mirror of https://github.com/rusefi/lua.git
added comments to several functions
This commit is contained in:
Roberto Ierusalimschy
parent
626124d2d8
commit
12bd01c567
148
lvm.c
148
lvm.c
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@ -1,5 +1,5 @@
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/*
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** $Id: lvm.c,v 2.205 2014/05/01 18:18:06 roberto Exp roberto $
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** $Id: lvm.c,v 2.206 2014/05/09 14:20:52 roberto Exp roberto $
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** Lua virtual machine
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** See Copyright Notice in lua.h
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*/
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@ -56,7 +56,8 @@ static int tofloat (const TValue *obj, lua_Number *n) {
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/*
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** Try to convert a value to a float
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** Try to convert a value to a float. Check 'isinteger' first, because
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** in general the float case is already handled by the macro 'tonumber'.
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*/
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int luaV_tonumber_ (const TValue *obj, lua_Number *n) {
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TValue v;
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@ -69,7 +70,7 @@ int luaV_tonumber_ (const TValue *obj, lua_Number *n) {
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*n = fltvalue(obj);
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return 1;
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}
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else if (ttisstring(obj) &&
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else if (ttisstring(obj) && /* string convertible to number? */
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luaO_str2num(svalue(obj), &v) == tsvalue(obj)->len + 1) {
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obj = &v;
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goto again; /* convert result from 'luaO_str2num' to a float */
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@ -178,8 +179,12 @@ static int forlimit (const TValue *obj, lua_Integer *p, lua_Integer step,
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}
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/*
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** Main function for table access (invoking metamethods if needed).
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** Compute 'val = t[key]'
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*/
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void luaV_gettable (lua_State *L, const TValue *t, TValue *key, StkId val) {
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int loop;
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int loop; /* counter to avoid infinite loops */
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for (loop = 0; loop < MAXTAGLOOP; loop++) {
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const TValue *tm;
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if (ttistable(t)) { /* `t' is a table? */
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@ -187,32 +192,36 @@ void luaV_gettable (lua_State *L, const TValue *t, TValue *key, StkId val) {
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const TValue *res = luaH_get(h, key); /* do a primitive get */
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if (!ttisnil(res) || /* result is not nil? */
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(tm = fasttm(L, h->metatable, TM_INDEX)) == NULL) { /* or no TM? */
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setobj2s(L, val, res);
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setobj2s(L, val, res); /* result is the raw get */
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return;
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}
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/* else will try the tag method */
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/* else will try metamethod */
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}
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else if (ttisnil(tm = luaT_gettmbyobj(L, t, TM_INDEX)))
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luaG_typeerror(L, t, "index");
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if (ttisfunction(tm)) {
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luaG_typeerror(L, t, "index"); /* no metamethod */
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if (ttisfunction(tm)) { /* metamethod is a function */
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luaT_callTM(L, tm, t, key, val, 1);
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return;
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}
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t = tm; /* else repeat with 'tm' */
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t = tm; /* else repeat access over 'tm' */
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}
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luaG_runerror(L, "gettable chain too long; possible loop");
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}
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/*
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** Main function for table assignment (invoking metamethods if needed).
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** Compute 't[key] = val'
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*/
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void luaV_settable (lua_State *L, const TValue *t, TValue *key, StkId val) {
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int loop;
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int loop; /* counter to avoid infinite loops */
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for (loop = 0; loop < MAXTAGLOOP; loop++) {
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const TValue *tm;
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if (ttistable(t)) { /* `t' is a table? */
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Table *h = hvalue(t);
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TValue *oldval = cast(TValue *, luaH_get(h, key));
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/* if previous value is not nil, there must be a previous entry
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in the table; moreover, a metamethod has no relevance */
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in the table; a metamethod has no relevance */
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if (!ttisnil(oldval) ||
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/* previous value is nil; must check the metamethod */
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((tm = fasttm(L, h->metatable, TM_NEWINDEX)) == NULL &&
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@ -232,32 +241,40 @@ void luaV_settable (lua_State *L, const TValue *t, TValue *key, StkId val) {
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else /* not a table; check metamethod */
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if (ttisnil(tm = luaT_gettmbyobj(L, t, TM_NEWINDEX)))
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luaG_typeerror(L, t, "index");
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/* there is a metamethod */
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/* try the metamethod */
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if (ttisfunction(tm)) {
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luaT_callTM(L, tm, t, key, val, 0);
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return;
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}
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t = tm; /* else repeat with 'tm' */
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t = tm; /* else repeat assginment over 'tm' */
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}
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luaG_runerror(L, "settable chain too long; possible loop");
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}
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/*
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** Compare two strings 'ls' x 'rs', returning an integer smaller-equal-
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** -larger than zero if 'ls' is smaller-equal-larger than 'rs'.
