1 files changed, 153 insertions, 0 deletions
diff --git a/src/minutils/s6ps_ttycache.c b/src/minutils/s6ps_ttycache.c
new file mode 100644
index 0000000..c50c3ea
--- /dev/null
+++ b/src/minutils/s6ps_ttycache.c
@@ -0,0 +1,153 @@
+/* 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 ;
+}