More disciplined use of 'getstr' and 'tsslen'

We may want to add other string variants in the future; this change
documents better where the code may need to handle those variants.

lapi.c

@@ -417,9 +417,9 @@ LUA_API const char *lua_tolstring (lua_State *L, int idx, size_t *len) {
     o = index2value(L, idx);  /* previous call may reallocate the stack */
   }
   if (len != NULL)
-    *len = vslen(o);
+    *len = tsslen(tsvalue(o));
   lua_unlock(L);
-  return svalue(o);
+  return getstr(tsvalue(o));
 }
 
 

ldebug.c

@@ -426,7 +426,7 @@ static const char *getobjname (const Proto *p, int lastpc, int reg,
 */
 static void kname (const Proto *p, int c, const char **name) {
   TValue *kvalue = &p->k[c];
-  *name = (ttisstring(kvalue)) ? svalue(kvalue) : "?";
+  *name = (ttisstring(kvalue)) ? getstr(tsvalue(kvalue)) : "?";
 }
 
 
@@ -569,7 +569,7 @@ static const char *getobjname (const Proto *p, int lastpc, int reg,
         int b = (op == OP_LOADK) ? GETARG_Bx(i)
                                  : GETARG_Ax(p->code[pc + 1]);
         if (ttisstring(&p->k[b])) {
-          *name = svalue(&p->k[b]);
+          *name = getstr(tsvalue(&p->k[b]));
           return "constant";
         }
         break;
@@ -627,7 +627,7 @@ static const char *funcnamefromcode (lua_State *L, const Proto *p,
     default:
       return NULL;  /* cannot find a reasonable name */
   }
-  *name = getstr(G(L)->tmname[tm]) + 2;
+  *name = getshrstr(G(L)->tmname[tm]) + 2;
   return "metamethod";
 }
 

lgc.c

@@ -542,10 +542,12 @@ static void traversestrongtable (global_State *g, Table *h) {
 static lu_mem traversetable (global_State *g, Table *h) {
   const char *weakkey, *weakvalue;
   const TValue *mode = gfasttm(g, h->metatable, TM_MODE);
+  TString *smode;
   markobjectN(g, h->metatable);
-  if (mode && ttisstring(mode) &&  /* is there a weak mode? */
-      (cast_void(weakkey = strchr(svalue(mode), 'k')),
-       cast_void(weakvalue = strchr(svalue(mode), 'v')),
+  if (mode && ttisshrstring(mode) &&  /* is there a weak mode? */
+      (cast_void(smode = tsvalue(mode)),
+       cast_void(weakkey = strchr(getshrstr(smode), 'k')),
+       cast_void(weakvalue = strchr(getshrstr(smode), 'v')),
        (weakkey || weakvalue))) {  /* is really weak? */
     if (!weakkey)  /* strong keys? */
       traverseweakvalue(g, h);

lobject.c

@@ -542,7 +542,7 @@ const char *luaO_pushvfstring (lua_State *L, const char *fmt, va_list argp) {
   addstr2buff(&buff, fmt, strlen(fmt));  /* rest of 'fmt' */
   clearbuff(&buff);  /* empty buffer into the stack */
   lua_assert(buff.pushed == 1);
-  return svalue(s2v(L->top.p - 1));
+  return getstr(tsvalue(s2v(L->top.p - 1)));
 }
 
 

lobject.h

@@ -386,7 +386,7 @@ typedef struct GCObject {
 typedef struct TString {
   CommonHeader;
   lu_byte extra;  /* reserved words for short strings; "has hash" for longs */
-  lu_byte shrlen;  /* length for short strings */
+  lu_byte shrlen;  /* length for short strings, 0xFF for long strings */
   unsigned int hash;
   union {
     size_t lnglen;  /* length for long strings */
@@ -398,19 +398,17 @@ typedef struct TString {
 
 
 /*
-** Get the actual string (array of bytes) from a 'TString'.
+** Get the actual string (array of bytes) from a 'TString'. (Generic
+** version and specialized versions for long and short strings.)
 */
-#define getstr(ts)  ((ts)->contents)
+#define getstr(ts)	((ts)->contents)
+#define getlngstr(ts)	check_exp((ts)->shrlen == 0xFF, (ts)->contents)
+#define getshrstr(ts)	check_exp((ts)->shrlen != 0xFF, (ts)->contents)
 
 
-/* get the actual string (array of bytes) from a Lua value */
-#define svalue(o)       getstr(tsvalue(o))
-
 /* get string length from 'TString *s' */
-#define tsslen(s)	((s)->tt == LUA_VSHRSTR ? (s)->shrlen : (s)->u.lnglen)
-
-/* get string length from 'TValue *o' */
-#define vslen(o)	tsslen(tsvalue(o))
+#define tsslen(s)  \
+	((s)->shrlen != 0xFF ? (s)->shrlen : (s)->u.lnglen)
 
 /* }================================================================== */
 

lstate.c

@@ -433,7 +433,7 @@ void luaE_warning (lua_State *L, const char *msg, int tocont) {
 void luaE_warnerror (lua_State *L, const char *where) {
   TValue *errobj = s2v(L->top.p - 1);  /* error object */
   const char *msg = (ttisstring(errobj))
-                  ? svalue(errobj)
+                  ? getstr(tsvalue(errobj))
                   : "error object is not a string";
   /* produce warning "error in %s (%s)" (where, msg) */
   luaE_warning(L, "error in ", 1);

lstring.c

@@ -36,7 +36,7 @@ int luaS_eqlngstr (TString *a, TString *b) {
   lua_assert(a->tt == LUA_VLNGSTR && b->tt == LUA_VLNGSTR);
   return (a == b) ||  /* same instance or... */
     ((len == b->u.lnglen) &&  /* equal length and ... */
-     (memcmp(getstr(a), getstr(b), len) == 0));  /* equal contents */
+     (memcmp(getlngstr(a), getlngstr(b), len) == 0));  /* equal contents */
 }
 
