1 /* An interface to read and write that retries (if necessary) until complete.
   2 
   3    Copyright (C) 1993, 1994, 1997, 1998, 1999, 2000, 2001, 2002, 2003,
   4    2004, 2005, 2006 Free Software Foundation, Inc.
   5 
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 2, or (at your option)
   9    any later version.
  10 
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15 
  16    You should have received a copy of the GNU General Public License
  17    along with this program; if not, write to the Free Software Foundation,
  18    Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */
  19 
  20 #include <config.h>
  21 
  22 /* Specification.  */
  23 #ifdef FULL_READ
  24 # include "full-read.h"
  25 #else
  26 # include "full-write.h"
  27 #endif
  28 
  29 #include <errno.h>
  30 
  31 #ifdef FULL_READ
  32 # include "safe-read.h"
  33 # define safe_rw safe_read
  34 # define full_rw full_read
  35 # undef const
  36 # define const /* empty */
  37 #else
  38 # include "safe-write.h"
  39 # define safe_rw safe_write
  40 # define full_rw full_write
  41 #endif
  42 
  43 #ifdef FULL_READ
  44 /* Set errno to zero upon EOF.  */
  45 # define ZERO_BYTE_TRANSFER_ERRNO 0
  46 #else
  47 /* Some buggy drivers return 0 when one tries to write beyond
  48    a device's end.  (Example: Linux 1.2.13 on /dev/fd0.)
  49    Set errno to ENOSPC so they get a sensible diagnostic.  */
  50 # define ZERO_BYTE_TRANSFER_ERRNO ENOSPC
  51 #endif
  52 
  53 /* Write(read) COUNT bytes at BUF to(from) descriptor FD, retrying if
  54    interrupted or if a partial write(read) occurs.  Return the number
  55    of bytes transferred.
  56    When writing, set errno if fewer than COUNT bytes are written.
  57    When reading, if fewer than COUNT bytes are read, you must examine
  58    errno to distinguish failure from EOF (errno == 0).  */
  59 size_t
  60 full_rw (int fd, const void *buf, size_t count)
  61 {
  62   size_t total = 0;
  63   const char *ptr = (const char *) buf;
  64 
  65   while (count > 0)
  66     {
  67       size_t n_rw = safe_rw (fd, ptr, count);
  68       if (n_rw == (size_t) -1)
  69         break;
  70       if (n_rw == 0)
  71         {
  72           errno = ZERO_BYTE_TRANSFER_ERRNO;
  73           break;
  74         }
  75       total += n_rw;
  76       ptr += n_rw;
  77       count -= n_rw;
  78     }
  79 
  80   return total;
  81 }