proxmark3/liblua/lapi.c

/*
** $Id: lapi.c,v 2.171 2013/03/16 21:10:18 roberto Exp $
** Lua API
** See Copyright Notice in lua.h
*/


#include <stdarg.h>
#include <string.h>

#define lapi_c
#define LUA_CORE

#include "lua.h"

#include "lapi.h"
#include "ldebug.h"
#include "ldo.h"
#include "lfunc.h"
#include "lgc.h"
#include "lmem.h"
#include "lobject.h"
#include "lstate.h"
#include "lstring.h"
#include "ltable.h"
#include "ltm.h"
#include "lundump.h"
#include "lvm.h"



const char lua_ident[] =
    "$LuaVersion: " LUA_COPYRIGHT " $"
    "$LuaAuthors: " LUA_AUTHORS " $";


/* value at a non-valid index */
#define NONVALIDVALUE cast(TValue *, luaO_nilobject)

/* corresponding test */
#define isvalid(o) ((o) != luaO_nilobject)

/* test for pseudo index */
#define ispseudo(i) ((i) <= LUA_REGISTRYINDEX)

/* test for valid but not pseudo index */
#define isstackindex(i, o) (isvalid(o) && !ispseudo(i))

#define api_checkvalidindex(L, o)  api_check(L, isvalid(o), "invalid index")

#define api_checkstackindex(L, i, o)  \
    api_check(L, isstackindex(i, o), "index not in the stack")


static TValue *index2addr(lua_State *L, int idx) {
    CallInfo *ci = L->ci;
    if (idx > 0) {
        TValue *o = ci->func + idx;
        api_check(L, idx <= ci->top - (ci->func + 1), "unacceptable index");
        if (o >= L->top) return NONVALIDVALUE;
        else return o;
    } else if (!ispseudo(idx)) { /* negative index */
        api_check(L, idx != 0 && -idx <= L->top - (ci->func + 1), "invalid index");
        return L->top + idx;
    } else if (idx == LUA_REGISTRYINDEX)
        return &G(L)->l_registry;
    else {  /* upvalues */
        idx = LUA_REGISTRYINDEX - idx;
        api_check(L, idx <= MAXUPVAL + 1, "upvalue index too large");
        if (ttislcf(ci->func))  /* light C function? */
            return NONVALIDVALUE;  /* it has no upvalues */
        else {
            CClosure *func = clCvalue(ci->func);
            return (idx <= func->nupvalues) ? &func->upvalue[idx - 1] : NONVALIDVALUE;
        }
    }
}


/*
** to be called by 'lua_checkstack' in protected mode, to grow stack
** capturing memory errors
*/
static void growstack(lua_State *L, void *ud) {
    int size = *(int *)ud;
    luaD_growstack(L, size);
}


LUA_API int lua_checkstack(lua_State *L, int size) {
    int res;
    CallInfo *ci = L->ci;
    lua_lock(L);
    if (L->stack_last - L->top > size)  /* stack large enough? */
        res = 1;  /* yes; check is OK */
    else {  /* no; need to grow stack */
        int inuse = cast_int(L->top - L->stack) + EXTRA_STACK;
        if (inuse > LUAI_MAXSTACK - size)  /* can grow without overflow? */
            res = 0;  /* no */
        else  /* try to grow stack */
            res = (luaD_rawrunprotected(L, &growstack, &size) == LUA_OK);
    }
    if (res && ci->top < L->top + size)
        ci->top = L->top + size;  /* adjust frame top */
    lua_unlock(L);
    return res;
}


LUA_API void lua_xmove(lua_State *from, lua_State *to, int n) {
    int i;
    if (from == to) return;
    lua_lock(to);
    api_checknelems(from, n);
    api_check(from, G(from) == G(to), "moving among independent states");
    api_check(from, to->ci->top - to->top >= n, "not enough elements to move");
    from->top -= n;
    for (i = 0; i < n; i++) {
        setobj2s(to, to->top++, from->top + i);
    }
    lua_unlock(to);
}


LUA_API lua_CFunction lua_atpanic(lua_State *L, lua_CFunction panicf) {
    lua_CFunction old;
    lua_lock(L);
    old = G(L)->panic;
    G(L)->panic = panicf;
    lua_unlock(L);
    return old;
}


LUA_API const lua_Number *lua_version(lua_State *L) {
    static const lua_Number version = LUA_VERSION_NUM;
    if (L == NULL) return &version;
    else return G(L)->version;
}



/*
** basic stack manipulation
*/


/*
** convert an acceptable stack index into an absolute index
*/
LUA_API int lua_absindex(lua_State *L, int idx) {
    return (idx > 0 || ispseudo(idx))
           ? idx
           : cast_int(L->top - L->ci->func + idx);
}


LUA_API int lua_gettop(lua_State *L) {
    return cast_int(L->top - (L->ci->func + 1));
}


