text: /*
  ** $Id: ldblib.c,v 1.104.1.3 2008/01/21 13:11:21 roberto Exp $
  ** Interface from Lua to its debug API
  ** See Copyright Notice in lua.h
  */
  
  
  #include <stdio.h>
  #include <stdlib.h>
  #include <string.h>
  
  #define ldblib_c
  #define LUA_LIB
  
  #include "lua.h"
  
  #include "lauxlib.h"
  #include "lualib.h"
  
  
  
  static int db_getregistry (lua_State *L) {
    lua_pushvalue(L, LUA_REGISTRYINDEX);
    return 1;
  }
  
  
  static int db_getmetatable (lua_State *L) {
    luaL_checkany(L, 1);
    if (!lua_getmetatable(L, 1)) {
      lua_pushnil(L);  /* no metatable */
    }
    return 1;
  }
  
  
  static int db_setmetatable (lua_State *L) {
    int t = lua_type(L, 2);
    luaL_argcheck(L, t == LUA_TNIL || t == LUA_TTABLE, 2,
                      "nil or table expected");
    lua_settop(L, 2);
    lua_pushboolean(L, lua_setmetatable(L, 1));
    return 1;
  }
  
  
  static int db_getfenv (lua_State *L) {
    lua_getfenv(L, 1);
    return 1;
  }
  
  
  static int db_setfenv (lua_State *L) {
    luaL_checktype(L, 2, LUA_TTABLE);
    lua_settop(L, 2);
    if (lua_setfenv(L, 1) == 0)
      luaL_error(L, LUA_QL("setfenv")
                    " cannot change environment of given object");
    return 1;
  }
  
  
  static void settabss (lua_State *L, const char *i, const char *v) {
    lua_pushstring(L, v);
    lua_setfield(L, -2, i);
  }
  
  
  static void settabsi (lua_State *L, const char *i, int v) {
    lua_pushinteger(L, v);
    lua_setfield(L, -2, i);
  }
  
  
  static lua_State *getthread (lua_State *L, int *arg) {
    if (lua_isthread(L, 1)) {
      *arg = 1;
      return lua_tothread(L, 1);
    }
    else {
      *arg = 0;
      return L;
    }
  }
  
  
  static void treatstackoption (lua_State *L, lua_State *L1, const char *fname) {
    if (L == L1) {
      lua_pushvalue(L, -2);
      lua_remove(L, -3);
    }
    else
      lua_xmove(L1, L, 1);
    lua_setfield(L, -2, fname);
  }
  
  
  static int db_getinfo (lua_State *L) {
    lua_Debug ar;
    int arg;
    lua_State *L1 = getthread(L, &arg);
    const char *options = luaL_optstring(L, arg+2, "flnSu");
    if (lua_isnumber(L, arg+1)) {
      if (!lua_getstack(L1, (int)lua_tointeger(L, arg+1), &ar)) {
        lua_pushnil(L);  /* level out of range */
        return 1;
      }
    }
    else if (lua_isfunction(L, arg+1)) {
      lua_pushfstring(L, ">%s", options);
      options = lua_tostring(L, -1);
      lua_pushvalue(L, arg+1);
      lua_xmove(L, L1, 1);
    }
    else
      return luaL_argerror(L, arg+1, "function or level expected");
    if (!lua_getinfo(L1, options, &ar))
      return luaL_argerror(L, arg+2, "invalid option");
    lua_createtable(L, 0, 2);
    if (strchr(options, 'S')) {
      settabss(L, "source", ar.source);
      settabss(L, "short_src", ar.short_src);
      settabsi(L, "linedefined", ar.linedefined);
      settabsi(L, "lastlinedefined", ar.lastlinedefined);
      settabss(L, "what", ar.what);
    }
    if (strchr(options, 'l'))
      settabsi(L, "currentline", ar.currentline);
    if (strchr(options, 'u'))
      settabsi(L, "nups", ar.nups);
    if (strchr(options, 'n')) {
      settabss(L, "name", ar.name);
      settabss(L, "namewhat", ar.namewhat);
    }
    if (strchr(options, 'L'))
      treatstackoption(L, L1, "activelines");
    if (strchr(options, 'f'))
      treatstackoption(L, L1, "func");
    return 1;  /* return table */
  }
      
