86 lines
1.6 KiB
C
86 lines
1.6 KiB
C
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/*
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* Copyright (C) Igor Sysoev
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* Copyright (C) NGINX, Inc.
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*/
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#include <nxt_main.h>
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/*
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* Find the middle queue element if the queue has odd number of elements,
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* or the first element of the queue's second part otherwise.
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*/
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nxt_queue_link_t *
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nxt_queue_middle(nxt_queue_t *queue)
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{
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nxt_queue_link_t *middle, *next;
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middle = nxt_queue_first(queue);
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if (middle == nxt_queue_last(queue)) {
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return middle;
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}
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next = middle;
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for ( ;; ) {
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middle = nxt_queue_next(middle);
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next = nxt_queue_next(next);
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if (next == nxt_queue_last(queue)) {
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return middle;
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}
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next = nxt_queue_next(next);
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if (next == nxt_queue_last(queue)) {
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return middle;
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}
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}
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}
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/*
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* nxt_queue_sort() provides a stable sort because it uses the insertion
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* sort algorithm. Its worst and average computational complexity is O^2.
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*/
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void
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nxt_queue_sort(nxt_queue_t *queue,
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nxt_int_t (*cmp)(const void *data, const nxt_queue_link_t *,
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const nxt_queue_link_t *), const void *data)
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{
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nxt_queue_link_t *link, *prev, *next;
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link = nxt_queue_first(queue);
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if (link == nxt_queue_last(queue)) {
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return;
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}
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for (link = nxt_queue_next(link);
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link != nxt_queue_tail(queue);
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link = next)
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{
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prev = nxt_queue_prev(link);
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next = nxt_queue_next(link);
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nxt_queue_remove(link);
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do {
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if (cmp(data, prev, link) <= 0) {
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break;
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}
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prev = nxt_queue_prev(prev);
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} while (prev != nxt_queue_head(queue));
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nxt_queue_insert_after(prev, link);
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}
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}
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