LUA_API void lua_settop(lua_State *L, int idx) {
    StkId func = L->ci->func;
    lua_lock(L);
    if (idx >= 0) {
        api_check(L, idx <= L->stack_last - (func + 1), "new top too large");
        while (L->top < (func + 1) + idx)
            setnilvalue(L->top++);
        L->top = (func + 1) + idx;
    } else {
        api_check(L, -(idx + 1) <= (L->top - (func + 1)), "invalid new top");
        L->top += idx + 1; /* `subtract' index (index is negative) */
    }
    lua_unlock(L);
}


LUA_API void lua_remove(lua_State *L, int idx) {
    StkId p;
    lua_lock(L);
    p = index2addr(L, idx);
    api_checkstackindex(L, idx, p);
    while (++p < L->top) setobjs2s(L, p - 1, p);
    L->top--;
    lua_unlock(L);
}


LUA_API void lua_insert(lua_State *L, int idx) {
    StkId p;
    StkId q;
    lua_lock(L);
    p = index2addr(L, idx);
    api_checkstackindex(L, idx, p);
    for (q = L->top; q > p; q--)  /* use L->top as a temporary */
        setobjs2s(L, q, q - 1);
    setobjs2s(L, p, L->top);
    lua_unlock(L);
}


static void moveto(lua_State *L, TValue *fr, int idx) {
    TValue *to = index2addr(L, idx);
    api_checkvalidindex(L, to);
    setobj(L, to, fr);
    if (idx < LUA_REGISTRYINDEX)  /* function upvalue? */
        luaC_barrier(L, clCvalue(L->ci->func), fr);
    /* LUA_REGISTRYINDEX does not need gc barrier
       (collector revisits it before finishing collection) */
}


LUA_API void lua_replace(lua_State *L, int idx) {
    lua_lock(L);
    api_checknelems(L, 1);
    moveto(L, L->top - 1, idx);
    L->top--;
    lua_unlock(L);
}


LUA_API void lua_copy(lua_State *L, int fromidx, int toidx) {
    TValue *fr;
    lua_lock(L);
    fr = index2addr(L, fromidx);
    moveto(L, fr, toidx);
    lua_unlock(L);
}


LUA_API void lua_pushvalue(lua_State *L, int idx) {
    lua_lock(L);
    setobj2s(L, L->top, index2addr(L, idx));
    api_incr_top(L);
    lua_unlock(L);
}



/*
** access functions (stack -> C)
*/


LUA_API int lua_type(lua_State *L, int idx) {
    StkId o = index2addr(L, idx);
    return (isvalid(o) ? ttypenv(o) : LUA_TNONE);
}


LUA_API const char *lua_typename(lua_State *L, int t) {
    UNUSED(L);
    return ttypename(t);
}


LUA_API int lua_iscfunction(lua_State *L, int idx) {
    StkId o = index2addr(L, idx);
    return (ttislcf(o) || (ttisCclosure(o)));
}


LUA_API int lua_isnumber(lua_State *L, int idx) {
    TValue n;
    const TValue *o = index2addr(L, idx);
    return tonumber(o, &n);
}


LUA_API int lua_isstring(lua_State *L, int idx) {
    int t = lua_type(L, idx);
    return (t == LUA_TSTRING || t == LUA_TNUMBER);
}


LUA_API int lua_isuserdata(lua_State *L, int idx) {
    const TValue *o = index2addr(L, idx);
    return (ttisuserdata(o) || ttislightuserdata(o));
}


LUA_API int lua_rawequal(lua_State *L, int index1, int index2) {
    StkId o1 = index2addr(L, index1);
    StkId o2 = index2addr(L, index2);
    return (isvalid(o1) && isvalid(o2)) ? luaV_rawequalobj(o1, o2) : 0;
}


LUA_API void lua_arith(lua_State *L, int op) {
    StkId o1;  /* 1st operand */
    StkId o2;  /* 2nd operand */
    lua_lock(L);
    if (op != LUA_OPUNM) /* all other operations expect two operands */
        api_checknelems(L, 2);
    else {  /* for unary minus, add fake 2nd operand */
        api_checknelems(L, 1);
        setobjs2s(L, L->top, L->top - 1);
        L->top++;
    }
    o1 = L->top - 2;
    o2 = L->top - 1;
    if (ttisnumber(o1) && ttisnumber(o2)) {
        setnvalue(o1, luaO_arith(op, nvalue(o1), nvalue(o2)));
    } else
        luaV_arith(L, o1, o1, o2, cast(TMS, op - LUA_OPADD + TM_ADD));
    L->top--;
    lua_unlock(L);
}


