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/*
* Copyright 2016 Garrett D'Amore <garrett@damore.org>
*
* This software is supplied under the terms of the MIT License, a
* copy of which should be located in the distribution where this
* file was obtained (LICENSE.txt). A copy of the license may also be
* found online at https://opensource.org/licenses/MIT.
*/
#ifndef CORE_MSGQUEUE_H
#define CORE_MSGQUEUE_H
#include "nng.h"
/*
* Message queues. Message queues work in some ways like Go channels;
* they are a thread-safe way to pass messages between subsystems.
*/
typedef struct nni_msgqueue * nni_msgqueue_t;
/*
* nni_msgqueue_create creates a message queue with the given capacity,
* which must be a positive number. It returns NNG_EINVAL if the capacity
* is invalid, or NNG_ENOMEM if resources cannot be allocated.
*/
extern int nni_msgqueue_create(nni_msgqueue_t *, int);
/*
* nni_msgqueue_destroy destroys a message queue. It will also free any
* messages that may be in the queue.
*/
extern void nni_msgqueue_destroy(nni_msgqueue_t);
/*
* nni_msgqueue_put attempts to put a message to the queue. It will wait
* for the timeout (us), if the value is positive. If the value is negative
* then it will wait forever. If the value is zero, it will just check, and
* return immediately whether a message can be put or not. Valid returns are
* NNG_ECLOSED if the queue is closed or NNG_ETIMEDOUT if the message cannot
* be placed after a time, or NNG_EAGAIN if the operation cannot succeed
* immediately and a zero timeout is specified. Note that timeout granularity
* may be limited -- for example Windows systems have a millisecond resolution
* timeout capability.
*/
extern int nni_msgqueue_put(nni_msgqueue_t, nng_msg_t, int);
/*
* nni_msgqueue_get gets the message from the queue, using a timeout just
* like nni_msgqueue_put.
*/
extern int nni_msgqueue_get(nni_msgqueue_t, nng_msg_t *, int);
/*
* The following two functions are interruptible versions of msgqueue_get
* and msgqueue_put. The signal argument (pointer) must be initialized
* to zero. Then, we can raise a signal, by calling nni_msgqueue_signal
* on the same object. The signal flag will remain raised until it is
* cleared to zero. If a routine is interrupted, it will return NNG_EINTR.
* Note that only threads using the signal object will be interrupted;
* this has no effect on other threads that may be waiting on the msgqueue
* as well.
*/
extern int nni_msgqueue_put_sig(nni_msgqueue_t, nng_msg_t, int, int *);
extern int nni_msgqueue_get_sig(nni_msgqueue_t, nng_msg_t *, int, int *);
extern void nni_msgqueue_signal(nni_msgqueue_t, int *);
/*
* nni_msgqueue_close closes the queue. After this all operates on the
* message queue will return NNG_ECLOSED. Messages inside the queue
* are freed. Unlike closing a go channel, this operation is idempotent.
*/
extern void nni_msgqueue_close(nni_msgqueue_t);
#endif /* CORE_MSQUEUE_H */
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