programming_in_lua_4th/ex28.2.c at main · drcxd/programming_in_lua_4th · GitHub

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#include <stdarg.h>

void call_va(lua_State *L, 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);
  /* push function */
  // push and count arguments (Figure 28.6, “Pushing arguments for the
  // generic
  for (narg = 0; *sig; narg++) {
    /* repeat for each argument */
    /* check stack space */
    luaL_checkstack(L, 1, "too many arguments");
    switch (*sig++) {
    case 'b':
      lua_pushboolean(L, va_arg(vl, int));
    case 'd': /* double argument */
      lua_pushnumber(L, va_arg(vl, double));
      break;
    case 'i': /* int argument */
      lua_pushinteger(L, va_arg(vl, int));
      break;
    case 's': /* string argument */
      lua_pushstring(L, va_arg(vl, char *));
      break;
    case '>':       /* end of arguments */
      goto endargs; /* break the loop */
    default:
      error(L, "invalid option (%c)", *(sig - 1));
    }
  }
endargs:
  nres = strlen(sig);
  /* number of expected results */
  if (lua_pcall(L, narg, nres, 0) != 0) { /* do the call */
    error(L, "error calling '%s': %s", func, lua_tostring(L, -1));
  }
  nres = -nres;  /* stack index of first result */
  while (*sig) { /* repeat for each result */
    switch (*sig++) {
    case 'b': {
      int b = lua_toboolean(L, nres);
      *va_arg(vl, int *) = b;
      break;
    }
    case 'd': { /* double result */
      int isnum;
      double n = lua_tonumberx(L, nres, &isnum);
      if (!isnum)
        error(L, "wrong result type");
      *va_arg(vl, double *) = n;
      break;
    }
    case 'i': { /* int result */
      int isnum;
      int n = lua_tointegerx(L, nres, &isnum);
      if (!isnum)
        error(L, "wrong result type");
      *va_arg(vl, int *) = n;
      break;
    }
    case 's': { /* string result */
      const char *s = lua_tostring(L, nres);
      if (s == NULL)
        error(L, "wrong result type");
      *va_arg(vl, const char **) = s;
      break;
    }
    default:
      error(L, "invalid option (%c)", *(sig - 1));
    }
    nres++;
  } // retrieve results (Figure 28.7, “Retrieving results for the generic call
    // fun
  va_end(vl);
}