1 files changed, 118 insertions, 0 deletions
diff --git a/src/libs6ps/s6ps_ttycache.c b/src/libs6ps/s6ps_ttycache.c
new file mode 100644
index 0000000..583ab03
--- /dev/null
+++ b/src/libs6ps/s6ps_ttycache.c
@@ -0,0 +1,118 @@
+/* ISC license. */
+
+#include <string.h>
+#include <stdint.h>
+#include <sys/stat.h>
+#include <sys/sysmacros.h>
+#include <errno.h>
+
+#include <skalibs/types.h>
+#include <skalibs/allreadwrite.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 "s6ps.h"
+#include "s6ps-internal.h"
+
+static int check (char const *s, dev_t 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, dev_t 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)
+  {
+    unsigned int n = ((maj - 136) << 20) | min ;
+    char tmp[9 + UINT_FMT] = "/dev/pts/" ;
+    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 ;
+    size_t pos = 14 ;
+    char path[23 + 2 * UINT_FMT] = "/sys/dev/char/" ;
+    pos += uint_fmt(path + pos, maj) ;
+    path[pos++] = ':' ;
+    pos += uint_fmt(path + pos, min) ;
+    memcpy(path + pos, "/uevent", 8) ;
+    fd = open_read(path) ;
+    if (fd >= 0)
+    {
+      char buf[4097] ;
+      buffer b = BUFFER_INIT(&fd_readv, fd, buf, 4097) ;
+      size_t start = satmp.len ;
+      int r ;
+      for (;;)
+      {
+        satmp.len = start ;
+        r = skagetln(&b, &satmp, '\n') ;
+        if (r <= 0) break ;
+        if ((satmp.len - start) > 8 && !memcmp(satmp.s + start, "DEVNAME=", 8)) break ;
+      }
+      fd_close(fd) ;
+      if (r > 0)
+      {
+        satmp.s[satmp.len - 1] = 0 ;
+        satmp.len = start ;
+        memcpy(satmp.s + start + 3, "/dev/", 5) ;
+        if (check(satmp.s + start + 3, ttynr))
+          return stralloc_cats(sa, satmp.s + start + 8) && stralloc_0(sa) ;
+      }
+    }
+  }
+
+ /* Fallback: print explicit maj:min */
+  {
+    size_t pos = 1 ;
+    char tmp[3 + 2 * UINT_FMT] = "(" ;
+    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 (s6ps_cache_t *cache, stralloc *sa, dev_t ttynr)
+{
+  dius_t d = { .left = (uint32_t)ttynr, .right = satmp.len } ;
+  uint32_t i ;
+  if (!avltree_search(&cache->tree, &d.left, &i))
+  {
+    size_t n = genalloc_len(dius_t, &cache->index) ;
+    if (!ttyguess(&satmp, ttynr)) return 0 ;
+    if (!genalloc_append(dius_t, &cache->index, &d)) goto err ;
+    if (!avltree_insert(&cache->tree, n))
+    {
+      genalloc_setlen(dius_t, &cache->index, n) ;
+      goto err ;
+    }
+    i = n ;
+  }
+  return stralloc_cats(sa, satmp.s + genalloc_s(dius_t, &cache->index)[i].right) ;
+ err:
+  satmp.len = d.right ;
+  return 0 ;
+}