# HG changeset patch
# User Jim Meyering <jim@meyering.net>
# Date 774938566 0
# Node ID ea96d91a16768becb6e0962bc250ef923253771c
# Parent  fe9e6561a5469f5ffa86670d1675ec4c228a72b2
.

diff --git a/lib/group-member.c b/lib/group-member.c
new file mode 100644
--- /dev/null
+++ b/lib/group-member.c
@@ -0,0 +1,158 @@
+/* group-member.c -- determine whether group id is in calling user's group list
+   Copyright (C) 1994 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 2, 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, write to the Free Software
+   Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.  */
+
+#ifdef HAVE_CONFIG_H
+#if defined (CONFIG_BROKETS)
+/* We use <config.h> instead of "config.h" so that a compilation
+   using -I. -I$srcdir will use ./config.h rather than $srcdir/config.h
+   (which it would do because it found this file in $srcdir).  */
+#include <config.h>
+#else
+#include "config.h"
+#endif
+#endif
+
+#include <stdio.h>
+#include <sys/types.h>
+
+#ifdef STDC_HEADERS
+#include <stdlib.h>
+#endif
+
+#ifdef HAVE_UNISTD_H
+#include <unistd.h>
+#endif
+
+#include "group-member.h"
+
+char *xmalloc ();
+char *xrealloc ();
+
+struct group_info
+  {
+    int n_groups;
+    GETGROUPS_T *group;
+  };
+
+#ifdef HAVE_GETGROUPS
+
+static void
+free_group_info (g)
+     struct group_info *g;
+{
+  free (g->group);
+  free (g);
+}
+
+static struct group_info *
+get_group_info ()
+{
+  int n_groups;
+  int n_group_slots;
+  struct group_info *gi;
+  GETGROUPS_T *group;
+
+  /* getgroups () returns the number of elements that it was able to
+     place into the array.  We simply continue to call getgroups ()
+     until the number of elements placed into the array is smaller than
+     the physical size of the array. */
+
+  group = NULL;
+  n_groups = 0;
+  n_group_slots = 0;
+  while (n_groups == n_group_slots)
+    {
+      n_group_slots += 64;
+      group = (GETGROUPS_T *) xrealloc (group,
+					n_group_slots * sizeof (GETGROUPS_T));
+      n_groups = getgroups (n_group_slots, group);
+    }
+
+  /* In case of error, the user loses. */
+  if (n_groups < 0)
+    {
+      free (group);
+      return NULL;
+    }
+
+  gi = (struct group_info *) xmalloc (sizeof (*gi));
+  gi->n_groups = n_groups;
+  gi->group = group;
+
+  return gi;
+}
+
+#endif /* not HAVE_GETGROUPS */
+
+/* Return non-zero if GID is one that we have in our groups list.
+   If there is no getgroups function, return non-zero if GID matches
+   either of the current or effective group IDs.  */
+
+int
+group_member (gid)
+     gid_t gid;
+{
+#ifndef HAVE_GETGROUPS
+  return ((gid == getgid ()) || (gid == getegid ()));
+#else
+  int i;
+  int found;
+  struct group_info *gi;
+
+  gi = get_group_info ();
+  if (gi == NULL)
+    return 0;
+
+  /* Search through the list looking for GID. */
+  found = 0;
+  for (i = 0; i < gi->n_groups; i++)
+    {
+      if (gid == gi->group[i])
+	{
+	  found = 1;
+	  break;
+	}
+    }
+  
+  free_group_info (gi);
+
+  return found;
+#endif /* HAVE_GETGROUPS */
+}
+
+#ifdef TEST
+
+char *program_name;
+
+int
+main (int argc, char** argv)
+{
+  int i;
+
+  program_name = argv[0];
+
+  for (i=1; i<argc; i++)
+    {
+      gid_t gid;
+
+      gid = atoi (argv[i]);
+      printf ("%d: %s\n", gid, group_member (gid) ? "yes" : "no");
+    }
+  exit (0);
+}
+
+#endif /* TEST */
diff --git a/lib/group-member.h b/lib/group-member.h
new file mode 100644
--- /dev/null
+++ b/lib/group-member.h
@@ -0,0 +1,7 @@
+#ifndef _group_member_h_
+#define _group_member_h_ 1
+
+int
+  group_member ();
+
+#endif /* _group_member_h_ */