Streaming hash about wyhash HOT 1 OPEN

@smarchini: I have tried that before and there is a problem which you briefly, almost enigmatically mentioned in caveat 2 - last round (finalizing part as you said) takes 1-48 bytes, and that 48 is that problem as you have to feed digest part (wyhash_update()) with full round (of 48 bytes) and know, whether it is last 48 bytes, and then mix it in final stage (wyhash_finalize()). The thing is - in streaming scenario, one doesn't know whether it is a last byte/s or not, so there is no way to recognize 48 bytes received on input as last bytes or not, so there is no way to know whether to use full round or finalize. It would only work if that thing would change, and every multiple of full round (here: 48 bytes) was digested (wyhash_update()) and not finalized. That is, what you meant as wyhash uses > instead of >=, in line 127. And yes, it would make it streamable if that thing was changed - that comparison changed to >=.

--- wyhash.h~	2023-09-28 17:07:03.953024424 +0000
+++ wyhash.h	2023-09-28 17:35:22.079782532 +0000
@@ -124,14 +124,14 @@ static inline uint64_t wyhash(const void
   }
   else{
     size_t i=len; 
-    if(_unlikely_(i>48)){
+    if(_unlikely_(i>=48)){
       uint64_t see1=seed, see2=seed;
       do{
         seed=_wymix(_wyr8(p)^secret[1],_wyr8(p+8)^seed);
         see1=_wymix(_wyr8(p+16)^secret[2],_wyr8(p+24)^see1);
         see2=_wymix(_wyr8(p+32)^secret[3],_wyr8(p+40)^see2);
         p+=48; i-=48;
-      }while(_likely_(i>48));
+      }while(_likely_(i>=48));
       seed^=see1^see2;
     }
     while(_unlikely_(i>16)){  seed=_wymix(_wyr8(p)^secret[1],_wyr8(p+8)^seed);  i-=16; p+=16;  }

from wyhash.