 
@@ -52,7 +52,7 @@ unsigned int luaS_hashlongstr (TString *ts) {
   lua_assert(ts->tt == LUA_VLNGSTR);
   if (ts->extra == 0) {  /* no hash? */
     size_t len = ts->u.lnglen;
-    ts->hash = luaS_hash(getstr(ts), len, ts->hash);
+    ts->hash = luaS_hash(getlngstr(ts), len, ts->hash);
     ts->extra = 1;  /* now it has its hash */
   }
   return ts->hash;
@@ -157,6 +157,7 @@ static TString *createstrobj (lua_State *L, size_t l, int tag, unsigned int h) {
 TString *luaS_createlngstrobj (lua_State *L, size_t l) {
   TString *ts = createstrobj(L, l, LUA_VLNGSTR, G(L)->seed);
   ts->u.lnglen = l;
+  ts->shrlen = 0xFF;  /* signals that it is a long string */
   return ts;
 }
 
@@ -193,7 +194,7 @@ static TString *internshrstr (lua_State *L, const char *str, size_t l) {
   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) {
-    if (l == ts->shrlen && (memcmp(str, getstr(ts), l * sizeof(char)) == 0)) {
+    if (l == ts->shrlen && (memcmp(str, getshrstr(ts), l * sizeof(char)) == 0)) {
       /* found! */
       if (isdead(g, ts))  /* dead (but not collected yet)? */
         changewhite(ts);  /* resurrect it */
@@ -206,7 +207,7 @@ static TString *internshrstr (lua_State *L, const char *str, size_t l) {
     list = &tb->hash[lmod(h, tb->size)];  /* rehash with new size */
   }
   ts = createstrobj(L, l, LUA_VSHRSTR, h);
-  memcpy(getstr(ts), str, l * sizeof(char));
+  memcpy(getshrstr(ts), str, l * sizeof(char));
   ts->shrlen = cast_byte(l);
   ts->u.hnext = *list;
   *list = ts;
@@ -226,7 +227,7 @@ TString *luaS_newlstr (lua_State *L, const char *str, size_t l) {
     if (l_unlikely(l >= (MAX_SIZE - sizeof(TString))/sizeof(char)))
       luaM_toobig(L);
     ts = luaS_createlngstrobj(L, l);
-    memcpy(getstr(ts), str, l * sizeof(char));
+    memcpy(getlngstr(ts), str, l * sizeof(char));
     return ts;
   }
 }

lundump.c

@@ -122,7 +122,7 @@ static TString *loadStringN (LoadState *S, Proto *p) {
     ts = luaS_createlngstrobj(L, size);  /* create string */
     setsvalue2s(L, L->top.p, ts);  /* anchor it ('loadVector' can GC) */
     luaD_inctop(L);
-    loadVector(S, getstr(ts), size);  /* load directly in final place */
+    loadVector(S, getlngstr(ts), size);  /* load directly in final place */
     L->top.p--;  /* pop string */
   }
   luaC_objbarrier(L, p, ts);

lvm.c

@@ -91,8 +91,10 @@ static int l_strton (const TValue *obj, TValue *result) {
   lua_assert(obj != result);
   if (!cvt2num(obj))  /* is object not a string? */
     return 0;
-  else
-    return (luaO_str2num(svalue(obj), result) == vslen(obj) + 1);
+  else {
+  TString *st = tsvalue(obj);
+    return (luaO_str2num(getstr(st), result) == tsslen(st) + 1);
+  }
 }
 
 
@@ -626,8 +628,9 @@ int luaV_equalobj (lua_State *L, const TValue *t1, const TValue *t2) {
 static void copy2buff (StkId top, int n, char *buff) {
   size_t tl = 0;  /* size already copied */
   do {
-    size_t l = vslen(s2v(top - n));  /* length of string being copied */
-    memcpy(buff + tl, svalue(s2v(top - n)), l * sizeof(char));
+    TString *st = tsvalue(s2v(top - n));
+    size_t l = tsslen(st);  /* length of string being copied */
+    memcpy(buff + tl, getstr(st), l * sizeof(char));
     tl += l;
   } while (--n > 0);
 }
@@ -653,11 +656,11 @@ 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(s2v(top - 1));
+      size_t tl = tsslen(tsvalue(s2v(top - 1)));
       TString *ts;
       /* collect total length and number of strings */
       for (n = 1; n < total && tostring(L, s2v(top - n - 1)); n++) {
-        size_t l = vslen(s2v(top - n - 1));
+        size_t l = tsslen(tsvalue(s2v(top - n - 1)));
         if (l_unlikely(l >= (MAX_SIZE/sizeof(char)) - tl)) {
           L->top.p = top - total;  /* pop strings to avoid wasting stack */
           luaG_runerror(L, "string length overflow");
@@ -671,7 +674,7 @@ void luaV_concat (lua_State *L, int total) {
       }
       else {  /* long string; copy strings directly to final result */
         ts = luaS_createlngstrobj(L, tl);
-        copy2buff(top, n, getstr(ts));
+        copy2buff(top, n, getlngstr(ts));
       }
       setsvalue2s(L, top - n, ts);  /* create result */
     }