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