1 files changed, 41 insertions, 0 deletions
diff --git a/src/mongo/util/mongoutils/hash.h b/src/mongo/util/mongoutils/hash.h
new file mode 100644
index 00000000000..49f30b3242a
--- /dev/null
+++ b/src/mongo/util/mongoutils/hash.h
@@ -0,0 +1,41 @@
+/** @file hash.h */
+
+/*    Copyright 2009 10gen Inc.
+ *
+ *    Licensed under the Apache License, Version 2.0 (the "License");
+ *    you may not use this file except in compliance with the License.
+ *    You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ *    Unless required by applicable law or agreed to in writing, software
+ *    distributed under the License is distributed on an "AS IS" BASIS,
+ *    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *    See the License for the specific language governing permissions and
+ *    limitations under the License.
+ */
+
+#pragma once
+
+namespace mongoutils {
+
+    /** @return hash of a pointer to an unsigned. so you get a 32 bit hash out, regardless of whether
+                pointers are 32 or 64 bit on the particular platform.
+
+        is there a faster way to impl this that hashes just as well?
+    */
+    inline unsigned hashPointer(void *v) {
+        unsigned x = 0;
+        unsigned char *p = (unsigned char *) &v;
+        for( unsigned i = 0; i < sizeof(void*); i++ ) {
+            x = x * 131 + p[i];
+        }
+        return x;
+    }
+
+    inline unsigned hash(unsigned u) {
+        unsigned char *p = (unsigned char *) &u;
+        return (((((p[3] * 131) + p[2]) * 131) + p[1]) * 131) + p[0];
+    }
+
+}