From: Marko Kreen <markokr@gmail.com>
Date: Thu, 6 Dec 2007 09:18:15 +0000 (+0000)
Subject: int/ptr hash function
X-Git-Tag: pgbouncer_1_2_rc2~113
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=ad09f3e93adac5d1d4ce098ce4cfbfe1bb440218;p=pgbouncer

int/ptr hash function
---

diff --git a/include/hash.h b/include/hash.h
index 3a82476..fb2e67f 100644
--- a/include/hash.h
+++ b/include/hash.h
@@ -1,3 +1,10 @@
 
 uint32_t lookup3_hash(const void *data, size_t len);
 
+uint32_t hash32(uint32_t v);
+
+static inline uint32_t ptr_hash32(const void *ptr)
+{
+	return hash32((uint32_t)(long)ptr);
+}
+
diff --git a/src/hash.c b/src/hash.c
index 80179a8..5c9a736 100644
--- a/src/hash.c
+++ b/src/hash.c
@@ -16,6 +16,9 @@
  * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
  */
 
+#include "system.h"
+#include "hash.h"
+
 /*
  * A simple version of Bob Jenkins' lookup3.c hash.
  *
@@ -26,9 +29,6 @@
  * Actual difference varies as it depends on cpu/compiler/libc details.
  */
 
-#include "system.h"
-#include "hash.h"
-
 /* rotate uint32 */
 #define rot(x,k) (((x)<<(k)) | ((x)>>(32-(k))))
 
@@ -84,3 +84,19 @@ done:
 	return c;
 }
 
+
+/*
+ * Reversible integer hash function by Thomas Wang.
+ */
+
+uint32_t hash32(uint32_t v)
+{
+	v = ~v + (v << 15);
+	v = v ^ (v >> 12);
+	v = v + (v << 2);
+	v = v ^ (v >> 4);
+	v = v * 2057;
+	v = v ^ (v >> 16);
+	return v;
+}
+