15057632786

Committed 15 May 2025 09:01PM UTC coverage: 72.267% (+0.02%) from 72.244%

Build # 15057632786

Build Type

push

github

Committed by

bluca

Commit Message

man: document how to hook stuff into system wakeup

Fixes: #6364

Coverage Stats

298523 of 413084 relevant lines covered (72.27%)

738132.88 hits per line

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76.03

/src/basic/io-util.c

/* SPDX-License-Identifier: LGPL-2.1-or-later */

#include <errno.h>
#include <limits.h>
#include <stdio.h>
#include <unistd.h>

#include "errno-util.h"
#include "io-util.h"
#include "iovec-util.h"
#include "string-util.h"
#include "time-util.h"

int flush_fd(int fd) {
        int count = 0;

        /* Read from the specified file descriptor, until POLLIN is not set anymore, throwing away everything
         * read. Note that some file descriptors (notable IP sockets) will trigger POLLIN even when no data can be read
         * (due to IP packet checksum mismatches), hence this function is only safe to be non-blocking if the fd used
         * was set to non-blocking too. */

        for (;;) {
                char buf[LINE_MAX];
                ssize_t l;
                int r;

                r = fd_wait_for_event(fd, POLLIN, 0);
                if (r < 0) {
                        if (r == -EINTR)
                                continue;

                        return r;
                }
                if (r == 0)
                        return count;

                l = read(fd, buf, sizeof(buf));
                if (l < 0) {
                        if (errno == EINTR)
                                continue;

                        if (errno == EAGAIN)
                                return count;

                        return -errno;
                } else if (l == 0)
                        return count;

                count += (int) l;
        }
}

ssize_t loop_read(int fd, void *buf, size_t nbytes, bool do_poll) {
        uint8_t *p = ASSERT_PTR(buf);
        ssize_t n = 0;

        assert(fd >= 0);

        /* If called with nbytes == 0, let's call read() at least once, to validate the operation */

        if (nbytes > (size_t) SSIZE_MAX)
                return -EINVAL;

        do {
                ssize_t k;

                k = read(fd, p, nbytes);
                if (k < 0) {
                        if (errno == EINTR)
                                continue;

                        if (errno == EAGAIN && do_poll) {

                                /* We knowingly ignore any return value here,
                                 * and expect that any error/EOF is reported
                                 * via read() */

                                (void) fd_wait_for_event(fd, POLLIN, USEC_INFINITY);
                                continue;
                        }

                        return n > 0 ? n : -errno;
                }

                if (k == 0)
                        return n;

                assert((size_t) k <= nbytes);
                assert(k <= SSIZE_MAX - n);

                p += k;
                nbytes -= k;
                n += k;
        } while (nbytes > 0);

        return n;
}

int loop_read_exact(int fd, void *buf, size_t nbytes, bool do_poll) {
        ssize_t n;

        n = loop_read(fd, buf, nbytes, do_poll);
        if (n < 0)
                return (int) n;
        if ((size_t) n != nbytes)
                return -EIO;

        return 0;
}

int loop_write_full(int fd, const void *buf, size_t nbytes, usec_t timeout) {
        const uint8_t *p;
        usec_t end;
        int r;

        assert(fd >= 0);
        assert(buf || nbytes == 0);

        if (nbytes == 0) {
                static const dummy_t dummy[0];
                assert_cc(sizeof(dummy) == 0);
                p = (const void*) dummy; /* Some valid pointer, in case NULL was specified */
        } else {
                if (nbytes == SIZE_MAX)
                        nbytes = strlen(buf);
                else if (_unlikely_(nbytes > (size_t) SSIZE_MAX))
                        return -EINVAL;

                p = buf;
        }

        /* When timeout is 0 or USEC_INFINITY this is not used. But we initialize it to a sensible value. */
        end = timestamp_is_set(timeout) ? usec_add(now(CLOCK_MONOTONIC), timeout) : USEC_INFINITY;

        do {
                ssize_t k;

                k = write(fd, p, nbytes);
                if (k < 0) {
                        if (errno == EINTR)
                                continue;

