1 /* $NetBSD: poll_fd.c,v 1.1.1.1 2014/07/06 19:27:58 tron Exp $ */
2
3 /*++
4 /* NAME
5 /* poll_fd 3
6 /* SUMMARY
7 /* wait until file descriptor becomes readable or writable
8 /* SYNOPSIS
9 /* #include <iostuff.h>
10 /*
11 /* int readable(fd)
12 /* int fd;
13 /*
14 /* int writable(fd)
15 /* int fd;
16 /*
17 /* int read_wait(fd, time_limit)
18 /* int fd;
19 /* int time_limit;
20 /*
21 /* int write_wait(fd, time_limit)
22 /* int fd;
23 /* int time_limit;
24 /*
25 /* int poll_fd(fd, request, time_limit, true_res, false_res)
26 /* int fd;
27 /* int request;
28 /* int time_limit;
29 /* int true_res;
30 /* int false_res;
31 /* DESCRIPTION
32 /* The read*() and write*() functions in this module are macros
33 /* that provide a convenient interface to poll_fd().
34 /*
35 /* readable() asks the kernel if the specified file descriptor
36 /* is readable, i.e. a read operation would not block.
37 /*
38 /* writable() asks the kernel if the specified file descriptor
39 /* is writable, i.e. a write operation would not block.
40 /*
41 /* read_wait() waits until the specified file descriptor becomes
42 /* readable, or until the time limit is reached.
43 /*
44 /* write_wait() waits until the specified file descriptor
45 /* becomes writable, or until the time limit is reached.
46 /*
47 /* poll_fd() waits until the specified file descriptor becomes
48 /* readable or writable, or until the time limit is reached.
49 /*
50 /* Arguments:
51 /* .IP fd
52 /* File descriptor. With implementations based on select(), a
53 /* best effort is made to handle descriptors >=FD_SETSIZE.
54 /* .IP request
55 /* POLL_FD_READ (wait until readable) or POLL_FD_WRITE (wait
56 /* until writable).
57 /* .IP time_limit
58 /* A positive value specifies a time limit in seconds. A zero
59 /* value effects a poll (return immediately). A negative value
60 /* means wait until the requested POLL_FD_READ or POLL_FD_WRITE
61 /* condition becomes true.
62 /* .IP true_res
63 /* Result value when the requested POLL_FD_READ or POLL_FD_WRITE
64 /* condition is true.
65 /* .IP false_res
66 /* Result value when the requested POLL_FD_READ or POLL_FD_WRITE
67 /* condition is false.
68 /* DIAGNOSTICS
69 /* Panic: interface violation. All system call errors are fatal
70 /* unless specified otherwise.
71 /*
72 /* readable() and writable() return 1 when the requested
73 /* POLL_FD_READ or POLL_FD_WRITE condition is true, zero when
74 /* it is false. They never return an error indication.
75 /*
76 /* read_wait() and write_wait() return zero when the requested
77 /* POLL_FD_READ or POLL_FD_WRITE condition is true, -1 (with
78 /* errno set to ETIMEDOUT) when it is false.
79 /*
80 /* poll_fd() returns true_res when the requested POLL_FD_READ
81 /* or POLL_FD_WRITE condition is true, false_res when it is
82 /* false. When poll_fd() returns a false_res value < 0, it
83 /* also sets errno to ETIMEDOUT.
84 /* LICENSE
85 /* .ad
86 /* .fi
87 /* The Secure Mailer license must be distributed with this software.
88 /* AUTHOR(S)
89 /* Wietse Venema
90 /* IBM T.J. Watson Research
91 /* P.O. Box 704
92 /* Yorktown Heights, NY 10598, USA
93 /*--*/
94
95 /* System library. */
96
97 #include <sys_defs.h>
98 #include <sys/time.h>
99 #include <signal.h>
100 #include <errno.h>
101 #include <unistd.h>
102 #include <string.h>
103
104 /*
105 * Use poll() with fall-back to select(). MacOSX needs this for devices.
106 */
107 #if defined(USE_SYSV_POLL_THEN_SELECT)
108 #define poll_fd_sysv poll_fd
109 #define USE_SYSV_POLL
110 #define USE_BSD_SELECT
111 int poll_fd_bsd(int, int, int, int, int);
112
113 /*
114 * Use select() only.
115 */
116 #elif defined(USE_BSD_SELECT)
117 #define poll_fd_bsd poll_fd
118 #undef USE_SYSV_POLL
119
120 /*
121 * Use poll() only.
122 */
123 #elif defined(USE_SYSV_POLL)
124 #define poll_fd_sysv poll_fd
125
126 /*
127 * Sanity check.
