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2026
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1
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2 /*
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3 * Copyright (C) Igor Sysoev
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4 */
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5
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6
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7 #include <ngx_config.h>
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8 #include <ngx_core.h>
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9
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10
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11 /*
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12 * find the middle queue element if the queue has odd number of elements
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13 * or the first element of the queue's second part otherwise
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14 */
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15
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16 ngx_queue_t *
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17 ngx_queue_middle(ngx_queue_t *queue)
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18 {
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19 ngx_queue_t *middle, *next;
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20
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21 middle = ngx_queue_head(queue);
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22
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23 if (middle == ngx_queue_last(queue)) {
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24 return middle;
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25 }
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26
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27 next = ngx_queue_head(queue);
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28
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29 for ( ;; ) {
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30 middle = ngx_queue_next(middle);
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31
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32 next = ngx_queue_next(next);
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33
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34 if (next == ngx_queue_last(queue)) {
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35 return middle;
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36 }
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37
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38 next = ngx_queue_next(next);
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39
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40 if (next == ngx_queue_last(queue)) {
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41 return middle;
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42 }
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43 }
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44 }
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45
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46
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47 /* the stable insertion sort */
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48
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49 void
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50 ngx_queue_sort(ngx_queue_t *queue,
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51 ngx_int_t (*cmp)(const ngx_queue_t *, const ngx_queue_t *))
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52 {
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53 ngx_queue_t *q, *prev, *next;
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54
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55 q = ngx_queue_head(queue);
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56
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57 if (q == ngx_queue_last(queue)) {
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58 return;
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59 }
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60
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61 for (q = ngx_queue_next(q); q != ngx_queue_sentinel(queue); q = next) {
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62
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63 prev = ngx_queue_prev(q);
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64 next = ngx_queue_next(q);
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65
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66 ngx_queue_remove(q);
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67
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68 do {
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69 if (cmp(prev, q) <= 0) {
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70 break;
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71 }
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72
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73 prev = ngx_queue_prev(prev);
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74
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75 } while (prev != ngx_queue_sentinel(queue));
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76
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77 ngx_queue_insert_after(prev, q);
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78 }
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79 }
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