                        if (errno != EAGAIN || timeout == 0)
                                return -errno;

                        usec_t wait_for;

                        if (timeout == USEC_INFINITY)
                                wait_for = USEC_INFINITY;
                        else {
                                usec_t t = now(CLOCK_MONOTONIC);
                                if (t >= end)
                                        return -ETIME;

                                wait_for = usec_sub_unsigned(end, t);
                        }

                        r = fd_wait_for_event(fd, POLLOUT, wait_for);
                        if (timeout == USEC_INFINITY || ERRNO_IS_NEG_TRANSIENT(r))
                                /* If timeout == USEC_INFINITY we knowingly ignore any return value
                                 * here, and expect that any error/EOF is reported via write() */
                                continue;
                        if (r < 0)
                                return r;
                        if (r == 0)
                                return -ETIME;
                        continue;
                }

                if (_unlikely_(nbytes > 0 && k == 0)) /* Can't really happen */
                        return -EIO;

                assert((size_t) k <= nbytes);

                p += k;
                nbytes -= k;
        } while (nbytes > 0);

        return 0;
}

int pipe_eof(int fd) {
        int r;

        r = fd_wait_for_event(fd, POLLIN, 0);
        if (r <= 0)
                return r;

        return !!(r & POLLHUP);
}

int ppoll_usec_full(struct pollfd *fds, size_t nfds, usec_t timeout, const sigset_t *ss) {
        int r;

        assert(fds || nfds == 0);

        /* This is a wrapper around ppoll() that does primarily two things:
         *
         *  ✅ Takes a usec_t instead of a struct timespec
         *
         *  ✅ Guarantees that if an invalid fd is specified we return EBADF (i.e. converts POLLNVAL to
         *     EBADF). This is done because EBADF is a programming error usually, and hence should bubble up
         *     as error, and not be eaten up as non-error POLLNVAL event.
         *
         *  ⚠️ ⚠️ ⚠️ Note that this function does not add any special handling for EINTR. Don't forget
         *  poll()/ppoll() will return with EINTR on any received signal always, there is no automatic
         *  restarting via SA_RESTART available. Thus, typically you want to handle EINTR not as an error,
         *  but just as reason to restart things, under the assumption you use a more appropriate mechanism
         *  to handle signals, such as signalfd() or signal handlers. ⚠️ ⚠️ ⚠️
         */

        if (nfds == 0 && timeout == 0)
                return 0;

        r = ppoll(fds, nfds, timeout == USEC_INFINITY ? NULL : TIMESPEC_STORE(timeout), ss);
        if (r < 0)
                return -errno;
        if (r == 0)
                return 0;

        for (size_t i = 0, n = r; i < nfds && n > 0; i++) {
                if (fds[i].revents == 0)
                        continue;
                if (fds[i].revents & POLLNVAL)
                        return -EBADF;
                n--;
        }

        return r;
}

int fd_wait_for_event(int fd, int event, usec_t timeout) {
        struct pollfd pollfd = {
                .fd = fd,
                .events = event,
        };
        int r;

        /* ⚠️ ⚠️ ⚠️ Keep in mind you almost certainly want to handle -EINTR gracefully in the caller, see
         * ppoll_usec() above! ⚠️ ⚠️ ⚠️ */

        r = ppoll_usec(&pollfd, 1, timeout);
        if (r <= 0)
                return r;

        return pollfd.revents;
}

static size_t nul_length(const uint8_t *p, size_t sz) {
        size_t n = 0;

        while (sz > 0) {
                if (*p != 0)
                        break;

                n++;
                p++;
                sz--;
        }

        return n;
}

ssize_t sparse_write(int fd, const void *p, size_t sz, size_t run_length) {
        const uint8_t *q, *w, *e;
        ssize_t l;

        q = w = p;
        e = q + sz;
        while (q < e) {
                size_t n;

                n = nul_length(q, e - q);

