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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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4412
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4 * Copyright (C) Nginx, Inc.
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2026
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5 */
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6
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7
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8 #include <ngx_config.h>
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9 #include <ngx_core.h>
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10
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11
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12 /*
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13 * find the middle queue element if the queue has odd number of elements
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14 * or the first element of the queue's second part otherwise
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15 */
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16
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17 ngx_queue_t *
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18 ngx_queue_middle(ngx_queue_t *queue)
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19 {
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20 ngx_queue_t *middle, *next;
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21
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22 middle = ngx_queue_head(queue);
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23
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24 if (middle == ngx_queue_last(queue)) {
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25 return middle;
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26 }
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27
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28 next = ngx_queue_head(queue);
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29
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30 for ( ;; ) {
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31 middle = ngx_queue_next(middle);
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32
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33 next = ngx_queue_next(next);
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34
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35 if (next == ngx_queue_last(queue)) {
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36 return middle;
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37 }
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38
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39 next = ngx_queue_next(next);
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40
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41 if (next == ngx_queue_last(queue)) {
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42 return middle;
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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
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48 /* the stable insertion sort */
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49
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50 void
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51 ngx_queue_sort(ngx_queue_t *queue,
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52 ngx_int_t (*cmp)(const ngx_queue_t *, const ngx_queue_t *))
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53 {
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54 ngx_queue_t *q, *prev, *next;
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55
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56 q = ngx_queue_head(queue);
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57
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58 if (q == ngx_queue_last(queue)) {
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59 return;
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60 }
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61
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62 for (q = ngx_queue_next(q); q != ngx_queue_sentinel(queue); q = next) {
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63
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64 prev = ngx_queue_prev(q);
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65 next = ngx_queue_next(q);
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66
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67 ngx_queue_remove(q);
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68
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69 do {
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70 if (cmp(prev, q) <= 0) {
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71 break;
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72 }
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73
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74 prev = ngx_queue_prev(prev);
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75
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76 } while (prev != ngx_queue_sentinel(queue));
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77
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78 ngx_queue_insert_after(prev, q);
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79 }
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80 }
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