add FNV hashing algorithm

include/util.h

@@ -82,6 +82,15 @@ const char* utilBaseName(const char* path_str);
 // NOTE: returns true if the first 'sz' characters from each string match
 bool utilMatchPrefix(const char* lhs, const char* rhs, int sz);
 
+//-----------------
+// Hashing
+
+// NOTE: FNV1a hashing algorithm http://www.isthe.com/chongo/tech/comp/fnv/
+#define FNV1_64_INIT ((uint64_t) 0xcbf29ce484222325ULL)
+#define FNV_64_PRIME ((uint64_t) 0x100000001b3ULL)
+uint64_t
+utilFNV64a_str(char *str, uint64_t hval = FNV1_64_INIT);
+
 //-----------------
 // Memory allocation
 

src/util.cpp

@@ -58,6 +58,25 @@ utilMatchPrefix(const char* lhs, const char* rhs, int sz)
 	return (rc >= 0);
 }
 
+//-----------------
+// Hashing
+
+uint64_t
+utilFNV64a_str(char* str, uint64_t hval)
+{
+	unsigned char* s = (unsigned char *)str; // unsigned string
+
+	// FNV-1a hash each octet of the string
+	while (*s) {
+		// xor the bottom with the current octet
+		hval ^= (uint64_t)*s++;
+		// multiply by the 64 bit FNV magic prime mod 2^64
+		hval *= FNV_64_PRIME;
+	}
+
+	return hval;
+}
+
 //-----------------
 // Memory allocation