add a FNV string hash function

Author: xtaci

include/hash_string.h

@@ -5,10 +5,10 @@
  * /--\ | (_| (_) | | |_ | | | | | _> 
  * _| 
  *
- * STRING HASH FUNCTION
+ * STRING HASH FUNCTIONS
  *
- * code taken from: 
- * http://en.wikipedia.org/wiki/Java_hashCode()
+ * 1. http://en.wikipedia.org/wiki/Java_hashCode()
+ * 2. http://www.isthe.com/chongo/tech/comp/fnv/
  *
  ******************************************************************************/
 
@@ -33,6 +33,19 @@ namespace alg
 
 return hash;
 }
+
+static uint32_t hash_fnv1a(const char * str, uint32_t len)
+{
+uint32_t prime = 16777619U;
+uint32_t hash = 2166136261U;
+
+for (int i=0;i<len;i++) {
+hash = hash ^ str[i];
+hash = hash * prime;
+}
+
+return hash;
+}
 }
 
 #endif //

src/hash_string_demo.cpp

@@ -7,15 +7,25 @@ using namespace alg;
 int main(void)
 {
 const char * strs[] = {
+"",
+"a",
+"foobar",
 "first string",
 "second string",
 "third string",
 "this is the fourth string",
 "and finally this is the fifth string"
 };
 
+printf("using java hash\n");
 for (uint32_t i=0;i<sizeof(strs)/sizeof(char*);i++) {
-printf("hash string: %s --> %u\n", strs[i], hash_string(strs[i], strlen(strs[i])));
+printf("java hash: %s --> %x\n", strs[i], hash_string(strs[i], strlen(strs[i])));
 }
+
+printf("using FNV hash\n");
+for (uint32_t i=0;i<sizeof(strs)/sizeof(char*);i++) {
+printf("fnv hash: %s --> %x\n", strs[i], hash_fnv1a(strs[i], strlen(strs[i])));
+}
+
 return 0;
 }