Synchronization enhancements - inproc & msgqueue. Absolute waits...

1 files changed, 54 insertions, 61 deletions

diff --git a/src/core/msgqueue.h b/src/core/msgqueue.h
index dbf21d11..e44e203a 100644
--- a/src/core/msgqueue.h
+++ b/src/core/msgqueue.h
@@ -1,74 +1,67 @@
-/*
- * 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.
- */
+//
+// 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"
+#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.
- */
+// 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_t *, int);
+// 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_t);
+// 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_t, nng_msg_t, int);
+// 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_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 *, nni_msg **, 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_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_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);
+// 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 *);
 
-#endif  /* CORE_MSQUEUE_H */
+// 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