Remove premature optimization in the FNV-1a while loop, the difference is negligible...

diff --git a/lib/isc/hash.c b/lib/isc/hash.c
index cfa9a3bec4f57138be7f7b84870e1be58acc6bd3..b7bb41a4576e89bc43a9435c3ebdb659036ff4ae 100644 (file)
--- a/lib/isc/hash.c
+++ b/lib/isc/hash.c
@@ -9,6 +9,10 @@
  * information regarding copyright ownership.
  */
 
+/*
+ * 32 bit Fowler/Noll/Vo FNV-1a hash code with modification for BIND
+ */
+
 #include <config.h>
 #include <isc/entropy.h>
 #include <isc/hash.h>
@@ -96,6 +100,8 @@ isc_hash_set_initializer(const void *initializer) {
        fnv_offset_basis = *((const unsigned int *) initializer);
 }
 
+#define FNV_32_PRIME ((isc_uint32_t)0x01000193)
+
 isc_uint32_t
 isc_hash_function(const void *data, size_t length,
                  isc_boolean_t case_sensitive,
@@ -107,14 +113,16 @@ isc_hash_function(const void *data, size_t length,
 
        REQUIRE(length == 0 || data != NULL);
 
-       if (ISC_UNLIKELY(!fnv_initialized))
+       if (ISC_UNLIKELY(!fnv_initialized)) {
                RUNTIME_CHECK(isc_once_do(&fnv_once, fnv_initialize) == ISC_R_SUCCESS);
+       }
 
        hval = ISC_UNLIKELY(previous_hashp != NULL) ?
                *previous_hashp : fnv_offset_basis;
 
-       if (length == 0)
+       if (length == 0) {
                return (hval);
+       }
 
        bp = (const unsigned char *) data;
        be = bp + length;
@@ -129,36 +137,14 @@ isc_hash_function(const void *data, size_t length,
         */
 
        if (case_sensitive) {
-               while (bp <= be - 4) {
-                       hval ^= bp[0];
-                       hval *= 16777619;
-                       hval ^= bp[1];
-                       hval *= 16777619;
-                       hval ^= bp[2];
-                       hval *= 16777619;
-                       hval ^= bp[3];
-                       hval *= 16777619;
-                       bp += 4;
-               }
                while (bp < be) {
                        hval ^= *bp++;
-                       hval *= 16777619;
+                       hval *= FNV_32_PRIME;
                }
        } else {
-               while (bp <= be - 4) {
-                       hval ^= maptolower[bp[0]];
-                       hval *= 16777619;
-                       hval ^= maptolower[bp[1]];
-                       hval *= 16777619;
-                       hval ^= maptolower[bp[2]];
-                       hval *= 16777619;
-                       hval ^= maptolower[bp[3]];
-                       hval *= 16777619;
-                       bp += 4;
-               }
                while (bp < be) {
                        hval ^= maptolower[*bp++];
-                       hval *= 16777619;
+                       hval *= FNV_32_PRIME;
                }
        }
 
@@ -176,14 +162,16 @@ isc_hash_function_reverse(const void *data, size_t length,
 
        REQUIRE(length == 0 || data != NULL);
 
-       if (ISC_UNLIKELY(!fnv_initialized))
+       if (ISC_UNLIKELY(!fnv_initialized)) {
                RUNTIME_CHECK(isc_once_do(&fnv_once, fnv_initialize) == ISC_R_SUCCESS);
+       }
 
        hval = ISC_UNLIKELY(previous_hashp != NULL) ?
                *previous_hashp : fnv_offset_basis;
 
-       if (length == 0)
+       if (length == 0) {
                return (hval);
+       }
 
        bp = (const unsigned char *) data;
        be = bp + length;
@@ -198,36 +186,14 @@ isc_hash_function_reverse(const void *data, size_t length,
         */
 
        if (case_sensitive) {
-               while (be >= bp + 4) {
-                       be -= 4;
-                       hval ^= be[3];
-                       hval *= 16777619;
-                       hval ^= be[2];
-                       hval *= 16777619;
-                       hval ^= be[1];
-                       hval *= 16777619;
-                       hval ^= be[0];
-                       hval *= 16777619;
-               }
                while (--be >= bp) {
                        hval ^= *be;
-                       hval *= 16777619;
+                       hval *= FNV_32_PRIME;
                }
        } else {
-               while (be >= bp + 4) {
-                       be -= 4;
-                       hval ^= maptolower[be[3]];
-                       hval *= 16777619;
-                       hval ^= maptolower[be[2]];
-                       hval *= 16777619;
-                       hval ^= maptolower[be[1]];
-                       hval *= 16777619;
-                       hval ^= maptolower[be[0]];
-                       hval *= 16777619;
-               }
                while (--be >= bp) {
                        hval ^= maptolower[*be];
-                       hval *= 16777619;
+                       hval *= FNV_32_PRIME;
                }
        }