src/basic/fileio.c

   1 /* SPDX-License-Identifier: LGPL-2.1+ */
   2
   3 #include <ctype.h>
   4 #include <errno.h>
   5 #include <fcntl.h>
   6 #include <limits.h>
   7 #include <stdarg.h>
   8 #include <stdint.h>
   9 #include <stdio_ext.h>
  10 #include <stdlib.h>
  11 #include <string.h>
  12 #include <sys/stat.h>
  13 #include <sys/types.h>
  14 #include <unistd.h>
  15
  16 #include "alloc-util.h"
  17 #include "fd-util.h"
  18 #include "fileio.h"
  19 #include "fs-util.h"
  20 #include "hexdecoct.h"
  21 #include "log.h"
  22 #include "macro.h"
  23 #include "missing.h"
  24 #include "parse-util.h"
  25 #include "path-util.h"
  26 #include "stdio-util.h"
  27 #include "string-util.h"
  28 #include "tmpfile-util.h"
  29
  30 #define READ_FULL_BYTES_MAX (4U*1024U*1024U)
  31
  32 int fopen_unlocked(const char *path, const char *options, FILE **ret) {
  33         assert(ret);
  34
  35         FILE *f = fopen(path, options);
  36         if (!f)
  37                 return -errno;
  38
  39         (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
  40
  41         *ret = f;
  42         return 0;
  43 }
  44
  45 int fdopen_unlocked(int fd, const char *options, FILE **ret) {
  46         assert(ret);
  47
  48         FILE *f = fdopen(fd, options);
  49         if (!f)
  50                 return -errno;
  51
  52         (void) __fsetlocking(f, FSETLOCKING_BYCALLER);
  53
  54         *ret = f;
  55         return 0;
  56 }
  57
  58 int write_string_stream_ts(
  59                 FILE *f,
  60                 const char *line,
  61                 WriteStringFileFlags flags,
  62                 struct timespec *ts) {
  63
  64         bool needs_nl;
  65         int r;
  66
  67         assert(f);
  68         assert(line);
  69
  70         if (ferror(f))
  71                 return -EIO;
  72
  73         needs_nl = !(flags & WRITE_STRING_FILE_AVOID_NEWLINE) && !endswith(line, "\n");
  74
  75         if (needs_nl && (flags & WRITE_STRING_FILE_DISABLE_BUFFER)) {
  76                 /* If STDIO buffering was disabled, then let's append the newline character to the string itself, so
  77                  * that the write goes out in one go, instead of two */
  78
  79                 line = strjoina(line, "\n");
  80                 needs_nl = false;
  81         }
  82
  83         if (fputs(line, f) == EOF)
  84                 return -errno;
  85
  86         if (needs_nl)
  87                 if (fputc('\n', f) == EOF)
  88                         return -errno;
  89
  90         if (flags & WRITE_STRING_FILE_SYNC)
  91                 r = fflush_sync_and_check(f);
  92         else
  93                 r = fflush_and_check(f);
  94         if (r < 0)
  95                 return r;
  96
  97         if (ts) {
  98                 struct timespec twice[2] = {*ts, *ts};
  99
 100                 if (futimens(fileno(f), twice) < 0)
 101                         return -errno;
 102         }
 103
 104         return 0;
 105 }
 106
 107 static int write_string_file_atomic(
 108                 const char *fn,
 109                 const char *line,
 110                 WriteStringFileFlags flags,
 111                 struct timespec *ts) {
 112
 113         _cleanup_fclose_ FILE *f = NULL;
 114         _cleanup_free_ char *p = NULL;
 115         int r;
 116
 117         assert(fn);
 118         assert(line);
 119
 120         r = fopen_temporary(fn, &f, &p);
 121         if (r < 0)
 122                 return r;
 123
 124         (void) fchmod_umask(fileno(f), 0644);
 125
 126         r = write_string_stream_ts(f, line, flags, ts);
 127         if (r < 0)
 128                 goto fail;
 129
 130         if (rename(p, fn) < 0) {
 131                 r = -errno;
 132                 goto fail;
 133         }
 134
 135         return 0;
 136
 137 fail:
