src/basic/io-util.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <errno.h>
   4 #include <limits.h>
   5 #include <poll.h>
   6 #include <stdio.h>
   7 #include <time.h>
   8 #include <unistd.h>
   9
  10 #include "io-util.h"
  11 #include "string-util.h"
  12 #include "time-util.h"
  13
  14 int flush_fd(int fd) {
  15         struct pollfd pollfd = {
  16                 .fd = fd,
  17                 .events = POLLIN,
  18         };
  19         int count = 0;
  20
  21         /* Read from the specified file descriptor, until POLLIN is not set anymore, throwing away everything
  22          * read. Note that some file descriptors (notable IP sockets) will trigger POLLIN even when no data can be read
  23          * (due to IP packet checksum mismatches), hence this function is only safe to be non-blocking if the fd used
  24          * was set to non-blocking too. */
  25
  26         for (;;) {
  27                 char buf[LINE_MAX];
  28                 ssize_t l;
  29                 int r;
  30
  31                 r = poll(&pollfd, 1, 0);
  32                 if (r < 0) {
  33                         if (errno == EINTR)
  34                                 continue;
  35
  36                         return -errno;
  37
  38                 } else if (r == 0)
  39                         return count;
  40
  41                 l = read(fd, buf, sizeof(buf));
  42                 if (l < 0) {
  43
  44                         if (errno == EINTR)
  45                                 continue;
  46
  47                         if (errno == EAGAIN)
  48                                 return count;
  49
  50                         return -errno;
  51                 } else if (l == 0)
  52                         return count;
  53
  54                 count += (int) l;
  55         }
  56 }
  57
  58 ssize_t loop_read(int fd, void *buf, size_t nbytes, bool do_poll) {
  59         uint8_t *p = buf;
  60         ssize_t n = 0;
  61
  62         assert(fd >= 0);
  63         assert(buf);
  64
  65         /* If called with nbytes == 0, let's call read() at least
  66          * once, to validate the operation */
  67
  68         if (nbytes > (size_t) SSIZE_MAX)
  69                 return -EINVAL;
  70
  71         do {
  72                 ssize_t k;
  73
  74                 k = read(fd, p, nbytes);
  75                 if (k < 0) {
  76                         if (errno == EINTR)
  77                                 continue;
  78
  79                         if (errno == EAGAIN && do_poll) {
  80
  81                                 /* We knowingly ignore any return value here,
  82                                  * and expect that any error/EOF is reported
  83                                  * via read() */
  84
  85                                 (void) fd_wait_for_event(fd, POLLIN, USEC_INFINITY);
  86                                 continue;
  87                         }
  88
  89                         return n > 0 ? n : -errno;
  90                 }
  91
  92                 if (k == 0)
  93                         return n;
  94
  95                 assert((size_t) k <= nbytes);
  96
  97                 p += k;
  98                 nbytes -= k;
  99                 n += k;
 100         } while (nbytes > 0);
 101
 102         return n;
 103 }
 104
 105 int loop_read_exact(int fd, void *buf, size_t nbytes, bool do_poll) {
 106         ssize_t n;
 107
 108         n = loop_read(fd, buf, nbytes, do_poll);
 109         if (n < 0)
 110                 return (int) n;
 111         if ((size_t) n != nbytes)
 112                 return -EIO;
 113
 114         return 0;
 115 }
 116
 117 int loop_write(int fd, const void *buf, size_t nbytes, bool do_poll) {
 118         const uint8_t *p = buf;
 119
 120         assert(fd >= 0);
 121         assert(buf);
 122
 123         if (_unlikely_(nbytes > (size_t) SSIZE_MAX))
 124                 return -EINVAL;
 125
 126         do {
 127                 ssize_t k;
 128
 129                 k = write(fd, p, nbytes);
 130                 if (k < 0) {
 131                         if (errno == EINTR)
 132                                 continue;
 133
 134                         if (errno == EAGAIN && do_poll) {
 135                                 /* We knowingly ignore any return value here,
 136                                  * and expect that any error/EOF is reported
 137                                  * via write() */
 138
 139                                 (void) fd_wait_for_event(fd, POLLOUT, USEC_INFINITY);
 140                                 continue;
 141                         }
 142
 143                         return -errno;
 144                 }
 145
 146                 if (_unlikely_(nbytes > 0 && k == 0)) /* Can't really happen */
 147                         return -EIO;
 148
 149                 assert((size_t) k <= nbytes);
 150
 151                 p += k;
 152                 nbytes -= k;
 153         } while (nbytes > 0);
 154
 155         return 0;
 156 }
 157
 158 int pipe_eof(int fd) {
 159         struct pollfd pollfd = {
 160                 .fd = fd,
 161                 .events = POLLIN|POLLHUP,
 162         };
 163
 164         int r;
 165
 166         r = poll(&pollfd, 1, 0);
 167         if (r < 0)
 168                 return -errno;
 169
 170         if (r == 0)
 171                 return 0;
 172
 173         return pollfd.revents & POLLHUP;
 174 }
 175
 176 int fd_wait_for_event(int fd, int event, usec_t t) {
 177
 178         struct pollfd pollfd = {
 179                 .fd = fd,
 180                 .events = event,
 181         };
 182
 183         struct timespec ts;
 184         int r;
 185
 186         r = ppoll(&pollfd, 1, t == USEC_INFINITY ? NULL : timespec_store(&ts, t), NULL);
 187         if (r < 0)
 188                 return -errno;
 189         if (r == 0)
 190                 return 0;
 191
 192         return pollfd.revents;
 193 }
 194
 195 static size_t nul_length(const uint8_t *p, size_t sz) {
 196         size_t n = 0;
 197
 198         while (sz > 0) {
 199                 if (*p != 0)
 200                         break;
 201
 202                 n++;
 203                 p++;
 204                 sz--;
 205         }
 206
 207         return n;
 208 }
 209
 210 ssize_t sparse_write(int fd, const void *p, size_t sz, size_t run_length) {
 211         const uint8_t *q, *w, *e;
 212         ssize_t l;
 213
 214         q = w = p;
 215         e = q + sz;
 216         while (q < e) {
 217                 size_t n;
 218
 219                 n = nul_length(q, e - q);
 220
 221                 /* If there are more than the specified run length of
 222                  * NUL bytes, or if this is the beginning or the end
 223                  * of the buffer, then seek instead of write */
 224                 if ((n > run_length) ||
 225                     (n > 0 && q == p) ||
 226                     (n > 0 && q + n >= e)) {
 227                         if (q > w) {
 228                                 l = write(fd, w, q - w);
 229                                 if (l < 0)
 230                                         return -errno;
 231                                 if (l != q -w)
 232                                         return -EIO;
 233                         }
 234
 235                         if (lseek(fd, n, SEEK_CUR) == (off_t) -1)
 236                                 return -errno;
 237
 238                         q += n;
 239                         w = q;
 240                 } else if (n > 0)
 241                         q += n;
 242                 else
 243                         q++;
 244         }
 245
 246         if (q > w) {
 247                 l = write(fd, w, q - w);
 248                 if (l < 0)
 249                         return -errno;
 250                 if (l != q - w)
 251                         return -EIO;
 252         }
 253
 254         return q - (const uint8_t*) p;
 255 }
 256
 257 char* set_iovec_string_field(struct iovec *iovec, size_t *n_iovec, const char *field, const char *value) {
 258         char *x;
 259
 260         x = strappend(field, value);
 261         if (x)
 262                 iovec[(*n_iovec)++] = IOVEC_MAKE_STRING(x);
 263         return x;
 264 }