Re: to be effcient or not to be efficient

On Thu, 8 Jan 2004, Toby Hudon wrote:

>> >  .seek_frame = NULL; /* not implemented call */
>> If the vtable is set up by the API library (as opposed to a specific
>> codec/filter) it might be nicer to set unimplemented functions to
>> some dummy functions which just return an error instead of NULL; otherwise
>Umm... but if you have a function that just returns "not supported", won't
>you have to check for that every time after you call to see if what you

- If the pointer may be NULL, you must check for it _before_ calling a
  function and then you need another check _after_ the function to check
  the return value for possible other errors anyway.
  Therefore, dummy non-NULL pointers are more efficient (faster).

- You might not care about possible errors, and in that case no
  checks are necessary at all if non-NULL pointers are guaranteed
  (it's also safer: some buggy code might not check for NULL
  pointers but just call directly a function that is usually
  implemented anyway, with dummy pointers no harm is done,
  but with NULL function pointer there would be a segfault).