109 lines
2.8 KiB
C
109 lines
2.8 KiB
C
void mq_nanosleep(unsigned ns);
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/*
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* Simple templated message queue implementation that relies on only mutexes for
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* synchronization (which reduces portability issues). Given the following
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* setup:
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*
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* typedef struct mq_msg_s mq_msg_t;
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* struct mq_msg_s {
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* mq_msg(mq_msg_t) link;
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* [message data]
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* };
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* mq_gen(, mq_, mq_t, mq_msg_t, link)
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*
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* The API is as follows:
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*
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* bool mq_init(mq_t *mq);
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* void mq_fini(mq_t *mq);
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* unsigned mq_count(mq_t *mq);
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* mq_msg_t *mq_tryget(mq_t *mq);
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* mq_msg_t *mq_get(mq_t *mq);
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* void mq_put(mq_t *mq, mq_msg_t *msg);
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*
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* The message queue linkage embedded in each message is to be treated as
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* externally opaque (no need to initialize or clean up externally). mq_fini()
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* does not perform any cleanup of messages, since it knows nothing of their
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* payloads.
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*/
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#define mq_msg(a_mq_msg_type) ql_elm(a_mq_msg_type)
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#define mq_gen(a_attr, a_prefix, a_mq_type, a_mq_msg_type, a_field) \
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typedef struct { \
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mtx_t lock; \
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ql_head(a_mq_msg_type) msgs; \
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unsigned count; \
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} a_mq_type; \
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a_attr bool \
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a_prefix##init(a_mq_type *mq) { \
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\
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if (mtx_init(&mq->lock)) \
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return (true); \
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ql_new(&mq->msgs); \
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mq->count = 0; \
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return (false); \
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} \
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a_attr void \
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a_prefix##fini(a_mq_type *mq) \
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{ \
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mtx_fini(&mq->lock); \
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} \
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a_attr unsigned \
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a_prefix##count(a_mq_type *mq) \
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{ \
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unsigned count; \
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\
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mtx_lock(&mq->lock); \
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count = mq->count; \
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mtx_unlock(&mq->lock); \
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return (count); \
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} \
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a_attr a_mq_msg_type * \
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a_prefix##tryget(a_mq_type *mq) \
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{ \
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a_mq_msg_type *msg; \
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\
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mtx_lock(&mq->lock); \
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msg = ql_first(&mq->msgs); \
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if (msg != NULL) { \
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ql_head_remove(&mq->msgs, a_mq_msg_type, a_field); \
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mq->count--; \
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} \
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mtx_unlock(&mq->lock); \
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return (msg); \
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} \
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a_attr a_mq_msg_type * \
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a_prefix##get(a_mq_type *mq) \
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{ \
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a_mq_msg_type *msg; \
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unsigned ns; \
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\
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msg = a_prefix##tryget(mq); \
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if (msg != NULL) \
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return (msg); \
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\
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ns = 1; \
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while (true) { \
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mq_nanosleep(ns); \
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msg = a_prefix##tryget(mq); \
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if (msg != NULL) \
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return (msg); \
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if (ns < 1000*1000*1000) { \
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/* Double sleep time, up to max 1 second. */ \
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ns <<= 1; \
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if (ns > 1000*1000*1000) \
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ns = 1000*1000*1000; \
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} \
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} \
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} \
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a_attr void \
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a_prefix##put(a_mq_type *mq, a_mq_msg_type *msg) \
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{ \
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\
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mtx_lock(&mq->lock); \
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ql_elm_new(msg, a_field); \
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ql_tail_insert(&mq->msgs, msg, a_field); \
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mq->count++; \
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mtx_unlock(&mq->lock); \
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}
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