LUA_API int lua_compare(lua_State *L, int index1, int index2, int op) {
    StkId o1, o2;
    int i = 0;
    lua_lock(L);  /* may call tag method */
    o1 = index2addr(L, index1);
    o2 = index2addr(L, index2);
    if (isvalid(o1) && isvalid(o2)) {
        switch (op) {
            case LUA_OPEQ:
                i = equalobj(L, o1, o2);
                break;
            case LUA_OPLT:
                i = luaV_lessthan(L, o1, o2);
                break;
            case LUA_OPLE:
                i = luaV_lessequal(L, o1, o2);
                break;
            default:
                api_check(L, 0, "invalid option");
        }
    }
    lua_unlock(L);
    return i;
}


LUA_API lua_Number lua_tonumberx(lua_State *L, int idx, int *isnum) {
    TValue n;
    const TValue *o = index2addr(L, idx);
    if (tonumber(o, &n)) {
        if (isnum) *isnum = 1;
        return nvalue(o);
    } else {
        if (isnum) *isnum = 0;
        return 0;
    }
}


LUA_API lua_Integer lua_tointegerx(lua_State *L, int idx, int *isnum) {
    TValue n;
    const TValue *o = index2addr(L, idx);
    if (tonumber(o, &n)) {
        lua_Integer res;
        lua_Number num = nvalue(o);
        lua_number2integer(res, num);
        if (isnum) *isnum = 1;
        return res;
    } else {
        if (isnum) *isnum = 0;
        return 0;
    }
}


LUA_API lua_Unsigned lua_tounsignedx(lua_State *L, int idx, int *isnum) {
    TValue n;
    const TValue *o = index2addr(L, idx);
    if (tonumber(o, &n)) {
        lua_Unsigned res;
        lua_Number num = nvalue(o);
        lua_number2unsigned(res, num);
        if (isnum) *isnum = 1;
        return res;
    } else {
        if (isnum) *isnum = 0;
        return 0;
    }
}


LUA_API int lua_toboolean(lua_State *L, int idx) {
    const TValue *o = index2addr(L, idx);
    return !l_isfalse(o);
}


LUA_API const char *lua_tolstring(lua_State *L, int idx, size_t *len) {
    StkId o = index2addr(L, idx);
    if (!ttisstring(o)) {
        lua_lock(L);  /* `luaV_tostring' may create a new string */
        if (!luaV_tostring(L, o)) {  /* conversion failed? */
            if (len != NULL) *len = 0;
            lua_unlock(L);
            return NULL;
        }
        luaC_checkGC(L);
        o = index2addr(L, idx);  /* previous call may reallocate the stack */
        lua_unlock(L);
    }
    if (len != NULL) *len = tsvalue(o)->len;
    return svalue(o);
}


LUA_API size_t lua_rawlen(lua_State *L, int idx) {
    StkId o = index2addr(L, idx);
    switch (ttypenv(o)) {
        case LUA_TSTRING:
            return tsvalue(o)->len;
        case LUA_TUSERDATA:
            return uvalue(o)->len;
        case LUA_TTABLE:
            return luaH_getn(hvalue(o));
        default:
            return 0;
    }
}


LUA_API lua_CFunction lua_tocfunction(lua_State *L, int idx) {
    StkId o = index2addr(L, idx);
    if (ttislcf(o)) return fvalue(o);
    else if (ttisCclosure(o))
        return clCvalue(o)->f;
    else return NULL;  /* not a C function */
}


LUA_API void *lua_touserdata(lua_State *L, int idx) {
    StkId o = index2addr(L, idx);
    switch (ttypenv(o)) {
        case LUA_TUSERDATA:
            return (rawuvalue(o) + 1);
        case LUA_TLIGHTUSERDATA:
            return pvalue(o);
        default:
            return NULL;
    }
}


LUA_API lua_State *lua_tothread(lua_State *L, int idx) {
    StkId o = index2addr(L, idx);
    return (!ttisthread(o)) ? NULL : thvalue(o);
}


LUA_API const void *lua_topointer(lua_State *L, int idx) {
    StkId o = index2addr(L, idx);
    switch (ttype(o)) {
        case LUA_TTABLE:
            return hvalue(o);
        case LUA_TLCL:
            return clLvalue(o);
        case LUA_TCCL:
            return clCvalue(o);
        case LUA_TLCF:
            return cast(void *, cast(size_t, fvalue(o)));
        case LUA_TTHREAD:
            return thvalue(o);
        case LUA_TUSERDATA:
        case LUA_TLIGHTUSERDATA:
            return lua_touserdata(L, idx);
        default:
            return NULL;
    }
}



/*
** push functions (C -> stack)
*/


LUA_API void lua_pushnil(lua_State *L) {
    lua_lock(L);
    setnilvalue(L->top);
    api_incr_top(L);
    lua_unlock(L);
}


LUA_API void lua_pushnumber(lua_State *L, lua_Number n) {
    lua_lock(L);
    setnvalue(L->top, n);
    luai_checknum(L, L->top,
                  luaG_runerror(L, "C API - attempt to push a signaling NaN"));
    api_incr_top(L);
    lua_unlock(L);
}