 138         (void) unlink(p);
 139         return r;
 140 }
 141
 142 int write_string_file_ts(
 143                 const char *fn,
 144                 const char *line,
 145                 WriteStringFileFlags flags,
 146                 struct timespec *ts) {
 147
 148         _cleanup_fclose_ FILE *f = NULL;
 149         int q, r;
 150
 151         assert(fn);
 152         assert(line);
 153
 154         /* We don't know how to verify whether the file contents was already on-disk. */
 155         assert(!((flags & WRITE_STRING_FILE_VERIFY_ON_FAILURE) && (flags & WRITE_STRING_FILE_SYNC)));
 156
 157         if (flags & WRITE_STRING_FILE_ATOMIC) {
 158                 assert(flags & WRITE_STRING_FILE_CREATE);
 159
 160                 r = write_string_file_atomic(fn, line, flags, ts);
 161                 if (r < 0)
 162                         goto fail;
 163
 164                 return r;
 165         } else
 166                 assert(!ts);
 167
 168         if (flags & WRITE_STRING_FILE_CREATE) {
 169                 r = fopen_unlocked(fn, "we", &f);
 170                 if (r < 0)
 171                         goto fail;
 172         } else {
 173                 int fd;
 174
 175                 /* We manually build our own version of fopen(..., "we") that
 176                  * works without O_CREAT */
 177                 fd = open(fn, O_WRONLY|O_CLOEXEC|O_NOCTTY | ((flags & WRITE_STRING_FILE_NOFOLLOW) ? O_NOFOLLOW : 0));
 178                 if (fd < 0) {
 179                         r = -errno;
 180                         goto fail;
 181                 }
 182
 183                 r = fdopen_unlocked(fd, "w", &f);
 184                 if (r < 0) {
 185                         safe_close(fd);
 186                         goto fail;
 187                 }
 188         }
 189
 190         if (flags & WRITE_STRING_FILE_DISABLE_BUFFER)
 191                 setvbuf(f, NULL, _IONBF, 0);
 192
 193         r = write_string_stream_ts(f, line, flags, ts);
 194         if (r < 0)
 195                 goto fail;
 196
 197         return 0;
 198
 199 fail:
 200         if (!(flags & WRITE_STRING_FILE_VERIFY_ON_FAILURE))
 201                 return r;
 202
 203         f = safe_fclose(f);
 204
 205         /* OK, the operation failed, but let's see if the right
 206          * contents in place already. If so, eat up the error. */
 207
 208         q = verify_file(fn, line, !(flags & WRITE_STRING_FILE_AVOID_NEWLINE));
 209         if (q <= 0)
 210                 return r;
 211
 212         return 0;
 213 }
 214
 215 int write_string_filef(
 216                 const char *fn,
 217                 WriteStringFileFlags flags,
 218                 const char *format, ...) {
 219
 220         _cleanup_free_ char *p = NULL;
 221         va_list ap;
 222         int r;
 223
 224         va_start(ap, format);
 225         r = vasprintf(&p, format, ap);
 226         va_end(ap);
 227
 228         if (r < 0)
 229                 return -ENOMEM;
 230
 231         return write_string_file(fn, p, flags);
 232 }
 233
 234 int read_one_line_file(const char *fn, char **line) {
 235         _cleanup_fclose_ FILE *f = NULL;
 236         int r;
 237
 238         assert(fn);
 239         assert(line);
 240
 241         r = fopen_unlocked(fn, "re", &f);
 242         if (r < 0)
 243                 return r;
 244
 245         return read_line(f, LONG_LINE_MAX, line);
 246 }
 247
 248 int verify_file(const char *fn, const char *blob, bool accept_extra_nl) {
 249         _cleanup_fclose_ FILE *f = NULL;
 250         _cleanup_free_ char *buf = NULL;
 251         size_t l, k;
 252         int r;
 253
 254         assert(fn);
 255         assert(blob);
 256
 257         l = strlen(blob);
 258
 259         if (accept_extra_nl && endswith(blob, "\n"))
 260                 accept_extra_nl = false;
 261
