add id for short string

src/lobject.h

@@ -364,6 +364,7 @@ typedef struct TString {
   lu_byte extra;  /* reserved words for short strings; "has hash" for longs */
   lu_byte shrlen;  /* length for short strings */
   unsigned int hash;
+  size_t id;	/* id for short strings */
   union {
     size_t lnglen;  /* length for long strings */
     struct TString *hnext;  /* linked list for hash table */

src/lstate.c

@@ -55,7 +55,7 @@ typedef struct LG {
 ** A macro to create a "random" seed when a state is created;
 ** the seed is used to randomize string hashes.
 */
-#if !defined(luai_makeseed)
+#if 0 && !defined(luai_makeseed)
 
 #include <time.h>
 
@@ -394,7 +394,6 @@ LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {
   g->warnf = NULL;
   g->ud_warn = NULL;
   g->mainthread = L;
-  g->seed = luai_makeseed(L);
   g->gcrunning = 0;  /* no GC while building state */
   g->strt.size = g->strt.nuse = 0;
   g->strt.hash = NULL;

src/lstate.h

@@ -234,7 +234,6 @@ typedef struct global_State {
   stringtable strt;  /* hash table for strings */
   TValue l_registry;
   TValue nilvalue;  /* a nil value */
-  unsigned int seed;  /* randomized seed for hashes */
   lu_byte currentwhite;
   lu_byte gcstate;  /* state of garbage collector */
   lu_byte gckind;  /* kind of GC running */

src/lstring.c

@@ -20,7 +20,10 @@
 #include "lobject.h"
 #include "lstate.h"
 #include "lstring.h"
+#include "atomic.h"
 
+static unsigned int STRSEED;
+static size_t STRID = 0;
 
 /*
 ** Lua will use at most ~(2^LUAI_HASHLIMIT) bytes from a long string to
@@ -49,6 +52,26 @@ int luaS_eqlngstr (TString *a, TString *b) {
      (memcmp(getstr(a), getstr(b), len) == 0));  /* equal contents */
 }
 
+int luaS_eqshrstr (TString *a, TString *b) {
+  lu_byte len = a->shrlen;
+  lua_assert(b->tt == LUA_TSHRSTR);
+  int r = len == b->shrlen && (memcmp(getstr(a), getstr(b), len) == 0);
+  if (r) {
+    if (a->id < b->id) {
+      a->id = b->id;
+    } else {
+      b->id = a->id;
+    }
+  }
+  return r;
+}
+
+void luaS_share (TString *ts) {
+  if (ts == NULL)
+    return;
+  makeshared(ts);
+  ts->id = ATOM_DEC(&STRID);
+}
 
 unsigned int luaS_hash (const char *str, size_t l, unsigned int seed,
                         size_t step) {
@@ -128,13 +151,31 @@ void luaS_clearcache (global_State *g) {
     }
 }
 
+#if !defined(luai_makeseed)
+
+#include <time.h>
+
+static unsigned int luai_makeseed(lua_State *L) {
+	size_t buff[4];
+	unsigned int h = time(NULL);
+	buff[0] = cast(size_t, h);
+	buff[1] = cast(size_t, &STRSEED);
+	buff[2] = cast(size_t, &luai_makeseed);
+	buff[3] = cast(size_t, L);
+	return luaS_hash((const char*)buff, sizeof(buff), h, 1);
+}
+
+#endif
 
 /*
 ** Initialize the string table and the string cache
 */
 void luaS_init (lua_State *L) {
   global_State *g = G(L);
   int i, j;
+  if (STRSEED == 0) {
+    STRSEED = luai_makeseed(L);
+  }
   stringtable *tb = &G(L)->strt;
   tb->hash = luaM_newvector(L, MINSTRTABSIZE, TString*);
   tablerehash(tb->hash, 0, MINSTRTABSIZE);  /* clear array */
@@ -161,13 +202,14 @@ static TString *createstrobj (lua_State *L, size_t l, int tag, unsigned int h) {
   ts = gco2ts(o);
   ts->hash = h;
   ts->extra = 0;
+  ts->id = 0;
   getstr(ts)[l] = '\0';  /* ending 0 */
   return ts;
 }
 
 
 TString *luaS_createlngstrobj (lua_State *L, size_t l) {
-  TString *ts = createstrobj(L, l, LUA_VLNGSTR, G(L)->seed);
+  TString *ts = createstrobj(L, l, LUA_VLNGSTR, STRSEED);
   ts->u.lnglen = l;
   return ts;
 }
@@ -201,7 +243,7 @@ static TString *internshrstr (lua_State *L, const char *str, size_t l) {
   TString *ts;
   global_State *g = G(L);
   stringtable *tb = &g->strt;
-  unsigned int h = luaS_hash(str, l, g->seed, 1);
+  unsigned int h = luaS_hash(str, l, STRSEED, 1);
   TString **list = &tb->hash[lmod(h, tb->size)];
   lua_assert(str != NULL);  /* otherwise 'memcmp'/'memcpy' are undefined */
   for (ts = *list; ts != NULL; ts = ts->u.hnext) {

src/lstring.h

@@ -32,15 +32,16 @@
 
 
 /*
-** equality for short strings, which are always internalized
+** equality for short strings, compare id first
 */
-#define eqshrstr(a,b)	check_exp((a)->tt == LUA_VSHRSTR, (a) == (b))
-
+#define eqshrstr(a,b)	check_exp((a)->tt == LUA_VSHRSTR, (a) == (b) || \
+       ( ((a)->id == (b)->id) ? ((a)->id != 0) : ((a)->hash == (b)->hash && luaS_eqshrstr(a,b)) ) )
 
 LUAI_FUNC unsigned int luaS_hash (const char *str, size_t l,
                                   unsigned int seed, size_t step);
 LUAI_FUNC unsigned int luaS_hashlongstr (TString *ts);
 LUAI_FUNC int luaS_eqlngstr (TString *a, TString *b);
+LUAI_FUNC int luaS_eqshrstr (TString *a, TString *b);
 LUAI_FUNC void luaS_resize (lua_State *L, int newsize);
 LUAI_FUNC void luaS_clearcache (global_State *g);
 LUAI_FUNC void luaS_init (lua_State *L);
@@ -49,6 +50,6 @@ LUAI_FUNC Udata *luaS_newudata (lua_State *L, size_t s, int nuvalue);
 LUAI_FUNC TString *luaS_newlstr (lua_State *L, const char *str, size_t l);
 LUAI_FUNC TString *luaS_new (lua_State *L, const char *str);
 LUAI_FUNC TString *luaS_createlngstrobj (lua_State *L, size_t l);
-
+LUAI_FUNC void luaS_share(TString *ts);
 
 #endif