| 1 | /* insque(3C) routines |
| 2 | This file is in the public domain. */ |
| 3 | |
| 4 | /* |
| 5 | |
| 6 | @deftypefn Supplemental void insque (struct qelem *@var{elem}, @ |
| 7 | struct qelem *@var{pred}) |
| 8 | @deftypefnx Supplemental void remque (struct qelem *@var{elem}) |
| 9 | |
| 10 | Routines to manipulate queues built from doubly linked lists. The |
| 11 | @code{insque} routine inserts @var{elem} in the queue immediately |
| 12 | after @var{pred}. The @code{remque} routine removes @var{elem} from |
| 13 | its containing queue. These routines expect to be passed pointers to |
| 14 | structures which have as their first members a forward pointer and a |
| 15 | back pointer, like this prototype (although no prototype is provided): |
| 16 | |
| 17 | @example |
| 18 | struct qelem @{ |
| 19 | struct qelem *q_forw; |
| 20 | struct qelem *q_back; |
| 21 | char q_data[]; |
| 22 | @}; |
| 23 | @end example |
| 24 | |
| 25 | @end deftypefn |
| 26 | |
| 27 | */ |
| 28 | |
| 29 | |
| 30 | struct qelem { |
| 31 | struct qelem *q_forw; |
| 32 | struct qelem *q_back; |
| 33 | }; |
| 34 | |
| 35 | |
| 36 | void |
| 37 | insque (struct qelem *elem, struct qelem *pred) |
| 38 | { |
| 39 | elem -> q_forw = pred -> q_forw; |
| 40 | pred -> q_forw -> q_back = elem; |
| 41 | elem -> q_back = pred; |
| 42 | pred -> q_forw = elem; |
| 43 | } |
| 44 | |
| 45 | |
| 46 | void |
| 47 | remque (struct qelem *elem) |
| 48 | { |
| 49 | elem -> q_forw -> q_back = elem -> q_back; |
| 50 | elem -> q_back -> q_forw = elem -> q_forw; |
| 51 | } |