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/***
This file is part of systemd.
Copyright 2010 Lennart Poettering
systemd is free software; you can redistribute it and/or modify it
under the terms of the GNU Lesser General Public License as published by
the Free Software Foundation; either version 2.1 of the License, or
(at your option) any later version.
systemd is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
Lesser General Public License for more details.
You should have received a copy of the GNU Lesser General Public License
along with systemd; If not, see <http://www.gnu.org/licenses/>.
***/
#include <errno.h>
#include <limits.h>
#include <poll.h>
#include <stdio.h>
#include <time.h>
#include <unistd.h>
#include "io-util.h"
#include "time-util.h"
int flush_fd(int fd) {
struct pollfd pollfd = {
.fd = fd,
.events = POLLIN,
};
/* 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 = poll(&pollfd, 1, 0);
if (r < 0) {
if (errno == EINTR)
continue;
return -errno;
} else if (r == 0)
return 0;
l = read(fd, buf, sizeof(buf));
if (l < 0) {
if (errno == EINTR)
continue;
if (errno == EAGAIN)
return 0;
return -errno;
} else if (l == 0)
return 0;
}
}
ssize_t loop_read(int fd, void *buf, size_t nbytes, bool do_poll) {
uint8_t *p = buf;
ssize_t n = 0;
assert(fd >= 0);
assert(buf);
/* 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(int fd, const void *buf, size_t nbytes, bool do_poll) {
const uint8_t *p = buf;
assert(fd >= 0);
assert(buf);
if (nbytes > (size_t) SSIZE_MAX)
return -EINVAL;
do {
ssize_t k;
k = write(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 write() */
(void) fd_wait_for_event(fd, POLLOUT, USEC_INFINITY);
continue;
}
return -errno;
}
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) {
struct pollfd pollfd = {
.fd = fd,
.events = POLLIN|POLLHUP,
};
int r;
r = poll(&pollfd, 1, 0);
if (r < 0)
return -errno;
if (r == 0)
return 0;
return pollfd.revents & POLLHUP;
}
int fd_wait_for_event(int fd, int event, usec_t t) {
struct pollfd pollfd = {
.fd = fd,
.events = event,
};
struct timespec ts;
int r;
r = ppoll(&pollfd, 1, t == USEC_INFINITY ? NULL : timespec_store(&ts, t), NULL);
if (r < 0)
return -errno;
if (r == 0)
return 0;
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) == (off_t) -1)
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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