1 files changed, 42 insertions, 0 deletions
diff --git a/lib/gl/hash-pjw-bare.c b/lib/gl/hash-pjw-bare.c
new file mode 100644
index 0000000..01552ab
--- /dev/null
+++ b/lib/gl/hash-pjw-bare.c
@@ -0,0 +1,42 @@
+/* hash-pjw-bare.c -- compute a hash value from a provided buffer.
+
+   Copyright (C) 2012-2019 Free Software Foundation, Inc.
+
+   This program 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 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
+   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-bare.h"
+
+#include <limits.h>
+
+#define SIZE_BITS (sizeof (size_t) * CHAR_BIT)
+
+/* Return a hash of the N bytes of X using the method described by
+   Bruno Haible in https://www.haible.de/bruno/hashfunc.html.
+   Note that while many hash functions reduce their result via modulo
+   to a 0..table_size-1 range, this function does not do that.  */
+
+size_t
+hash_pjw_bare (const void *x, size_t n)
+{
+  const unsigned char *s = x;
+  size_t h = 0;
+  unsigned i;
+
+  for (i = 0; i < n; i++)
+    h = s[i] + ((h << 9) | (h >> (SIZE_BITS - 9)));
+
+  return h;
+}