Re: [CODE CONCEPTS] Linked lists / reenterant list iterators

From: Gary Barnett (gbarnett@POLARNET.COM)
Date: 03/25/98

From: Chris Jacobson <fear@ATHENET.NET>

>So I was thinking, what would be the SAFEST way to implement linked
>lists, and to iterate through the list without losing place, when there
>is the chance that the current, previous, next, or any other item in the
>list could be removed in mid-iteration....

How about marking any 'deleted' entry with a flag variable, then using that
variable to skip processing that element of the list.

Then have a seperate routine to run  every so often to compact the list. I
assume you only have one thread and just need to do stuff inside the loop
construct that might affect the linked list in a random location.

That'd keep your links happy and allow simple code (read: easy to debug). I
use this approach in a few places on Antares and find it works quite well.

Something like this fragment :-)

#define my_stuff_flag_deleted  (1 <<0)
#define my_stuff_flag_blah1    (1 <<1)
#define my_stuff_flag_blahn    (1 <<n)

struct my_stuff {
    int flags;
    int mynumber;
    char *mystring;
struct my_stuff *stuff;

void look_through_stuff () {
   struct my_stuff *stuff_next, *blah;
   for (blah=stuff;blah;blah=stuff_next) {
       if (IS_SET(blah->flags, my_stuff_flag_deleted))
       /* handle element */


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