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** The code is a little tricky because it allows '\0' in the strings
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** and it uses 'strcoll' (to respect locales) for each segments
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** of the strings.
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*/
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static int l_strcmp (const TString *ls, const TString *rs) {
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const char *l = getstr(ls);
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size_t ll = ls->tsv.len;
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const char *r = getstr(rs);
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size_t lr = rs->tsv.len;
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for (;;) {
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for (;;) { /* for each segment */
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int temp = strcoll(l, r);
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if (temp != 0) return temp;
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else { /* strings are equal up to a `\0' */
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if (temp != 0) /* not equal? */
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return temp; /* done */
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else { /* strings are equal up to a '\0' */
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size_t len = strlen(l); /* index of first `\0' in both strings */
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if (len == lr) /* r is finished? */
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return (len == ll) ? 0 : 1;
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else if (len == ll) /* l is finished? */
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return -1; /* l is smaller than r (because r is not finished) */
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/* both strings longer than `len'; go on comparing (after the `\0') */
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if (len == lr) /* 'rs' is finished? */
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return (len == ll) ? 0 : 1; /* check 'ls' */
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else if (len == ll) /* 'ls' is finished? */
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return -1; /* 'ls' is smaller than 'rs' ('rs' is not finished) */
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/* both strings longer than `len'; go on comparing after the '\0' */
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len++;
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l += len; ll -= len; r += len; lr -= len;
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}
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@ -265,29 +282,35 @@ static int l_strcmp (const TString *ls, const TString *rs) {
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}
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/*
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** Main operation less than; return 'l < r'.
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*/
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int luaV_lessthan (lua_State *L, const TValue *l, const TValue *r) {
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int res;
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lua_Number nl, nr;
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if (ttisinteger(l) && ttisinteger(r))
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if (ttisinteger(l) && ttisinteger(r)) /* both operands are integers? */
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return (ivalue(l) < ivalue(r));
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else if (tofloat(l, &nl) && tofloat(r, &nr))
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else if (tofloat(l, &nl) && tofloat(r, &nr)) /* both are numbers? */
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return luai_numlt(nl, nr);
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else if (ttisstring(l) && ttisstring(r))
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else if (ttisstring(l) && ttisstring(r)) /* both are strings? */
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return l_strcmp(rawtsvalue(l), rawtsvalue(r)) < 0;
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else if ((res = luaT_callorderTM(L, l, r, TM_LT)) < 0)
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luaG_ordererror(L, l, r);
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else if ((res = luaT_callorderTM(L, l, r, TM_LT)) < 0) /* no metamethod? */
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luaG_ordererror(L, l, r); /* error */
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return res;
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}
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/*
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** Main operation less than or equal to; return 'l <= r'.
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*/
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int luaV_lessequal (lua_State *L, const TValue *l, const TValue *r) {
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int res;
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lua_Number nl, nr;
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if (ttisinteger(l) && ttisinteger(r))
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if (ttisinteger(l) && ttisinteger(r)) /* both operands are integers? */
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return (ivalue(l) <= ivalue(r));
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else if (tofloat(l, &nl) && tofloat(r, &nr))
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else if (tofloat(l, &nl) && tofloat(r, &nr)) /* both are numbers? */
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return luai_numle(nl, nr);
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else if (ttisstring(l) && ttisstring(r))
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else if (ttisstring(l) && ttisstring(r)) /* both are strings? */
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return l_strcmp(rawtsvalue(l), rawtsvalue(r)) <= 0;
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else if ((res = luaT_callorderTM(L, l, r, TM_LE)) >= 0) /* first try `le' */
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return res;
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@ -298,15 +321,16 @@ int luaV_lessequal (lua_State *L, const TValue *l, const TValue *r) {
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/*
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** equality of Lua values. L == NULL means raw equality (no metamethods)
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** Main operation for equality of Lua values; return 't1 == t2'.
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** L == NULL means raw equality (no metamethods)
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*/
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int luaV_equalobj (lua_State *L, const TValue *t1, const TValue *t2) {
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const TValue *tm;
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if (ttype(t1) != ttype(t2)) {
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if (ttype(t1) != ttype(t2)) { /* not the same variant? */
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if (ttnov(t1) != ttnov(t2) || ttnov(t1) != LUA_TNUMBER)
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return 0; /* only numbers can be equal with different variants */
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else { /* two numbers with different variants */
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lua_Number n1, n2;
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lua_Number n1, n2; /* compare them as floats */
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lua_assert(ttisnumber(t1) && ttisnumber(t2));
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cast_void(tofloat(t1, &n1)); cast_void(tofloat(t2, &n2));
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return luai_numeq(n1, n2);
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@ -343,8 +367,13 @@ int luaV_equalobj (lua_State *L, const TValue *t1, const TValue *t2) {
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}
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/* macro used by 'luaV_concat' to ensure that element at 'o' is a string */
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#define tostring(L,o) (ttisstring(o) || (luaV_tostring(L, o)))
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/*
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** Main operation for concatenation: concat 'total' values in the stack,
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** from 'L->top - total' up to 'L->top - 1'.
