1/*
2 Simple DirectMedia Layer
3 Copyright (C) 1997-2025 Sam Lantinga <slouken@libsdl.org>
4
5 This software is provided 'as-is', without any express or implied
6 warranty. In no event will the authors be held liable for any damages
7 arising from the use of this software.
8
9 Permission is granted to anyone to use this software for any purpose,
10 including commercial applications, and to alter it and redistribute it
11 freely, subject to the following restrictions:
12
13 1. The origin of this software must not be misrepresented; you must not
14 claim that you wrote the original software. If you use this software
15 in a product, an acknowledgment in the product documentation would be
16 appreciated but is not required.
17 2. Altered source versions must be plainly marked as such, and must not be
18 misrepresented as being the original software.
19 3. This notice may not be removed or altered from any source distribution.
20*/
21
22#include "SDL_internal.h"
23
24#include "SDL_poll.h"
25
26#ifdef HAVE_POLL
27#include <poll.h>
28#else
29#include <sys/time.h>
30#include <sys/types.h>
31#include <unistd.h>
32#endif
33#include <errno.h>
34
35int SDL_IOReady(int fd, int flags, Sint64 timeoutNS)
36{
37 int result;
38
39 SDL_assert(flags & (SDL_IOR_READ | SDL_IOR_WRITE));
40
41 // Note: We don't bother to account for elapsed time if we get EINTR
42 do {
43#ifdef HAVE_POLL
44 struct pollfd info;
45 int timeoutMS;
46
47 info.fd = fd;
48 info.events = 0;
49 if (flags & SDL_IOR_READ) {
50 info.events |= POLLIN | POLLPRI;
51 }
52 if (flags & SDL_IOR_WRITE) {
53 info.events |= POLLOUT;
54 }
55 // FIXME: Add support for ppoll() for nanosecond precision
56 if (timeoutNS > 0) {
57 timeoutMS = (int)SDL_NS_TO_MS(timeoutNS + (SDL_NS_PER_MS - 1));
58 } else if (timeoutNS == 0) {
59 timeoutMS = 0;
60 } else {
61 timeoutMS = -1;
62 }
63 result = poll(&info, 1, timeoutMS);
64#else
65 fd_set rfdset, *rfdp = NULL;
66 fd_set wfdset, *wfdp = NULL;
67 struct timeval tv, *tvp = NULL;
68
69 // If this assert triggers we'll corrupt memory here
70 SDL_assert(fd >= 0 && fd < FD_SETSIZE);
71
72 if (flags & SDL_IOR_READ) {
73 FD_ZERO(&rfdset);
74 FD_SET(fd, &rfdset);
75 rfdp = &rfdset;
76 }
77 if (flags & SDL_IOR_WRITE) {
78 FD_ZERO(&wfdset);
79 FD_SET(fd, &wfdset);
80 wfdp = &wfdset;
81 }
82
83 if (timeoutNS >= 0) {
84 tv.tv_sec = (timeoutNS / SDL_NS_PER_SECOND);
85 tv.tv_usec = SDL_NS_TO_US((timeoutNS % SDL_NS_PER_SECOND) + (SDL_NS_PER_US - 1));
86 tvp = &tv;
87 }
88
89 result = select(fd + 1, rfdp, wfdp, NULL, tvp);
90#endif // HAVE_POLL
91
92 } while (result < 0 && errno == EINTR && !(flags & SDL_IOR_NO_RETRY));
93
94 return result;
95}
96