On Wed, Oct 3, 2012 at 11:19 AM, Lubos Lunak <l.lu...@suse.cz> wrote: > On Monday 01 of October 2012, Michael Stahl wrote: >> On 01/10/12 11:40, Noel Grandin wrote: >> > On 2012-10-01 10:15, Stephan Bergmann wrote: >> >> While that argument is irrelevant in a C/C++ context, immutability is >> >> also an important concept when reasoning about multi-threaded code. >> >> Therefore, the distinction between OUString and OUStringBuffer IMO >> >> does make sense after all. >> > >> > I don't see how the design helps you in a multithreaded context. >> > If you share an OUString instance between two threads, either thread >> > could assign to it, replacing it's contents, and invalidating what the >> > other thread sees. >> >> but if you share 2 copies of an OUString instance in 2 threads, they >> could access the one underlying buffer concurrently without issue, and >> when they want to point their copy at a different value, they can do >> that independently of the other -- again, OUString works in exactly the >> same way as a pointer to an immutable object here, if you copy the >> pointer you can dereference it without issue and point your copy to a >> different object; you only need a lock if you don't copy the pointer and >> share a single pointer that one thread may update (which depending on >> the situation may be necessary, say you don't just want to save memory >> but actually always want the threads to point to the same value). > > Either I don't get what immutable actually means in this context (in which > case I'd like to be enlightened), or you are talking about things that > actually have nothing to do with immutability. OUString is not the same like > a pointer to an immutable object, because this object contains a reference > count
No it does not... the underlying rtl_uString (the part that _is_ immutable) is ref-counted but OUString itself is not. iow: a given OUString may be changed to point to a rlt_ustring instance or another, but cannot mess with the one it points to Norbert _______________________________________________ LibreOffice mailing list LibreOffice@lists.freedesktop.org http://lists.freedesktop.org/mailman/listinfo/libreoffice