LUA_API void lua_pushinteger(lua_State *L, lua_Integer n) {
    lua_lock(L);
    setnvalue(L->top, cast_num(n));
    api_incr_top(L);
    lua_unlock(L);
}


LUA_API void lua_pushunsigned(lua_State *L, lua_Unsigned u) {
    lua_Number n;
    lua_lock(L);
    n = lua_unsigned2number(u);
    setnvalue(L->top, n);
    api_incr_top(L);
    lua_unlock(L);
}


LUA_API const char *lua_pushlstring(lua_State *L, const char *s, size_t len) {
    TString *ts;
    lua_lock(L);
    luaC_checkGC(L);
    ts = luaS_newlstr(L, s, len);
    setsvalue2s(L, L->top, ts);
    api_incr_top(L);
    lua_unlock(L);
    return getstr(ts);
}


LUA_API const char *lua_pushstring(lua_State *L, const char *s) {
    if (s == NULL) {
        lua_pushnil(L);
        return NULL;
    } else {
        TString *ts;
        lua_lock(L);
        luaC_checkGC(L);
        ts = luaS_new(L, s);
        setsvalue2s(L, L->top, ts);
        api_incr_top(L);
        lua_unlock(L);
        return getstr(ts);
    }
}


LUA_API const char *lua_pushvfstring(lua_State *L, const char *fmt,
                                     va_list argp) {
    const char *ret;
    lua_lock(L);
    luaC_checkGC(L);
    ret = luaO_pushvfstring(L, fmt, argp);
    lua_unlock(L);
    return ret;
}


LUA_API const char *lua_pushfstring(lua_State *L, const char *fmt, ...) {
    const char *ret;
    va_list argp;
    lua_lock(L);
    luaC_checkGC(L);
    va_start(argp, fmt);
    ret = luaO_pushvfstring(L, fmt, argp);
    va_end(argp);
    lua_unlock(L);
    return ret;
}


LUA_API void lua_pushcclosure(lua_State *L, lua_CFunction fn, int n) {
    lua_lock(L);
    if (n == 0) {
        setfvalue(L->top, fn);
    } else {
        Closure *cl;
        api_checknelems(L, n);
        api_check(L, n <= MAXUPVAL, "upvalue index too large");
        luaC_checkGC(L);
        cl = luaF_newCclosure(L, n);
        cl->c.f = fn;
        L->top -= n;
        while (n--)
            setobj2n(L, &cl->c.upvalue[n], L->top + n);
        setclCvalue(L, L->top, cl);
    }
    api_incr_top(L);
    lua_unlock(L);
}


LUA_API void lua_pushboolean(lua_State *L, int b) {
    lua_lock(L);
    setbvalue(L->top, (b != 0));  /* ensure that true is 1 */
    api_incr_top(L);
    lua_unlock(L);
}


LUA_API void lua_pushlightuserdata(lua_State *L, void *p) {
    lua_lock(L);
    setpvalue(L->top, p);
    api_incr_top(L);
    lua_unlock(L);
}


LUA_API int lua_pushthread(lua_State *L) {
    lua_lock(L);
    setthvalue(L, L->top, L);
    api_incr_top(L);
    lua_unlock(L);
    return (G(L)->mainthread == L);
}



/*
** get functions (Lua -> stack)
*/


LUA_API void lua_getglobal(lua_State *L, const char *var) {
    Table *reg = hvalue(&G(L)->l_registry);
    const TValue *gt;  /* global table */
    lua_lock(L);
    gt = luaH_getint(reg, LUA_RIDX_GLOBALS);
    setsvalue2s(L, L->top++, luaS_new(L, var));
    luaV_gettable(L, gt, L->top - 1, L->top - 1);
    lua_unlock(L);
}


LUA_API void lua_gettable(lua_State *L, int idx) {
    StkId t;
    lua_lock(L);
    t = index2addr(L, idx);
    luaV_gettable(L, t, L->top - 1, L->top - 1);
    lua_unlock(L);
}


LUA_API void lua_getfield(lua_State *L, int idx, const char *k) {
    StkId t;
    lua_lock(L);
    t = index2addr(L, idx);
    setsvalue2s(L, L->top, luaS_new(L, k));
    api_incr_top(L);
    luaV_gettable(L, t, L->top - 1, L->top - 1);
    lua_unlock(L);
}


LUA_API void lua_rawget(lua_State *L, int idx) {
    StkId t;
    lua_lock(L);
    t = index2addr(L, idx);
    api_check(L, ttistable(t), "table expected");
    setobj2s(L, L->top - 1, luaH_get(hvalue(t), L->top - 1));
    lua_unlock(L);
}


LUA_API void lua_rawgeti(lua_State *L, int idx, int n) {
    StkId t;
    lua_lock(L);
    t = index2addr(L, idx);
    api_check(L, ttistable(t), "table expected");
    setobj2s(L, L->top, luaH_getint(hvalue(t), n));
    api_incr_top(L);
    lua_unlock(L);
}


