Added murmur_hash3_3()

dlib/general_hash/murmur_hash3.h

@@ -255,6 +255,53 @@ namespace dlib
         return h1;
     } 
 
+// ----------------------------------------------------------------------------------------
+
+    inline uint32 murmur_hash3_3 ( 
+        const uint32 v1,
+        const uint32 v2, 
+        const uint32 v3 
+    )
+    {
+
+        uint32 h1 = v3;
+
+        uint32 c1 = 0xcc9e2d51;
+        uint32 c2 = 0x1b873593;
+
+        //----------
+        // body
+
+
+        uint32 k1 = v1;
+
+        k1 *= c1;
+        k1 = DLIB_ROTL32(k1,15);
+        k1 *= c2;
+
+        h1 ^= k1;
+        h1 = DLIB_ROTL32(h1,13); 
+        h1 = h1*5+0xe6546b64;
+
+        k1 = v2;
+        k1 *= c1;
+        k1 = DLIB_ROTL32(k1,15);
+        k1 *= c2;
+
+        h1 ^= k1;
+        h1 = DLIB_ROTL32(h1,13); 
+        h1 = h1*5+0xe6546b64;
+
+        //----------
+        // finalization
+
+        h1 ^= 8; // =^ by length in bytes
+
+        h1 = murmur_fmix(h1);
+
+        return h1;
+    } 
+
 // ----------------------------------------------------------------------------------------
 
     inline std::pair<uint64,uint64> murmur_hash3_128bit ( 

dlib/general_hash/murmur_hash3_abstract.h

@@ -44,6 +44,22 @@ namespace dlib
               See: http://code.google.com/p/smhasher/
     !*/
 
+// ----------------------------------------------------------------------------------------
+
+    inline uint32 murmur_hash3_3 ( 
+        const uint32 v1,
+        const uint32 v2,
+        const uint32 v3 
+    );
+    /*!
+        ensures
+            - returns a 32bit hash of the three integers given to this function.  
+            - This function is machine architecture agnostic and should always give the same
+              hash value when presented with the same inputs.
+            - This hashing algorithm is Austin Appleby's excellent MurmurHash3_x86_32.  
+              See: http://code.google.com/p/smhasher/
+    !*/
+
 // ----------------------------------------------------------------------------------------
 
     std::pair<uint64,uint64> murmur_hash3_128bit (