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