 262         buf = malloc(l + accept_extra_nl + 1);
 263         if (!buf)
 264                 return -ENOMEM;
 265
 266         r = fopen_unlocked(fn, "re", &f);
 267         if (r < 0)
 268                 return r;
 269
 270         /* We try to read one byte more than we need, so that we know whether we hit eof */
 271         errno = 0;
 272         k = fread(buf, 1, l + accept_extra_nl + 1, f);
 273         if (ferror(f))
 274                 return errno > 0 ? -errno : -EIO;
 275
 276         if (k != l && k != l + accept_extra_nl)
 277                 return 0;
 278         if (memcmp(buf, blob, l) != 0)
 279                 return 0;
 280         if (k > l && buf[l] != '\n')
 281                 return 0;
 282
 283         return 1;
 284 }
 285
 286 int read_full_stream_full(
 287                 FILE *f,
 288                 const char *filename,
 289                 ReadFullFileFlags flags,
 290                 char **ret_contents,
 291                 size_t *ret_size) {
 292
 293         _cleanup_free_ char *buf = NULL;
 294         struct stat st;
 295         size_t n, n_next, l;
 296         int fd, r;
 297
 298         assert(f);
 299         assert(ret_contents);
 300         assert(!(flags & READ_FULL_FILE_UNBASE64) || ret_size);
 301
 302         n_next = LINE_MAX; /* Start size */
 303
 304         fd = fileno(f);
 305         if (fd >= 0) { /* If the FILE* object is backed by an fd (as opposed to memory or such, see fmemopen(), let's
 306                         * optimize our buffering) */
 307
 308                 if (fstat(fd, &st) < 0)
 309                         return -errno;
 310
 311                 if (S_ISREG(st.st_mode)) {
 312
 313                         /* Safety check */
 314                         if (st.st_size > READ_FULL_BYTES_MAX)
 315                                 return -E2BIG;
 316
 317                         /* Start with the right file size, but be prepared for files from /proc which generally report a file
 318                          * size of 0. Note that we increase the size to read here by one, so that the first read attempt
 319                          * already makes us notice the EOF. */
 320                         if (st.st_size > 0)
 321                                 n_next = st.st_size + 1;
 322
 323                         if (flags & READ_FULL_FILE_SECURE)
 324                                 (void) warn_file_is_world_accessible(filename, &st, NULL, 0);
 325                 }
 326         }
 327
 328         n = l = 0;
 329         for (;;) {
 330                 char *t;
 331                 size_t k;
 332
 333                 if (flags & READ_FULL_FILE_SECURE) {
 334                         t = malloc(n_next + 1);
 335                         if (!t) {
 336                                 r = -ENOMEM;
 337                                 goto finalize;
 338                         }
 339                         memcpy_safe(t, buf, n);
 340                         explicit_bzero_safe(buf, n);
 341                 } else {
 342                         t = realloc(buf, n_next + 1);
 343                         if (!t)
 344                                 return -ENOMEM;
 345                 }
 346
 347                 buf = t;
 348                 n = n_next;
 349
 350                 errno = 0;
 351                 k = fread(buf + l, 1, n - l, f);
 352                 if (k > 0)
 353                         l += k;
 354
 355                 if (ferror(f)) {
 356                         r = errno > 0 ? -errno : -EIO;
 357                         goto finalize;
 358                 }
 359
 360                 if (feof(f))
 361                         break;
 362
 363                 /* We aren't expecting fread() to return a short read outside
 364                  * of (error && eof), assert buffer is full and enlarge buffer.
