1 files changed, 164 insertions, 0 deletions
diff --git a/lib/readutmp.c b/lib/readutmp.c
new file mode 100644
index 0000000..1b6f843
--- /dev/null
+++ b/lib/readutmp.c
@@ -0,0 +1,164 @@
+/* GNU's read utmp module.
+
+   Copyright (C) 1992-2001, 2003-2006, 2009-2022 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+/* Written by jla; revised by djm */
+
+#include <config.h>
+
+#include "readutmp.h"
+
+#include <errno.h>
+#include <stdio.h>
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <signal.h>
+#include <stdbool.h>
+#include <string.h>
+#include <stdlib.h>
+#include <stdint.h>
+
+#include "xalloc.h"
+
+/* Each of the FILE streams in this file is only used in a single thread.  */
+#include "unlocked-io.h"
+
+#if 8 <= __GNUC__
+# pragma GCC diagnostic ignored "-Wsizeof-pointer-memaccess"
+#endif
+
+/* Copy UT->ut_name into storage obtained from malloc.  Then remove any
+   trailing spaces from the copy, NUL terminate it, and return the copy.  */
+
+char *
+extract_trimmed_name (const STRUCT_UTMP *ut)
+{
+  char *p, *trimmed_name;
+
+  trimmed_name = xmalloc (sizeof (UT_USER (ut)) + 1);
+  strncpy (trimmed_name, UT_USER (ut), sizeof (UT_USER (ut)));
+  /* Append a trailing NUL.  Some systems pad names shorter than the
+     maximum with spaces, others pad with NULs.  Remove any trailing
+     spaces.  */
+  trimmed_name[sizeof (UT_USER (ut))] = '\0';
+  for (p = trimmed_name + strlen (trimmed_name);
+       trimmed_name < p && p[-1] == ' ';
+       *--p = '\0')
+    continue;
+  return trimmed_name;
+}
+
+/* Is the utmp entry U desired by the user who asked for OPTIONS?  */
+
+static bool
+desirable_utmp_entry (STRUCT_UTMP const *u, int options)
+{
+  bool user_proc = IS_USER_PROCESS (u);
+  if ((options & READ_UTMP_USER_PROCESS) && !user_proc)
+    return false;
+  if ((options & READ_UTMP_CHECK_PIDS)
+      && user_proc
+      && 0 < UT_PID (u)
+      && (kill (UT_PID (u), 0) < 0 && errno == ESRCH))
+    return false;
+  return true;
+}
+
+/* Read the utmp entries corresponding to file FILE into freshly-
+   malloc'd storage, set *UTMP_BUF to that pointer, set *N_ENTRIES to
+   the number of entries, and return zero.  If there is any error,
+   return -1, setting errno, and don't modify the parameters.
+   If OPTIONS & READ_UTMP_CHECK_PIDS is nonzero, omit entries whose
+   process-IDs do not currently exist.  */
+
+#ifdef UTMP_NAME_FUNCTION
+
+int
+read_utmp (char const *file, size_t *n_entries, STRUCT_UTMP **utmp_buf,
+           int options)
+{
+  idx_t n_read = 0;
+  idx_t n_alloc = 0;
+  STRUCT_UTMP *utmp = NULL;
+  STRUCT_UTMP *u;
+
+  /* Ignore the return value for now.
+     Solaris' utmpname returns 1 upon success -- which is contrary
+     to what the GNU libc version does.  In addition, older GNU libc
+     versions are actually void.   */
+  UTMP_NAME_FUNCTION ((char *) file);
+
+  SET_UTMP_ENT ();
+
+  while ((u = GET_UTMP_ENT ()) != NULL)
+    if (desirable_utmp_entry (u, options))
+      {
+        if (n_read == n_alloc)
+          utmp = xpalloc (utmp, &n_alloc, 1, -1, sizeof *utmp);
+
+        utmp[n_read++] = *u;
+      }
+
+  END_UTMP_ENT ();
+
+  *n_entries = n_read;
+  *utmp_buf = utmp;
+
+  return 0;
+}
+
+#else
+
+int
+read_utmp (char const *file, size_t *n_entries, STRUCT_UTMP **utmp_buf,
+           int options)
+{
+  idx_t n_read = 0;
+  idx_t n_alloc = 0;
+  STRUCT_UTMP *utmp = NULL;
+  int saved_errno;
+  FILE *f = fopen (file, "re");
+
+  if (! f)
+    return -1;
+
+  for (;;)
+    {
+      if (n_read == n_alloc)
+        utmp = xpalloc (utmp, &n_alloc, 1, -1, sizeof *utmp);
+      if (fread (&utmp[n_read], sizeof utmp[n_read], 1, f) == 0)
+        break;
+      n_read += desirable_utmp_entry (&utmp[n_read], options);
+    }
+
+  saved_errno = ferror (f) ? errno : 0;
+  if (fclose (f) != 0)
+    saved_errno = errno;
+  if (saved_errno != 0)
+    {
+      free (utmp);
+      errno = saved_errno;
+      return -1;
+    }
+
+  *n_entries = n_read;
+  *utmp_buf = utmp;
+
+  return 0;
+}
+
+#endif