LUA_API void lua_rawgetp(lua_State *L, int idx, const void *p) {
    StkId t;
    TValue k;
    lua_lock(L);
    t = index2addr(L, idx);
    api_check(L, ttistable(t), "table expected");
    setpvalue(&k, cast(void *, p));
    setobj2s(L, L->top, luaH_get(hvalue(t), &k));
    api_incr_top(L);
    lua_unlock(L);
}


LUA_API void lua_createtable(lua_State *L, int narray, int nrec) {
    Table *t;
    lua_lock(L);
    luaC_checkGC(L);
    t = luaH_new(L);
    sethvalue(L, L->top, t);
    api_incr_top(L);
    if (narray > 0 || nrec > 0)
        luaH_resize(L, t, narray, nrec);
    lua_unlock(L);
}


LUA_API int lua_getmetatable(lua_State *L, int objindex) {
    const TValue *obj;
    Table *mt = NULL;
    int res;
    lua_lock(L);
    obj = index2addr(L, objindex);
    switch (ttypenv(obj)) {
        case LUA_TTABLE:
            mt = hvalue(obj)->metatable;
            break;
        case LUA_TUSERDATA:
            mt = uvalue(obj)->metatable;
            break;
        default:
            mt = G(L)->mt[ttypenv(obj)];
            break;
    }
    if (mt == NULL)
        res = 0;
    else {
        sethvalue(L, L->top, mt);
        api_incr_top(L);
        res = 1;
    }
    lua_unlock(L);
    return res;
}


LUA_API void lua_getuservalue(lua_State *L, int idx) {
    StkId o;
    lua_lock(L);
    o = index2addr(L, idx);
    api_check(L, ttisuserdata(o), "userdata expected");
    if (uvalue(o)->env) {
        sethvalue(L, L->top, uvalue(o)->env);
    } else
        setnilvalue(L->top);
    api_incr_top(L);
    lua_unlock(L);
}


/*
** set functions (stack -> Lua)
*/


LUA_API void lua_setglobal(lua_State *L, const char *var) {
    Table *reg = hvalue(&G(L)->l_registry);
    const TValue *gt;  /* global table */
    lua_lock(L);
    api_checknelems(L, 1);
    gt = luaH_getint(reg, LUA_RIDX_GLOBALS);
    setsvalue2s(L, L->top++, luaS_new(L, var));
    luaV_settable(L, gt, L->top - 1, L->top - 2);
    L->top -= 2;  /* pop value and key */
    lua_unlock(L);
}


LUA_API void lua_settable(lua_State *L, int idx) {
    StkId t;
    lua_lock(L);
    api_checknelems(L, 2);
    t = index2addr(L, idx);
    luaV_settable(L, t, L->top - 2, L->top - 1);
    L->top -= 2;  /* pop index and value */
    lua_unlock(L);
}


LUA_API void lua_setfield(lua_State *L, int idx, const char *k) {
    StkId t;
    lua_lock(L);
    api_checknelems(L, 1);
    t = index2addr(L, idx);
    setsvalue2s(L, L->top++, luaS_new(L, k));
    luaV_settable(L, t, L->top - 1, L->top - 2);
    L->top -= 2;  /* pop value and key */
    lua_unlock(L);
}


LUA_API void lua_rawset(lua_State *L, int idx) {
    StkId t;
    lua_lock(L);
    api_checknelems(L, 2);
    t = index2addr(L, idx);
    api_check(L, ttistable(t), "table expected");
    setobj2t(L, luaH_set(L, hvalue(t), L->top - 2), L->top - 1);
    invalidateTMcache(hvalue(t));
    luaC_barrierback(L, gcvalue(t), L->top - 1);
    L->top -= 2;
    lua_unlock(L);
}


LUA_API void lua_rawseti(lua_State *L, int idx, int n) {
    StkId t;
    lua_lock(L);
    api_checknelems(L, 1);
    t = index2addr(L, idx);
    api_check(L, ttistable(t), "table expected");
    luaH_setint(L, hvalue(t), n, L->top - 1);
    luaC_barrierback(L, gcvalue(t), L->top - 1);
    L->top--;
    lua_unlock(L);
}


LUA_API void lua_rawsetp(lua_State *L, int idx, const void *p) {
    StkId t;
    TValue k;
    lua_lock(L);
    api_checknelems(L, 1);
    t = index2addr(L, idx);
    api_check(L, ttistable(t), "table expected");
    setpvalue(&k, cast(void *, p));
    setobj2t(L, luaH_set(L, hvalue(t), &k), L->top - 1);
    luaC_barrierback(L, gcvalue(t), L->top - 1);
    L->top--;
    lua_unlock(L);
}