  
  static int db_getlocal (lua_State *L) {
    int arg;
    lua_State *L1 = getthread(L, &arg);
    lua_Debug ar;
    const char *name;
    if (!lua_getstack(L1, luaL_checkint(L, arg+1), &ar))  /* out of range? */
      return luaL_argerror(L, arg+1, "level out of range");
    name = lua_getlocal(L1, &ar, luaL_checkint(L, arg+2));
    if (name) {
      lua_xmove(L1, L, 1);
      lua_pushstring(L, name);
      lua_pushvalue(L, -2);
      return 2;
    }
    else {
      lua_pushnil(L);
      return 1;
    }
  }
  
  
  static int db_setlocal (lua_State *L) {
    int arg;
    lua_State *L1 = getthread(L, &arg);
    lua_Debug ar;
    if (!lua_getstack(L1, luaL_checkint(L, arg+1), &ar))  /* out of range? */
      return luaL_argerror(L, arg+1, "level out of range");
    luaL_checkany(L, arg+3);
    lua_settop(L, arg+3);
    lua_xmove(L, L1, 1);
    lua_pushstring(L, lua_setlocal(L1, &ar, luaL_checkint(L, arg+2)));
    return 1;
  }
  
  
  static int auxupvalue (lua_State *L, int get) {
    const char *name;
    int n = luaL_checkint(L, 2);
    luaL_checktype(L, 1, LUA_TFUNCTION);
    if (lua_iscfunction(L, 1)) return 0;  /* cannot touch C upvalues from Lua */
    name = get ? lua_getupvalue(L, 1, n) : lua_setupvalue(L, 1, n);
    if (name == NULL) return 0;
    lua_pushstring(L, name);
    lua_insert(L, -(get+1));
    return get + 1;
  }
  
  
  static int db_getupvalue (lua_State *L) {
    return auxupvalue(L, 1);
  }
  
  
  static int db_setupvalue (lua_State *L) {
    luaL_checkany(L, 3);
    return auxupvalue(L, 0);
  }
  
  
  
  static const char KEY_HOOK = 'h';
  
  
  static void hookf (lua_State *L, lua_Debug *ar) {
    static const char *const hooknames[] =
      {"call", "return", "line", "count", "tail return"};
    lua_pushlightuserdata(L, (void *)&KEY_HOOK);
    lua_rawget(L, LUA_REGISTRYINDEX);
    lua_pushlightuserdata(L, L);
    lua_rawget(L, -2);
    if (lua_isfunction(L, -1)) {
      lua_pushstring(L, hooknames[(int)ar->event]);
      if (ar->currentline >= 0)
        lua_pushinteger(L, ar->currentline);
      else lua_pushnil(L);
      lua_assert(lua_getinfo(L, "lS", ar));
      lua_call(L, 2, 0);
    }
  }
  
  
  static int makemask (const char *smask, int count) {
    int mask = 0;
    if (strchr(smask, 'c')) mask |= LUA_MASKCALL;
    if (strchr(smask, 'r')) mask |= LUA_MASKRET;
    if (strchr(smask, 'l')) mask |= LUA_MASKLINE;
    if (count > 0) mask |= LUA_MASKCOUNT;
    return mask;
  }
  
  
  static char *unmakemask (int mask, char *smask) {
    int i = 0;
    if (mask & LUA_MASKCALL) smask[i++] = 'c';
    if (mask & LUA_MASKRET) smask[i++] = 'r';
    if (mask & LUA_MASKLINE) smask[i++] = 'l';
    smask[i] = '\0';
    return smask;
  }
  
  
  static void gethooktable (lua_State *L) {
    lua_pushlightuserdata(L, (void *)&KEY_HOOK);
    lua_rawget(L, LUA_REGISTRYINDEX);
    if (!lua_istable(L, -1)) {
      lua_pop(L, 1);
      lua_createtable(L, 0, 1);
      lua_pushlightuserdata(L, (void *)&KEY_HOOK);
      lua_pushvalue(L, -2);
      lua_rawset(L, LUA_REGISTRYINDEX);
    }
  }
  
  
  static int db_sethook (lua_State *L) {
    int arg, mask, count;
    lua_Hook func;
    lua_State *L1 = getthread(L, &arg);
    if (lua_isnoneornil(L, arg+1)) {
      lua_settop(L, arg+1);
      func = NULL; mask = 0; count = 0;  /* turn off hooks */
    }
    else {
      const char *smask = luaL_checkstring(L, arg+2);
      luaL_checktype(L, arg+1, LUA_TFUNCTION);
      count = luaL_optint(L, arg+3, 0);
      func = hookf; mask = makemask(smask, count);
    }
    gethooktable(L);
    lua_pushlightuserdata(L, L1);
    lua_pushvalue(L, arg+1);
    lua_rawset(L, -3);  /* set new hook */
    lua_pop(L, 1);  /* remove hook table */
    lua_sethook(L1, func, mask, count);  /* set hooks */
    return 0;
  }
  
