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//
// Copyright 2017 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_impl.h"
// Message queues. Message queues work in some ways like Go channels;
// they are a thread-safe way to pass messages between subsystems. They
// do have additional capabilities though.
//
// A closed message queue cannot be written to, but if there are messages
// still in it and it is draining, it can be read from. This permits
// linger operations to work.
//
// Message queues can be closed many times safely.
//
// Readers & writers in a message queue can be woken either by a timeout
// or by a specific signal (arranged by the caller).
typedef struct nni_msgq nni_msgq;
// nni_msgq_init 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_msgq_init(nni_msgq **, int);
// nni_msgq_fini destroys a message queue. It will also free any
// messages that may be in the queue.
extern void nni_msgq_fini(nni_msgq *);
extern int nni_msgq_canget(nni_msgq *);
extern int nni_msgq_canput(nni_msgq *);
extern void nni_msgq_aio_put(nni_msgq *, nni_aio *);
extern void nni_msgq_aio_get(nni_msgq *, nni_aio *);
extern void nni_msgq_aio_notify_get(nni_msgq *, nni_aio *);
extern void nni_msgq_aio_notify_put(nni_msgq *, nni_aio *);
// nni_msgq_put puts the message to the queue. It blocks until it
// was able to do so, or the queue is closed, or a timeout is reached.
// It returns 0 on success, NNG_ECLOSED if the queue was closed, or
// NNG_ETIMEDOUT if the timeout is reached. If an error is returned,
// the caller is responsible for freeing the message with nni_msg_free(),
// otherwise the message is "owned" by the queue, and the caller is not
// permitted to access it further.
extern int nni_msgq_put_until(nni_msgq *, nni_msg *, nni_time);
// nni_msgq_tryput performs a non-blocking attempt to put a message on
// the message queue. It is the same as calling nng_msgq_put_until with
// a zero time.
extern int nni_msgq_tryput(nni_msgq *, nni_msg *);
// nni_msgq_get_until gets a message from the queue. It blocks until a
// message is available, the queue is closed, or time out is reached.
// It returns 0 on success, NNG_ECLOSED if the queue was closed, or
// NNG_ETIMEDOUT if the timeout is reached. On successful return,
// the caller assumes ownership of the message and must call
// nni_msg_free() when it is finished with it.
extern int nni_msgq_get_until(nni_msgq *, nni_msg **, nni_time);
// nni_msgq_set_error sets an error condition on the message queue,
// which causes all current and future readers/writes to return the
// given error condition (if non-zero). Threads waiting to put or get
// are woken as well, if non-zero. If zero, then any present error
// condition is cleared, and waiters are not woken (there shouldn't be
// any waiters unless it was already zero.)
extern void nni_msgq_set_error(nni_msgq *, int);
// nni_msgq_set_put_error sets an error condition on the put side of the
// message queue, and for that side behaves like nni_msgq_set_error.
// Readers (nni_msgq_get*) are unaffected.
extern void nni_msgq_set_put_error(nni_msgq *, int);
// nni_msgq_set_get_error sets an error condition on the get side of the
// message queue, and for that side behaves like nni_msgq_set_error.
// Readers (nni_msgq_put*) are unaffected.
extern void nni_msgq_set_get_error(nni_msgq *, int);
// nni_msgq_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_msgq_close(nni_msgq *);
// nni_msgq_drain is like nng_msgq_close, except that reads
// against the queue are permitted for up to the time limit. The
// operation blocks until either the queue is empty, or the timeout
// has expired. Any messages still in the queue at the timeout are freed.
extern void nni_msgq_drain(nni_msgq *, nni_time);
// nni_msgq_resize resizes the message queue; messages already in the queue
// will be preserved as long as there is room. Messages that are dropped
// due to no room are taken from the most recent. (Oldest messages are
// preserved.)
extern int nni_msgq_resize(nni_msgq *, int);
// nni_msgq_cap returns the "capacity" of the message queue. This does not
// include the extra room for pushback, nor the extra slot reserved to make
// zero-length message queues possible. As a consequence, it is possible
// for the message queue to contain up to 2 more messages than the capacity.
extern int nni_msgq_cap(nni_msgq *mq);
// nni_msgq_len returns the number of messages currently in the queue.
extern int nni_msgq_len(nni_msgq *mq);
#endif // CORE_MSQUEUE_H
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