 0 {
53			return string(n[:i]), nil
54		}
55	}
56	return "", errors.New("TIOCPTYGNAME string not NUL-terminated")
57}
58
59func grantpt(f *os.File) error {
60	return ioctl(f.Fd(), syscall.TIOCPTYGRANT, 0)
61}
62
63func unlockpt(f *os.File) error {
64	return ioctl(f.Fd(), syscall.TIOCPTYUNLK, 0)
65}
66