 365                  */
 366                 assert(l == n);
 367
 368                 /* Safety check */
 369                 if (n >= READ_FULL_BYTES_MAX) {
 370                         r = -E2BIG;
 371                         goto finalize;
 372                 }
 373
 374                 n_next = MIN(n * 2, READ_FULL_BYTES_MAX);
 375         }
 376
 377         if (flags & READ_FULL_FILE_UNBASE64) {
 378                 buf[l++] = 0;
 379                 r = unbase64mem_full(buf, l, flags & READ_FULL_FILE_SECURE, (void **) ret_contents, ret_size);
 380                 goto finalize;
 381         }
 382
 383         if (!ret_size) {
 384                 /* Safety check: if the caller doesn't want to know the size of what we just read it will rely on the
 385                  * trailing NUL byte. But if there's an embedded NUL byte, then we should refuse operation as otherwise
 386                  * there'd be ambiguity about what we just read. */
 387
 388                 if (memchr(buf, 0, l)) {
 389                         r = -EBADMSG;
 390                         goto finalize;
 391                 }
 392         }
 393
 394         buf[l] = 0;
 395         *ret_contents = TAKE_PTR(buf);
 396
 397         if (ret_size)
 398                 *ret_size = l;
 399
 400         return 0;
 401
 402 finalize:
 403         if (flags & READ_FULL_FILE_SECURE)
 404                 explicit_bzero_safe(buf, n);
 405
 406         return r;
 407 }
 408
 409 int read_full_file_full(const char *filename, ReadFullFileFlags flags, char **contents, size_t *size) {
 410         _cleanup_fclose_ FILE *f = NULL;
 411         int r;
 412
 413         assert(filename);
 414         assert(contents);
 415
 416         r = fopen_unlocked(filename, "re", &f);
 417         if (r < 0)
 418                 return r;
 419
 420         return read_full_stream_full(f, filename, flags, contents, size);
 421 }
 422
 423 int executable_is_script(const char *path, char **interpreter) {
 424         _cleanup_free_ char *line = NULL;
 425         size_t len;
 426         char *ans;
 427         int r;
 428
 429         assert(path);
 430
 431         r = read_one_line_file(path, &line);
 432         if (r == -ENOBUFS) /* First line overly long? if so, then it's not a script */
 433                 return 0;
 434         if (r < 0)
 435                 return r;
 436
 437         if (!startswith(line, "#!"))
 438                 return 0;
 439
 440         ans = strstrip(line + 2);
 441         len = strcspn(ans, " \t");
 442
 443         if (len == 0)
 444                 return 0;
 445
 446         ans = strndup(ans, len);
 447         if (!ans)
 448                 return -ENOMEM;
 449
 450         *interpreter = ans;
 451         return 1;
 452 }
 453
 454 /**
 455  * Retrieve one field from a file like /proc/self/status.  pattern
 456  * should not include whitespace or the delimiter (':'). pattern matches only
 457  * the beginning of a line. Whitespace before ':' is skipped. Whitespace and
 458  * zeros after the ':' will be skipped. field must be freed afterwards.
 459  * terminator specifies the terminating characters of the field value (not
 460  * included in the value).
 461  */
 462 int get_proc_field(const char *filename, const char *pattern, const char *terminator, char **field) {
 463         _cleanup_free_ char *status = NULL;
 464         char *t, *f;
 465         size_t len;
 466         int r;
 467
 468         assert(terminator);
 469         assert(filename);
 470         assert(pattern);
 471         assert(field);
 472
 473         r = read_full_file(filename, &status, NULL);
 474         if (r < 0)
 475                 return r;
 476
 477         t = status;
 478
 479         do {
 480                 bool pattern_ok;
 481
 482                 do {
 483                         t = strstr(t, pattern);
 484                         if (!t)
 485                                 return -ENOENT;
 486
 487                         /* Check that pattern occurs in beginning of line. */
 488                         pattern_ok = (t == status || t[-1] == '\n');
 489
 490                         t += strlen(pattern);
 491
 492                 } while (!pattern_ok);
 493
 494                 t += strspn(t, " \t");
 495                 if (!*t)
 496                         return -ENOENT;
 497
 498         } while (*t != ':');
 499
 500         t++;