                /* If there are more than the specified run length of
                 * NUL bytes, or if this is the beginning or the end
                 * of the buffer, then seek instead of write */
                if ((n > run_length) ||
                    (n > 0 && q == p) ||
                    (n > 0 && q + n >= e)) {
                        if (q > w) {
                                l = write(fd, w, q - w);
                                if (l < 0)
                                        return -errno;
                                if (l != q -w)
                                        return -EIO;
                        }

                        if (lseek(fd, n, SEEK_CUR) < 0)
                                return -errno;

                        q += n;
                        w = q;
                } else if (n > 0)
                        q += n;
                else
                        q++;
        }

        if (q > w) {
                l = write(fd, w, q - w);
                if (l < 0)
                        return -errno;
                if (l != q - w)
                        return -EIO;
        }

        return q - (const uint8_t*) p;
}

1	/* SPDX-License-Identifier: LGPL-2.1-or-later */
2
3	#include <errno.h>
4	#include <limits.h>
5	#include <stdio.h>
6	#include <unistd.h>
7
8	#include "errno-util.h"
9	#include "io-util.h"
10	#include "iovec-util.h"
11	#include "string-util.h"
12	#include "time-util.h"
13
14	int flush_fd(int fd) {	3,851✔
15	int count = 0;	3,851✔
16
17	/* Read from the specified file descriptor, until POLLIN is not set anymore, throwing away everything
18	* read. Note that some file descriptors (notable IP sockets) will trigger POLLIN even when no data can be read
19	* (due to IP packet checksum mismatches), hence this function is only safe to be non-blocking if the fd used
20	* was set to non-blocking too. */
21
22	for (;;) {	7,009✔
23	char buf[LINE_MAX];	7,009✔
24	ssize_t l;	7,009✔
25	int r;	7,009✔
26
27	r = fd_wait_for_event(fd, POLLIN, 0);	7,009✔
28	if (r < 0) {	7,009✔
29	if (r == -EINTR)	×
30	continue;	×
31
32	return r;	3,851✔
33	}
34	if (r == 0)	7,009✔
35	return count;
36
37	l = read(fd, buf, sizeof(buf));	3,158✔
38	if (l < 0) {	3,158✔
39	if (errno == EINTR)	×
40	continue;	×
41
42	if (errno == EAGAIN)	×
43	return count;
44
45	return -errno;	×
46	} else if (l == 0)	3,158✔
47	return count;
48
49	count += (int) l;	3,158✔
50	}
51	}
52
53	ssize_t loop_read(int fd, void *buf, size_t nbytes, bool do_poll) {	12,977✔
54	uint8_t *p = ASSERT_PTR(buf);	12,977✔
55	ssize_t n = 0;	12,977✔
56
57	assert(fd >= 0);	12,977✔
58
59	/* If called with nbytes == 0, let's call read() at least once, to validate the operation */
60
61	if (nbytes > (size_t) SSIZE_MAX)	12,977✔
62	return -EINVAL;
63
64	do {	24,250✔
65	ssize_t k;	24,250✔
66
67	k = read(fd, p, nbytes);	24,250✔
68	if (k < 0) {	24,250✔
69	if (errno == EINTR)	×
70	continue;	×
71
72	if (errno == EAGAIN && do_poll) {	×
73
74	/* We knowingly ignore any return value here,
75	* and expect that any error/EOF is reported
76	* via read() */
77
78	(void) fd_wait_for_event(fd, POLLIN, USEC_INFINITY);	×
