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 insque(struct qelem * elem,struct qelem * pred)37insque (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 remque(struct qelem * elem)47remque (struct qelem *elem) 48 { 49 elem -> q_forw -> q_back = elem -> q_back; 50 elem -> q_back -> q_forw = elem -> q_forw; 51 } 52