147 lines
2.6 KiB
C
147 lines
2.6 KiB
C
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/*
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* Copyright (C) NGINX, Inc.
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*/
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#ifndef _NXT_NVBCQ_H_INCLUDED_
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#define _NXT_NVBCQ_H_INCLUDED_
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/* Numeric VBart Circular Queue */
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#define NXT_NVBCQ_SIZE 16384
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typedef uint32_t nxt_nvbcq_atomic_t;
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struct nxt_nvbcq_s {
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nxt_nvbcq_atomic_t head;
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nxt_nvbcq_atomic_t entries[NXT_NVBCQ_SIZE];
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nxt_nvbcq_atomic_t tail;
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};
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typedef struct nxt_nvbcq_s nxt_nvbcq_t;
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static inline nxt_nvbcq_atomic_t
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nxt_nvbcq_head(nxt_nvbcq_t const volatile *q)
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{
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return q->head;
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}
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static inline nxt_nvbcq_atomic_t
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nxt_nvbcq_tail(nxt_nvbcq_t const volatile *q)
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{
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return q->tail;
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}
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static inline void
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nxt_nvbcq_tail_cmp_inc(nxt_nvbcq_t volatile *q, nxt_nvbcq_atomic_t t)
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{
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nxt_atomic_cmp_set(&q->tail, t, t + 1);
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}
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static inline nxt_nvbcq_atomic_t
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nxt_nvbcq_index(nxt_nvbcq_t const volatile *q, nxt_nvbcq_atomic_t i)
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{
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return i % NXT_NVBCQ_SIZE;
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}
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static inline nxt_nvbcq_atomic_t
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nxt_nvbcq_map(nxt_nvbcq_t const volatile *q, nxt_nvbcq_atomic_t i)
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{
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return i % NXT_NVBCQ_SIZE;
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}
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static inline nxt_nvbcq_atomic_t
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nxt_nvbcq_empty(nxt_nvbcq_t const volatile *q)
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{
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return NXT_NVBCQ_SIZE;
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}
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static inline void
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nxt_nvbcq_init(nxt_nvbcq_t volatile *q)
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{
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nxt_nvbcq_atomic_t i;
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q->head = 0;
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for (i = 0; i < NXT_NVBCQ_SIZE; i++) {
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q->entries[i] = NXT_NVBCQ_SIZE;
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}
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q->tail = NXT_NVBCQ_SIZE;
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}
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static inline void
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nxt_nvbcq_enqueue(nxt_nvbcq_t volatile *q, nxt_nvbcq_atomic_t val)
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{
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nxt_nvbcq_atomic_t t, h, i;
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t = nxt_nvbcq_tail(q);
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h = t - NXT_NVBCQ_SIZE;
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for ( ;; ) {
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i = nxt_nvbcq_map(q, t);
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if (q->entries[i] == NXT_NVBCQ_SIZE
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&& nxt_atomic_cmp_set(&q->entries[i], NXT_NVBCQ_SIZE, val))
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{
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nxt_nvbcq_tail_cmp_inc(q, t);
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return;
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}
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if ((t - h) == NXT_NVBCQ_SIZE) {
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h = nxt_nvbcq_head(q);
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if ((t - h) == NXT_NVBCQ_SIZE) {
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return;
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}
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}
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t++;
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}
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}
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static inline nxt_nvbcq_atomic_t
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nxt_nvbcq_dequeue(nxt_nvbcq_t volatile *q)
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{
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nxt_nvbcq_atomic_t h, t, i, e;
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h = nxt_nvbcq_head(q);
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t = h + NXT_NVBCQ_SIZE;
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for ( ;; ) {
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i = nxt_nvbcq_map(q, h);
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e = q->entries[i];
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if (e < NXT_NVBCQ_SIZE
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&& nxt_atomic_cmp_set(&q->entries[i], e, NXT_NVBCQ_SIZE))
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{
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nxt_atomic_cmp_set(&q->head, h, h + 1);
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return e;
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}
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if ((t - h) == NXT_NVBCQ_SIZE) {
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t = nxt_nvbcq_tail(q);
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if ((t - h) == NXT_NVBCQ_SIZE) {
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return NXT_NVBCQ_SIZE;
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}
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}
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h++;
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}
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}
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#endif /* _NXT_NVBCQ_H_INCLUDED_ */
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