1  /* An interface to read and write that retries after interrupts.
       2  
       3     Copyright (C) 1993-1994, 1998, 2002-2006, 2009-2023 Free Software
       4     Foundation, Inc.
       5  
       6     This file is free software: you can redistribute it and/or modify
       7     it under the terms of the GNU Lesser General Public License as
       8     published by the Free Software Foundation; either version 2.1 of the
       9     License, or (at your option) any later version.
      10  
      11     This file 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 Lesser General Public License for more details.
      15  
      16     You should have received a copy of the GNU Lesser General Public License
      17     along with this program.  If not, see <https://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 "sys-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    for (;;)
      59      {
      60        ssize_t result = rw (fd, buf, count);
      61  
      62        if (0 <= result)
      63          return result;
      64        else if (IS_EINTR (errno))
      65          continue;
      66        else if (errno == EINVAL && SYS_BUFSIZE_MAX < count)
      67          count = SYS_BUFSIZE_MAX;
      68        else
      69          return result;
      70      }
      71  }