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diff --git a/doc/ck_ring_trydequeue_spmc b/doc/ck_ring_trydequeue_spmc new file mode 100644 index 0000000..16f83ee --- /dev/null +++ b/doc/ck_ring_trydequeue_spmc @@ -0,0 +1,126 @@ +.\" +.\" Copyright 2012-2013 Samy Al Bahra. +.\" All rights reserved. +.\" +.\" Redistribution and use in source and binary forms, with or without +.\" modification, are permitted provided that the following conditions +.\" are met: +.\" 1. Redistributions of source code must retain the above copyright +.\" notice, this list of conditions and the following disclaimer. +.\" 2. Redistributions in binary form must reproduce the above copyright +.\" notice, this list of conditions and the following disclaimer in the +.\" documentation and/or other materials provided with the distribution. +.\" +.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND +.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE +.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE +.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE +.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL +.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS +.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) +.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT +.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY +.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF +.\" SUCH DAMAGE. +.\" +.\" +.Dd April 20, 2013 +.Dt CK_RING_TRYDEQUEUE_SPMC 3 +.Sh NAME +.Nm ck_ring_trydequeue_spmc +.Nd dequeue from bounded FIFO and allow for spurious failure +.Sh LIBRARY +Concurrency Kit (libck, \-lck) +.Sh SYNOPSIS +.In ck_ring.h +.Ft bool +.Fn ck_ring_trydequeue_spmc "ck_ring_t *ring" "ck_ring_buffer_t *buffer" "void *result" +.Sh DESCRIPTION +The +.Fn ck_ring_trydequeue_spmc 3 +function attempts to dequeue a pointer from the bounded buffer +pointed to by +.Fa ring +in FIFO fashion. The pointer is stored in the pointer +pointed to by +.Fa result . +The buffer pointed to by +.Fa buffer +must be unique to +.Fa ring +and point to an array of ck_ring_buffer_t of sufficient +length (according to the power-of-2 elements in the buffer). +The decoupling of the ring from the buffer serves +to address use-cases involving multiple address spaces +and DMA, among others. +If you are on non-POSIX platforms or wish for strict +compliance with C, then it is recommended to pass a +pointer of type void ** for +.Fa result . +This function is safe to call without locking for UINT_MAX +concurrent +.Fn ck_ring_dequeue_spmc 3 +or +.Fn ck_ring_trydequeue_spmc 3 +invocations and up to one concurrent +.Fn ck_ring_enqueue_spmc 3 +or +.Fn ck_ring_tryenqueue_spmc 3 +invocation. This operation will always complete +in a bounded number of steps. It is +possible for the function to return false even +if +.Fa ring +is non-empty. This +.Sh EXAMPLE +.Bd -literal -offset indent +#include <ck_ring.h> + +/* This ring was previously initialized with ck_ring_init. */ +ck_ring_t ring; + +/* The ring was initialized for 1023 elements. */ +ck_ring_buffer_t buffer[1024]; + +void +dequeue(void) +{ + void *result; + + /* Dequeue from ring until contention is actively observed. */ + while (ck_ring_trydequeue_spmc(&ring, &buffer, &result) == true) { + /* + * Results contains the oldest pointer in ring + * since the dequeue operation returned true. + */ + operation(result); + } + + /* An empty ring was encountered, leave. */ + return; +} +.Ed +.Sh RETURN VALUES +The function returns true if the dequeue operation +completely successfully in a bounded number of steps. +The result of the dequeue operation is stored in the +value pointed to by +.Fa result . +Otherwise, the function will return false if the buffer was empty +or if the operation could not be completed in a bounded +number of steps. If the function returns false, then the contents +of +.Fa result +are undefined. +.Sh SEE ALSO +.Xr ck_ring_init 3 , +.Xr ck_ring_dequeue_spmc 3 , +.Xr ck_ring_enqueue_spmc 3 , +.Xr ck_ring_enqueue_spmc_size 3 , +.Xr ck_ring_dequeue_spsc 3 , +.Xr ck_ring_enqueue_spsc 3 , +.Xr ck_ring_enqueue_spsc_size 3 , +.Xr ck_ring_capacity 3 , +.Xr ck_ring_size 3 +.Pp +Additional information available at http://concurrencykit.org/ |