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