/*

** $Id: ltm.c $

** Tag methods

** See Copyright Notice in lua.h

*/

#define ltm_c

#define LUA_CORE

#include "lprefix.h"

#include <string.h>

#include "lua.h"

#include "ldebug.h"

#include "ldo.h"

#include "lgc.h"

#include "lobject.h"

#include "lstate.h"

#include "lstring.h"

#include "ltable.h"

#include "ltm.h"

#include "lvm.h"

static const char udatatypename[] = "userdata";

LUAI_DDEF const char *const luaT_typenames_[LUA_TOTALTYPES] = {

  "no value",

  "nil", "boolean", udatatypename, "number",

  "string", "table", "function", udatatypename, "thread",

  "upvalue", "proto" /* these last cases are used for tests only */

};

void luaT_init (lua_State *L) {

  static const char *const luaT_eventname[] = {  /* ORDER TM */

    "__index", "__newindex",

    "__gc", "__mode", "__len", "__eq",

    "__add", "__sub", "__mul", "__mod", "__pow",

    "__div", "__idiv",

    "__band", "__bor", "__bxor", "__shl", "__shr",

    "__unm", "__bnot", "__lt", "__le",

    "__concat", "__call", "__close"

  };

  int i;

  for (i=0; i<TM_N; i++) {

    G(L)->tmname[i] = luaS_new(L, luaT_eventname[i]);

    luaC_fix(L, obj2gco(G(L)->tmname[i]));  /* never collect these names */

  }

}

/*

** function to be used with macro "fasttm": optimized for absence of

** tag methods

*/

const TValue *luaT_gettm (Table *events, TMS event, TString *ename) {

  const TValue *tm = luaH_Hgetshortstr(events, ename);

  lua_assert(event <= TM_EQ);

  if (notm(tm)) {  /* no tag method? */

    events->flags |= cast_byte(1u<<event);  /* cache this fact */

    return NULL;

  }

  else return tm;

}

const TValue *luaT_gettmbyobj (lua_State *L, const TValue *o, TMS event) {

  Table *mt;

  switch (ttype(o)) {

    case LUA_TTABLE:

      mt = hvalue(o)->metatable;

      break;

    case LUA_TUSERDATA:

      mt = uvalue(o)->metatable;

      break;

    default:

      mt = G(L)->mt[ttype(o)];

  }

  return (mt ? luaH_Hgetshortstr(mt, G(L)->tmname[event]) : &G(L)->nilvalue);

}

/*

** Return the name of the type of an object. For tables and userdata

** with metatable, use their '__name' metafield, if present.

*/

const char *luaT_objtypename (lua_State *L, const TValue *o) {

  Table *mt;

  if ((ttistable(o) && (mt = hvalue(o)->metatable) != NULL) ||

      (ttisfulluserdata(o) && (mt = uvalue(o)->metatable) != NULL)) {

    const TValue *name = luaH_Hgetshortstr(mt, luaS_new(L, "__name"));

    if (ttisstring(name))  /* is '__name' a string? */

      return getstr(tsvalue(name));  /* use it as type name */

  }

  return ttypename(ttype(o));  /* else use standard type name */

}

void luaT_callTM (lua_State *L, const TValue *f, const TValue *p1,

                  const TValue *p2, const TValue *p3) {

  StkId func = L->top.p;

  setobj2s(L, func, f);  /* push function (assume EXTRA_STACK) */

  setobj2s(L, func + 1, p1);  /* 1st argument */

  setobj2s(L, func + 2, p2);  /* 2nd argument */

  setobj2s(L, func + 3, p3);  /* 3rd argument */

  L->top.p = func + 4;

  /* metamethod may yield only when called from Lua code */

  if (isLuacode(L->ci))

    luaD_call(L, func, 0);

  else

    luaD_callnoyield(L, func, 0);

}

lu_byte luaT_callTMres (lua_State *L, const TValue *f, const TValue *p1,

                        const TValue *p2, StkId res) {

  ptrdiff_t result = savestack(L, res);

  StkId func = L->top.p;

  setobj2s(L, func, f);  /* push function (assume EXTRA_STACK) */

  setobj2s(L, func + 1, p1);  /* 1st argument */

  setobj2s(L, func + 2, p2);  /* 2nd argument */

  L->top.p += 3;

  /* metamethod may yield only when called from Lua code */

  if (isLuacode(L->ci))

    luaD_call(L, func, 1);

  else

    luaD_callnoyield(L, func, 1);

  res = restorestack(L, result);

  setobjs2s(L, res, --L->top.p);  /* move result to its place */

  return ttypetag(s2v(res));  /* return tag of the result */

}

static int callbinTM (lua_State *L, const TValue *p1, const TValue *p2,

                      StkId res, TMS event) {

  const TValue *tm = luaT_gettmbyobj(L, p1, event);  /* try first operand */

  if (notm(tm))

    tm = luaT_gettmbyobj(L, p2, event);  /* try second operand */

  if (notm(tm))

    return -1;  /* tag method not found */

  else  /* call tag method and return the tag of the result */

    return luaT_callTMres(L, tm, p1, p2, res);

