gold/ftruncate.c

   1 /* ftruncate emulations that work on some System V's.
   2    This file is in the public domain.  */
   3
   4 #include <config.h>
   5
   6 /* Specification.  */
   7 #include <unistd.h>
   8
   9 #include <sys/types.h>
  10 #include <fcntl.h>
  11
  12 extern int ftruncate (int, off_t);
  13
  14 #ifdef F_CHSIZE
  15
  16 int
  17 ftruncate (int fd, off_t length)
  18 {
  19   return fcntl (fd, F_CHSIZE, length);
  20 }
  21
  22 #else /* not F_CHSIZE */
  23 # ifdef F_FREESP
  24
  25 /* By William Kucharski <kucharsk@netcom.com>.  */
  26
  27 #  include <sys/stat.h>
  28 #  include <errno.h>
  29
  30 int
  31 ftruncate (int fd, off_t length)
  32 {
  33   struct flock fl;
  34   struct stat filebuf;
  35
  36   if (fstat (fd, &filebuf) < 0)
  37     return -1;
  38
  39   if (filebuf.st_size < length)
  40     {
  41       /* Extend file length. */
  42       if (lseek (fd, (length - 1), SEEK_SET) < 0)
  43         return -1;
  44
  45       /* Write a "0" byte. */
  46       if (write (fd, "", 1) != 1)
  47         return -1;
  48     }
  49   else
  50     {
  51
  52       /* Truncate length. */
  53
  54       fl.l_whence = 0;
  55       fl.l_len = 0;
  56       fl.l_start = length;
  57       fl.l_type = F_WRLCK;      /* write lock on file space */
  58
  59       /* This relies on the *undocumented* F_FREESP argument to fcntl,
  60          which truncates the file so that it ends at the position
  61          indicated by fl.l_start.  Will minor miracles never cease?  */
  62
  63       if (fcntl (fd, F_FREESP, &fl) < 0)
  64         return -1;
  65     }
  66
  67   return 0;
  68 }
  69
  70 # else /* not F_CHSIZE nor F_FREESP */
  71 #  if HAVE_CHSIZE                      /* native Windows, e.g. mingw */
  72
  73 int
  74 ftruncate (int fd, off_t length)
  75 {
  76   return chsize (fd, length);
  77 }
  78
  79 #  else /* not F_CHSIZE nor F_FREESP nor HAVE_CHSIZE */
  80
  81 #   include <errno.h>
  82
  83 int
  84 ftruncate (int fd, off_t length)
  85 {
  86   errno = EIO;
  87   return -1;
  88 }
  89
  90 #  endif /* not HAVE_CHSIZE */
  91 # endif /* not F_FREESP */
  92 #endif /* not F_CHSIZE */