add pjwhash

c/include/pjwhash-inline.h

@@ -0,0 +1,53 @@
+/* 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
+
+/**
+ * unsigned int pjwhash - PJW hash function
+ * @key:    the key address.
+ * @length: the length of key.
+ *
+ * This hash was created by Peter Jay Weinberger (AT&T Bell Labs):
+ * https://en.wikipedia.org/wiki/PJW_hash_function
+ *
+ * Return: the PJW hash.
+ */
+_pjw_inline uint pjwhash(const void* key, uint length)
+{
+   uint hash = 0, high;
+   const u8 *k = key;
+
+   for (uint i = 0; i < length; ++k, ++i) {
+       hash = (hash << ONE_EIGHTH) + *k;
+      high = hash & HIGH_BITS;
+      if (high != 0) {
+          hash ^= high >> THREE_QUARTERS;
+          hash &= ~high;
+      }
+   }
+   return hash;
+}
+
+#endif  /* _PJWHASH_INLINE_H */

c/include/pjwhash.h

@@ -0,0 +1,30 @@
+/* pjwhash.h - PJW hash function, extern 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_H
+#define _PJWHASH_H
+
+#include "bits.h"
+
+/**
+ * unsigned int pjwhash - PJW hash function
+ * @key:    the key address.
+ * @length: the length of key.
+ *
+ * This hash was created by Peter Jay Weinberger (AT&T Bell Labs):
+ * https://en.wikipedia.org/wiki/PJW_hash_function
+ *
+ * Return: the PJW hash.
+ */
+extern uint  pjwhash (const void* key, uint length);
+
+#endif  /* _PJWHASH_H */

c/pjwhash.c

@@ -0,0 +1,20 @@
+/* pjwhash.c - PJW hash function.
+ *
+ * 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>
+ *
+ */
+
+#define _pjw_inline extern
+
+//#include "bits.h"
+//extern unsigned int  pjwhash (const void* key, uint length);
+
+#include "pjwhash.h"
+#include "pjwhash-inline.h"