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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_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.
typedef struct nni_msgqueue * nni_msgqueue_t;
typedef struct nni_msgqueue nni_msgqueue;
// 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 **, 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 *);
// 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 *, nni_msg *, 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 *, nni_msg **, int);
// nni_msgqueue_put_sig is an enhanced version of nni_msgqueue_put, but it
// can be interrupted by nni_msgqueue_signal using the same final pointer,
// which can be thought of as a turnstile. If interrupted it returns EINTR.
// The turnstile should be initialized to zero.
extern int nni_msgqueue_put_sig(nni_msgqueue *, nni_msg *, int, int *);
// nni_msgqueue_get_sig is an enhanced version of nni_msgqueue_get_t, but it
// can be interrupted by nni_msgqueue_signal using the same final pointer,
// which can be thought of as a turnstile. If interrupted it returns EINTR.
// The turnstile should be initialized to zero.
extern int nni_msgqueue_get_sig(nni_msgqueue *, nni_msg **, int, int *);
// nni_msgqueue_signal delivers a signal / interrupt to waiters blocked in
// the msgqueue, if they have registered an interest in the same turnstile.
// It modifies the turnstile's value under the lock to a non-zero value.
extern void nni_msgqueue_signal(nni_msgqueue *, 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 *);
#endif // CORE_MSQUEUE_H
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