  
  static int db_gethook (lua_State *L) {
    int arg;
    lua_State *L1 = getthread(L, &arg);
    char buff[5];
    int mask = lua_gethookmask(L1);
    lua_Hook hook = lua_gethook(L1);
    if (hook != NULL && hook != hookf)  /* external hook? */
      lua_pushliteral(L, "external hook");
    else {
      gethooktable(L);
      lua_pushlightuserdata(L, L1);
      lua_rawget(L, -2);   /* get hook */
      lua_remove(L, -2);  /* remove hook table */
    }
    lua_pushstring(L, unmakemask(mask, buff));
    lua_pushinteger(L, lua_gethookcount(L1));
    return 3;
  }
  
  
  static int db_debug (lua_State *L) {
    for (;;) {
      char buffer[250];
      fputs("lua_debug> ", stderr);
      if (fgets(buffer, sizeof(buffer), stdin) == 0 ||
          strcmp(buffer, "cont\n") == 0)
        return 0;
      if (luaL_loadbuffer(L, buffer, strlen(buffer), "=(debug command)") ||
          lua_pcall(L, 0, 0, 0)) {
        fputs(lua_tostring(L, -1), stderr);
        fputs("\n", stderr);
      }
      lua_settop(L, 0);  /* remove eventual returns */
    }
  }
  
  
  #define LEVELS1	12	/* size of the first part of the stack */
  #define LEVELS2	10	/* size of the second part of the stack */
  
  static int db_errorfb (lua_State *L) {
    int level;
    int firstpart = 1;  /* still before eventual `...' */
    int arg;
    lua_State *L1 = getthread(L, &arg);
    lua_Debug ar;
    if (lua_isnumber(L, arg+2)) {
      level = (int)lua_tointeger(L, arg+2);
      lua_pop(L, 1);
    }
    else
      level = (L == L1) ? 1 : 0;  /* level 0 may be this own function */
    if (lua_gettop(L) == arg)
      lua_pushliteral(L, "");
    else if (!lua_isstring(L, arg+1)) return 1;  /* message is not a string */
    else lua_pushliteral(L, "\n");
    lua_pushliteral(L, "stack traceback:");
    while (lua_getstack(L1, level++, &ar)) {
      if (level > LEVELS1 && firstpart) {
        /* no more than `LEVELS2' more levels? */
        if (!lua_getstack(L1, level+LEVELS2, &ar))
          level--;  /* keep going */
        else {
          lua_pushliteral(L, "\n\t...");  /* too many levels */
          while (lua_getstack(L1, level+LEVELS2, &ar))  /* find last levels */
            level++;
        }
        firstpart = 0;
        continue;
      }
      lua_pushliteral(L, "\n\t");
      lua_getinfo(L1, "Snl", &ar);
      lua_pushfstring(L, "%s:", ar.short_src);
      if (ar.currentline > 0)
        lua_pushfstring(L, "%d:", ar.currentline);
      if (*ar.namewhat != '\0')  /* is there a name? */
          lua_pushfstring(L, " in function " LUA_QS, ar.name);
      else {
        if (*ar.what == 'm')  /* main? */
          lua_pushfstring(L, " in main chunk");
        else if (*ar.what == 'C' || *ar.what == 't')
          lua_pushliteral(L, " ?");  /* C function or tail call */
        else
          lua_pushfstring(L, " in function <%s:%d>",
                             ar.short_src, ar.linedefined);
      }
      lua_concat(L, lua_gettop(L) - arg);
    }
    lua_concat(L, lua_gettop(L) - arg);
    return 1;
  }
  
  
  
  static const luaL_Reg dblib[] = {
    {"debug", db_debug},
    {"getfenv", db_getfenv},
    {"gethook", db_gethook},
    {"getinfo", db_getinfo},
    {"getlocal", db_getlocal},
    {"getregistry", db_getregistry},
    {"getmetatable", db_getmetatable},
    {"getupvalue", db_getupvalue},
    {"setfenv", db_setfenv},
    {"sethook", db_sethook},
    {"setlocal", db_setlocal},
    {"setmetatable", db_setmetatable},
    {"setupvalue", db_setupvalue},
    {"traceback", db_errorfb},
    {NULL, NULL}
  };
  
  
  LUALIB_API int luaopen_debug (lua_State *L) {
    luaL_register(L, LUA_DBLIBNAME, dblib);
    return 1;
  }
  