From 7e56bd72d60caae88b422b8a979d0e259a829ead Mon Sep 17 00:00:00 2001
From: Stefen Guzik <guzik2@llnl.gov>
Date: Sat, 30 Sep 2006 02:36:54 +0000
Subject: [PATCH] *** empty log message ***
---
Common/Hash.h | 49 +++++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 49 insertions(+)
create mode 100644 Common/Hash.h
diff --git a/Common/Hash.h b/Common/Hash.h
new file mode 100644
index 0000000000..3fd2004628
--- /dev/null
+++ b/Common/Hash.h
@@ -0,0 +1,49 @@
+#ifndef _HASH_H_
+#define _HASH_H_
+
+#if defined(HAVE_64BIT_SIZE_T)
+#define FNV_PRIME 1099511628211UL
+#define FNV_OFFSET_BASIS 14695981039346656037UL
+#else
+#define FNV_PRIME 16777619UL
+#define FNV_OFFSET_BASIS 2166136261UL
+#endif
+
+//--Hash FNV1a implemented via for loop. "key" has size "len" bytes.
+
+inline size_t hash_FNV1a(const void *const key, const int len)
+{
+ const unsigned char *p = static_cast<const unsigned char*>(key);
+ size_t hash = FNV_OFFSET_BASIS;
+ for(int n = len; n--; ) hash = (hash^static_cast<size_t>(*p++))*FNV_PRIME;
+ return hash;
+}
+
+//--Hash FNV1a implemented via template-metaprogramming loop. This should be
+//--used if the length N is known at compile time. "key" has size "N" bytes.
+//--Use the entry point HashFNV1a<N>::eval(key).
+
+template <int N> struct Hash1FNV1a {
+ static size_t eval(size_t hash, const unsigned char *p)
+ {
+ return Hash1FNV1a<N-1>::eval((hash^static_cast<size_t>(*p))*FNV_PRIME, p+1);
+ }
+};
+
+template <> struct Hash1FNV1a<1> {
+ static size_t eval(size_t hash, const unsigned char *p)
+ {
+ return (hash^static_cast<size_t>(*p))*FNV_PRIME;
+ }
+};
+
+// Entry point
+template <int N> struct HashFNV1a {
+ static size_t eval(const void *const key)
+ {
+ size_t hash = FNV_OFFSET_BASIS;
+ return Hash1FNV1a<N>::eval(hash, static_cast<const unsigned char*>(key));
+ }
+};
+
+#endif
--
GitLab