How to quit this group? -----Original Message----- From: open-iscsi@googlegroups.com [mailto:open-is...@googlegroups.com] On Behalf Of Jack Z Sent: 2010年1月28日 15:53 To: open-iscsi Subject: Re: explanation of some pieces of code?
Hi Ulrich, Thanks for your reply. That for sure increased my understanding about the "hook"s a lot. I think what I really want to know is the latter one, i.e. " what the routine is supposed to do?". To reorganize the question, what is sk- >sk_write_space usually supposed to do? On Jan 28, 12:16 am, "Ulrich Windl" <ulrich.wi...@rz.uni- regensburg.de> wrote: > On 27 Jan 2010 at 9:59, Jack Z wrote: > > > Hi Ulrich, > > > Thanks for your comment. > > > So by "implement polymorphism", do you mean sk->sw_write_space is > > platform dependent or it does different jobs when called from > > different functions in the open-iscsi code? > > Hi, > > I mean: If you call a routine indirect through a function pointer, the > reason is that you want to call different routines at runtime. > Otherwise this is unnecessary and shows poor performance. > > So if calling different routines through a pointer, there must exist a > common expectation what the code being called does (i.e. the common > subset of expectations that every possible routine fulfills). > > [If you want to look it up somewhere else, try "dynamic binding", > "polymorphism" or Bertrand Meyers "Object-Oriented software > construction"] > > Therefore you should not ask which specific routine will be called > through the pointer at some moment in time, but what the routine > (whatever it is) is expected to do. > > (I know it's theoretical, but just introducing "hooks" (as function > pointers are frequently called) can be a source of errors unless the > semantics of such a hook are well defined). > > Now: Do you really want to know which specific routine is called, or do > you want to know what the routine is supposed to do? > > [...] > > Regards, > Ulrich -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To post to this group, send email to open-is...@googlegroups.com. To unsubscribe from this group, send email to open-iscsi+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/open-iscsi?hl=en. -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To post to this group, send email to open-is...@googlegroups.com. To unsubscribe from this group, send email to open-iscsi+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/open-iscsi?hl=en.