128 */
129 #else
130 #error "specify USE_SYSV_POLL, USE_BSD_SELECT or USE_SYSV_POLL_THEN_SELECT"
131 #endif
132
133 #ifdef USE_SYSV_POLL
134 #include <poll.h>
135 #endif
136
137 #ifdef USE_SYS_SELECT_H
138 #include <sys/select.h>
139 #endif
140
141 /* Utility library. */
142
143 #include <msg.h>
144 #include <iostuff.h>
145
146 #ifdef USE_BSD_SELECT
147
148 /* poll_fd_bsd - block with time_limit until file descriptor is ready */
149
poll_fd_bsd(int fd,int request,int time_limit,int true_res,int false_res)150 int poll_fd_bsd(int fd, int request, int time_limit,
151 int true_res, int false_res)
152 {
153 fd_set req_fds;
154 fd_set *read_fds;
155 fd_set *write_fds;
156 fd_set except_fds;
157 struct timeval tv;
158 struct timeval *tp;
159 int temp_fd = -1;
160
161 /*
162 * Sanity checks.
163 */
164 if (FD_SETSIZE <= fd) {
165 if ((temp_fd = dup(fd)) < 0 || temp_fd >= FD_SETSIZE)
166 msg_fatal("descriptor %d does not fit FD_SETSIZE %d", fd, FD_SETSIZE);
167 fd = temp_fd;
168 }
169
170 /*
171 * Use select() so we do not depend on alarm() and on signal() handlers.
172 * Restart select() when interrupted by some signal. Some select()
173 * implementations reduce the time to wait when interrupted, which is
174 * exactly what we want.
175 */
176 FD_ZERO(&req_fds);
177 FD_SET(fd, &req_fds);
178 except_fds = req_fds;
179 if (request == POLL_FD_READ) {
180 read_fds = &req_fds;
181 write_fds = 0;
182 } else if (request == POLL_FD_WRITE) {
183 read_fds = 0;
184 write_fds = &req_fds;
185 } else {
186 msg_panic("poll_fd: bad request %d", request);
187 }
188
189 if (time_limit >= 0) {
190 tv.tv_usec = 0;
191 tv.tv_sec = time_limit;
192 tp = &tv;
193 } else {
194 tp = 0;
195 }
196
197 for (;;) {
198 switch (select(fd + 1, read_fds, write_fds, &except_fds, tp)) {
199 case -1:
200 if (errno != EINTR)
201 msg_fatal("select: %m");
202 continue;
203 case 0:
204 if (temp_fd != -1)
205 (void) close(temp_fd);
206 if (false_res < 0)
207 errno = ETIMEDOUT;
208 return (false_res);
209 default:
210 if (temp_fd != -1)
211 (void) close(temp_fd);
212 return (true_res);
213 }
214 }
215 }
216
217 #endif
218
219 #ifdef USE_SYSV_POLL
220
221 #ifdef USE_SYSV_POLL_THEN_SELECT
222 #define HANDLE_SYSV_POLL_ERROR(fd, req, time_limit, true_res, false_res) \
223 return (poll_fd_bsd((fd), (req), (time_limit), (true_res), (false_res)))
224 #else
225 #define HANDLE_SYSV_POLL_ERROR(fd, req, time_limit, true_res, false_res) \
226 msg_fatal("poll: %m")
227 #endif
228
229 /* poll_fd_sysv - block with time_limit until file descriptor is ready */
230
poll_fd_sysv(int fd,int request,int time_limit,int true_res,int false_res)231 int poll_fd_sysv(int fd, int request, int time_limit,
232 int true_res, int false_res)
233 {
234 struct pollfd pollfd;
235
236 /*
237 * System-V poll() is optimal for polling a few descriptors.
238 */
239 #define WAIT_FOR_EVENT (-1)
240
241 pollfd.fd = fd;
242 if (request == POLL_FD_READ) {
243 pollfd.events = POLLIN;
244 } else if (request == POLL_FD_WRITE) {
245 pollfd.events = POLLOUT;
246 } else {
247 msg_panic("poll_fd: bad request %d", request);
248 }
249
250 for (;;) {
251 switch (poll(&pollfd, 1, time_limit < 0 ?
252 WAIT_FOR_EVENT : time_limit * 1000)) {
253 case -1:
254 if (errno != EINTR)
255 HANDLE_SYSV_POLL_ERROR(fd, request, time_limit,
256 true_res, false_res);
257 continue;
258 case 0:
259 if (false_res < 0)
260 errno = ETIMEDOUT;
261 return (false_res);
262 default:
263 if (pollfd.revents & POLLNVAL)
264 HANDLE_SYSV_POLL_ERROR(fd, request, time_limit,
265 true_res, false_res);
266 return (true_res);
267 }
268 }
269 }
270
271 #endif
272