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//
// Copyright 2020 Staysail Systems, Inc. <info@staysail.tech>
// Copyright 2018 Capitar IT Group BV <info@capitar.com>
//
// 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.
//
#include "core/nng_impl.h"
// We pack the wfd and rfd into a uint64_t so that we can update the pair
// atomically and use nni_atomic_cas64, to be lock free.
#define WFD(fds) ((int) ((fds) &0xffffffffu))
#define RFD(fds) ((int) (((fds) >> 32u) & 0xffffffffu))
#define FD_JOIN(wfd, rfd) ((uint64_t)(wfd) + ((uint64_t)(rfd) << 32u))
void
nni_pollable_init(nni_pollable *p)
{
nni_atomic_init_bool(&p->p_raised);
nni_atomic_set64(&p->p_fds, (uint64_t) -1);
}
void
nni_pollable_fini(nni_pollable *p)
{
uint64_t fds;
fds = nni_atomic_get64(&p->p_fds);
if (fds != (uint64_t) -1) {
int rfd, wfd;
// Read in the high order, write in the low order.
rfd = RFD(fds);
wfd = WFD(fds);
nni_plat_pipe_close(rfd, wfd);
}
}
int
nni_pollable_alloc(nni_pollable **pp)
{
nni_pollable *p;
if ((p = NNI_ALLOC_STRUCT(p)) == NULL) {
return (NNG_ENOMEM);
}
nni_pollable_init(p);
*pp = p;
return (0);
}
void
nni_pollable_free(nni_pollable *p)
{
if (p == NULL) {
return;
}
nni_pollable_fini(p);
NNI_FREE_STRUCT(p);
}
void
nni_pollable_raise(nni_pollable *p)
{
if (p == NULL) {
return;
}
if (!nni_atomic_swap_bool(&p->p_raised, true)) {
uint64_t fds;
if ((fds = nni_atomic_get64(&p->p_fds)) != (uint64_t) -1) {
nni_plat_pipe_raise(WFD(fds));
}
}
}
void
nni_pollable_clear(nni_pollable *p)
{
if (p == NULL) {
return;
}
if (nni_atomic_swap_bool(&p->p_raised, false)) {
uint64_t fds;
if ((fds = nni_atomic_get64(&p->p_fds)) != (uint64_t) -1) {
nni_plat_pipe_clear(RFD(fds));
}
}
}
int
nni_pollable_getfd(nni_pollable *p, int *fdp)
{
if (p == NULL) {
return (NNG_EINVAL);
}
for (;;) {
int rfd;
int wfd;
int rv;
uint64_t fds;
if ((fds = nni_atomic_get64(&p->p_fds)) != (uint64_t) -1) {
*fdp = RFD(fds);
return (0);
}
if ((rv = nni_plat_pipe_open(&wfd, &rfd)) != 0) {
return (rv);
}
fds = FD_JOIN(wfd, rfd);
if (nni_atomic_cas64(&p->p_fds, (uint64_t) -1, fds)) {
if (nni_atomic_get_bool(&p->p_raised)) {
nni_plat_pipe_raise(wfd);
}
*fdp = rfd;
return (0);
}
// Someone beat us. Close ours, and try again.
nni_plat_pipe_close(wfd, rfd);
}
}
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