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Initial revision

    1: /* An interface to read and write that retries after interrupts.
    2: 
    3:    Copyright (C) 1993-1994, 1998, 2002-2006, 2009-2011 Free Software
    4:    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 3 of the License, or
    9:    (at your option) 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, see <http://www.gnu.org/licenses/>.  */
   18: 
   19: #include <config.h>
   20: 
   21: /* Specification.  */
   22: #ifdef SAFE_WRITE
   23: # include "safe-write.h"
   24: #else
   25: # include "safe-read.h"
   26: #endif
   27: 
   28: /* Get ssize_t.  */
   29: #include <sys/types.h>
   30: #include <unistd.h>
   31: 
   32: #include <errno.h>
   33: 
   34: #ifdef EINTR
   35: # define IS_EINTR(x) ((x) == EINTR)
   36: #else
   37: # define IS_EINTR(x) 0
   38: #endif
   39: 
   40: #include <limits.h>
   41: 
   42: #ifdef SAFE_WRITE
   43: # define safe_rw safe_write
   44: # define rw write
   45: #else
   46: # define safe_rw safe_read
   47: # define rw read
   48: # undef const
   49: # define const /* empty */
   50: #endif
   51: 
   52: /* Read(write) up to COUNT bytes at BUF from(to) descriptor FD, retrying if
   53:    interrupted.  Return the actual number of bytes read(written), zero for EOF,
   54:    or SAFE_READ_ERROR(SAFE_WRITE_ERROR) upon error.  */
   55: size_t
   56: safe_rw (int fd, void const *buf, size_t count)
   57: {
   58:   /* Work around a bug in Tru64 5.1.  Attempting to read more than
   59:      INT_MAX bytes fails with errno == EINVAL.  See
   60:      <http://lists.gnu.org/archive/html/bug-gnu-utils/2002-04/msg00010.html>.
   61:      When decreasing COUNT, keep it block-aligned.  */
   62:   enum { BUGGY_READ_MAXIMUM = INT_MAX & ~8191 };
   63: 
   64:   for (;;)
   65:     {
   66:       ssize_t result = rw (fd, buf, count);
   67: 
   68:       if (0 <= result)
   69:         return result;
   70:       else if (IS_EINTR (errno))
   71:         continue;
   72:       else if (errno == EINVAL && BUGGY_READ_MAXIMUM < count)
   73:         count = BUGGY_READ_MAXIMUM;
   74:       else
   75:         return result;
   76:     }
   77: }