Cache string hashes in TString

3 files changed, 21 insertions, 11 deletions

diff --git a/src/llex.js b/src/llex.js
index 220f45d..2e37eca 100644
--- a/src/llex.js
+++ b/src/llex.js
@@ -208,7 +208,7 @@ const luaX_newstring = function(ls, str) {
         o.setbvalue(true);
     } else { /* string already present */
         /* HACK: Workaround lack of ltable 'keyfromval' */
-        let tpair = ls.h.strong.get(lstring.luaS_hash(ts));
+        let tpair = ls.h.strong.get(lstring.luaS_hashlongstr(ts));
         assert(tpair.value == o);
         ts = tpair.key.tsvalue(); /* re-use value previously stored */
     }
diff --git a/src/lstring.js b/src/lstring.js
index 3e94171..cc399b8 100644
--- a/src/lstring.js
+++ b/src/lstring.js
@@ -7,6 +7,7 @@ const defs = require('./defs.js');
 class TString {
 
     constructor(L, str) {
+        this.hash = null;
         this.realstring = str;
     }
 
@@ -28,8 +29,16 @@ const luaS_eqlngstr = function(a, b) {
 
 /* converts strings (arrays) to a consistent map key */
 const luaS_hash = function(str) {
-    assert(str instanceof TString);
-    return str.realstring.map(e => `${e}|`).join('');
+    assert(Array.isArray(str));
+    return str.map(e => `${e}|`).join('');
+};
+
+const luaS_hashlongstr = function(ts) {
+    assert(ts instanceof TString);
+    if(ts.hash === null) {
+        ts.hash = luaS_hash(ts.getstr());
+    }
+    return ts.hash;
 };
 
 /* variant that takes ownership of array */
@@ -48,9 +57,10 @@ const luaS_newliteral = function(L, str) {
     return luaS_bless(L, defs.to_luastring(str));
 };
 
-module.exports.luaS_eqlngstr   = luaS_eqlngstr;
-module.exports.luaS_hash       = luaS_hash;
-module.exports.luaS_bless      = luaS_bless;
-module.exports.luaS_new        = luaS_new;
-module.exports.luaS_newliteral = luaS_newliteral;
-module.exports.TString         = TString;
+module.exports.luaS_eqlngstr    = luaS_eqlngstr;
+module.exports.luaS_hash        = luaS_hash;
+module.exports.luaS_hashlongstr = luaS_hashlongstr;
+module.exports.luaS_bless       = luaS_bless;
+module.exports.luaS_new         = luaS_new;
+module.exports.luaS_newliteral  = luaS_newliteral;
+module.exports.TString          = TString;
diff --git a/src/ltable.js b/src/ltable.js
index a2987d3..1b55256 100644
--- a/src/ltable.js
+++ b/src/ltable.js
@@ -24,7 +24,7 @@ const table_hash = function(key) {
         return key.value;
     case CT.LUA_TSHRSTR:
     case CT.LUA_TLNGSTR:
-        return lstring.luaS_hash(key.value);
+        return lstring.luaS_hashlongstr(key.tsvalue());
     default:
         throw new Error("unknown key type: " + key.type);
     }
@@ -54,7 +54,7 @@ const luaH_getint = function(t, key) {
 
 const luaH_getstr = function(t, key) {
     assert(key instanceof lstring.TString);
-    return getgeneric(t, lstring.luaS_hash(key));
+    return getgeneric(t, lstring.luaS_hashlongstr(key));
 };
 
 const luaH_get = function(t, key) {