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