Some improvements in hash functions.

1 files changed, 4 insertions, 4 deletions

diff --git a/stc/cmap.h b/stc/cmap.h
index 0252e14e..d5fae750 100644
--- a/stc/cmap.h
+++ b/stc/cmap.h
@@ -339,9 +339,9 @@ typedef struct {size_t idx; uint32_t hx;} chash_bucket_t;
 

 STC_API    uint64_t c_default_hash(const void *data, size_t len);

 STC_INLINE uint64_t c_default_hash32(const void* data, size_t ignored)

-           {return *(const uint32_t *)data * 2654435769u;}

+           {return *(const uint32_t *)data * 0xc6a4a7935bd1e99d;}

 STC_INLINE uint64_t c_default_hash64(const void* data, size_t ignored)

-           {return *(const uint64_t *)data * 11400714819323198485ull;}

+           {return *(const uint64_t *)data * 0xc6a4a7935bd1e99d;}

 

 /* -------------------------- IMPLEMENTATION ------------------------- */

 

@@ -481,10 +481,10 @@ enum {chash_HASH = 0x7f, chash_USED = 0x80};
     }

 

 STC_DEF uint64_t c_default_hash(const void *key, size_t len) {

-    const uint64_t m = 0xc6a4a7935bd1e995;

+    const uint64_t m = 0xb5ad4eceda1ce2a9;

     uint64_t k, h = m + len;

     const uint8_t *p = (const uint8_t *)key, *end = p + (len & ~7ull);

-    for (; p != end; p += 8) {memcpy(&k, p, 8); h ^= k*m;}

+    for (; p != end; p += 8) {memcpy(&k, p, 8); h ^= m*k;}

     switch (len & 7) {

         case 7: h ^= (uint64_t) p[6] << 48;

         case 6: h ^= (uint64_t) p[5] << 40;