//
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// Copyright 2020 Staysail Systems, Inc. <info@staysail.tech>
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// Copyright 2018 Capitar IT Group BV <info@capitar.com>
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//
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// This software is supplied under the terms of the MIT License, a
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// copy of which should be located in the distribution where this
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// file was obtained (LICENSE.txt). A copy of the license may also be
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// found online at https://opensource.org/licenses/MIT.
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//
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#ifndef CORE_MSGQUEUE_H
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#define CORE_MSGQUEUE_H
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#include "nng_impl.h"
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#include "pollable.h"
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// Message queues. Message queues work in some ways like Go channels;
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// they are a thread-safe way to pass messages between subsystems. They
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// do have additional capabilities though.
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//
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// Message queues can be closed many times safely.
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//
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// Readers & writers in a message queue can be woken either by a timeout
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// or by a specific signal (arranged by the caller).
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typedef struct nni_msgq nni_msgq;
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// nni_msgq_init creates a message queue with the given capacity.
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// (If the capacity is zero, then the queue is unbuffered.)
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// It returns NNG_ENOMEM if resources cannot be allocated.
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extern int nni_msgq_init(nni_msgq **, unsigned);
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// nni_msgq_fini destroys a message queue. It will also free any
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// messages that may be in the queue.
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extern void nni_msgq_fini(nni_msgq *);
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extern void nni_msgq_aio_put(nni_msgq *, nni_aio *);
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extern void nni_msgq_aio_get(nni_msgq *, nni_aio *);
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// nni_msgq_tryput performs a non-blocking attempt to put a message on
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// the message queue.
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extern int nni_msgq_tryput(nni_msgq *, nni_msg *);
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// nni_msgq_close closes the queue. After this all operates on the
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// message queue will return NNG_ECLOSED. Messages inside the queue
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// are freed. Unlike closing a go channel, this operation is idempotent.
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extern void nni_msgq_close(nni_msgq *);
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// nni_msgq_resize resizes the message queue; messages already in the queue
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// will be preserved as long as there is room. Messages that are dropped
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// due to no room are taken from the most recent. (Oldest messages are
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// preserved.)
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extern int nni_msgq_resize(nni_msgq *, int);
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// nni_msgq_cap returns the "capacity" of the message queue. This does not
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// include the extra room for pushback, nor the extra slot reserved to make
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// zero-length message queues possible. As a consequence, it is possible
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// for the message queue to contain up to 2 more messages than the capacity.
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extern int nni_msgq_cap(nni_msgq *mq);
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extern int nni_msgq_get_recvable(nni_msgq *mq, nni_pollable **);
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extern int nni_msgq_get_sendable(nni_msgq *mq, nni_pollable **);
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#endif // CORE_MSQUEUE_H
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