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| From | cri@tiac.net (Richard Harter) |
|---|---|
| Newsgroups | comp.lang.c |
| Subject | Re: Reference counting |
| Date | 2011-06-05 17:11 +0000 |
| Message-ID | <4debb114.751423946@text.giganews.com> (permalink) |
| References | <4deb6008$0$28457$703f8584@textnews.kpn.nl> |
On Sun, 5 Jun 2011 12:52:56 +0200, daknok <radekslupik@gmail.com>
wrote:
>Hi,
>
>If I want to do simple reference counting for different structures I
>would go like this:
>
>struct String {
> unsigned references;
> char *cString;
> size_t length;
>};
>
>void StringRelease(struct String *str) {
> str->references--;
> if (str->references == 0) {
> free(str->cString);
> free(str);
> }
>}
>
>struct String *StringRetain(struct String *str) {
> str->references++;
> return str;
>}
>
>Though if I have about ten structs, I have ten different functions to
>increase and decrease the reference count. Is it, in some way, possible
>to just provide one function for increasing and one function for
>decreasing the reference count which can be used for all structs with a
>reference count?
There are many ways to skin this particular cat. A simple way is to
pass in the addresses of the components. In the case of retain you
have one argument, the address of the reference counter. Thus you
call Retain thusly:
Retain(&(str->references));
By the by, you don't need to return the pointer to str in the Retain
functions.
The Release functions are a potential problem because different things
might require different numbers of calls to free. However it looks
like they would each have two - the data array and the struct itself.
Here I will commend to you a little trick. In your struct you have a
little struct that looks like this:
struct releasables {
void * first;
void * second;
};
When you init the struct you set first to the payload and second to
the struct itself. Thus the Release code looks like this.
Release(&(str->references),str->releasables);
The Release code then looks something like this:
void Release(unsigned *references, struct releasables releasables)
{
(*references)--;
if (*references == 0) {
free(releasables->first);
free(releasable->second);
}
}
Incidentally I don't think much of making your Release functions void.
You should return something that indicates whether the struct still
exists or whether it has been freed. Checking the validity of
pointers has a way of preventing unpleasant surprises.
I am sure that you can come up with something slicker and less
cumbersome that the above, which is an off the top of my head sort of
thing. The important thing is this: If you can make all of the
release/retain functions somehow smell the same then you can handle
them all the same.
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Reference counting daknok <radekslupik@gmail.com> - 2011-06-05 12:52 +0200
Re: Reference counting Angel <angel+news@spamcop.net> - 2011-06-05 11:17 +0000
Re: Reference counting Gene <gene.ressler@gmail.com> - 2011-06-06 20:07 -0700
Multiple Inheritance (Was Re: Reference counting) Shao Miller <sha0.miller@gmail.com> - 2011-06-11 03:57 -0500
Re: Multiple Inheritance (Was Re: Reference counting) Dr Nick <3-nospam@temporary-address.org.uk> - 2011-06-12 07:22 +0100
Re: Reference counting China Blue Angels <chine.bleu@yahoo.com> - 2011-06-05 05:07 -0700
Re: Reference counting "BartC" <bc@freeuk.com> - 2011-06-05 13:14 +0100
Re: Reference counting daknok <daknok@example.com> - 2011-06-05 14:22 +0200
Re: Reference counting "BartC" <bc@freeuk.com> - 2011-06-05 14:45 +0100
Re: Reference counting daknok <daknok@example.com> - 2011-06-05 17:01 +0200
Re: Reference counting Eric Sosman <esosman@ieee-dot-org.invalid> - 2011-06-05 18:06 -0400
Re: Reference counting Dr Nick <3-nospam@temporary-address.org.uk> - 2011-06-12 07:25 +0100
Re: Reference counting daknok <daknok@example.com> - 2011-06-05 15:29 +0200
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-05 12:17 -0500
Re: Reference counting cri@tiac.net (Richard Harter) - 2011-06-05 17:11 +0000
Re: Reference counting ImpalerCore <jadill33@gmail.com> - 2011-06-10 11:30 -0700
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-10 16:04 -0400
Re: Reference counting James Kuyper <jameskuyper@verizon.net> - 2011-06-10 22:56 -0400
Re: Reference counting ImpalerCore <jadill33@gmail.com> - 2011-06-11 12:36 -0700
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-11 17:23 -0500
Re: Reference counting luser- -droog <mijoryx@yahoo.com> - 2011-06-12 15:15 -0700
