From 9fa99306140f5d16f43b3fe3e495e8a95a87e20d Mon Sep 17 00:00:00 2001
From: Sears Russell <sears@cs.berkeley.edu>
Date: Sun, 3 Oct 2010 18:00:34 +0000
Subject: [PATCH] added fnv-1 hash implementation

---
 src/stasis/CMakeLists.txt       |   2 +-
 src/stasis/util/hashFunctions.c |   7 +++
 stasis/util/hashFunctions.h     | 107 ++++++++++++++++++++++++++++++++
 3 files changed, 115 insertions(+), 1 deletion(-)
 create mode 100644 src/stasis/util/hashFunctions.c
 create mode 100644 stasis/util/hashFunctions.h

diff --git a/src/stasis/CMakeLists.txt b/src/stasis/CMakeLists.txt
index a33a1e2..095fd2e 100644
--- a/src/stasis/CMakeLists.txt
+++ b/src/stasis/CMakeLists.txt
@@ -46,7 +46,7 @@ ADD_LIBRARY(stasis crc32.c redblack.c tsearchcompat.c lhtable.c concurrentHash.c
                    bufferManager/pageArray.c
                    bufferManager/bufferHash.c replacementPolicy/lru.c
                    replacementPolicy/lruFast.c replacementPolicy/threadsafeWrapper.c replacementPolicy/concurrentWrapper.c
-                   util/log2.c util/histogram.c
+                   util/log2.c util/histogram.c util//hashFunctions.c
                    stlredblack.cpp)
 
 INSTALL(TARGETS stasis LIBRARY DESTINATION lib)
diff --git a/src/stasis/util/hashFunctions.c b/src/stasis/util/hashFunctions.c
new file mode 100644
index 0000000..6a3c6ce
--- /dev/null
+++ b/src/stasis/util/hashFunctions.c
@@ -0,0 +1,7 @@
+/*
+ * hashFunctions.c
+ *
+ *  Created on: Oct 3, 2010
+ *      Author: sears
+ */
+#include <stasis/util/hashFunctions.h>
diff --git a/stasis/util/hashFunctions.h b/stasis/util/hashFunctions.h
new file mode 100644
index 0000000..924c5f6
--- /dev/null
+++ b/stasis/util/hashFunctions.h
@@ -0,0 +1,107 @@
+/*
+ * hashFunctions.h
+ *
+ *  Created on: Oct 3, 2010
+ *      Author: sears
+ */
+
+#ifndef HASHFUNCTIONS_H_
+#define HASHFUNCTIONS_H_
+
+/**
+ * This file contains a number of hash function implementations.
+ *
+ * Some are expensive, but general-purpose, and choose values with good
+ * mathematical properties (i.e. CRC32).  Others are faster, but special
+ * purpose (assume their input is an integer), or provide weaker guarantees
+ * about their outputs.
+ *
+ * FNV-1 hash implementations all have the following form:
+ * <code>
+ * hash = offset_basis
+ * for each octet_of_data to be hashed
+ *   hash = hash * FNV_prime
+ *   hash = hash xor octet_of_data
+ * return hash
+ * </code>
+ *
+ * (From http://isthe.com/chongo/tech/comp/fnv/)
+ */
+
+#include <stasis/common.h>
+
+#define stasis_hash_util_define_fnv_1(TYPE, FNV_prime, offset_basis)          \
+static inline TYPE stasis_util_hash_fnv_1_##TYPE(const byte* octets, int len){\
+  TYPE hash = offset_basis;                                                   \
+                                                                              \
+  for(int i = 0; i < len; i++) {                                              \
+    hash = hash * FNV_prime;                                                  \
+    hash ^= octets[i];                                                        \
+  }                                                                           \
+  return hash;                                                                \
+}                                                                             \
+/**
+ * Implementation of FNV-1 (32-bit).  Function is called stasis_util_hash_fnv_uint32_t().
+ */
+stasis_hash_util_define_fnv_1(uint32_t, 16777619U, 2166136261U)
+/**
+ * Implementation of FNV-1 (64-bit).  Function is called stasis_util_hash_fnv_uint64_t().
+ */
+stasis_hash_util_define_fnv_1(uint64_t, 1099511628211ULL, 14695981039346656037ULL)
+
+/**
+ * Macro to define xor folding for dynamically set of bits.  This is static inline,
+ * so you can call the function and pass a constant value in as the second argument.
+ * With gcc and -O2, it should propagate the constant, and this is as good as a
+ * separte macro for each possible value of bits.
+ *
+ * Do not call this function if bits is less than 16.
+ */
+#define stasis_util_hash_define_fnv_xor_fold_big(TYPE)                        \
+static inline TYPE stasis_util_hash_fnv_xor_fold_big_##TYPE(TYPE val, uint8_t bits) {\
+  const TYPE mask = ((TYPE)1<<bits)-1;                                        \
+  return (val>>bits) ^ (val & mask);                                          \
+}
+
+stasis_util_hash_define_fnv_xor_fold_big(uint32_t)
+stasis_util_hash_define_fnv_xor_fold_big(uint64_t)
+
+/**
+ * @see stasis_util_hash_define_fnv_xor_fold_big
+ *
+ * Do not call this function if bits is greater than 16.
+ */
+#define stasis_util_hash_define_fnv_xor_fold_tiny(TYPE)                       \
+static inline TYPE stasis_util_hash_fnv_xor_fold_tiny_##TYPE(TYPE val, uint8_t bits) {\
+  const TYPE mask = ((TYPE)1<<bits)-1;                                        \
+  return (val>>bits ^ val) & mask;                                            \
+}
+
+stasis_util_hash_define_fnv_xor_fold_tiny(uint32_t)
+
+static inline uint64_t stasis_util_hash_fnv_xor_fold_uint64_t(uint64_t val, uint8_t bits) {
+  if(bits < 16) {
+    return
+      stasis_util_hash_fnv_xor_fold_tiny_uint32_t(
+        stasis_util_hash_fnv_xor_fold_big_uint64_t(val, 32), bits
+       );
+  } else if(bits < 32) {
+    return
+      stasis_util_hash_fnv_xor_fold_big_uint32_t(
+        stasis_util_hash_fnv_xor_fold_big_uint64_t(val, 32), bits
+        );
+  } else {
+    return stasis_util_hash_fnv_xor_fold_big_uint64_t(val, bits);
+  }
+}
+static inline uint32_t stasis_util_hash_fnv_xor_fold_uint32_t(uint32_t val, uint8_t bits) {
+  if(bits < 16) {
+    return
+      stasis_util_hash_fnv_xor_fold_tiny_uint32_t(val, bits);
+  } else {
+    return
+      stasis_util_hash_fnv_xor_fold_big_uint32_t(val, bits);
+  }
+}
+
+#endif /* HASHFUNCTIONS_H_ */