luaS_newlstr() with str == NULL

Since longs strings are not interned it's ok to initialize their
contents later. This can elliminate bounce buffers in many cases.

src/ldo.c

@@ -684,7 +684,7 @@ static void f_parser (lua_State *L, void *ud) {
   int c = zgetc(p->z);  /* read first character */
   if (c == LUA_SIGNATURE[0]) {
     checkmode(L, p->mode, "binary");
-    cl = luaU_undump(L, p->z, &p->buff, p->name);
+    cl = luaU_undump(L, p->z, p->name);
   }
   else {
     checkmode(L, p->mode, "text");

src/lgc.c

@@ -774,7 +774,6 @@ static GCObject **sweeptolive (lua_State *L, GCObject **p, int *n) {
 static void checkSizes (lua_State *L, global_State *g) {
   if (g->gckind != KGC_EMERGENCY) {
     l_mem olddebt = g->GCdebt;
-    luaZ_freebuffer(L, &g->buff);  /* free concatenation buffer */
     if (g->strt.nuse < g->strt.size / 4)  /* string table too big? */
       luaS_resize(L, g->strt.size / 2);  /* shrink it a little */
     g->GCestimate += g->GCdebt - olddebt;  /* update estimate */

src/lstate.c

@@ -237,7 +237,6 @@ static void close_state (lua_State *L) {
   if (g->version)  /* closing a fully built state? */
     luai_userstateclose(L);
   luaM_freearray(L, G(L)->strt.hash, G(L)->strt.size);
-  luaZ_freebuffer(L, &g->buff);
   freestack(L);
   lua_assert(gettotalbytes(g) == sizeof(LG));
   (*g->frealloc)(g->ud, fromstate(L), sizeof(LG), 0);  /* free main block */
@@ -306,7 +305,6 @@ LUA_API lua_State *lua_newstate (lua_Alloc f, void *ud) {
   g->strt.size = g->strt.nuse = 0;
   g->strt.hash = NULL;
   setnilvalue(&g->l_registry);
-  luaZ_initbuffer(L, &g->buff);
   g->panic = NULL;
   g->version = NULL;
   g->gcstate = GCSpause;

src/lstate.h

@@ -131,7 +131,7 @@ typedef struct global_State {
   GCObject *tobefnz;  /* list of userdata to be GC */
   GCObject *fixedgc;  /* list of objects not to be collected */
   struct lua_State *twups;  /* list of threads with open upvalues */
-  Mbuffer buff;  /* temporary buffer for string concatenation */
+  char buff[LUAI_MAXSHORTLEN];  /* temporary buffer for string concatenation */
   unsigned int gcfinnum;  /* number of finalizers to call in each GC step */
   int gcpause;  /* size of pause between successive GCs */
   int gcstepmul;  /* GC 'granularity' */

src/lstring.c

@@ -119,7 +119,7 @@ void luaS_init (lua_State *L) {
 /*
 ** creates a new string object
 */
-static TString *createstrobj (lua_State *L, const char *str, size_t l,
+static TString *createstrobj (lua_State *L, size_t l,
                               int tag, unsigned int h) {
   TString *ts;
   GCObject *o;
@@ -129,7 +129,6 @@ static TString *createstrobj (lua_State *L, const char *str, size_t l,
   ts = gco2ts(o);
   ts->hash = h;
   ts->extra = 0;
-  memcpy(getaddrstr(ts), str, l * sizeof(char));
   getaddrstr(ts)[l] = '\0';  /* ending 0 */
   return ts;
 }
@@ -166,7 +165,8 @@ static TString *internshrstr (lua_State *L, const char *str, size_t l) {
     luaS_resize(L, g->strt.size * 2);
     list = &g->strt.hash[lmod(h, g->strt.size)];  /* recompute with new size */
   }
-  ts = createstrobj(L, str, l, LUA_TSHRSTR, h);
+  ts = createstrobj(L, l, LUA_TSHRSTR, h);
+  memcpy(getaddrstr(ts), str, l * sizeof(char));
   ts->shrlen = cast_byte(l);
   ts->u.hnext = *list;
   *list = ts;
@@ -185,7 +185,9 @@ TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {
     TString *ts;
     if (l + 1 > (MAX_SIZE - sizeof(TString))/sizeof(char))
       luaM_toobig(L);
-    ts = createstrobj(L, str, l, LUA_TLNGSTR, G(L)->seed);
+    ts = createstrobj(L, l, LUA_TLNGSTR, G(L)->seed);
+    if (str != NULL)
+      memcpy(getaddrstr(ts), str, l * sizeof(char));
     ts->u.lnglen = l;
     return ts;
   }

src/lundump.c

@@ -32,7 +32,6 @@
 typedef struct {
   lua_State *L;
   ZIO *Z;
-  Mbuffer *b;
   const char *name;
 } LoadState;
 