LUA_API int lua_setmetatable(lua_State *L, int objindex) {
    TValue *obj;
    Table *mt;
    lua_lock(L);
    api_checknelems(L, 1);
    obj = index2addr(L, objindex);
    if (ttisnil(L->top - 1))
        mt = NULL;
    else {
        api_check(L, ttistable(L->top - 1), "table expected");
        mt = hvalue(L->top - 1);
    }
    switch (ttypenv(obj)) {
        case LUA_TTABLE: {
            hvalue(obj)->metatable = mt;
            if (mt) {
                luaC_objbarrierback(L, gcvalue(obj), mt);
                luaC_checkfinalizer(L, gcvalue(obj), mt);
            }
            break;
        }
        case LUA_TUSERDATA: {
            uvalue(obj)->metatable = mt;
            if (mt) {
                luaC_objbarrier(L, rawuvalue(obj), mt);
                luaC_checkfinalizer(L, gcvalue(obj), mt);
            }
            break;
        }
        default: {
            G(L)->mt[ttypenv(obj)] = mt;
            break;
        }
    }
    L->top--;
    lua_unlock(L);
    return 1;
}


LUA_API void lua_setuservalue(lua_State *L, int idx) {
    StkId o;
    lua_lock(L);
    api_checknelems(L, 1);
    o = index2addr(L, idx);
    api_check(L, ttisuserdata(o), "userdata expected");
    if (ttisnil(L->top - 1))
        uvalue(o)->env = NULL;
    else {
        api_check(L, ttistable(L->top - 1), "table expected");
        uvalue(o)->env = hvalue(L->top - 1);
        luaC_objbarrier(L, gcvalue(o), hvalue(L->top - 1));
    }
    L->top--;
    lua_unlock(L);
}


/*
** `load' and `call' functions (run Lua code)
*/


#define checkresults(L,na,nr) \
    api_check(L, (nr) == LUA_MULTRET || (L->ci->top - L->top >= (nr) - (na)), \
              "results from function overflow current stack size")


LUA_API int lua_getctx(lua_State *L, int *ctx) {
    if (L->ci->callstatus & CIST_YIELDED) {
        if (ctx) *ctx = L->ci->u.c.ctx;
        return L->ci->u.c.status;
    } else return LUA_OK;
}


LUA_API void lua_callk(lua_State *L, int nargs, int nresults, int ctx,
                       lua_CFunction k) {
    StkId func;
    lua_lock(L);
    api_check(L, k == NULL || !isLua(L->ci),
              "cannot use continuations inside hooks");
    api_checknelems(L, nargs + 1);
    api_check(L, L->status == LUA_OK, "cannot do calls on non-normal thread");
    checkresults(L, nargs, nresults);
    func = L->top - (nargs + 1);
    if (k != NULL && L->nny == 0) {  /* need to prepare continuation? */
        L->ci->u.c.k = k;  /* save continuation */
        L->ci->u.c.ctx = ctx;  /* save context */
        luaD_call(L, func, nresults, 1);  /* do the call */
    } else /* no continuation or no yieldable */
        luaD_call(L, func, nresults, 0);  /* just do the call */
    adjustresults(L, nresults);
    lua_unlock(L);
}



/*
** Execute a protected call.
*/
struct CallS {  /* data to `f_call' */
    StkId func;
    int nresults;
};


static void f_call(lua_State *L, void *ud) {
    struct CallS *c = cast(struct CallS *, ud);
    luaD_call(L, c->func, c->nresults, 0);
}



LUA_API int lua_pcallk(lua_State *L, int nargs, int nresults, int errfunc,
                       int ctx, lua_CFunction k) {
    struct CallS c;
    int status;
    ptrdiff_t func;
    lua_lock(L);
    api_check(L, k == NULL || !isLua(L->ci),
              "cannot use continuations inside hooks");
    api_checknelems(L, nargs + 1);
    api_check(L, L->status == LUA_OK, "cannot do calls on non-normal thread");
    checkresults(L, nargs, nresults);
    if (errfunc == 0)
        func = 0;
    else {
        StkId o = index2addr(L, errfunc);
        api_checkstackindex(L, errfunc, o);
        func = savestack(L, o);
    }
    c.func = L->top - (nargs + 1); /* function to be called */
    if (k == NULL || L->nny > 0) {  /* no continuation or no yieldable? */
        c.nresults = nresults;  /* do a 'conventional' protected call */
        status = luaD_pcall(L, f_call, &c, savestack(L, c.func), func);
    } else { /* prepare continuation (call is already protected by 'resume') */
        CallInfo *ci = L->ci;
        ci->u.c.k = k;  /* save continuation */
        ci->u.c.ctx = ctx;  /* save context */
        /* save information for error recovery */
        ci->extra = savestack(L, c.func);
        ci->u.c.old_allowhook = L->allowhook;
        ci->u.c.old_errfunc = L->errfunc;
        L->errfunc = func;
        /* mark that function may do error recovery */
        ci->callstatus |= CIST_YPCALL;
        luaD_call(L, c.func, nresults, 1);  /* do the call */
        ci->callstatus &= ~CIST_YPCALL;
        L->errfunc = ci->u.c.old_errfunc;
        status = LUA_OK;  /* if it is here, there were no errors */
    }
    adjustresults(L, nresults);
    lua_unlock(L);
    return status;
}


