src/ltm.c

   1 /*
   2 ** $Id: ltm.c,v 1.56 2000/10/31 13:10:24 roberto Exp $
   3 ** Tag methods
   4 ** See Copyright Notice in lua.h
   5 */
   6
   7
   8 #include <stdio.h>
   9 #include <string.h>
  10
  11 #include "lua.h"
  12
  13 #include "ldo.h"
  14 #include "lmem.h"
  15 #include "lobject.h"
  16 #include "lstate.h"
  17 #include "ltm.h"
  18
  19
  20 const char *const luaT_eventname[] = {  /* ORDER TM */
  21   "gettable", "settable", "index", "getglobal", "setglobal", "add", "sub",
  22   "mul", "div", "pow", "unm", "lt", "concat", "gc", "function",
  23   "le", "gt", "ge",  /* deprecated options!! */
  24   NULL
  25 };
  26
  27
  28 static int findevent (const char *name) {
  29   int i;
  30   for (i=0; luaT_eventname[i]; i++)
  31     if (strcmp(luaT_eventname[i], name) == 0)
  32       return i;
  33   return -1;  /* name not found */
  34 }
  35
  36
  37 static int luaI_checkevent (lua_State *L, const char *name, int t) {
  38   int e = findevent(name);
  39   if (e >= TM_N)
  40     luaO_verror(L, "event `%.50s' is deprecated", name);
  41   if (e == TM_GC && t == LUA_TTABLE)
  42     luaO_verror(L, "event `gc' for tables is deprecated");
  43   if (e < 0)
  44     luaO_verror(L, "`%.50s' is not a valid event name", name);
  45   return e;
  46 }
  47
  48
  49
  50 /* events in LUA_TNIL are all allowed, since this is used as a
  51 *  'placeholder' for "default" fallbacks
  52 */
  53 /* ORDER LUA_T, ORDER TM */
  54 static const char luaT_validevents[NUM_TAGS][TM_N] = {
  55   {1, 1, 0, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1},  /* LUA_TUSERDATA */
  56   {1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},  /* LUA_TNIL */
  57   {1, 1, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1},  /* LUA_TNUMBER */
  58   {1, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1},  /* LUA_TSTRING */
  59   {0, 0, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 0, 1},  /* LUA_TTABLE */
  60   {1, 1, 0, 0, 1, 1, 1, 1, 1, 1, 1, 1, 1, 0, 0}   /* LUA_TFUNCTION */
  61 };
  62
  63 int luaT_validevent (int t, int e) {  /* ORDER LUA_T */
  64   return (t >= NUM_TAGS) ?  1 : luaT_validevents[t][e];
  65 }
  66
  67
  68 static void init_entry (lua_State *L, int tag) {
  69   int i;
  70   for (i=0; i<TM_N; i++)
  71     luaT_gettm(L, tag, i) = NULL;
  72   L->TMtable[tag].collected = NULL;
  73 }
  74
  75
  76 void luaT_init (lua_State *L) {
  77   int t;
  78   luaM_growvector(L, L->TMtable, 0, NUM_TAGS, struct TM, "", MAX_INT);
  79   L->nblocks += NUM_TAGS*sizeof(struct TM);
  80   L->last_tag = NUM_TAGS-1;
  81   for (t=0; t<=L->last_tag; t++)
  82     init_entry(L, t);
  83 }
  84
  85
  86 LUA_API int lua_newtag (lua_State *L) {
  87   luaM_growvector(L, L->TMtable, L->last_tag, 1, struct TM,
  88                   "tag table overflow", MAX_INT);
  89   L->nblocks += sizeof(struct TM);
  90   L->last_tag++;
  91   init_entry(L, L->last_tag);
  92   return L->last_tag;
  93 }
  94
  95
  96 static void checktag (lua_State *L, int tag) {
  97   if (!(0 <= tag && tag <= L->last_tag))
  98     luaO_verror(L, "%d is not a valid tag", tag);
  99 }
 100
 101 void luaT_realtag (lua_State *L, int tag) {
 102   if (!validtag(tag))
 103     luaO_verror(L, "tag %d was not created by `newtag'", tag);
 104 }
 105
 106
 107 LUA_API int lua_copytagmethods (lua_State *L, int tagto, int tagfrom) {
 108   int e;
 109   checktag(L, tagto);
 110   checktag(L, tagfrom);
 111   for (e=0; e<TM_N; e++) {
 112     if (luaT_validevent(tagto, e))
 113       luaT_gettm(L, tagto, e) = luaT_gettm(L, tagfrom, e);
 114   }
 115   return tagto;
 116 }
 117
 118
 119 int luaT_tag (const TObject *o) {
 120   int t = ttype(o);
 121   switch (t) {
 122     case LUA_TUSERDATA: return tsvalue(o)->u.d.tag;
 123     case LUA_TTABLE:    return hvalue(o)->htag;
 124     default:            return t;
 125   }
 126 }
 127
 128
 129 LUA_API void lua_gettagmethod (lua_State *L, int t, const char *event) {
 130   int e;
 131   e = luaI_checkevent(L, event, t);
 132   checktag(L, t);
 133   if (luaT_validevent(t, e) && luaT_gettm(L, t, e)) {
 134     clvalue(L->top) = luaT_gettm(L, t, e);
 135     ttype(L->top) = LUA_TFUNCTION;
 136   }
 137   else
 138     ttype(L->top) = LUA_TNIL;
 139   incr_top;
 140 }
 141
 142
 143 LUA_API void lua_settagmethod (lua_State *L, int t, const char *event) {
 144   int e = luaI_checkevent(L, event, t);
 145   checktag(L, t);
 146   if (!luaT_validevent(t, e))
 147     luaO_verror(L, "cannot change `%.20s' tag method for type `%.20s'%.20s",
 148                 luaT_eventname[e], luaO_typenames[t],
 149                 (t == LUA_TTABLE || t == LUA_TUSERDATA) ?
 150                    " with default tag" : "");
 151   switch (ttype(L->top - 1)) {
 152     case LUA_TNIL:
 153       luaT_gettm(L, t, e) = NULL;
 154       break;
 155     case LUA_TFUNCTION:
 156       luaT_gettm(L, t, e) = clvalue(L->top - 1);
 157       break;
 158     default:
 159       lua_error(L, "tag method must be a function (or nil)");
 160   }
 161   L->top--;
 162 }
 163