compiler/posixc/ftruncate.c

   1 /*
   2     Copyright © 1995-2012, The AROS Development Team. All rights reserved.
   3     $Id$
   4
   5     POSIX.1-2008 function ftruncate().
   6 */
   7
   8 #include <dos/dos.h>
   9 #include <proto/dos.h>
  10 #include <fcntl.h>
  11 #include <errno.h>
  12 #include "__fdesc.h"
  13
  14 /*****************************************************************************
  15
  16     NAME */
  17 #include <unistd.h>
  18
  19         int ftruncate (
  20
  21 /*  SYNOPSIS */
  22         int   fd,
  23         off_t length)
  24
  25 /*  FUNCTION
  26         Truncate a file to a specified length
  27
  28     INPUTS
  29         fd     - the descriptor of the file being truncated.
  30                  The file must be open for writing
  31         lenght - The file will have at most this size
  32
  33     RESULT
  34         0 on success or -1 on errorr.
  35
  36     NOTES
  37         If the file previously was larger than this size, the extra  data
  38         is  lost.   If  the  file  previously  was  shorter, it is
  39         unspecified whether the  file  is  left  unchanged  or  is
  40         extended.  In  the  latter case the extended part reads as
  41         zero bytes.
  42
  43
  44     EXAMPLE
  45
  46     BUGS
  47
  48     SEE ALSO
  49         open(), truncate()
  50
  51     INTERNALS
  52
  53 ******************************************************************************/
  54 {
  55     ULONG oldpos;
  56     size_t size;
  57
  58     fdesc *fdesc = __getfdesc(fd);
  59
  60     if (!fdesc)
  61     {
  62         errno = EBADF;
  63         return -1;
  64     }
  65
  66     if(fdesc->fcb->privflags & _FCB_ISDIR)
  67     {
  68         errno = EISDIR;
  69         return -1;
  70     }
  71
  72     if (!(fdesc->fcb->flags & (O_WRONLY|O_RDWR)))
  73     {
  74         errno = EINVAL;
  75         return -1;
  76     }
  77
  78     oldpos = Seek(fdesc->fcb->handle, 0, OFFSET_END);
  79     size   = Seek(fdesc->fcb->handle, 0, OFFSET_CURRENT);
  80     Seek(fdesc->fcb->handle, oldpos, OFFSET_BEGINNING);
  81
  82     if ((length = SetFileSize(fdesc->fcb->handle, length, OFFSET_BEGINNING)) == -1)
  83     {
  84         errno = __stdc_ioerr2errno(IoErr());
  85         return -1;
  86     }
  87     else
  88     if (size < length)
  89     {
  90         char buf[16]={0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0};
  91
  92         length -= size;
  93
  94         oldpos = Seek(fdesc->fcb->handle, size, OFFSET_BEGINNING);
  95
  96         while (length >= 16)
  97         {
  98             FWrite(fdesc->fcb->handle, buf, 16, 1);
  99             length -= 16;
 100         }
 101         if (length)
 102             FWrite(fdesc->fcb->handle, buf, length, 1);
 103
 104         Flush(fdesc->fcb->handle);
 105         Seek(fdesc->fcb->handle, oldpos, OFFSET_BEGINNING);
 106     }
 107
 108     return 0;
 109 }