 501
 502         if (*t) {
 503                 t += strspn(t, " \t");
 504
 505                 /* Also skip zeros, because when this is used for
 506                  * capabilities, we don't want the zeros. This way the
 507                  * same capability set always maps to the same string,
 508                  * irrespective of the total capability set size. For
 509                  * other numbers it shouldn't matter. */
 510                 t += strspn(t, "0");
 511                 /* Back off one char if there's nothing but whitespace
 512                    and zeros */
 513                 if (!*t || isspace(*t))
 514                         t--;
 515         }
 516
 517         len = strcspn(t, terminator);
 518
 519         f = strndup(t, len);
 520         if (!f)
 521                 return -ENOMEM;
 522
 523         *field = f;
 524         return 0;
 525 }
 526
 527 DIR *xopendirat(int fd, const char *name, int flags) {
 528         int nfd;
 529         DIR *d;
 530
 531         assert(!(flags & O_CREAT));
 532
 533         nfd = openat(fd, name, O_RDONLY|O_NONBLOCK|O_DIRECTORY|O_CLOEXEC|flags, 0);
 534         if (nfd < 0)
 535                 return NULL;
 536
 537         d = fdopendir(nfd);
 538         if (!d) {
 539                 safe_close(nfd);
 540                 return NULL;
 541         }
 542
 543         return d;
 544 }
 545
 546 static int search_and_fopen_internal(const char *path, const char *mode, const char *root, char **search, FILE **_f) {
 547         char **i;
 548
 549         assert(path);
 550         assert(mode);
 551         assert(_f);
 552
 553         if (!path_strv_resolve_uniq(search, root))
 554                 return -ENOMEM;
 555
 556         STRV_FOREACH(i, search) {
 557                 _cleanup_free_ char *p = NULL;
 558                 FILE *f;
 559
 560                 if (root)
 561                         p = strjoin(root, *i, "/", path);
 562                 else
 563                         p = strjoin(*i, "/", path);
 564                 if (!p)
 565                         return -ENOMEM;
 566
 567                 f = fopen(p, mode);
 568                 if (f) {
 569                         *_f = f;
 570                         return 0;
 571                 }
 572
 573                 if (errno != ENOENT)
 574                         return -errno;
 575         }
 576
 577         return -ENOENT;
 578 }
 579
 580 int search_and_fopen(const char *path, const char *mode, const char *root, const char **search, FILE **_f) {
 581         _cleanup_strv_free_ char **copy = NULL;
 582
 583         assert(path);
 584         assert(mode);
 585         assert(_f);
 586
 587         if (path_is_absolute(path)) {
 588                 FILE *f;
 589
 590                 f = fopen(path, mode);
 591                 if (f) {
 592                         *_f = f;
 593                         return 0;
 594                 }
 595
 596                 return -errno;
 597         }
 598
 599         copy = strv_copy((char**) search);
 600         if (!copy)
 601                 return -ENOMEM;
 602
 603         return search_and_fopen_internal(path, mode, root, copy, _f);
 604 }
 605
 606 int search_and_fopen_nulstr(const char *path, const char *mode, const char *root, const char *search, FILE **_f) {
 607         _cleanup_strv_free_ char **s = NULL;
 608
 609         if (path_is_absolute(path)) {
 610                 FILE *f;
 611
 612                 f = fopen(path, mode);
 613                 if (f) {
 614                         *_f = f;
 615                         return 0;
 616                 }
 617
 618                 return -errno;
 619         }
 620
 621         s = strv_split_nulstr(search);
 622         if (!s)
 623                 return -ENOMEM;
 624
 625         return search_and_fopen_internal(path, mode, root, s, _f);
 626 }
 627
 628 int fflush_and_check(FILE *f) {
 629         assert(f);
 630
 631         errno = 0;
 632         fflush(f);
 633
 634         if (ferror(f))
 635                 return errno > 0 ? -errno : -EIO;
 636
 637         return 0;
 638 }
 639
 640 int fflush_sync_and_check(FILE *f) {
 641         int r;
 642
 643         assert(f);
 644
 645         r = fflush_and_check(f);
 646         if (r < 0)
 647                 return r;
 648
 649         if (fsync(fileno(f)) < 0)
 650                 return -errno;
 651