@@ -93,9 +92,14 @@ static TString *LoadString (LoadState *S) {
   if (size == 0)
     return NULL;
   else {
-    char *s = luaZ_openspace(S->L, S->b, --size);
+    TString *ts = NULL;
+    char *s = G(S->L)->buff;
+    if (--size > LUAI_MAXSHORTLEN)
+      s = getaddrstr(ts = luaS_newlstr(S->L, NULL, size));
     LoadVector(S, s, size);
-    return luaS_newlstr(S->L, s, size);
+    if (ts == NULL)
+      ts = luaS_newlstr(S->L, s, size);
+    return ts;
   }
 }
 
@@ -251,8 +255,7 @@ static void checkHeader (LoadState *S) {
 /*
 ** load precompiled chunk
 */
-LClosure *luaU_undump(lua_State *L, ZIO *Z, Mbuffer *buff,
-                      const char *name) {
+LClosure *luaU_undump(lua_State *L, ZIO *Z, const char *name) {
   LoadState S;
   LClosure *cl;
   if (*name == '@' || *name == '=')
@@ -263,7 +266,6 @@ LClosure *luaU_undump(lua_State *L, ZIO *Z, Mbuffer *buff,
     S.name = name;
   S.L = L;
   S.Z = Z;
-  S.b = buff;
   checkHeader(&S);
   cl = luaF_newLclosure(L, LoadByte(&S));
   setclLvalue(L, L->top, cl);

src/lundump.h

@@ -23,8 +23,7 @@
 #define LUAC_FORMAT	0	/* this is the official format */
 
 /* load one chunk; from lundump.c */
-LUAI_FUNC LClosure* luaU_undump (lua_State* L, ZIO* Z, Mbuffer* buff,
-                                 const char* name);
+LUAI_FUNC LClosure* luaU_undump (lua_State* L, ZIO* Z, const char* name);
 
 /* dump one chunk; from ldump.c */
 LUAI_FUNC int luaU_dump (lua_State* L, const Proto* f, lua_Writer w,

src/lvm.c

@@ -462,7 +462,8 @@ void luaV_concat (lua_State *L, int total) {
     else {
       /* at least two non-empty string values; get as many as possible */
       size_t tl = vslen(top - 1);
-      char *buffer;
+      TString *ts = NULL;
+      char *buffer = G(L)->buff;
       int i;
       /* collect total length */
       for (i = 1; i < total && tostring(L, top-i-1); i++) {
@@ -471,15 +472,18 @@ void luaV_concat (lua_State *L, int total) {
           luaG_runerror(L, "string length overflow");
         tl += l;
       }
-      buffer = luaZ_openspace(L, &G(L)->buff, tl);
+      if (tl > LUAI_MAXSHORTLEN)
+        buffer = getaddrstr(ts = luaS_newlstr(L, NULL, tl));
       tl = 0;
       n = i;
       do {  /* copy all strings to buffer */
         size_t l = vslen(top - i);
         memcpy(buffer+tl, svalue(top-i), l * sizeof(char));
         tl += l;
       } while (--i > 0);
-      setsvalue2s(L, top-n, luaS_newlstr(L, buffer, tl));  /* create result */
+	  if (ts == NULL)
+        ts = luaS_newlstr(L, buffer, tl);
+      setsvalue2s(L, top-n, ts);  /* create result */
     }
     total -= n-1;  /* got 'n' strings to create 1 new */
     L->top -= n-1;  /* popped 'n' strings and pushed one */

src/lzio.c

@@ -66,13 +66,3 @@ size_t luaZ_read (ZIO *z, void *b, size_t n) {
   return 0;
 }
 
-/* ------------------------------------------------------------------------ */
-char *luaZ_openspace (lua_State *L, Mbuffer *buff, size_t n) {
-  if (n > buff->buffsize) {
-    if (n < LUA_MINBUFFER) n = LUA_MINBUFFER;
-    luaZ_resizebuffer(L, buff, n);
-  }
-  return buff->buffer;
-}
-
-

src/lzio.h

@@ -44,7 +44,6 @@ typedef struct Mbuffer {
 #define luaZ_freebuffer(L, buff)	luaZ_resizebuffer(L, buff, 0)
 
 
-LUAI_FUNC char *luaZ_openspace (lua_State *L, Mbuffer *buff, size_t n);
 LUAI_FUNC void luaZ_init (lua_State *L, ZIO *z, lua_Reader reader,
                                         void *data);
 LUAI_FUNC size_t luaZ_read (ZIO* z, void *b, size_t n);	/* read next n bytes */