54 lines
1.1 KiB
C
54 lines
1.1 KiB
C
/* insque(3C) routines
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This file is in the public domain. */
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/*
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@deftypefn Supplemental void insque (struct qelem *@var{elem}, struct qelem *@var{pred})
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@deftypefnx Supplemental void remque (struct qelem *@var{elem})
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Routines to manipulate queues built from doubly linked lists. The
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@code{insque} routine inserts @var{elem} in the queue immediately
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after @var{pred}. The @code{remque} routine removes @var{elem} from
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its containing queue. These routines expect to be passed pointers to
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structures which have as their first members a forward pointer and a
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back pointer, like this prototype (although no prototype is provided):
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@example
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struct qelem @{
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struct qelem *q_forw;
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struct qelem *q_back;
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char q_data[];
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@};
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@end example
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@end deftypefn
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*/
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struct qelem {
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struct qelem *q_forw;
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struct qelem *q_back;
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};
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void
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insque (elem, pred)
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struct qelem *elem;
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struct qelem *pred;
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{
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elem -> q_forw = pred -> q_forw;
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pred -> q_forw -> q_back = elem;
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elem -> q_back = pred;
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pred -> q_forw = elem;
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}
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void
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remque (elem)
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struct qelem *elem;
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{
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elem -> q_forw -> q_back = elem -> q_back;
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elem -> q_back -> q_forw = elem -> q_forw;
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}
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