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 10Routines to manipulate queues built from doubly linked lists. The 11@code{insque} routine inserts @var{elem} in the queue immediately 12after @var{pred}. The @code{remque} routine removes @var{elem} from 13its containing queue. These routines expect to be passed pointers to 14structures which have as their first members a forward pointer and a 15back pointer, like this prototype (although no prototype is provided): 16 17@example 18struct 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 30struct qelem { 31 struct qelem *q_forw; 32 struct qelem *q_back; 33}; 34 35 36void 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 46void 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