ltm.c revision 344220 
1/*
2** $Id: ltm.c,v 2.38.1.1 2017/04/19 17:39:34 roberto Exp $
3** Tag methods
4** See Copyright Notice in lua.h
5*/
6
7#define ltm_c
8#define LUA_CORE
9
10#include "lprefix.h"
11
12
13#include <string.h>
14
15#include "lua.h"
16
17#include "ldebug.h"
18#include "ldo.h"
19#include "lobject.h"
20#include "lstate.h"
21#include "lstring.h"
22#include "ltable.h"
23#include "ltm.h"
24#include "lvm.h"
25
26
27static const char udatatypename[] = "userdata";
28
29LUAI_DDEF const char *const luaT_typenames_[LUA_TOTALTAGS] = {
30  "no value",
31  "nil", "boolean", udatatypename, "number",
32  "string", "table", "function", udatatypename, "thread",
33  "proto" /* this last case is used for tests only */
34};
35
36
37void luaT_init (lua_State *L) {
38  static const char *const luaT_eventname[] = {  /* ORDER TM */
39    "__index", "__newindex",
40    "__gc", "__mode", "__len", "__eq",
41    "__add", "__sub", "__mul", "__mod", "__pow",
42    "__div", "__idiv",
43    "__band", "__bor", "__bxor", "__shl", "__shr",
44    "__unm", "__bnot", "__lt", "__le",
45    "__concat", "__call"
46  };
47  int i;
48  for (i=0; i<TM_N; i++) {
49    G(L)->tmname[i] = luaS_new(L, luaT_eventname[i]);
50    luaC_fix(L, obj2gco(G(L)->tmname[i]));  /* never collect these names */
51  }
52}
53
54
55/*
56** function to be used with macro "fasttm": optimized for absence of
57** tag methods
58*/
59const TValue *luaT_gettm (Table *events, TMS event, TString *ename) {
60  const TValue *tm = luaH_getshortstr(events, ename);
61  lua_assert(event <= TM_EQ);
62  if (ttisnil(tm)) {  /* no tag method? */
63    events->flags |= cast_byte(1u<<event);  /* cache this fact */
64    return NULL;
65  }
66  else return tm;
67}
68
69
70const TValue *luaT_gettmbyobj (lua_State *L, const TValue *o, TMS event) {
71  Table *mt;
72  switch (ttnov(o)) {
73    case LUA_TTABLE:
74      mt = hvalue(o)->metatable;
75      break;
76    case LUA_TUSERDATA:
77      mt = uvalue(o)->metatable;
78      break;
79    default:
80      mt = G(L)->mt[ttnov(o)];
81  }
82  return (mt ? luaH_getshortstr(mt, G(L)->tmname[event]) : luaO_nilobject);
83}
84
85
86/*
87** Return the name of the type of an object. For tables and userdata
88** with metatable, use their '__name' metafield, if present.
89*/
90const char *luaT_objtypename (lua_State *L, const TValue *o) {
91  Table *mt;
92  if ((ttistable(o) && (mt = hvalue(o)->metatable) != NULL) ||
93      (ttisfulluserdata(o) && (mt = uvalue(o)->metatable) != NULL)) {
94    const TValue *name = luaH_getshortstr(mt, luaS_new(L, "__name"));
95    if (ttisstring(name))  /* is '__name' a string? */
96      return getstr(tsvalue(name));  /* use it as type name */
97  }
98  return ttypename(ttnov(o));  /* else use standard type name */
99}
100
101
102void luaT_callTM (lua_State *L, const TValue *f, const TValue *p1,
103                  const TValue *p2, TValue *p3, int hasres) {
104  ptrdiff_t result = savestack(L, p3);
105  StkId func = L->top;
106  setobj2s(L, func, f);  /* push function (assume EXTRA_STACK) */
107  setobj2s(L, func + 1, p1);  /* 1st argument */
108  setobj2s(L, func + 2, p2);  /* 2nd argument */
109  L->top += 3;
110  if (!hasres)  /* no result? 'p3' is third argument */
111    setobj2s(L, L->top++, p3);  /* 3rd argument */
112  /* metamethod may yield only when called from Lua code */
113  if (isLua(L->ci))
114    luaD_call(L, func, hasres);
115  else
116    luaD_callnoyield(L, func, hasres);
117  if (hasres) {  /* if has result, move it to its place */
118    p3 = restorestack(L, result);
119    setobjs2s(L, p3, --L->top);
120  }
121}
122
123
124int luaT_callbinTM (lua_State *L, const TValue *p1, const TValue *p2,
125                    StkId res, TMS event) {
126  const TValue *tm = luaT_gettmbyobj(L, p1, event);  /* try first operand */
127  if (ttisnil(tm))
128    tm = luaT_gettmbyobj(L, p2, event);  /* try second operand */
129  if (ttisnil(tm)) return 0;
130  luaT_callTM(L, tm, p1, p2, res, 1);
131  return 1;
132}
133
134
135void luaT_trybinTM (lua_State *L, const TValue *p1, const TValue *p2,
136                    StkId res, TMS event) {
137  if (!luaT_callbinTM(L, p1, p2, res, event)) {
138    switch (event) {
139      case TM_CONCAT:
140        luaG_concaterror(L, p1, p2);
141      /* call never returns, but to avoid warnings: *//* FALLTHROUGH */
142      case TM_BAND: case TM_BOR: case TM_BXOR:
143      case TM_SHL: case TM_SHR: case TM_BNOT: {
144        lua_Number dummy;
145        if (tonumber(p1, &dummy) && tonumber(p2, &dummy))
146          luaG_tointerror(L, p1, p2);
147        else
148          luaG_opinterror(L, p1, p2, "perform bitwise operation on");
149      }
150      /* calls never return, but to avoid warnings: *//* FALLTHROUGH */
151      default:
152        luaG_opinterror(L, p1, p2, "perform arithmetic on");
153    }
154  }
155}
156
157
158int luaT_callorderTM (lua_State *L, const TValue *p1, const TValue *p2,
159                      TMS event) {
160  if (!luaT_callbinTM(L, p1, p2, L->top, event))
161    return -1;  /* no metamethod */
162  else
163    return !l_isfalse(L->top);
164}
165
166