}

void luaT_trybinTM (lua_State *L, const TValue *p1, const TValue *p2,

                    StkId res, TMS event) {

  if (l_unlikely(callbinTM(L, p1, p2, res, event) < 0)) {

    switch (event) {

      case TM_BAND: case TM_BOR: case TM_BXOR:

      case TM_SHL: case TM_SHR: case TM_BNOT: {

        if (ttisnumber(p1) && ttisnumber(p2))

          luaG_tointerror(L, p1, p2);

        else

          luaG_opinterror(L, p1, p2, "perform bitwise operation on");

      }

      /* calls never return, but to avoid warnings: *//* FALLTHROUGH */

      default:

        luaG_opinterror(L, p1, p2, "perform arithmetic on");

    }

  }

}

/*

** The use of 'p1' after 'callbinTM' is safe because, when a tag

** method is not found, 'callbinTM' cannot change the stack.

*/

void luaT_tryconcatTM (lua_State *L) {

  StkId p1 = L->top.p - 2;  /* first argument */

  if (l_unlikely(callbinTM(L, s2v(p1), s2v(p1 + 1), p1, TM_CONCAT) < 0))

    luaG_concaterror(L, s2v(p1), s2v(p1 + 1));

}

void luaT_trybinassocTM (lua_State *L, const TValue *p1, const TValue *p2,

                                       int flip, StkId res, TMS event) {

  if (flip)

    luaT_trybinTM(L, p2, p1, res, event);

  else

    luaT_trybinTM(L, p1, p2, res, event);

}

void luaT_trybiniTM (lua_State *L, const TValue *p1, lua_Integer i2,

                                   int flip, StkId res, TMS event) {

  TValue aux;

  setivalue(&aux, i2);

  luaT_trybinassocTM(L, p1, &aux, flip, res, event);

}

/*

** Calls an order tag method.

*/

int luaT_callorderTM (lua_State *L, const TValue *p1, const TValue *p2,

                      TMS event) {

  int tag = callbinTM(L, p1, p2, L->top.p, event);  /* try original event */

  if (tag >= 0)  /* found tag method? */

    return !tagisfalse(tag);

  luaG_ordererror(L, p1, p2);  /* no metamethod found */

  return 0;  /* to avoid warnings */

}

int luaT_callorderiTM (lua_State *L, const TValue *p1, int v2,

                       int flip, int isfloat, TMS event) {

  TValue aux; const TValue *p2;

  if (isfloat) {

    setfltvalue(&aux, cast_num(v2));

  }

  else

    setivalue(&aux, v2);

  if (flip) {  /* arguments were exchanged? */

    p2 = p1; p1 = &aux;  /* correct them */

  }

  else

    p2 = &aux;

  return luaT_callorderTM(L, p1, p2, event);

}

void luaT_adjustvarargs (lua_State *L, int nfixparams, CallInfo *ci,

                         const Proto *p) {

  int i;

  int actual = cast_int(L->top.p - ci->func.p) - 1;  /* number of arguments */

  int nextra = actual - nfixparams;  /* number of extra arguments */

  ci->u.l.nextraargs = nextra;

  luaD_checkstack(L, p->maxstacksize + 1);

  /* copy function to the top of the stack */

  setobjs2s(L, L->top.p++, ci->func.p);

  /* move fixed parameters to the top of the stack */

  for (i = 1; i <= nfixparams; i++) {

    setobjs2s(L, L->top.p++, ci->func.p + i);

    setnilvalue(s2v(ci->func.p + i));  /* erase original parameter (for GC) */

  }

  ci->func.p += actual + 1;

  ci->top.p += actual + 1;

  lua_assert(L->top.p <= ci->top.p && ci->top.p <= L->stack_last.p);

}

void luaT_getvarargs (lua_State *L, CallInfo *ci, StkId where, int wanted) {

  int i;

  int nextra = ci->u.l.nextraargs;

  if (wanted < 0) {

    wanted = nextra;  /* get all extra arguments available */

    checkstackp(L, nextra, where);  /* ensure stack space */

    L->top.p = where + nextra;  /* next instruction will need top */

  }

  for (i = 0; i < wanted && i < nextra; i++)

    setobjs2s(L, where + i, ci->func.p - nextra + i);

  for (; i < wanted; i++)   /* complete required results with nil */

    setnilvalue(s2v(where + i));

}