summaryrefslogtreecommitdiff
path: root/src/minutils/s6ps_ttycache.c
blob: c50c3eab7519d367fbb9dfe6174c43a0b33a5654 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
/* ISC license. */

#ifndef _BSD_SOURCE
#define _BSD_SOURCE
#endif

#include <sys/types.h>
#include <sys/stat.h>
#include <errno.h>
#include <skalibs/bytestr.h>
#include <skalibs/uint.h>
#include <skalibs/uint32.h>
#include <skalibs/diuint32.h>
#include <skalibs/buffer.h>
#include <skalibs/stralloc.h>
#include <skalibs/genalloc.h>
#include <skalibs/djbunix.h>
#include <skalibs/skamisc.h>
#include <skalibs/avltree.h>
#include "s6-ps.h"

static avltree ttycache_tree = AVLTREE_ZERO ;
static genalloc ttycache_index = GENALLOC_ZERO ;

static void *left32_dtok (unsigned int d, void *x)
{
  return (void *)&genalloc_s(diuint32, (genalloc *)x)[d].left ;
}

static int uint32_cmp (void const *a, void const *b, void *x)
{
  register uint32 aa = *(uint32 *)a ;
  register uint32 bb = *(uint32 *)b ;
  (void)x ;
  return (aa < bb) ? -1 : (aa > bb) ;
}

int s6ps_ttycache_init (void)
{
  avltree_init(&ttycache_tree, 5, 3, 8, &left32_dtok, &uint32_cmp, &ttycache_index) ;
  return 1 ;
}

void s6ps_ttycache_finish (void)
{
  avltree_free(&ttycache_tree) ;
  genalloc_free(diuint, &ttycache_index) ;
}

static int check (char const *s, uint32 ttynr)
{
  struct stat st ;
  if (stat(s, &st) < 0) return 0 ;
  return S_ISCHR(st.st_mode) && (st.st_rdev == ttynr) ;
}


 /* No blind scanning of all /dev or /sys/devices, kthx */

static int ttyguess (stralloc *sa, uint32 ttynr)
{
  unsigned int maj = major(ttynr), min = minor(ttynr) ;

 /* Try /dev/tty? and /dev/pts/? */
  if (maj == 4 && min < 64)
  {
    char tmp[11] = "/dev/tty" ;
    tmp[uint_fmt(tmp+8, min)] = 0 ;
    if (check(tmp, ttynr)) return stralloc_cats(sa, tmp+5) && stralloc_0(sa) ;
  }
  else if (maj >= 136 && maj < 144)
  {
    char tmp[9 + UINT_FMT] = "/dev/pts/" ;
    register unsigned int n = ((maj - 136) << 20) | min ;
    tmp[9 + uint_fmt(tmp+9, n)] = 0 ;
    if (check(tmp, ttynr)) return stralloc_cats(sa, tmp+5) && stralloc_0(sa) ;
  }

 /* Use /sys/dev/char/maj:min if it exists */
  {
    int fd ;
    char path[23 + 2 * UINT_FMT] = "/sys/dev/char/" ;
    register unsigned int pos = 14 ;
    pos += uint_fmt(path + pos, maj) ;
    path[pos++] = ':' ;
    pos += uint_fmt(path + pos, min) ;
    byte_copy(path + pos, 8, "/uevent") ;
    fd = open_read(path) ;
    if (fd >= 0)
    {
      char buf[4097] ;
      buffer b = BUFFER_INIT(&buffer_read, fd, buf, 4097) ;
      unsigned int start = satmp.len ;
      register int r ;
      for (;;)
      {
        satmp.len = start ;
        r = skagetln(&b, &satmp, '\n') ;
        if (r <= 0) break ;
        if ((satmp.len - start) > 8 && !byte_diff(satmp.s + start, 8, "DEVNAME=")) break ;
      }
      fd_close(fd) ;
      if (r > 0)
      {
        satmp.s[satmp.len - 1] = 0 ;
        satmp.len = start ;
        byte_copy(satmp.s + start + 3, 5, "/dev/") ;
        if (check(satmp.s + start + 3, ttynr))
          return stralloc_cats(sa, satmp.s + start + 8) && stralloc_0(sa) ;
      }
    }
  }

 /* Fallback: print explicit maj:min */
  {
    char tmp[3 + 2 * UINT_FMT] = "(" ;
    register unsigned int pos = 1 ;
    pos += uint_fmt(tmp + pos, maj) ;
    tmp[pos++] = ':' ;
    pos += uint_fmt(tmp + pos, min) ;
    tmp[pos++] = ')' ;
    tmp[pos++] = 0 ;
    return stralloc_catb(sa, tmp, pos) ;
  }
}

int s6ps_ttycache_lookup (stralloc *sa, uint32 ttynr)
{
  int wasnull = !satmp.s ;
  diuint32 d = { .left = ttynr, .right = satmp.len } ;
  unsigned int i ;
  if (!avltree_search(&ttycache_tree, &d.left, &i))
  {
    unsigned int n = genalloc_len(diuint32, &ttycache_index) ;
    if (!ttyguess(&satmp, ttynr)) return 0 ;
    if (!genalloc_append(diuint32, &ttycache_index, &d)) goto err ;
    if (!avltree_insert(&ttycache_tree, n))
    {
      genalloc_setlen(diuint32, &ttycache_index, n) ;
      goto err ;
    }
    i = n ;
  }
  return stralloc_cats(sa, satmp.s + genalloc_s(diuint32, &ttycache_index)[i].right) ;
 err:
  {
    register int e = errno ;
    if (wasnull) stralloc_free(&satmp) ;
    else satmp.len = d.right ;
    errno = e ;
  }
  return 0 ;
}