[Minor] Add fast 52 bits hash to Lua

diff --git a/src/lua/lua_util.c b/src/lua/lua_util.c
index 7b858f4ce76d33d03a7d395944ea574003e89404..220467664a2faa2fbe3beef289e41e99fc939457 100644 (file)
--- a/src/lua/lua_util.c
+++ b/src/lua/lua_util.c
@@ -453,6 +453,15 @@ LUA_FUNCTION_DEF (util, unpack);
  */
 LUA_FUNCTION_DEF (util, caseless_hash);
 
+/***
+ *  @function util.caseless_hash_fast(str[, seed])
+ * Calculates caseless non-crypto hash from a string or rspamd text
+ * @param str string or lua_text
+ * @param seed mandatory seed (0xdeadbabe by default)
+ * @return {number} number from int64_t
+ */
+LUA_FUNCTION_DEF (util, caseless_hash_fast);
+
 static const struct luaL_reg utillib_f[] = {
        LUA_INTERFACE_DEF (util, create_event_base),
        LUA_INTERFACE_DEF (util, load_rspamd_config),
@@ -492,6 +501,7 @@ static const struct luaL_reg utillib_f[] = {
        LUA_INTERFACE_DEF (util, zstd_decompress),
        LUA_INTERFACE_DEF (util, normalize_prob),
        LUA_INTERFACE_DEF (util, caseless_hash),
+       LUA_INTERFACE_DEF (util, caseless_hash_fast),
        LUA_INTERFACE_DEF (util, count_non_ascii),
        LUA_INTERFACE_DEF (util, pack),
        LUA_INTERFACE_DEF (util, unpack),
@@ -1833,6 +1843,49 @@ lua_util_caseless_hash (lua_State *L)
        return 1;
 }
 
+static gint
+lua_util_caseless_hash_fast (lua_State *L)
+{
+       guint64 seed = 0xdeadbabe, h;
+       struct rspamd_lua_text *t = NULL;
+       gsize sz;
+       union {
+               guint64 i;
+               double d;
+       } u;
+
+       if (lua_type (L, 1) == LUA_TSTRING) {
+               t = g_alloca (sizeof (*t));
+               t->start = lua_tolstring (L, 1, &sz);
+               t->len = sz;
+       }
+       else {
+               t = lua_check_text (L, 1);
+       }
+
+       if (t == NULL || t->start == NULL) {
+               return luaL_error (L, "invalid arguments");
+       }
+
+       if (lua_type (L, 2) == LUA_TNUMBER) {
+               seed = lua_tonumber (L, 2);
+       }
+       else if (lua_type (L, 2) == LUA_TUSERDATA) {
+               seed = lua_check_int64 (L, 2);
+       }
+
+       /*
+        * Here, we loose entropy from 64 bits to 52 bits roughly, however,
+        * it is still fine for practical applications
+        */
+
+       h = rspamd_icase_hash (t->start, t->len, seed);
+       u.i = G_GUINT64_CONSTANT(0x3FF) << 52 | h >> 12;
+       lua_pushnumber (L, u.d - 1.0);
+
+       return 1;
+}
+
 static gint
 lua_util_count_non_ascii (lua_State *L)
 {