lib/truncate.c

   1 /* truncate emulations for native Windows.
   2    Copyright (C) 2017-2024 Free Software Foundation, Inc.
   3
   4    This program is free software; you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation, either version 3, or (at your option)
   7    any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License along
  15    with this program; if not, see <https://www.gnu.org/licenses/>.  */
  16
  17 /* If the user's config.h happens to include <unistd.h>, let it include only
  18    the system's <unistd.h> here, so that orig_faccessat doesn't recurse to
  19    rpl_faccessat.  */
  20 #define _GL_INCLUDING_UNISTD_H
  21 #include <config.h>
  22
  23 /* Specification.  */
  24 #include <unistd.h>
  25
  26 #include <errno.h>
  27 #include <fcntl.h>
  28 #include <string.h>
  29 #include <sys/stat.h>
  30 #undef _GL_INCLUDING_UNISTD_H
  31
  32 #if TRUNCATE_TRAILING_SLASH_BUG
  33 static int
  34 orig_truncate (const char *filename, off_t length)
  35 {
  36   return truncate (filename, length);
  37 }
  38 #endif
  39
  40 #ifdef __osf__
  41 /* Write "unistd.h" here, not <unistd.h>, otherwise OSF/1 5.1 DTK cc
  42    eliminates this include because of the preliminary #include <unistd.h>
  43    above.  */
  44 # include "unistd.h"
  45 #else
  46 # include <unistd.h>
  47 #endif
  48
  49 int
  50 truncate (const char *filename, off_t length)
  51 {
  52 #if TRUNCATE_TRAILING_SLASH_BUG
  53   /* Use the original truncate(), but correct the trailing slash handling.  */
  54   size_t len = strlen (filename);
  55   if (len && filename[len - 1] == '/')
  56     {
  57       struct stat st;
  58       if (stat (filename, &st) == 0)
  59         errno = (S_ISDIR (st.st_mode) ? EISDIR : ENOTDIR);
  60       return -1;
  61     }
  62   return orig_truncate (filename, length);
  63 #else
  64   int fd;
  65
  66   if (length == 0)
  67     {
  68       fd = open (filename, O_WRONLY | O_TRUNC | O_CLOEXEC);
  69       if (fd < 0)
  70         return -1;
  71     }
  72   else
  73     {
  74       fd = open (filename, O_WRONLY | O_CLOEXEC);
  75       if (fd < 0)
  76         return -1;
  77       if (ftruncate (fd, length) < 0)
  78         {
  79           int saved_errno = errno;
  80           close (fd);
  81           errno = saved_errno;
  82           return -1;
  83         }
  84     }
  85   close (fd);
  86   return 0;
  87 #endif
  88 }