f43ad85edd
Guard against the possibility that the queue is emptied while we're iterating
over it. Simple test case:
#include "ngx-queue.h"
#include <assert.h>
int main(void) {
ngx_queue_t h;
ngx_queue_t v[2];
ngx_queue_t* q;
unsigned n = 0;
ngx_queue_init(&h);
ngx_queue_insert_tail(&h, v + 0);
ngx_queue_insert_tail(&h, v + 1);
ngx_queue_foreach(q, &h) {
ngx_queue_remove(v + 0);
ngx_queue_remove(v + 1);
n++;
}
assert(n == 1); // *not* 2
return 0;
}
Fixes #605.
109 lines
3.5 KiB
C
109 lines
3.5 KiB
C
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/*
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* Copyright (C) Igor Sysoev
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*/
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#ifndef NGX_QUEUE_H_INCLUDED_
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#define NGX_QUEUE_H_INCLUDED_
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typedef struct ngx_queue_s ngx_queue_t;
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struct ngx_queue_s {
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ngx_queue_t *prev;
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ngx_queue_t *next;
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};
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#define ngx_queue_init(q) \
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(q)->prev = q; \
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(q)->next = q
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#define ngx_queue_empty(h) \
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(h == (h)->prev)
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#define ngx_queue_insert_head(h, x) \
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(x)->next = (h)->next; \
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(x)->next->prev = x; \
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(x)->prev = h; \
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(h)->next = x
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#define ngx_queue_insert_after ngx_queue_insert_head
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#define ngx_queue_insert_tail(h, x) \
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(x)->prev = (h)->prev; \
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(x)->prev->next = x; \
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(x)->next = h; \
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(h)->prev = x
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#define ngx_queue_head(h) \
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(h)->next
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#define ngx_queue_last(h) \
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(h)->prev
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#define ngx_queue_sentinel(h) \
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(h)
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#define ngx_queue_next(q) \
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(q)->next
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#define ngx_queue_prev(q) \
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(q)->prev
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#if (NGX_DEBUG)
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#define ngx_queue_remove(x) \
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(x)->next->prev = (x)->prev; \
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(x)->prev->next = (x)->next; \
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(x)->prev = NULL; \
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(x)->next = NULL
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#else
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#define ngx_queue_remove(x) \
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(x)->next->prev = (x)->prev; \
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(x)->prev->next = (x)->next
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#endif
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#define ngx_queue_split(h, q, n) \
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(n)->prev = (h)->prev; \
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(n)->prev->next = n; \
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(n)->next = q; \
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(h)->prev = (q)->prev; \
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(h)->prev->next = h; \
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(q)->prev = n;
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#define ngx_queue_add(h, n) \
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(h)->prev->next = (n)->next; \
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(n)->next->prev = (h)->prev; \
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(h)->prev = (n)->prev; \
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(h)->prev->next = h;
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#define ngx_queue_data(q, type, link) \
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(type *) ((unsigned char *) q - offsetof(type, link))
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#define ngx_queue_foreach(q, h) \
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for ((q) = ngx_queue_head(h); \
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(q) != ngx_queue_sentinel(h) && !ngx_queue_empty(h); \
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(q) = ngx_queue_next(q))
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#endif /* NGX_QUEUE_H_INCLUDED_ */
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