commit 3ca3c94dcc29e97f0271125b7ae5f9dc3afaac2d
from: Stefan Sperling <stsp@stsp.name>
via: Thomas Adam <thomas@xteddy.org>
date: Fri Oct 15 19:22:03 2021 UTC

rework murmurhash2() to avoid potential unaligned memory access

pointed out by naddy@
ok millert@

commit - b7e0a38461dd7c0fb1261f45640ec533e7305709
commit + 3ca3c94dcc29e97f0271125b7ae5f9dc3afaac2d
blob - ac869f866068f2b1050c52779f2539890a8c877f
blob + d3a67547fa3ddbd12660f688766bd387d6ed905b
--- lib/murmurhash2.c
+++ lib/murmurhash2.c
@@ -5,11 +5,12 @@
 /* Obtained from https://github.com/aappleby/smhasher */
 
 #include <stdint.h>
+#include <string.h>
 
 #include "murmurhash2.h"
 
 uint32_t
-murmurhash2(const void * key, int len, uint32_t seed)
+murmurhash2(const unsigned char * key, int len, uint32_t seed)
 {
   // 'm' and 'r' are mixing constants generated offline.
   // They're not really 'magic', they just happen to work well.
@@ -23,12 +24,14 @@ murmurhash2(const void * key, int len, uint32_t seed)
 
   // Mix 4 bytes at a time into the hash
 
-  const unsigned char *data = (const unsigned char *)key;
+  const unsigned char *data = key;
 
   while(len >= 4)
   {
-    uint32_t k = *(uint32_t*)data;
+    uint32_t k;
 
+    memcpy(&k, data, sizeof(k));
+
     k *= m;
     k ^= k >> r;
     k *= m;
@@ -58,4 +61,4 @@ murmurhash2(const void * key, int len, uint32_t seed)
   h ^= h >> 15;
 
   return h;
-} 
+}
blob - bbd2bf3ef0309efebdfbb79dd75aa100d4fb0b74
blob + 8fa42cdb7d310218bbaff43e40157c42561bdebd
--- lib/murmurhash2.h
+++ lib/murmurhash2.h
@@ -4,4 +4,4 @@
 
 /* Obtained from https://github.com/aappleby/smhasher */
 
-uint32_t murmurhash2(const void *key, int len, uint32_t seed);
+uint32_t murmurhash2(const unsigned char *key, int len, uint32_t seed);