79	continue;	×
80	}
81
82	return n > 0 ? n : -errno;	×
83	}
84
85	if (k == 0)	24,250✔
86	return n;
87
88	assert((size_t) k <= nbytes);	12,885✔
89	assert(k <= SSIZE_MAX - n);	12,885✔
90
91	p += k;	12,885✔
92	nbytes -= k;	12,885✔
93	n += k;	12,885✔
94	} while (nbytes > 0);	12,885✔
95
96	return n;
97	}
98
99	int loop_read_exact(int fd, void *buf, size_t nbytes, bool do_poll) {	1,447✔
100	ssize_t n;	1,447✔
101
102	n = loop_read(fd, buf, nbytes, do_poll);	1,447✔
103	if (n < 0)	1,447✔
104	return (int) n;	×
105	if ((size_t) n != nbytes)	1,447✔
106	return -EIO;	×
107
108	return 0;
109	}
110
111	int loop_write_full(int fd, const void *buf, size_t nbytes, usec_t timeout) {	40,486✔
112	const uint8_t *p;	40,486✔
113	usec_t end;	40,486✔
114	int r;	40,486✔
115
116	assert(fd >= 0);	40,486✔
117	assert(buf \|\| nbytes == 0);	40,486✔
118
119	if (nbytes == 0) {	40,486✔
120	static const dummy_t dummy[0];
121	assert_cc(sizeof(dummy) == 0);
122	p = (const void) dummy; / Some valid pointer, in case NULL was specified */
123	} else {
124	if (nbytes == SIZE_MAX)	40,464✔
125	nbytes = strlen(buf);	410✔
126	else if (_unlikely_(nbytes > (size_t) SSIZE_MAX))	40,054✔
127	return -EINVAL;
128
129	p = buf;
130	}
131
132	/* When timeout is 0 or USEC_INFINITY this is not used. But we initialize it to a sensible value. */
133	end = timestamp_is_set(timeout) ? usec_add(now(CLOCK_MONOTONIC), timeout) : USEC_INFINITY;	40,587✔
134
135	do {	40,486✔
136	ssize_t k;	40,486✔
137
138	k = write(fd, p, nbytes);	40,486✔
139	if (k < 0) {	40,486✔
140	if (errno == EINTR)	1✔
141	continue;	×
142
143	if (errno != EAGAIN \|\| timeout == 0)	1✔
144	return -errno;	1✔
145
146	usec_t wait_for;	×
147
148	if (timeout == USEC_INFINITY)	×
149	wait_for = USEC_INFINITY;
150	else {
151	usec_t t = now(CLOCK_MONOTONIC);	×
152	if (t >= end)	×
153	return -ETIME;
154
155	wait_for = usec_sub_unsigned(end, t);	×
156	}
157
158	r = fd_wait_for_event(fd, POLLOUT, wait_for);	×
159	if (timeout == USEC_INFINITY \|\| ERRNO_IS_NEG_TRANSIENT(r))	×
160	/* If timeout == USEC_INFINITY we knowingly ignore any return value
161	* here, and expect that any error/EOF is reported via write() */
162	continue;	×
163	if (r < 0)	×
164	return r;
165	if (r == 0)	×
166	return -ETIME;
167	continue;	×
168	}
169
170	if (_unlikely_(nbytes > 0 && k == 0)) /* Can't really happen */	40,485✔
171	return -EIO;
172
173	assert((size_t) k <= nbytes);	40,485✔
174
175	p += k;	40,485✔
176	nbytes -= k;	40,485✔
177	} while (nbytes > 0);	40,485✔
178
179	return 0;
180	}
181
182	int pipe_eof(int fd) {	×
183	int r;	×
184
185	r = fd_wait_for_event(fd, POLLIN, 0);	×
186	if (r <= 0)	×
187	return r;
188
189	return !!(r & POLLHUP);	×
190	}
191
192	int ppoll_usec_full(struct pollfd fds, size_t nfds, usec_t timeout, const sigset_t ss) {	373,530✔
193	int r;	373,530✔
194
195	assert(fds \|\| nfds == 0);	373,530✔
196
197	/* This is a wrapper around ppoll() that does primarily two things:
198	*
199	* ✅ Takes a usec_t instead of a struct timespec
200	*
201	* ✅ Guarantees that if an invalid fd is specified we return EBADF (i.e. converts POLLNVAL to
