1 //
2 // Copyright 2020 Staysail Systems, Inc. <info@staysail.tech>
3 // Copyright 2018 Capitar IT Group BV <info@capitar.com>
4 //
5 // This software is supplied under the terms of the MIT License, a
6 // copy of which should be located in the distribution where this
7 // file was obtained (LICENSE.txt). A copy of the license may also be
8 // found online at https://opensource.org/licenses/MIT.
9 //
10
11 #include "core/nng_impl.h"
12
13 // We pack the wfd and rfd into a uint64_t so that we can update the pair
14 // atomically and use nni_atomic_cas64, to be lock free.
15 #define WFD(fds) ((int) ((fds) &0xffffffffu))
16 #define RFD(fds) ((int) (((fds) >> 32u) & 0xffffffffu))
17 #define FD_JOIN(wfd, rfd) ((uint64_t)(wfd) + ((uint64_t)(rfd) << 32u))
18
19 void
nni_pollable_init(nni_pollable * p)20 nni_pollable_init(nni_pollable *p)
21 {
22 nni_atomic_init_bool(&p->p_raised);
23 nni_atomic_set64(&p->p_fds, (uint64_t) -1);
24 }
25
26 void
nni_pollable_fini(nni_pollable * p)27 nni_pollable_fini(nni_pollable *p)
28 {
29 uint64_t fds;
30
31 fds = nni_atomic_get64(&p->p_fds);
32 if (fds != (uint64_t) -1) {
33 int rfd, wfd;
34 // Read in the high order, write in the low order.
35 rfd = RFD(fds);
36 wfd = WFD(fds);
37 nni_plat_pipe_close(rfd, wfd);
38 }
39 }
40
41 int
nni_pollable_alloc(nni_pollable ** pp)42 nni_pollable_alloc(nni_pollable **pp)
43 {
44 nni_pollable *p;
45 if ((p = NNI_ALLOC_STRUCT(p)) == NULL) {
46 return (NNG_ENOMEM);
47 }
48 nni_pollable_init(p);
49 *pp = p;
50 return (0);
51 }
52
53 void
nni_pollable_free(nni_pollable * p)54 nni_pollable_free(nni_pollable *p)
55 {
56 if (p == NULL) {
57 return;
58 }
59 nni_pollable_fini(p);
60 NNI_FREE_STRUCT(p);
61 }
62
63 void
nni_pollable_raise(nni_pollable * p)64 nni_pollable_raise(nni_pollable *p)
65 {
66 if (p == NULL) {
67 return;
68 }
69 if (!nni_atomic_swap_bool(&p->p_raised, true)) {
70 uint64_t fds;
71 if ((fds = nni_atomic_get64(&p->p_fds)) != (uint64_t) -1) {
72 nni_plat_pipe_raise(WFD(fds));
73 }
74 }
75 }
76
77 void
nni_pollable_clear(nni_pollable * p)78 nni_pollable_clear(nni_pollable *p)
79 {
80 if (p == NULL) {
81 return;
82 }
83 if (nni_atomic_swap_bool(&p->p_raised, false)) {
84 uint64_t fds;
85 if ((fds = nni_atomic_get64(&p->p_fds)) != (uint64_t) -1) {
86 nni_plat_pipe_clear(RFD(fds));
87 }
88 }
89 }
90
91 int
nni_pollable_getfd(nni_pollable * p,int * fdp)92 nni_pollable_getfd(nni_pollable *p, int *fdp)
93 {
94 if (p == NULL) {
95 return (NNG_EINVAL);
96 }
97
98 for (;;) {
99 int rfd;
100 int wfd;
101 int rv;
102 uint64_t fds;
103
104 if ((fds = nni_atomic_get64(&p->p_fds)) != (uint64_t) -1) {
105 *fdp = RFD(fds);
106 return (0);
107 }
108 if ((rv = nni_plat_pipe_open(&wfd, &rfd)) != 0) {
109 return (rv);
110 }
111 fds = FD_JOIN(wfd, rfd);
112
113 if (nni_atomic_cas64(&p->p_fds, (uint64_t) -1, fds)) {
114 if (nni_atomic_get_bool(&p->p_raised)) {
115 nni_plat_pipe_raise(wfd);
116 }
117 *fdp = rfd;
118 return (0);
119 }
120
121 // Someone beat us. Close ours, and try again.
122 nni_plat_pipe_close(wfd, rfd);
123 }
124 }
125