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*/
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void luaV_concat (lua_State *L, int total) {
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lua_assert(total >= 2);
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do {
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@ -372,12 +401,12 @@ void luaV_concat (lua_State *L, int total) {
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buffer = luaZ_openspace(L, &G(L)->buff, tl);
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tl = 0;
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n = i;
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do { /* concat all strings */
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do { /* copy all strings to buffer */
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size_t l = tsvalue(top-i)->len;
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memcpy(buffer+tl, svalue(top-i), l * sizeof(char));
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tl += l;
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} while (--i > 0);
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setsvalue2s(L, top-n, luaS_newlstr(L, buffer, tl));
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setsvalue2s(L, top-n, luaS_newlstr(L, buffer, tl)); /* create result */
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}
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total -= n-1; /* got 'n' strings to create 1 new */
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L->top -= n-1; /* popped 'n' strings and pushed one */
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@ -385,6 +414,9 @@ void luaV_concat (lua_State *L, int total) {
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}
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/*
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** Main operation 'ra' = #rb'.
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*/
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void luaV_objlen (lua_State *L, StkId ra, const TValue *rb) {
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const TValue *tm;
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switch (ttnov(rb)) {
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@ -410,15 +442,18 @@ void luaV_objlen (lua_State *L, StkId ra, const TValue *rb) {
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}
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lua_Integer luaV_div (lua_State *L, lua_Integer x, lua_Integer y) {
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if (l_castS2U(y) + 1u <= 1u) { /* special cases: -1 or 0 */
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if (y == 0)
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/*
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** Integer division; return 'm // n'.
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*/
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lua_Integer luaV_div (lua_State *L, lua_Integer m, lua_Integer n) {
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if (l_castS2U(n) + 1u <= 1u) { /* special cases: -1 or 0 */
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if (n == 0)
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luaG_runerror(L, "attempt to divide by zero");
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return intop(-, 0, x); /* y==-1; avoid overflow with 0x80000...//-1 */
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return intop(-, 0, m); /* n==-1; avoid overflow with 0x80000...//-1 */
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}
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else {
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lua_Integer d = x / y; /* perform division */
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if ((x ^ y) >= 0 || x % y == 0) /* same signal or no rest? */
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lua_Integer d = m / n; /* perform division */
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if ((m ^ n) >= 0 || m % n == 0) /* same signal or no rest? */
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return d;
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else
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return d - 1; /* correct 'div' for negative case */
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@ -426,33 +461,36 @@ lua_Integer luaV_div (lua_State *L, lua_Integer x, lua_Integer y) {
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}
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lua_Integer luaV_mod (lua_State *L, lua_Integer x, lua_Integer y) {
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if (l_castS2U(y) + 1u <= 1u) { /* special cases: -1 or 0 */
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if (y == 0)
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/*
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** Integer modulus; return 'm % n'.
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*/
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lua_Integer luaV_mod (lua_State *L, lua_Integer m, lua_Integer n) {
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if (l_castS2U(n) + 1u <= 1u) { /* special cases: -1 or 0 */
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if (n == 0)
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luaG_runerror(L, "attempt to perform 'n%%0'");
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return 0; /* y==-1; avoid overflow with 0x80000...%-1 */
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return 0; /* m % -1 == 0; avoid overflow with 0x80000...%-1 */
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}
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else {
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lua_Integer r = x % y;
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if (r == 0 || (x ^ y) >= 0)
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lua_Integer r = m % n;
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if (r == 0 || (m ^ n) >= 0)
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return r;
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else
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return r + y; /* correct 'mod' for negative case */
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return r + n; /* correct 'mod' for negative case */
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}
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}
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lua_Integer luaV_pow (lua_Integer x, lua_Integer y) {
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lua_assert(y >= 0);
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if (y == 0)
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return 1; /* x^0 == 1 */
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lua_Integer luaV_pow (lua_Integer m, lua_Integer n) {
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lua_assert(n >= 0);
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if (n == 0)
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return 1; /* m^0 == 1 */
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else {
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lua_Integer r = 1;
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for (; y > 1; y >>= 1) {
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if (y & 1) r = intop(*, r, x);
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x = intop(*, x, x);
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for (; n > 1; n >>= 1) {
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if (n & 1) r = intop(*, r, m);
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m = intop(*, m, m);
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}
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r = intop(*, r, x);
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r = intop(*, r, m);
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return r;
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}
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}
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