Fix --x-initial and --x-assign random stability (#2662) (#5958) (#6018) (#6025)

src/V3String.cpp

@@ -342,6 +342,49 @@ string VString::aOrAn(const char* word) {
     }
 }
 
+// MurmurHash64A
+uint64_t VString::hashMurmur(const string& str) VL_PURE {
+    const char* key = str.c_str();
+    const size_t len = str.size();
+    const uint64_t seed = 0;
+    const uint64_t m = 0xc6a4a7935bd1e995ULL;
+    const int r = 47;
+
+    uint64_t h = seed ^ (len * m);
+
+    const uint64_t* data = (const uint64_t*)key;
+    const uint64_t* end = data + (len / 8);
+
+    while (data != end) {
+        uint64_t k = *data++;
+
+        k *= m;
+        k ^= k >> r;
+        k *= m;
+
+        h ^= k;
+        h *= m;
+    }
+
+    const unsigned char* data2 = (const unsigned char*)data;
+
+    switch (len & 7) {
+    case 7: h ^= uint64_t(data2[6]) << 48; /* fallthrough */
+    case 6: h ^= uint64_t(data2[5]) << 40; /* fallthrough */
+    case 5: h ^= uint64_t(data2[4]) << 32; /* fallthrough */
+    case 4: h ^= uint64_t(data2[3]) << 24; /* fallthrough */
+    case 3: h ^= uint64_t(data2[2]) << 16; /* fallthrough */
+    case 2: h ^= uint64_t(data2[1]) << 8; /* fallthrough */
+    case 1: h ^= uint64_t(data2[0]); h *= m; /* fallthrough */
+    };
+
+    h ^= h >> r;
+    h *= m;
+    h ^= h >> r;
+
+    return h;
+}
+
 //######################################################################
 // VHashSha256