1 /* SPDX-License-Identifier: LGPL-2.1+ */
3 Copyright 2010 Lennart Poettering
14 #include "time-util.h"
16 int flush_fd(int fd) {
17 struct pollfd pollfd = {
23 /* Read from the specified file descriptor, until POLLIN is not set anymore, throwing away everything
24 * read. Note that some file descriptors (notable IP sockets) will trigger POLLIN even when no data can be read
25 * (due to IP packet checksum mismatches), hence this function is only safe to be non-blocking if the fd used
26 * was set to non-blocking too. */
33 r = poll(&pollfd, 1, 0);
43 l = read(fd, buf, sizeof(buf));
60 ssize_t loop_read(int fd, void *buf, size_t nbytes, bool do_poll) {
67 /* If called with nbytes == 0, let's call read() at least
68 * once, to validate the operation */
70 if (nbytes > (size_t) SSIZE_MAX)
76 k = read(fd, p, nbytes);
81 if (errno == EAGAIN && do_poll) {
83 /* We knowingly ignore any return value here,
84 * and expect that any error/EOF is reported
87 (void) fd_wait_for_event(fd, POLLIN, USEC_INFINITY);
91 return n > 0 ? n : -errno;
97 assert((size_t) k <= nbytes);
102 } while (nbytes > 0);
107 int loop_read_exact(int fd, void *buf, size_t nbytes, bool do_poll) {
110 n = loop_read(fd, buf, nbytes, do_poll);
113 if ((size_t) n != nbytes)
119 int loop_write(int fd, const void *buf, size_t nbytes, bool do_poll) {
120 const uint8_t *p = buf;
125 if (_unlikely_(nbytes > (size_t) SSIZE_MAX))
131 k = write(fd, p, nbytes);
136 if (errno == EAGAIN && do_poll) {
137 /* We knowingly ignore any return value here,
138 * and expect that any error/EOF is reported
141 (void) fd_wait_for_event(fd, POLLOUT, USEC_INFINITY);
148 if (_unlikely_(nbytes > 0 && k == 0)) /* Can't really happen */
151 assert((size_t) k <= nbytes);
155 } while (nbytes > 0);
160 int pipe_eof(int fd) {
161 struct pollfd pollfd = {
163 .events = POLLIN|POLLHUP,
168 r = poll(&pollfd, 1, 0);
175 return pollfd.revents & POLLHUP;
178 int fd_wait_for_event(int fd, int event, usec_t t) {
180 struct pollfd pollfd = {
188 r = ppoll(&pollfd, 1, t == USEC_INFINITY ? NULL : timespec_store(&ts, t), NULL);
194 return pollfd.revents;
197 static size_t nul_length(const uint8_t *p, size_t sz) {
212 ssize_t sparse_write(int fd, const void *p, size_t sz, size_t run_length) {
213 const uint8_t *q, *w, *e;
221 n = nul_length(q, e - q);
223 /* If there are more than the specified run length of
224 * NUL bytes, or if this is the beginning or the end
225 * of the buffer, then seek instead of write */
226 if ((n > run_length) ||
228 (n > 0 && q + n >= e)) {
230 l = write(fd, w, q - w);
237 if (lseek(fd, n, SEEK_CUR) == (off_t) -1)
249 l = write(fd, w, q - w);
256 return q - (const uint8_t*) p;