LUA_API const char *lua_tolstring (lua_State *L, int idx, size_t *len) {
StkId o = index2addr(L, idx);
if (!ttisstring(o)) {
if (!cvt2str(o)) { /* not convertible? */
if (len != NULL) *len = 0;
return NULL;
}
lua_lock(L); /* 'luaO_tostring' may create a new string */
luaC_checkGC(L);
o = index2addr(L, idx); /* previous call may reallocate the stack */
luaO_tostring(L, o);
lua_unlock(L);
}
if (len != NULL) *len = tsvalue(o)->len;
return svalue(o);
}
/*
** Main operation for concatenation: concat 'total' values in the stack,
** from 'L->top - total' up to 'L->top - 1'.
*/
void luaV_concat (lua_State *L, int total) {
lua_assert(total >= 2);
do {
StkId top = L->top;
int n = 2; /* number of elements handled in this pass (at least 2) */
if (!(ttisstring(top-2) || cvt2str(top-2)) || !tostring(L, top-1))
luaT_trybinTM(L, top-2, top-1, top-2, TM_CONCAT);
else if (isemptystr(top - 1)) /* second operand is empty? */
cast_void(tostring(L, top - 2)); /* result is first operand */
else if (isemptystr(top - 2)) { /* first operand is an empty string? */
setobjs2s(L, top - 2, top - 1); /* result is second op. */
}
else {
/* at least two non-empty string values; get as many as possible */
size_t tl = vslen(top - 1);
TString *ts;
/* collect total length and number of strings */
for (n = 1; n < total && tostring(L, top - n - 1); n++) {
size_t l = vslen(top - n - 1);
if (l >= (MAX_SIZE/sizeof(char)) - tl)
luaG_runerror(L, "string length overflow");
tl += l;
}
if (tl <= LUAI_MAXSHORTLEN) { /* is result a short string? */
char buff[LUAI_MAXSHORTLEN];
copy2buff(top, n, buff); /* copy strings to buffer */
ts = luaS_newlstr(L, buff, tl);
}
else { /* long string; copy strings directly to final result */
ts = luaS_createlngstrobj(L, tl);
copy2buff(top, n, getstr(ts));
}
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 */
} while (total > 1); /* repeat until only 1 result left */
}
l_noret luaG_concaterror (lua_State *L, const TValue *p1, const TValue *p2) {
if (ttisstring(p1) || cvt2str(p1)) p1 = p2;
luaG_typeerror(L, p1, "concatenate");
}
LUA_API int lua_isstring (lua_State *L, int idx) {
const TValue *o = index2addr(L, idx);
return (ttisstring(o) || cvt2str(o));
}
