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c004493c LP |
1 | /*** |
2 | This file is part of systemd. | |
3 | ||
4 | Copyright 2010 Lennart Poettering | |
5 | ||
6 | systemd is free software; you can redistribute it and/or modify it | |
7 | under the terms of the GNU Lesser General Public License as published by | |
8 | the Free Software Foundation; either version 2.1 of the License, or | |
9 | (at your option) any later version. | |
10 | ||
11 | systemd is distributed in the hope that it will be useful, but | |
12 | WITHOUT ANY WARRANTY; without even the implied warranty of | |
13 | MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU | |
14 | Lesser General Public License for more details. | |
15 | ||
16 | You should have received a copy of the GNU Lesser General Public License | |
17 | along with systemd; If not, see <http://www.gnu.org/licenses/>. | |
18 | ***/ | |
19 | ||
11c3a366 TA |
20 | #include <errno.h> |
21 | #include <limits.h> | |
c004493c | 22 | #include <poll.h> |
11c3a366 TA |
23 | #include <stdio.h> |
24 | #include <time.h> | |
c004493c LP |
25 | #include <unistd.h> |
26 | ||
27 | #include "io-util.h" | |
11c3a366 | 28 | #include "time-util.h" |
c004493c LP |
29 | |
30 | int flush_fd(int fd) { | |
31 | struct pollfd pollfd = { | |
32 | .fd = fd, | |
33 | .events = POLLIN, | |
34 | }; | |
35 | ||
60d9771c LP |
36 | /* Read from the specified file descriptor, until POLLIN is not set anymore, throwing away everything |
37 | * read. Note that some file descriptors (notable IP sockets) will trigger POLLIN even when no data can be read | |
38 | * (due to IP packet checksum mismatches), hence this function is only safe to be non-blocking if the fd used | |
39 | * was set to non-blocking too. */ | |
40 | ||
c004493c LP |
41 | for (;;) { |
42 | char buf[LINE_MAX]; | |
43 | ssize_t l; | |
44 | int r; | |
45 | ||
46 | r = poll(&pollfd, 1, 0); | |
47 | if (r < 0) { | |
48 | if (errno == EINTR) | |
49 | continue; | |
50 | ||
51 | return -errno; | |
52 | ||
53 | } else if (r == 0) | |
54 | return 0; | |
55 | ||
56 | l = read(fd, buf, sizeof(buf)); | |
57 | if (l < 0) { | |
58 | ||
59 | if (errno == EINTR) | |
60 | continue; | |
61 | ||
62 | if (errno == EAGAIN) | |
63 | return 0; | |
64 | ||
65 | return -errno; | |
66 | } else if (l == 0) | |
67 | return 0; | |
68 | } | |
69 | } | |
70 | ||
71 | ssize_t loop_read(int fd, void *buf, size_t nbytes, bool do_poll) { | |
72 | uint8_t *p = buf; | |
73 | ssize_t n = 0; | |
74 | ||
75 | assert(fd >= 0); | |
76 | assert(buf); | |
77 | ||
78 | /* If called with nbytes == 0, let's call read() at least | |
79 | * once, to validate the operation */ | |
80 | ||
81 | if (nbytes > (size_t) SSIZE_MAX) | |
82 | return -EINVAL; | |
83 | ||
84 | do { | |
85 | ssize_t k; | |
86 | ||
87 | k = read(fd, p, nbytes); | |
88 | if (k < 0) { | |
89 | if (errno == EINTR) | |
90 | continue; | |
91 | ||
92 | if (errno == EAGAIN && do_poll) { | |
93 | ||
94 | /* We knowingly ignore any return value here, | |
95 | * and expect that any error/EOF is reported | |
96 | * via read() */ | |
97 | ||
98 | (void) fd_wait_for_event(fd, POLLIN, USEC_INFINITY); | |
99 | continue; | |
100 | } | |
101 | ||
102 | return n > 0 ? n : -errno; | |
103 | } | |
104 | ||
105 | if (k == 0) | |
106 | return n; | |
107 | ||
108 | assert((size_t) k <= nbytes); | |
109 | ||
110 | p += k; | |
111 | nbytes -= k; | |
112 | n += k; | |
113 | } while (nbytes > 0); | |
114 | ||
115 | return n; | |
116 | } | |
117 | ||
118 | int loop_read_exact(int fd, void *buf, size_t nbytes, bool do_poll) { | |
119 | ssize_t n; | |
120 | ||