LUA_API int lua_load(lua_State *L, lua_Reader reader, void *data,
                     const char *chunkname, const char *mode) {
    ZIO z;
    int status;
    lua_lock(L);
    if (!chunkname) chunkname = "?";
    luaZ_init(L, &z, reader, data);
    status = luaD_protectedparser(L, &z, chunkname, mode);
    if (status == LUA_OK) {  /* no errors? */
        LClosure *f = clLvalue(L->top - 1);  /* get newly created function */
        if (f->nupvalues == 1) {  /* does it have one upvalue? */
            /* get global table from registry */
            Table *reg = hvalue(&G(L)->l_registry);
            const TValue *gt = luaH_getint(reg, LUA_RIDX_GLOBALS);
            /* set global table as 1st upvalue of 'f' (may be LUA_ENV) */
            setobj(L, f->upvals[0]->v, gt);
            luaC_barrier(L, f->upvals[0], gt);
        }
    }
    lua_unlock(L);
    return status;
}


LUA_API int lua_dump(lua_State *L, lua_Writer writer, void *data) {
    int status;
    TValue *o;
    lua_lock(L);
    api_checknelems(L, 1);
    o = L->top - 1;
    if (isLfunction(o))
        status = luaU_dump(L, getproto(o), writer, data, 0);
    else
        status = 1;
    lua_unlock(L);
    return status;
}


LUA_API int lua_status(lua_State *L) {
    return L->status;
}


/*
** Garbage-collection function
*/

LUA_API int lua_gc(lua_State *L, int what, int data) {
    int res = 0;
    global_State *g;
    lua_lock(L);
    g = G(L);
    switch (what) {
        case LUA_GCSTOP: {
            g->gcrunning = 0;
            break;
        }
        case LUA_GCRESTART: {
            luaE_setdebt(g, 0);
            g->gcrunning = 1;
            break;
        }
        case LUA_GCCOLLECT: {
            luaC_fullgc(L, 0);
            break;
        }
        case LUA_GCCOUNT: {
            /* GC values are expressed in Kbytes: #bytes/2^10 */
            res = cast_int(gettotalbytes(g) >> 10);
            break;
        }
        case LUA_GCCOUNTB: {
            res = cast_int(gettotalbytes(g) & 0x3ff);
            break;
        }
        case LUA_GCSTEP: {
            if (g->gckind == KGC_GEN) {  /* generational mode? */
                res = (g->GCestimate == 0);  /* true if it will do major collection */
                luaC_forcestep(L);  /* do a single step */
            } else {
                lu_mem debt = cast(lu_mem, data) * 1024 - GCSTEPSIZE;
                if (g->gcrunning)
                    debt += g->GCdebt;  /* include current debt */
                luaE_setdebt(g, debt);
                luaC_forcestep(L);
                if (g->gcstate == GCSpause)  /* end of cycle? */
                    res = 1;  /* signal it */
            }
            break;
        }
        case LUA_GCSETPAUSE: {
            res = g->gcpause;
            g->gcpause = data;
            break;
        }
        case LUA_GCSETMAJORINC: {
            res = g->gcmajorinc;
            g->gcmajorinc = data;
            break;
        }
        case LUA_GCSETSTEPMUL: {
            res = g->gcstepmul;
            g->gcstepmul = data;
            break;
        }
        case LUA_GCISRUNNING: {
            res = g->gcrunning;
            break;
        }
        case LUA_GCGEN: {  /* change collector to generational mode */
            luaC_changemode(L, KGC_GEN);
            break;
        }
        case LUA_GCINC: {  /* change collector to incremental mode */
            luaC_changemode(L, KGC_NORMAL);
            break;
        }
        default:
            res = -1;  /* invalid option */
    }
    lua_unlock(L);
    return res;
}



/*
** miscellaneous functions
*/


LUA_API int lua_error(lua_State *L) {
    lua_lock(L);
    api_checknelems(L, 1);
    luaG_errormsg(L);
    /* code unreachable; will unlock when control actually leaves the kernel */
    return 0;  /* to avoid warnings */
}


LUA_API int lua_next(lua_State *L, int idx) {
    StkId t;
    int more;
    lua_lock(L);
    t = index2addr(L, idx);
    api_check(L, ttistable(t), "table expected");
    more = luaH_next(L, hvalue(t), L->top - 1);
    if (more) {
        api_incr_top(L);
    } else /* no more elements */
        L->top -= 1;  /* remove key */
    lua_unlock(L);
    return more;
}


