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/* 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);
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;
}
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(struct pollfd *fds, size_t nfds, usec_t timeout) {
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)
return 0;
r = ppoll(fds, nfds, timeout == USEC_INFINITY ? NULL : TIMESPEC_STORE(timeout), NULL);
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;
}
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