121 | n = loop_read(fd, buf, nbytes, do_poll); | |
122 | if (n < 0) | |
123 | return (int) n; | |
124 | if ((size_t) n != nbytes) | |
125 | return -EIO; | |
126 | ||
127 | return 0; | |
128 | } | |
129 | ||
130 | int loop_write(int fd, const void *buf, size_t nbytes, bool do_poll) { | |
131 | const uint8_t *p = buf; | |
132 | ||
133 | assert(fd >= 0); | |
134 | assert(buf); | |
135 | ||
136 | if (nbytes > (size_t) SSIZE_MAX) | |
137 | return -EINVAL; | |
138 | ||
139 | do { | |
140 | ssize_t k; | |
141 | ||
142 | k = write(fd, p, nbytes); | |
143 | if (k < 0) { | |
144 | if (errno == EINTR) | |
145 | continue; | |
146 | ||
147 | if (errno == EAGAIN && do_poll) { | |
148 | /* We knowingly ignore any return value here, | |
149 | * and expect that any error/EOF is reported | |
150 | * via write() */ | |
151 | ||
152 | (void) fd_wait_for_event(fd, POLLOUT, USEC_INFINITY); | |
153 | continue; | |
154 | } | |
155 | ||
156 | return -errno; | |
157 | } | |
158 | ||
159 | if (_unlikely_(nbytes > 0 && k == 0)) /* Can't really happen */ | |
160 | return -EIO; | |
161 | ||
162 | assert((size_t) k <= nbytes); | |
163 | ||
164 | p += k; | |
165 | nbytes -= k; | |
166 | } while (nbytes > 0); | |
167 | ||
168 | return 0; | |
169 | } | |
170 | ||
171 | int pipe_eof(int fd) { | |
172 | struct pollfd pollfd = { | |
173 | .fd = fd, | |
174 | .events = POLLIN|POLLHUP, | |
175 | }; | |
176 | ||
177 | int r; | |
178 | ||
179 | r = poll(&pollfd, 1, 0); | |
180 | if (r < 0) | |
181 | return -errno; | |
182 | ||
183 | if (r == 0) | |
184 | return 0; | |
185 | ||
186 | return pollfd.revents & POLLHUP; | |
187 | } | |
188 | ||
189 | int fd_wait_for_event(int fd, int event, usec_t t) { | |
190 | ||
191 | struct pollfd pollfd = { | |
192 | .fd = fd, | |
193 | .events = event, | |
194 | }; | |
195 | ||
196 | struct timespec ts; | |
197 | int r; | |
198 | ||
199 | r = ppoll(&pollfd, 1, t == USEC_INFINITY ? NULL : timespec_store(&ts, t), NULL); | |
200 | if (r < 0) | |
201 | return -errno; | |
202 | ||
203 | if (r == 0) | |
204 | return 0; | |
205 | ||
206 | return pollfd.revents; | |
207 | } | |
208 | ||
209 | static size_t nul_length(const uint8_t *p, size_t sz) { | |
210 | size_t n = 0; | |
211 | ||
212 | while (sz > 0) { | |
213 | if (*p != 0) | |
214 | break; | |
215 | ||
216 | n++; | |
217 | p++; | |
218 | sz--; | |
219 | } | |
220 | ||
221 | return n; | |
222 | } | |
223 | ||
224 | ssize_t sparse_write(int fd, const void *p, size_t sz, size_t run_length) { | |
225 | const uint8_t *q, *w, *e; | |
226 | ssize_t l; | |
227 | ||
228 | q = w = p; | |
229 | e = q + sz; | |
230 | while (q < e) { | |
231 | size_t n; | |
232 | ||
233 | n = nul_length(q, e - q); | |
234 | ||
235 | /* If there are more than the specified run length of | |
236 | * NUL bytes, or if this is the beginning or the end | |
237 | * of the buffer, then seek instead of write */ | |
238 | if ((n > run_length) || | |
239 | (n > 0 && q == p) || | |
240 | (n > 0 && q + n >= e)) { | |
241 | if (q > w) { | |
242 | l = write(fd, w, q - w); | |
243 | if (l < 0) | |
244 | return -errno; | |
245 | if (l != q -w) | |
246 | return -EIO; | |
247 | } | |
248 | ||
249 | if (lseek(fd, n, SEEK_CUR) == (off_t) -1) | |
250 | return -errno; | |
251 | ||
252 | q += n; | |
253 | w = q; | |
254 | } else if (n > 0) | |
255 | q += n; | |
256 | else | |
313cefa1 | 257 | q++; |
c004493c LP |
258 | } |
259 | ||
260 | if (q > w) { | |
261 | l = write(fd, w, q - w); | |
262 | if (l < 0) | |
263 | return -errno; | |
264 | if (l != q - w) | |
265 | return -EIO; | |
266 | } | |
267 | ||
268 | return q - (const uint8_t*) p; | |
269 | } |