 652         r = fsync_directory_of_file(fileno(f));
 653         if (r < 0)
 654                 return r;
 655
 656         return 0;
 657 }
 658
 659 int write_timestamp_file_atomic(const char *fn, usec_t n) {
 660         char ln[DECIMAL_STR_MAX(n)+2];
 661
 662         /* Creates a "timestamp" file, that contains nothing but a
 663          * usec_t timestamp, formatted in ASCII. */
 664
 665         if (n <= 0 || n >= USEC_INFINITY)
 666                 return -ERANGE;
 667
 668         xsprintf(ln, USEC_FMT "\n", n);
 669
 670         return write_string_file(fn, ln, WRITE_STRING_FILE_CREATE|WRITE_STRING_FILE_ATOMIC);
 671 }
 672
 673 int read_timestamp_file(const char *fn, usec_t *ret) {
 674         _cleanup_free_ char *ln = NULL;
 675         uint64_t t;
 676         int r;
 677
 678         r = read_one_line_file(fn, &ln);
 679         if (r < 0)
 680                 return r;
 681
 682         r = safe_atou64(ln, &t);
 683         if (r < 0)
 684                 return r;
 685
 686         if (t <= 0 || t >= (uint64_t) USEC_INFINITY)
 687                 return -ERANGE;
 688
 689         *ret = (usec_t) t;
 690         return 0;
 691 }
 692
 693 int fputs_with_space(FILE *f, const char *s, const char *separator, bool *space) {
 694         int r;
 695
 696         assert(s);
 697
 698         /* Outputs the specified string with fputs(), but optionally prefixes it with a separator. The *space parameter
 699          * when specified shall initially point to a boolean variable initialized to false. It is set to true after the
 700          * first invocation. This call is supposed to be use in loops, where a separator shall be inserted between each
 701          * element, but not before the first one. */
 702
 703         if (!f)
 704                 f = stdout;
 705
 706         if (space) {
 707                 if (!separator)
 708                         separator = " ";
 709
 710                 if (*space) {
 711                         r = fputs(separator, f);
 712                         if (r < 0)
 713                                 return r;
 714                 }
 715
 716                 *space = true;
 717         }
 718
 719         return fputs(s, f);
 720 }
 721
 722 /* A bitmask of the EOL markers we know */
 723 typedef enum EndOfLineMarker {
 724         EOL_NONE     = 0,
 725         EOL_ZERO     = 1 << 0,  /* \0 (aka NUL) */
 726         EOL_TEN      = 1 << 1,  /* \n (aka NL, aka LF)  */
 727         EOL_THIRTEEN = 1 << 2,  /* \r (aka CR)  */
 728 } EndOfLineMarker;
 729
 730 static EndOfLineMarker categorize_eol(char c, ReadLineFlags flags) {
 731
 732         if (!IN_SET(flags, READ_LINE_ONLY_NUL)) {
 733                 if (c == '\n')
 734                         return EOL_TEN;
 735                 if (c == '\r')
 736                         return EOL_THIRTEEN;
 737         }
 738
 739         if (c == '\0')
 740                 return EOL_ZERO;
 741
 742         return EOL_NONE;
 743 }
 744
 745 DEFINE_TRIVIAL_CLEANUP_FUNC(FILE*, funlockfile);
 746
 747 int read_line_full(FILE *f, size_t limit, ReadLineFlags flags, char **ret) {
 748         size_t n = 0, allocated = 0, count = 0;
 749         _cleanup_free_ char *buffer = NULL;
 750         int r;
 751
 752         assert(f);
 753
 754         /* Something like a bounded version of getline().
 755          *
 756          * Considers EOF, \n, \r and \0 end of line delimiters (or combinations of these), and does not include these
 757          * delimiters in the string returned. Specifically, recognizes the following combinations of markers as line
 758          * endings:
 759          *
 760          *     • \n        (UNIX)
 761          *     • \r        (old MacOS)
 762          *     • \0        (C strings)
 763          *     • \n\0
 764          *     • \r\0
 765          *     • \r\n      (Windows)
 766          *     • \n\r
 767          *     • \r\n\0
 768          *     • \n\r\0
 769          *
 770          * Returns the number of bytes read from the files (i.e. including delimiters — this hence usually differs from
 771          * the number of characters in the returned string). When EOF is hit, 0 is returned.
 772          *
 773          * The input parameter limit is the maximum numbers of characters in the returned string, i.e. excluding
 774          * delimiters. If the limit is hit we fail and return -ENOBUFS.