202	* EBADF). This is done because EBADF is a programming error usually, and hence should bubble up
203	* as error, and not be eaten up as non-error POLLNVAL event.
204	*
205	* ⚠️ ⚠️ ⚠️ Note that this function does not add any special handling for EINTR. Don't forget
206	* poll()/ppoll() will return with EINTR on any received signal always, there is no automatic
207	* restarting via SA_RESTART available. Thus, typically you want to handle EINTR not as an error,
208	* but just as reason to restart things, under the assumption you use a more appropriate mechanism
209	* to handle signals, such as signalfd() or signal handlers. ⚠️ ⚠️ ⚠️
210	*/
211
212	if (nfds == 0 && timeout == 0)	373,530✔
213	return 0;	373,530✔
214
215	r = ppoll(fds, nfds, timeout == USEC_INFINITY ? NULL : TIMESPEC_STORE(timeout), ss);	373,530✔
216	if (r < 0)	373,530✔
217	return -errno;	×
218	if (r == 0)	373,530✔
219	return 0;
220
221	for (size_t i = 0, n = r; i < nfds && n > 0; i++) {	647,230✔
222	if (fds[i].revents == 0)	324,234✔
223	continue;	1,182✔
224	if (fds[i].revents & POLLNVAL)	323,052✔
225	return -EBADF;
226	n--;	323,052✔
227	}
228
229	return r;
230	}
231
232	int fd_wait_for_event(int fd, int event, usec_t timeout) {	67,678✔
233	struct pollfd pollfd = {	67,678✔
234	.fd = fd,
235	.events = event,
236	};
237	int r;	67,678✔
238
239	/* ⚠️ ⚠️ ⚠️ Keep in mind you almost certainly want to handle -EINTR gracefully in the caller, see
240	* ppoll_usec() above! ⚠️ ⚠️ ⚠️ */
241
242	r = ppoll_usec(&pollfd, 1, timeout);	67,678✔
243	if (r <= 0)	67,678✔
244	return r;	67,678✔
245
246	return pollfd.revents;	17,147✔
247	}
248
249	static size_t nul_length(const uint8_t *p, size_t sz) {	315,274,448✔
250	size_t n = 0;	315,274,448✔
251
252	while (sz > 0) {	570,103,858✔
253	if (*p != 0)	570,086,757✔
254	break;
255
256	n++;	254,829,410✔
257	p++;	254,829,410✔
258	sz--;	254,829,410✔
259	}
260
261	return n;	315,274,448✔
262	}
263
264	ssize_t sparse_write(int fd, const void *p, size_t sz, size_t run_length) {	33,135✔
265	const uint8_t q, w, *e;	33,135✔
266	ssize_t l;	33,135✔
267
268	q = w = p;	33,135✔
269	e = q + sz;	33,135✔
270	while (q < e) {	315,307,583✔
271	size_t n;	315,274,448✔
272
273	n = nul_length(q, e - q);	315,274,448✔
274
275	/* If there are more than the specified run length of
276	* NUL bytes, or if this is the beginning or the end
277	* of the buffer, then seek instead of write */
278	if ((n > run_length) \|\|	315,274,448✔
279	(n > 0 && q == p) \|\|	315,107,520✔
280	(n > 0 && q + n >= e)) {	27,696,129✔
281	if (q > w) {	177,097✔
282	l = write(fd, w, q - w);	163,758✔
283	if (l < 0)	163,758✔
284	return -errno;	×
285	if (l != q -w)	163,758✔
286	return -EIO;
287	}
288
289	if (lseek(fd, n, SEEK_CUR) < 0)	177,097✔
290	return -errno;	×
291
292	q += n;	177,097✔
293	w = q;	177,097✔
294	} else if (n > 0)	27,689,775✔
295	q += n;
296	else
297	q++;	287,407,576✔
298	}
299
300	if (q > w) {	33,135✔
301	l = write(fd, w, q - w);	16,034✔
302	if (l < 0)	16,034✔
303	return -errno;	×
304	if (l != q - w)	16,034✔
305	return -EIO;
306	}
307
308	return q - (const uint8_t*) p;	33,135✔
309	}

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