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[Lua] 루아에서 임의의 갯수를 리턴할 때 받아오는 방법
Web, Script/Lua | 2010/01/08 00:23
출처 : http://www.lua.org/pil/25.3.html

As a more advanced example, we will build a wrapper for calling Lua functions, using the vararg facility in C. Our wrapper function (let us call it call_va) receives the name of the function to be called, a string describing the types of the arguments and results, then the list of arguments, and finally a list of pointers to variables to store the results; it handles all the details of the API. With this function, we could write our previous example simply as

    call_va("f", "dd>d", x, y, &z);

where the string "dd>d" means "two arguments of type double, one result of type double". This descriptor can use the letters `d´ for double, `i´ for integer, and `s´ for strings; a `>´ separates arguments from the results. If the function has no results, the `>´ is optional.

   #include <stdarg.h>
    
    void call_va (const char *func, const char *sig, ...) {
      va_list vl;
      int narg, nres;  /* number of arguments and results */
    
      va_start(vl, sig);
      lua_getglobal(L, func);  /* get function */
    
      /* push arguments */
      narg = 0;
      while (*sig) {  /* push arguments */
        switch (*sig++) {
    
          case 'd':  /* double argument */
            lua_pushnumber(L, va_arg(vl, double));
            break;
    
          case 'i':  /* int argument */
            lua_pushnumber(L, va_arg(vl, int));
            break;
    
          case 's':  /* string argument */
            lua_pushstring(L, va_arg(vl, char *));
            break;
    
          case '>':
            goto endwhile;
    
          default:
            error(L, "invalid option (%c)", *(sig - 1));
        }
        narg++;
        luaL_checkstack(L, 1, "too many arguments");
      } endwhile:
    
      /* do the call */
      nres = strlen(sig);  /* number of expected results */
      if (lua_pcall(L, narg, nres, 0) != 0)  /* do the call */
        error(L, "error running function `%s': %s",
                 func, lua_tostring(L, -1));
    
      /* retrieve results */
      nres = -nres;  /* stack index of first result */
      while (*sig) {  /* get results */
        switch (*sig++) {
    
          case 'd':  /* double result */
            if (!lua_isnumber(L, nres))
              error(L, "wrong result type");
            *va_arg(vl, double *) = lua_tonumber(L, nres);
            break;
    
          case 'i':  /* int result */
            if (!lua_isnumber(L, nres))
              error(L, "wrong result type");
            *va_arg(vl, int *) = (int)lua_tonumber(L, nres);
            break;
    
          case 's':  /* string result */
            if (!lua_isstring(L, nres))
              error(L, "wrong result type");
            *va_arg(vl, const char **) = lua_tostring(L, nres);
            break;
    
          default:
            error(L, "invalid option (%c)", *(sig - 1));
        }
        nres++;
      }
      va_end(vl);
    }


2010/01/08 00:23 2010/01/08 00:23
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