 775          *
 776          * If a line shall be skipped ret may be initialized as NULL. */
 777
 778         if (ret) {
 779                 if (!GREEDY_REALLOC(buffer, allocated, 1))
 780                         return -ENOMEM;
 781         }
 782
 783         {
 784                 _unused_ _cleanup_(funlockfilep) FILE *flocked = f;
 785                 EndOfLineMarker previous_eol = EOL_NONE;
 786                 flockfile(f);
 787
 788                 for (;;) {
 789                         EndOfLineMarker eol;
 790                         char c;
 791
 792                         if (n >= limit)
 793                                 return -ENOBUFS;
 794
 795                         if (count >= INT_MAX) /* We couldn't return the counter anymore as "int", hence refuse this */
 796                                 return -ENOBUFS;
 797
 798                         r = safe_fgetc(f, &c);
 799                         if (r < 0)
 800                                 return r;
 801                         if (r == 0) /* EOF is definitely EOL */
 802                                 break;
 803
 804                         eol = categorize_eol(c, flags);
 805
 806                         if (FLAGS_SET(previous_eol, EOL_ZERO) ||
 807                             (eol == EOL_NONE && previous_eol != EOL_NONE) ||
 808                             (eol != EOL_NONE && (previous_eol & eol) != 0)) {
 809                                 /* Previous char was a NUL? This is not an EOL, but the previous char was? This type of
 810                                  * EOL marker has been seen right before?  In either of these three cases we are
 811                                  * done. But first, let's put this character back in the queue. (Note that we have to
 812                                  * cast this to (unsigned char) here as ungetc() expects a positive 'int', and if we
 813                                  * are on an architecture where 'char' equals 'signed char' we need to ensure we don't
 814                                  * pass a negative value here. That said, to complicate things further ungetc() is
 815                                  * actually happy with most negative characters and implicitly casts them back to
 816                                  * positive ones as needed, except for \xff (aka -1, aka EOF), which it refuses. What a
 817                                  * godawful API!) */
 818                                 assert_se(ungetc((unsigned char) c, f) != EOF);
 819                                 break;
 820                         }
 821
 822                         count++;
 823
 824                         if (eol != EOL_NONE) {
 825                                 previous_eol |= eol;
 826                                 continue;
 827                         }
 828
 829                         if (ret) {
 830                                 if (!GREEDY_REALLOC(buffer, allocated, n + 2))
 831                                         return -ENOMEM;
 832
 833                                 buffer[n] = c;
 834                         }
 835
 836                         n++;
 837                 }
 838         }
 839
 840         if (ret) {
 841                 buffer[n] = 0;
 842
 843                 *ret = TAKE_PTR(buffer);
 844         }
 845
 846         return (int) count;
 847 }
 848
 849 int safe_fgetc(FILE *f, char *ret) {
 850         int k;
 851
 852         assert(f);
 853
 854         /* A safer version of plain fgetc(): let's propagate the error that happened while reading as such, and
 855          * separate the EOF condition from the byte read, to avoid those confusion signed/unsigned issues fgetc()
 856          * has. */
 857
 858         errno = 0;
 859         k = fgetc(f);
 860         if (k == EOF) {
 861                 if (ferror(f))
 862                         return errno > 0 ? -errno : -EIO;
 863
 864                 if (ret)
 865                         *ret = 0;
 866
 867                 return 0;
 868         }
 869
 870         if (ret)
 871                 *ret = k;
 872
 873         return 1;
 874 }
 875
 876 int warn_file_is_world_accessible(const char *filename, struct stat *st, const char *unit, unsigned line) {
 877         struct stat _st;
 878
 879         if (!filename)
 880                 return 0;
 881
 882         if (!st) {
 883                 if (stat(filename, &_st) < 0)
 884                         return -errno;
 885                 st = &_st;
 886         }
 887
 888         if ((st->st_mode & S_IRWXO) == 0)
 889                 return 0;
 890
 891         if (unit)
 892                 log_syntax(unit, LOG_WARNING, filename, line, 0,
 893                            "%s has %04o mode that is too permissive, please adjust the access mode.",
 894                            filename, st->st_mode & 07777);
 895         else
 896                 log_warning("%s has %04o mode that is too permissive, please adjust the access mode.",
 897                             filename, st->st_mode & 07777);
 898         return 0;
 899 }