Added MurmurHash2A test.

tests/hash_test.cpp

@@ -31,17 +31,18 @@ struct HashTest
 {
 	uint32_t crc32;
 	uint32_t adler32;
+	uint32_t murmur2a;
 	const char* input;
 };
 
 const HashTest s_hashTest[] =
 {
-	{ 0,          1,          ""       },
-	{ 0xe8b7be43, 0x00620062, "a"      },
-	{ 0x9e83486d, 0x012600c4, "ab"     },
-	{ 0xc340daab, 0x06060205, "abvgd"  },
-	{ 0x07642fe2, 0x020a00d6, "1389"   },
-	{ 0x26d75737, 0x04530139, "555333" },
+	{ 0,          1,          0,          ""       },
+	{ 0xe8b7be43, 0x00620062, 0x803888b,  "a"      },
+	{ 0x9e83486d, 0x012600c4, 0x618515af, "ab"     },
+	{ 0xc340daab, 0x06060205, 0x94e3dc4d, "abvgd"  },
+	{ 0x07642fe2, 0x020a00d6, 0xe602fc07, "1389"   },
+	{ 0x26d75737, 0x04530139, 0x58d37863, "555333" },
 };
 
 TEST_CASE("HashCrc32", "")
@@ -77,3 +78,73 @@ TEST_CASE("HashAdler32", "")
 		REQUIRE(test.adler32 == hash.end() );
 	}
 }
+
+/*-----------------------------------------------------------------------------
+// MurmurHash2A, by Austin Appleby
+//
+// This is a variant of MurmurHash2 modified to use the Merkle-Damgard
+// construction. Bulk speed should be identical to Murmur2, small-key speed
+// will be 10%-20% slower due to the added overhead at the end of the hash.
+//
+// This variant fixes a minor issue where null keys were more likely to
+// collide with each other than expected, and also makes the function
+// more amenable to incremental implementations.
+*/
+
+#define mmix(h,k) { k *= m; k ^= k >> r; k *= m; h *= m; h ^= k; }
+
+uint32_t MurmurHash2A ( const void * key, int len, uint32_t seed )
+{
+	const uint32_t m = 0x5bd1e995;
+	const int r = 24;
+	uint32_t l = len;
+
+	const unsigned char * data = (const unsigned char *)key;
+
+	uint32_t h = seed;
+
+	while(len >= 4)
+	{
+		uint32_t k = *(uint32_t*)data;
+
+		mmix(h,k);
+
+		data += 4;
+		len -= 4;
+	}
+
+	uint32_t t = 0;
+
+	switch(len)
+	{
+	case 3: t ^= data[2] << 16;
+	case 2: t ^= data[1] << 8;
+	case 1: t ^= data[0];
+	};
+
+	mmix(h,t);
+	mmix(h,l);
+
+	h ^= h >> 13;
+	h *= m;
+	h ^= h >> 15;
+
+	return h;
+}
+
+TEST_CASE("HashMurmur2A", "")
+{
+	uint32_t seed = 0;
+
+	for (uint32_t ii = 0; ii < BX_COUNTOF(s_hashTest); ++ii)
+	{
+		const HashTest& test = s_hashTest[ii];
+
+		bx::HashMurmur2A hash;
+		hash.begin(seed);
+		hash.add(test.input, bx::strLen(test.input) );
+		REQUIRE(test.murmur2a == hash.end() );
+
+		REQUIRE(test.murmur2a == MurmurHash2A(test.input, bx::strLen(test.input), seed) );
+	}
+}