2022: add PJW hash (lib)

2022/include/pjwhash-inline.h

@@ -0,0 +1,42 @@
+/* pjwhash-inline.h - PJW hash function, inline version.
+ *
+ * Copyright (C) 2021-2022 Bruno Raoult ("br")
+ * Licensed under the GNU General Public License v3.0 or later.
+ * Some rights reserved. See COPYING.
+ *
+ * You should have received a copy of the GNU General Public License along with this
+ * program. If not, see <https://www.gnu.org/licenses/gpl-3.0-standalone.html>.
+ *
+ * SPDX-License-Identifier: GPL-3.0-or-later <https://spdx.org/licenses/GPL-3.0-or-later.html>
+ *
+ */
+
+#ifndef _PJWHASH_INLINE_H
+#define _PJWHASH_INLINE_H
+
+#include "bits.h"
+
+#define THREE_QUARTERS ((int) ((BITS_PER_INT * 3) / 4))
+#define ONE_EIGHTH     ((int) (BITS_PER_INT / 8))
+#define HIGH_BITS      ( ~((uint)(~0) >> ONE_EIGHTH ))
+
+#ifndef _pjw_inline
+#define _pjw_inline static inline
+#endif
+
+_pjw_inline unsigned int pjwhash(const char* str, uint length)
+{
+   uint hash = 0, high;
+
+   for (uint i = 0; i < length; ++str, ++i) {
+      hash = (hash << ONE_EIGHTH) + *str;
+      high = hash & HIGH_BITS;
+      if (high != 0) {
+          hash ^= high >> THREE_QUARTERS;
+          hash &= ~high;
+      }
+   }
+   return hash;
+}
+
+#endif  /* _PJWHASH_INLINE_H */