Changeset 226 for cpp/frams/util

Timestamp:

04/18/14 01:51:17 (11 years ago)

Author:

Maciej Komosinski

Message:

• SString::hash() and HashTable? use FNV-1a instead of FNV-1
• fixed the initial hash value

Location:

cpp/frams/util

Files:

• hashtable.cpp (modified) (1 diff)
• hashtable.h (modified) (1 diff)
• sstring.cpp (modified) (4 diffs)

cpp/frams/util/hashtable.cpp

@@ -5 +5 @@
 #include "hashtable.h"
 
-int HashTable::hash(const char *s)
+int HashTable::hash(const SString &s)
 {
-int h=0;
-char c;
-while(c=*(s++))
-    h=31*h+c;
-return h&0x7fffffff;
+return s.hash()&0x7fffffff;
 }
 

cpp/frams/util/hashtable.h

@@ -31 +31 @@
 long sync;
 
-int hash(const char *s);
+int hash(const SString &s);
 void rehash(int newsize);
 public:

cpp/frams/util/sstring.cpp

@@ -116 +116 @@
 
 #define FNV_32_PRIME ((Fnv32_t)0x01000193)
-
-Fnv32_t fnv_32_buf(void *buf, size_t len, Fnv32_t hval)
+#define FNV1_32_INIT ((Fnv32_t)0x811c9dc5)
+#define FNV1_32A_INIT FNV1_32_INIT
+
+Fnv32_t fnv_32a_buf(void *buf, size_t len, Fnv32_t hval)
 {
     unsigned char *bp = (unsigned char *)buf;   /* start of buffer */
@@ -123 +125 @@
 
     while (bp < be) {
+
+        /* xor the bottom with the current octet */
+        hval ^= (Fnv32_t)*bp++;
 
         /* multiply by the 32 bit FNV magic prime mod 2^32 */
@@ -131 +136 @@
 #endif
 
-        /* xor the bottom with the current octet */
-        hval ^= (Fnv32_t)*bp++;
     }
 
@@ -142 +145 @@
 unsigned long SBuf::hash() const
 {
-return fnv_32_buf(txt,used,FNV_32_PRIME);
+return fnv_32a_buf(txt,used,FNV1_32A_INIT);
 }