1 files changed, 40 insertions, 0 deletions
diff --git a/lib/hash-pjw.c b/lib/hash-pjw.c
new file mode 100644
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--- /dev/null
+++ b/lib/hash-pjw.c
@@ -0,0 +1,40 @@
+/* hash-pjw.c -- compute a hash value from a NUL-terminated string.
+
+   Copyright (C) 2001, 2003, 2006, 2009-2022 Free Software Foundation, Inc.
+
+   This file is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
+
+   This file 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 Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#include <config.h>
+
+#include "hash-pjw.h"
+
+#include <limits.h>
+
+#define SIZE_BITS (sizeof (size_t) * CHAR_BIT)
+
+/* A hash function for NUL-terminated char* strings using
+   the method described by Bruno Haible.
+   See https://www.haible.de/bruno/hashfunc.html.  */
+
+size_t
+hash_pjw (const void *x, size_t tablesize)
+{
+  const char *s;
+  size_t h = 0;
+
+  for (s = x; *s; s++)
+    h = *s + ((h << 9) | (h >> (SIZE_BITS - 9)));
+
+  return h % tablesize;
+}