1 files changed, 57 insertions, 0 deletions
diff --git a/libshouldbeinlibc/shared-dom.c b/libshouldbeinlibc/shared-dom.c
new file mode 100644
index 00000000..0f8efdf8
--- /dev/null
+++ b/libshouldbeinlibc/shared-dom.c
@@ -0,0 +1,57 @@
+/* Deduce the shared portion of two hostnames
+
+   Copyright (C) 1996 Free Software Foundation, Inc.
+
+   Written by Miles Bader <miles@gnu.ai.mit.edu>
+
+   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.  */
+
+#include <unistd.h>
+#include <malloc.h>
+#include <string.h>
+#include <errno.h>
+
+/* Returns a pointer into HOST1 that is the part of the domain shared with
+   HOST2.  If the two do not share anything, the return value will point to
+   the end of HOST1.  If either host is NULL, NULL is returned.  */
+char *
+shared_domain (char *host1, char *host2)
+{
+  char *shared, *e1, *e2;
+
+  if (!host1 || !host2)
+    return 0;
+
+  /* Now compare HOST1 and HOST2 from the end.  */
+  e2 = host2 + strlen (host2);
+  e1 = host1 + strlen (host1);
+  shared = e1;
+
+  /* Ignore `absolute' syntax.  */
+  if (*e1 == '.')
+    e1--;
+  if (*e2 == '.')
+    e2--;
+
+  while (e1 > host1 && e2 > host2 && *e2 == *e1)
+    {
+      if (*e1 == '.')
+	shared = e1;		/* A common domain level has been passed. */
+      e1--;
+      e2--;
+    }
+
+  return shared;
+}