/* An interface to read and write that retries after interrupts.

   Copyright (C) 1993-1994, 1998, 2002-2006, 2009-2017 Free Software

   Foundation, Inc.

   This program is free software: you can redistribute it and/or modify

   it under the terms of the GNU General Public License as published by

   the Free Software Foundation; either version 3 of the License, or

   (at your option) any later version.

   This program is distributed in the hope that it will be useful,

   but WITHOUT ANY WARRANTY; without even the implied warranty of

   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License

   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include <config.h>

/* Specification.  */

#ifdef SAFE_WRITE

# include "safe-write.h"

#else

# include "safe-read.h"

#endif

/* Get ssize_t.  */

#include <sys/types.h>

#include <unistd.h>

#include <errno.h>

#ifdef EINTR

# define IS_EINTR(x) ((x) == EINTR)

#else

# define IS_EINTR(x) 0

#endif

#include <limits.h>

#ifdef SAFE_WRITE

# define safe_rw safe_write

# define rw write

#else

# define safe_rw safe_read

# define rw read

# undef const

# define const /* empty */

#endif

/* Read(write) up to COUNT bytes at BUF from(to) descriptor FD, retrying if

   interrupted.  Return the actual number of bytes read(written), zero for EOF,

   or SAFE_READ_ERROR(SAFE_WRITE_ERROR) upon error.  */

size_t

safe_rw (int fd, void const *buf, size_t count)

{

  /* Work around a bug in Tru64 5.1.  Attempting to read more than

     INT_MAX bytes fails with errno == EINVAL.  See

     <http://lists.gnu.org/archive/html/bug-gnu-utils/2002-04/msg00010.html>.

     When decreasing COUNT, keep it block-aligned.  */

  enum { BUGGY_READ_MAXIMUM = INT_MAX & ~8191 };

  for (;;)

    {

      ssize_t result = rw (fd, buf, count);

      if (0 <= result)

        return result;

      else if (IS_EINTR (errno))

        continue;

      else if (errno == EINVAL && BUGGY_READ_MAXIMUM < count)

        count = BUGGY_READ_MAXIMUM;

      else

        return result;

    }

}