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-12 21:13 -0500
Re: Reference counting "Chris M. Thomasson" <cristom@charter.net> - 2011-06-13 12:37 -0700
Re: Reference counting "Chris M. Thomasson" <cristom@charter.net> - 2011-06-13 12:54 -0700
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-13 16:40 -0500
Re: Reference counting ImpalerCore <jadill33@gmail.com> - 2011-06-13 07:34 -0700
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-13 14:26 -0500
Re: Reference counting ImpalerCore <jadill33@gmail.com> - 2011-06-13 12:47 -0700
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-13 17:33 -0500
Re: Reference counting ImpalerCore <jadill33@gmail.com> - 2011-06-14 12:14 -0700
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-15 02:16 -0500
Re: Reference counting "Chris M. Thomasson" <cristom@charter.net> - 2011-06-15 15:34 -0700
Re: Reference counting "Chris M. Thomasson" <cristom@charter.net> - 2011-06-15 15:42 -0700
Re: Reference counting "Chris M. Thomasson" <cristom@charter.net> - 2011-06-16 13:45 -0700
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-16 17:02 -0500
Re: Reference counting "Chris M. Thomasson" <cristom@charter.net> - 2011-06-16 15:18 -0700
Re: Reference counting "Chris M. Thomasson" <cristom@charter.net> - 2011-06-16 16:01 -0700
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-16 18:44 -0500
Re: Reference counting "Chris M. Thomasson" <cristom@charter.net> - 2011-06-16 17:11 -0700
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-16 18:39 -0500
Re: Reference counting "Chris M. Thomasson" <cristom@charter.net> - 2011-06-11 16:51 -0700
Re: Reference counting "Chris M. Thomasson" <cristom@charter.net> - 2011-06-11 18:28 -0700
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-12 16:10 -0500
Re: Reference counting ImpalerCore <jadill33@gmail.com> - 2011-06-13 07:36 -0700
Re: Reference counting Tim Rentsch <txr@alumni.caltech.edu> - 2011-06-14 15:00 -0700
Re: Reference counting luser- -droog <mijoryx@yahoo.com> - 2011-06-13 21:46 -0700
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-14 03:19 -0500
Re: Reference counting Angel <angel+news@spamcop.net> - 2011-06-14 07:31 +0000
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-14 05:02 -0500
Re: Reference counting Keith Thompson <kst-u@mib.org> - 2011-06-14 09:03 -0700
Re: Reference counting luser- -droog <mijoryx@yahoo.com> - 2011-06-14 10:23 -0700
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-14 13:46 -0500
Re: Reference counting Tim Rentsch <txr@alumni.caltech.edu> - 2011-06-14 15:05 -0700
Re: Reference counting Keith Thompson <kst-u@mib.org> - 2011-06-14 16:44 -0700
Re: Reference counting Tim Rentsch <txr@alumni.caltech.edu> - 2011-06-15 06:54 -0700
Re: Reference counting Keith Thompson <kst-u@mib.org> - 2011-06-15 08:46 -0700
Re: Reference counting pete <pfiland@mindspring.com> - 2011-06-15 22:19 -0400
Re: Reference counting James Kuyper <jameskuyper@verizon.net> - 2011-06-15 23:03 -0400
Re: Reference counting Tim Rentsch <txr@alumni.caltech.edu> - 2011-06-19 14:48 -0700
Re: Reference counting Seebs <usenet-nospam@seebs.net> - 2011-06-14 17:16 +0000
Re: Reference counting luser- -droog <mijoryx@yahoo.com> - 2011-06-14 20:53 -0700
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-16 18:49 -0500
Re: Reference counting "io_x" <a@b.c.invalid> - 2011-06-14 08:30 +0200
Re: Reference counting "io_x" <a@b.c.invalid> - 2011-06-14 09:15 +0200
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-14 04:21 -0500
Re: Reference counting "io_x" <a@b.c.invalid> - 2011-06-16 10:35 +0200
Re: Reference counting Ian Collins <ian-news@hotmail.com> - 2011-06-16 20:36 +1200
Re: Reference counting "io_x" <a@b.c.invalid> - 2011-06-16 11:21 +0200
Re: Reference counting "io_x" <a@b.c.invalid> - 2011-06-19 17:57 +0200
Re: Reference counting "io_x" <a@b.c.invalid> - 2011-06-19 20:01 +0200
Re: Reference counting Keith Thompson <kst-u@mib.org> - 2011-06-19 11:07 -0700
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-19 23:15 -0500
Re: Reference counting "io_x" <a@b.c.invalid> - 2011-06-20 08:21 +0200
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-16 19:05 -0500
Re: Reference counting Ian Collins <ian-news@hotmail.com> - 2011-06-17 12:09 +1200
Re: Reference counting luser- -droog <mijoryx@yahoo.com> - 2011-06-15 08:40 -0700
Re: Reference counting "christian.bau" <christian.bau@cbau.wanadoo.co.uk> - 2011-06-16 11:08 -0700
Re: Reference counting Shao Miller <sha0.miller@gmail.com> - 2011-06-16 14:42 -0400
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