LUA_API void lua_concat(lua_State *L, int n) {
    lua_lock(L);
    api_checknelems(L, n);
    if (n >= 2) {
        luaC_checkGC(L);
        luaV_concat(L, n);
    } else if (n == 0) { /* push empty string */
        setsvalue2s(L, L->top, luaS_newlstr(L, "", 0));
        api_incr_top(L);
    }
    /* else n == 1; nothing to do */
    lua_unlock(L);
}


LUA_API void lua_len(lua_State *L, int idx) {
    StkId t;
    lua_lock(L);
    t = index2addr(L, idx);
    luaV_objlen(L, L->top, t);
    api_incr_top(L);
    lua_unlock(L);
}


LUA_API lua_Alloc lua_getallocf(lua_State *L, void **ud) {
    lua_Alloc f;
    lua_lock(L);
    if (ud) *ud = G(L)->ud;
    f = G(L)->frealloc;
    lua_unlock(L);
    return f;
}


LUA_API void lua_setallocf(lua_State *L, lua_Alloc f, void *ud) {
    lua_lock(L);
    G(L)->ud = ud;
    G(L)->frealloc = f;
    lua_unlock(L);
}


LUA_API void *lua_newuserdata(lua_State *L, size_t size) {
    Udata *u;
    lua_lock(L);
    luaC_checkGC(L);
    u = luaS_newudata(L, size, NULL);
    setuvalue(L, L->top, u);
    api_incr_top(L);
    lua_unlock(L);
    return u + 1;
}



static const char *aux_upvalue(StkId fi, int n, TValue **val,
                               GCObject **owner) {
    switch (ttype(fi)) {
        case LUA_TCCL: {  /* C closure */
            CClosure *f = clCvalue(fi);
            if (!(1 <= n && n <= f->nupvalues)) return NULL;
            *val = &f->upvalue[n - 1];
            if (owner) *owner = obj2gco(f);
            return "";
        }
        case LUA_TLCL: {  /* Lua closure */
            LClosure *f = clLvalue(fi);
            TString *name;
            Proto *p = f->p;
            if (!(1 <= n && n <= p->sizeupvalues)) return NULL;
            *val = f->upvals[n - 1]->v;
            if (owner) *owner = obj2gco(f->upvals[n - 1]);
            name = p->upvalues[n - 1].name;
            return (name == NULL) ? "" : getstr(name);
        }
        default:
            return NULL;  /* not a closure */
    }
}


LUA_API const char *lua_getupvalue(lua_State *L, int funcindex, int n) {
    const char *name;
    TValue *val = NULL;  /* to avoid warnings */
    lua_lock(L);
    name = aux_upvalue(index2addr(L, funcindex), n, &val, NULL);
    if (name) {
        setobj2s(L, L->top, val);
        api_incr_top(L);
    }
    lua_unlock(L);
    return name;
}


LUA_API const char *lua_setupvalue(lua_State *L, int funcindex, int n) {
    const char *name;
    TValue *val = NULL;  /* to avoid warnings */
    GCObject *owner = NULL;  /* to avoid warnings */
    StkId fi;
    lua_lock(L);
    fi = index2addr(L, funcindex);
    api_checknelems(L, 1);
    name = aux_upvalue(fi, n, &val, &owner);
    if (name) {
        L->top--;
        setobj(L, val, L->top);
        luaC_barrier(L, owner, L->top);
    }
    lua_unlock(L);
    return name;
}


static UpVal **getupvalref(lua_State *L, int fidx, int n, LClosure **pf) {
    LClosure *f;
    StkId fi = index2addr(L, fidx);
    api_check(L, ttisLclosure(fi), "Lua function expected");
    f = clLvalue(fi);
    api_check(L, (1 <= n && n <= f->p->sizeupvalues), "invalid upvalue index");
    if (pf) *pf = f;
    return &f->upvals[n - 1];  /* get its upvalue pointer */
}


LUA_API void *lua_upvalueid(lua_State *L, int fidx, int n) {
    StkId fi = index2addr(L, fidx);
    switch (ttype(fi)) {
        case LUA_TLCL: {  /* lua closure */
            return *getupvalref(L, fidx, n, NULL);
        }
        case LUA_TCCL: {  /* C closure */
            CClosure *f = clCvalue(fi);
            api_check(L, 1 <= n && n <= f->nupvalues, "invalid upvalue index");
            return &f->upvalue[n - 1];
        }
        default: {
            api_check(L, 0, "closure expected");
            return NULL;
        }
    }
}


LUA_API void lua_upvaluejoin(lua_State *L, int fidx1, int n1,
                             int fidx2, int n2) {
    LClosure *f1;
    UpVal **up1 = getupvalref(L, fidx1, n1, &f1);
    UpVal **up2 = getupvalref(L, fidx2, n2, NULL);
    *up1 = *up2;
    luaC_objbarrier(L, f1, *up2);
}